highaltitude.log.20121001

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[04:34] <eroomde> anyone around?
[04:35] <nigelvh> Yes.
[04:35] <nigelvh> Though it depends on who counts as "anyone"
[04:36] <eroomde> you will do
[04:36] <eroomde> i foolishly went to bed early, at 10pm
[04:36] <eroomde> having had a big curry i thought i'd ride the wave of sleep
[04:36] <eroomde> wide awake at 4am as a result
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[04:37] <nigelvh> Ah, yeah, I'm about a half hour away from smartly going to bed at 10pm. That whole getting up at 5:45 for work requires going to bed reasonably early.
[04:37] <eroomde> not sure i should have a coffee as housemate might resent the sound of a coffee grinderat this hour
[04:37] <eroomde> nigelvh: ouch!
[04:37] <eroomde> what do you do?
[04:37] <nigelvh> I'm a systems administrator
[04:38] <nigelvh> Which most of the time means late schedules
[04:38] <nigelvh> But my company runs on a much earlier schedule.
[04:38] <nigelvh> Hardly anyone arrives after 8AM.
[04:38] <eroomde> ouch
[04:38] <nigelvh> I generally get there at about 7:15 or so, and get to leave for the day at 3:45 or so.
[04:38] <eroomde> hardly anyone arrives before 8am at mine
[04:39] <eroomde> usually about 10
[04:39] <nigelvh> Yeah, my previous job was much more like that
[04:39] <eroomde> but then 10 is not usual here either, it's just because we're just 4 people of a roughly similar (not good at mornings) schedule
[04:39] <nigelvh> My present company is an engineering software company, whereas the old one was a game development studio, so that explains the difference.
[04:40] <eroomde> and tend to work until some pre-arranged social engagement or until i just give up
[04:41] <eroomde> but finishing at 3.45 seems like an attractive thing
[04:41] <nigelvh> While the getting up early is less fun, I do have to say I enjoy being out early in the afternoon. Having time to do things in the afternoons is nice.
[04:42] <eroomde> yeah
[04:42] <nigelvh> So it's short of 5AM for you?
[04:43] <eroomde> 5:43
[04:43] <nigelvh> Or 6 now? Stupid daylight savings...
[04:43] <eroomde> just me and radio 4
[04:44] <nigelvh> I remember in college I'd procrastinate on homework, and get up early before class to do it. That was extremely productive time.
[04:45] <eroomde> no distractions
[04:45] <nigelvh> Yep
[04:45] <nigelvh> Also, teh lazy is strong in the evenings.
[04:46] <eroomde> :)
[04:46] <eroomde> i do like not having commitments in the evenings
[04:46] <eroomde> defintely
[04:46] <eroomde> spending the whole day knowing i have to work in the evenings is hell
[04:46] <eroomde> that's the nicest thing about A Job for me
[04:46] <nigelvh> Yeah.
[04:47] <eroomde> that i can nominally switch off
[04:47] <eroomde> i don't, of course. but the knowledge that I could is pleasing
[04:47] <nigelvh> My fiance can attest to my attitude about things in the evenings. Presently she's scheduling my evenings to check out caterers... great...
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[04:48] <nigelvh> Though, I can't complain too hard, she really is handling pretty much everything.
[04:50] <eroomde> it's eating
[04:50] <eroomde> could be worse
[04:51] <nigelvh> No, it's eating very small amounts of food that may or may not be tasty, in a large room stuffed with all sorts of other people, and random florists/planners/whonot else all wanting to talk to me.
[04:51] <nigelvh> "Just give me some food and leave me the hell alone. I'll call you if I like it."
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[04:52] <eroomde> :)
[04:52] <eroomde> see if they do delivery
[04:52] <nigelvh> HAHA
[04:52] <nigelvh> That would be brilliant.
[04:55] <nigelvh> Luckily she does all the talking. I just nod and say thank you occasionally.
[05:01] <nigelvh> Alright, well, it's bed time for me. Craaaazy me, going to bed at 10.
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[05:55] <eroomde> anyone else up?
[05:59] <Upu> me
[05:59] <eroomde> YAY
[05:59] <Upu> curry is bad for sleeping
[05:59] <Upu> just about to head off to work though
[05:59] <Upu> many things to solder
[06:00] <griffonbot> Received email: James Coxon "[UKHAS] Insurance Working Group"
[06:00] <Upu> I used to do IT you know
[06:00] <eroomde> :)
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[06:02] <eroomde> u think it's the curry?
[06:03] <Upu> I never sleep well after a big curry
[06:03] <Upu> makes me hot
[06:03] <eroomde> i was feeling a bit dry
[06:08] <Upu> rightwork bbs
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[07:29] <eroomde> dodged a bullet
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[07:36] <eroomde> Hola
[07:38] <fsphil> mourning
[07:38] <EspacioCercano> Hello
[07:39] <eroomde> we've echausted my spanish already so i'm glad you speak english
[07:39] <EspacioCercano> Hehe no problem
[07:39] <eroomde> exhausted*
[07:39] <fsphil> nearly at his english limits too :)
[07:39] <EspacioCercano> :D
[07:40] <eroomde> well actually my 1 year of spnish lessons age 14 should allow me something a little grander, on the subject of ballooning
[07:40] <eroomde> wait for it
[07:40] <eroomde> es una pasatiempo muy sympatico
[07:41] <EspacioCercano> Since you mention balloons, I've just bought a HAB-1200 from Kaymont& any recomendations for choosing the parachute?
[07:41] <eroomde> spherachutes are a common choice
[07:41] <EspacioCercano> un pasatiempo muy simpatico :P
[07:41] <eroomde> but really any of the outfits set up for hobby rocketry will sell parachutes of the right size
[07:41] <eroomde> all of them will be pretty horrible but that doesn;t seem to bother people
[07:42] <eroomde> gender issues are far beyond my recollection
[07:42] <eroomde> grammatically anyway
[07:42] <EspacioCercano> horrible as in eye-hurting stuff? or in terms of reliability?
[07:42] <eroomde> in terms of stability
[07:43] <eroomde> for example the ones that are cut from a flat sheet are very unstable
[07:43] <eroomde> they'll do the job
[07:43] <fsphil> they'll got a bit wibbly wobbly on the way down
[07:43] <eroomde> they'll get you down with a low enough vertical rate of descent if you pick one of the correct size
[07:43] <eroomde> but it's not a very stable shape
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[07:45] <eroomde> additionally to the wobbliness is that they tend to glide
[07:46] <eroomde> i.e. their air speed is sideways aswell as down
[07:46] <eroomde> 1:1 is not uncommon
[07:46] <eroomde> that makes a difference to landing predictions
[07:47] <radim_OM2AMR> EspacioCercano, we used rocketman 5ft chute fot 1.5kg payload, it did about 6-7 m/s descent
[07:48] <EspacioCercano> I understand& thanks for the info, guys!
[07:49] <eroomde> i don;t like those chutes either :(
[07:49] <radim_OM2AMR> When I compare this chute to original Totex chutes from meteosonde, this is little bit smaller, but better, as it has just 4 lines/ropes
[07:50] <radim_OM2AMR> eroomde, for what ?
[07:50] <eroomde> for providing drag
[07:51] <radim_OM2AMR> drag in which direction ?
[07:51] <costyn> haha
[07:51] <costyn> (morning btw)
[07:51] <eroomde> the opposite one to gravity
[07:52] <eroomde> again, just not a particularly stable or efficient shape.
[07:52] <eroomde> and the chap behind them is full of shit too
[07:53] <eroomde> EspacioCercano: so here's a the condensed thing to look out for
[07:54] <eroomde> see if the seller provides a value for Coefficient of Drag (Cd) with their chutes
[07:54] <radim_OM2AMR> we would like to record this chute behaviour durong descent, but our payload rotated upside down unfortunatelly :-|
[07:54] <eroomde> if they do, it's possibly a good sign
[07:56] <eroomde> but id the Cd is >~ 0.75, it's a bad sign
[07:56] <eroomde> because they don't understand parachutes or drag
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[07:59] <radim_OM2AMR> you're right, rocketman's don't provide such info, just descent rates
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[08:05] <EspacioCercano> I see& do you know of any seller who actually provides a Cd value for his balloons?
[08:05] <EspacioCercano> I mean, for his parachutes :)
[08:05] <eroomde> balloons or parachutes?
[08:05] <eroomde> lol
[08:05] <eroomde> well yes a few do
[08:05] <eroomde> but in hobby sphere's they often wildly wrong
[08:05] <eroomde> eg
[08:05] <eroomde> http://www.fruitychutes.com/
[08:06] <eroomde> "New Iris Ultra feature an ultra high drag Cd of 2.2! Choose a size smaller chute for your project."
[08:06] <eroomde> which is, to put it diplomatically, utter bollocks
[08:06] <EspacioCercano> lol, yeah, I was taking a look at that
[08:07] <eroomde> if you find a chute, i can estimate the drag for you
[08:07] <eroomde> the Cd, sorry
[08:09] <eroomde> i would avoid cruciform parachutes for habs
[08:09] <eroomde> they tend to start spinning when the rest of the balloon line flops onto them and causes a slight assymetry
[08:11] <EspacioCercano> I see& by the way, is there some "golden ratio" regarding the length of the cords between payload/parachute and parachute/balloon?
[08:12] <eroomde> nothing particularly scientific, so you could make it the golden ratio iuw
[08:12] <eroomde> but usually 2:1 payload-chute:chute-balloon
[08:12] <eroomde> so that the remanatns of the balloon can flop down and not intefer with the payload after burst
[08:13] <eroomde> remnants*
[08:14] <EspacioCercano> I see& any minimum length for the payload-chute cord?
[08:14] <eroomde> nope
[08:14] <eroomde> well
[08:15] <eroomde> parachute design rule of thumb is that the parachute mouth wants to be at least 6 forebody widths from the forebody to be free of forebody wake effects
[08:15] <eroomde> but that assumes you're trying to design something well and for stability which isn;t usually much of a concern in hab
[08:15] <eroomde> i tend to just do about 20m:10m
[08:16] <EspacioCercano> Ah, ok
[08:16] <radim_OM2AMR> I think more critical is minimum length chute-balloon, due the balloon remnants, isn't ?
[08:19] <eroomde> sure, you don;t really want them tangling with the chute
[08:22] <eroomde> EspacioCercano: i hope i've not put you off or confused things, this is just a pet annoyance of mine
[08:22] <eroomde> if you just want to launch a simple hab, grab a spherachute or something
[08:22] <radim_OM2AMR> eroomde, could you suggest any special cord (<230N), which will provide less rotation to payload ? ;-)
[08:23] <eroomde> pretend it has a Cd of 0.7
[08:23] <eroomde> radim_OM2AMR: tape
[08:23] <eroomde> or anything tubular
[08:23] <eroomde> we use tubular kevlar on our lines
[08:23] <eroomde> with chinese finger joints
[08:23] <EspacioCercano> eroomde: not at all, your experience on the matter is really useful for me :)
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[08:24] <eroomde> but yes, be warry that inflated Cd values usually mean it has a big glide ratio, and bear than in mind when looking at landing predictions
[08:25] <radim_OM2AMR> thanks eroomde
[08:25] <eroomde> either a big glide ratio or it will madly corkscrew at high altitudes
[08:25] <eroomde> which comes with its own risks
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[08:27] <eroomde> the difference between corkscrewing and gliding is to do mostly with where the centre of gravity of the system is. the centre of gravity goes up towards the parachute (a bit more stable) as you get lower, because the mass of the air entrained by the parachute (which counts as part of the system mass from a dynamics point of view) is more dense
[08:27] <eroomde> but up at high altitudes, with the centre of gravity down towards the payload, it can corkscrew and wobble about a lot. it's constantly trying to fall off its own bubble of air, if you see what i mean
[08:28] <eroomde> flat sheet parachutes are especially terrible for this
[08:30] <EspacioCercano> I see
[08:31] <costyn> eroomde: great... now I have to worry about all you just wrote, where before I was blissfully ignorant :)
[08:31] <eroomde> i'm the same with olive oil
[08:31] <EspacioCercano> lol
[08:31] <fsphil> stupid knowledge
[08:31] <eroomde> i see all these £20 tiny bottles of olive oil on the top shelves of supermarkets
[08:32] <eroomde> i don;t want to taste them, just incase they turn out to be much better and i'll always want to buy them
[08:32] <costyn> hahaha
[08:32] <eroomde> i'd rather live in ignorance
[08:33] <eroomde> costyn: i don;t think it bothers most hab peeps
[08:33] <costyn> I have a nice radio sonde parachute which is military surplus ; but unfortunately it didn't get to do its job as the balloon remnants embraced it as if it were it's long lost brother
[08:33] <eroomde> but every time you see those onboard descent videos where the world is spinning around madly and wildly, just know that it doesn't have to be that way :)
[08:34] <costyn> eroomde: right, I have wondered about that. just assumed that because there is virtually no air to work with the parachute can't really do its job anyways.
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[08:34] <eroomde> nope, it's usually just because the parachute and system design are poo
[08:35] <eroomde> or at least, more charitably, stability wasn't a design consideration
[08:35] <costyn> http://imgur.com/a/PrsuH#5 <-- parachte before ; parachute after: http://imgur.com/a/PrsuH#15
[08:35] <eroomde> ouch
[08:35] <eroomde> badness 10000
[08:35] <costyn> hehe
[08:36] <costyn> well at least this mess http://imgur.com/a/PrsuH#15 slowed it down to about the same rate
[08:36] <eroomde> it's enough to give you nightmares
[08:36] <costyn> yea... nightmares about eldritch deep sea creatures
[08:36] <eroomde> i think if people start using cutdowns more it should be encouraged to fire them after descent has been detected
[08:37] <eroomde> just to get rid of the balloon remnants
[08:37] <costyn> yea would be nice
[08:37] <costyn> still the problem remains how to cut the balloon without cutting the parachute
[08:38] <eroomde> for our parachute test vehicle pre-deployed parachute we ran thin speaker cable up to a pyro at the apex
[08:40] <costyn> what about sending a signal by radio from the payload to another tiny payload sitting above the parachute which cuts it away
[08:41] <costyn> fraught with pitfalls and unknowns of course
[08:41] <eroomde> darkside's talk was about exactly that
[08:41] <eroomde> and uplinking from the ground additionally
[08:42] <costyn> yea, saw it partially
[08:43] <eroomde> doing it with an accelerometer and pyro though means that you can be detached within about 200ms of burst
[08:43] <eroomde> which is nice
[08:44] <costyn> hmm that is nice
[08:46] <costyn> are there ways for us hobbyists to make reliable pyro cutdowns? everyone seems still to be using nichrome which requires a fair amount of juice
[08:46] <fsphil> they are safer though
[08:46] <eroomde> i have never used nichrome*
[08:46] <EspacioCercano> eroomde: is that talk available online somewhere?
[08:46] <costyn> EspacioCercano: http://www.youtube.com/watch?v=1LEaf1QLRUY
[08:46] <eroomde> http://www.youtube.com/watch?v=1LEaf1QLRUY#
[08:47] <eroomde> from 7 minutes
[08:47] <EspacioCercano> awesome, thanks guys
[08:47] <eroomde> but don;t watch the talk after the cutdown one
[08:47] <eroomde> it's shit
[08:47] <costyn> heheheheh
[08:47] <eroomde> costyn: we always used to fly only pyro cutdowns but people got a bit nervous about them legally
[08:47] <eroomde> but i think they're great
[08:49] <eroomde> there used to be a page about how to build them on the wiki
[08:49] <costyn> making a accellerometer cutdown would be fun.. now if only I had more free time
[08:49] <eroomde> but it got removed
[08:51] <eroomde> rob harrison did a flickr photoset of how we makes them, which is also how i make them
[08:51] <eroomde> http://www.flickr.com/photos/30721501@N05/3603060662/in/set-72157619368022480/
[08:52] <MrScienceMan> /fq 2
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[08:52] <fsphil> they remind me of Lemmings going "Oh no!" *pop*
[08:53] <eroomde> lucky you weren't christened Tom
[08:53] <costyn> eroomde: thanks, bookmarked ;)
[08:53] <eroomde> costyn: i tended to put little rods through the drilled holes, instead of the string directly
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[08:53] <eroomde> not a fun of having the string loops under such a tight radius like that
[08:54] <eroomde> it's quite a shear force
[08:54] <eroomde> fan*
[08:54] <costyn> plus the sides of the holes are likely to be sharp ?
[08:54] <eroomde> yes exactly
[08:54] <costyn> (edges)
[08:55] <EspacioCercano> eroomde: the wire used on those pyros is nichrome?
[08:56] <eroomde> yes, but i think they're off-the-shelf e-matches
[08:56] <eroomde> which i would recommend over just nichrome
[08:58] <fsphil> e-matchs sounds like a dating website
[08:58] <EspacioCercano> lol
[08:59] <eroomde> they come in slow burn or quick fire options too
[08:59] <costyn> yea stupid google comes with links to dating sites when googling ematches
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[08:59] Nick change: eroomde -> zeusbollocks
[09:00] <zeusbollocks> http://www.vernk.com/Igniters.htm
[09:00] Nick change: zeusbollocks -> eroomde
[09:00] <fsphil> smooth
[09:00] <EspacioCercano> so the idea is to put these around the chord on top of the parachute, right?
[09:02] <eroomde> that's what i do usually yep
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[12:44] <G7PMO_Kev> Guys, for a 300g payload, on a 500g balloon, guides:balloon_data suggests an 18" or maybe 24" chute. However the data data here guides:parachute_sizing_chart suggests maybe a .6m to 1m chute (24" to 36")?
[12:45] <costyn> G7PMO_Kev: that's too big
[12:45] <costyn> 18" sounds about right
[12:45] <eroomde> best ignore the charts, we can work it out easily enough
[12:46] <costyn> but it isn't good if the data in the wiki contradicts
[12:46] <eroomde> the drag equations is Drag = 0.5*density*velocity^2*drag_coefficient*area
[12:46] <eroomde> a parachute is in equilibrium, so the drag force is equal to the weight
[12:47] <eroomde> therefore substite 'drag' with 'mass * gravity'
[12:47] <eroomde> and we want to talk the sea level descent rate, so rearrange for velocity
[12:47] <eroomde> that gives
[12:47] <G7PMO_Kev> The guides:parachute_sizing_chart discusses many different drags - if you assume a best case chute (ie lots of drag for given diameter) and use the lowest line it just about matches up
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[12:47] <daveake> I use Spherachutes which are half-dome shaped (hence the name) and a 24" one means it's 24" from one side over the top to the other. i.e. 24" is half the circumference. I've found that if I use the lower solid line in http://www.ukhas.org.uk/guides:parachute_sizing_chart, that works out about right (5m/s landing speed)
[12:48] <eroomde> velocity = sqrt( (2 * mass * gravity) / (density * drag_coefficient * area) )
[12:48] <eroomde> we'll assume drag_coefficient = 0.7 because that's usually a good guess
[12:48] <G7PMO_Kev> So lower solid line and assume the reading on the left is the half dome measurement (ie 1/2 circumferance, rather than diameter)
[12:49] <eroomde> NO
[12:49] <Laurenceb_> http://uk.rs-online.com/web/p/pll-frequency-synthesizers/7154750/?searchTerm=mhz+%22frequency+control%2C+crystals%22+aker&relevancy-data=636F3D3126696E3D4931384E44656661756C74266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E5C442B5C735C442B2426706F3D3926736E3D592673743D4B4559574F52445F4D554C54495F414C504841267573743D6D687A20226672657175656E637920636F6E74726F6C2C206372797374616C732220616B65722673633D59
[12:49] <Laurenceb_> 2677633D4E4F4E4526
[12:49] <Laurenceb_> oops
[12:49] <costyn> Laurenceb_: lucky it wasn't anything more embarassing :)
[12:49] <Laurenceb_> lol
[12:50] <G7PMO_Kev> eroomde - No to my "assume the reading on the left is the half dome measurement"?
[12:50] <costyn> eroomde: so please keep going with your calculations :) I find it interesting
[12:50] <Laurenceb_> i meant to link to RS 715-4750
[12:51] <eroomde> 'no' as in, let's just ignore random graphs on the net that don;t have enough context, it's better to work it out properly
[12:51] <Laurenceb_> pll clk synthesiser that can run off 1KHz
[12:51] <daveake> That lower line happens to work with that design of chute and the sizes they sell them by. YMMV with other designs.
[12:51] <Laurenceb_> so it could clk directly off a ublox6
[12:51] <G7PMO_Kev> daveake - ta
[12:51] <eroomde> so anyway, v = sqrt( 2mg/(density*Cd*Area) )
[12:51] <eroomde> Cd = 0.7 say
[12:51] <Laurenceb_> up to 120mhz output :P
[12:52] <eroomde> Cd assumes the 'flat' diameter rather than the inflated diameter
[12:52] <radim_OM2AMR> daveake, so rocketman chute 5ft will fit fast line ?
[12:52] <costyn> eroomde: Cd of the chute? or of the whole parachute/payload train?
[12:52] <eroomde> of the chute
[12:52] <radim_OM2AMR> chute from random solution
[12:53] <eroomde> density at sea level = 1.22
[12:53] <daveake> radim No idea. I'm just going on my experience with one make and design. Anything else I have no idea, but there exists a man here who does
[12:53] <eroomde> mass = 300g did you say?
[12:53] <eroomde> so
[12:53] <eroomde> for your 1m dia chute, sqrt( 2*300*9.81 / 1.22*0.7*3.142 )
[12:53] <eroomde> woah, 0.3 not 300
[12:53] <eroomde> whoopsie
[12:54] <eroomde> = 1.5m/s descent rate, if i've not done any fat-fingers on my calculator
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[12:55] <radim_OM2AMR> Daveake, we had fully opened 5ft chute without any latex parts on it and we had about 6 to 7 m/s descend speed, but eroomde said, its bad chute type, due to drag
[12:55] <eroomde> but, different parachute designes will have different Cd for a given diameter. eg cruciform will be different to a flat sheet will be different to a hemisphere
[12:55] <eroomde> usually between about 0.55 - 0.75
[12:56] <G7PMO_Kev> ok
[12:56] <G7PMO_Kev> so going with a Spherachutes
[12:56] <eroomde> i should try and scan in a table in a textbook
[12:56] <G7PMO_Kev> and mass including the parachute it's self and line and balloon debry etc is more like 450g I guess
[12:57] <costyn> eroomde: if I paste it into excel, I get 3.257
[12:58] <eroomde> i do tend to be fat fingers with my casio
[12:58] <G7PMO_Kev> sqrt ( 2 * 450 * 9.81 / 1.22 * 0.55 * 3.142)
[12:58] <eroomde> G7PMO_Kev: do u have a link to the chute?
[12:58] <costyn> G7PMO_Kev: 0.450
[12:58] <costyn> G7PMO_Kev: (mass in KG)
[12:58] <G7PMO_Kev> either http://www.randomengineering.co.uk/Random_Aerospace/Parachutes.html
[12:58] <G7PMO_Kev> or https://spherachutes.storesecured.com/items/spherachutes/list.htm
[12:58] <eroomde> and the final number needs to be the parachute area in m^2
[12:59] <eroomde> so what size chute are you considering?
[12:59] <G7PMO_Kev> 18, 24 or 30 :)
[12:59] <eroomde> ok cool
[12:59] <eroomde> and you say that's the inflated mouth diameter?
[13:00] <G7PMO_Kev> that is 1/2 circumferance (ie 'over the top' diameter)
[13:00] <eroomde> ah right
[13:00] <costyn> eroomde: maybe we should make a chute calculator, like there's a burst calc :)
[13:00] <eroomde> ok, so the ratio of over the top to across is 0.71 for hemispherical chutes
[13:01] <eroomde> ah but that doesn't matter anyway because Cd is with respect to contructed diameter, ignore my previous point
[13:01] <radim_OM2AMR> costyn, or maybe we should ask steve to add Cd parameter to the web site ;-)
[13:01] <eroomde> so, The Cd of a hemispherical parachute is about 0.6
[13:01] <eroomde> 0.7 even, sorry
[13:01] <costyn> radim_OM2AMR: if he knows that data?
[13:02] <radim_OM2AMR> Mr. eroomde wil calculate it ;-)
[13:02] <G7PMO_Kev> so I get 3.5 out of the equation - thats diameter in M ?
[13:02] <costyn> G7PMO_Kev: descent velocity
[13:02] <G7PMO_Kev> ahhh, ok
[13:02] <eroomde> tha area of the 24" one is: 0.28m^2
[13:02] <costyn> last parameter is chute area
[13:02] <G7PMO_Kev> M/s :)
[13:02] <eroomde> so Cd = 0.7, A = 0.28, M = 0.45
[13:02] <eroomde> plug all that in
[13:03] <G7PMO_Kev> So A = 0.28 rather than 3.142?
[13:03] <costyn> let me adjust my excel
[13:03] <eroomde> correct
[13:03] <eroomde> i make that 6.1m/s
[13:03] <G7PMO_Kev> I make that 1.1 m/s! :)
[13:03] <G7PMO_Kev> =SQRT( 2 * 0.45 * 9.81 / 1.22 * 0.6 * 0.28)
[13:04] <eroomde> cd = 0.7
[13:04] <eroomde> but that doesn't account for the different
[13:04] <eroomde> put some brackets around the numerator and denominator parts if you're doing it in excel
[13:04] <eroomde> =SQRT( (2 * 0.45 * 9.81) /( 1.22 * 0.6 * 0.28))
[13:05] <G7PMO_Kev> =SQRT( (2 * 0.45 * 9.81) / (1.22 * 0.7 * 0.28))
[13:05] <eroomde> yes
[13:05] <G7PMO_Kev> 6.07ms/.....
[13:05] <G7PMO_Kev> m/s
[13:05] <eroomde> perfec
[13:05] <G7PMO_Kev> so thats a litle fast is it not?
[13:05] <eroomde> so, you could probably get away with that, though the received wisdom is <5m/s
[13:05] <eroomde> so we'll do it for the 30" chute
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[13:06] <costyn> eroomde: hmph... why does order of operations matter with only multiplication and division?
[13:06] <eroomde> i make that 4.8m/s with a 30" chute
[13:07] <eroomde> costyn: i do not leave things to chance with microsoft products
[13:08] <costyn> eroomde: no, but I get a different answer, I thought it shouldn't matter
[13:08] <costyn> I'm just confused
[13:08] <eroomde> because i suspect it puts Cd and area on the numerator
[13:08] <eroomde> so
[13:08] <eroomde> a * b * c / d * e * f
[13:08] <costyn> aah ok
[13:08] <eroomde> could be parsed as
[13:09] <eroomde> a * b * (c/d) * e * f
[13:09] <costyn> more likely (a*b*c)/d * e * f
[13:09] <eroomde> i.e. (a*b*c*e*f)/d
[13:09] <costyn> yes
[13:09] <eroomde> yeah
[13:09] <costyn> silly of me
[13:10] <eroomde> G7PMO_Kev: so i would go with the 30" cute
[13:10] <eroomde> chute*
[13:10] <eroomde> i am getting all these figures for Cd from a book in my bookshelf, 'Parachute Recovery Systems Design Manual' by Knacke
[13:10] <eroomde> if you're interested
[13:11] <costyn> eroomde: how are you calculating area from diameter? only pi r squared? or is it different for chute size?
[13:11] <eroomde> it's a good book to have if you start doing parachutey things, it's the sort of foundational text in the field. it does however have some mistakes we know about today, but it's still a good start. it's very well referenced so if you're in any doubt as to his interpretation, you can go and find the original reference
[13:12] <eroomde> costyn: yep, pi *r^2
[13:12] <eroomde> area being total canopy surface area
[13:12] <eroomde> rather than frontal area
[13:12] <eroomde> so the area calculated from the 'over the top' diameter
[13:12] <costyn> eroomde: ok
[13:12] <eroomde> which is the convention
[13:13] <costyn> so with 30" you get velocity of 4.7-ish right?
[13:13] <eroomde> yes
[13:13] <costyn> ok cool
[13:13] <G7PMO_Kev> thanks Eroomde, Costyn's gut feel said 18, Daveake's experience of using the graph says 24, the formulae says 30" :) I will go away and consider :)
[13:13] <costyn> then I've done my excel correctly
[13:13] <costyn> hehe
[13:14] <costyn> G7PMO_Kev: when in doubt, science! (ie eroomde)
[13:14] <eroomde> correct!
[13:14] <eroomde> the numbers are what you should go with
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[13:15] <costyn> eroomde: so there are a number of set Cd's for parachute types?
[13:15] <eroomde> yes indeed
[13:15] <eroomde> let me do a naughty thing and take a camera phone pic of a page in the textbook
[13:15] <costyn> then it should be easy to add the Cd type to Steve's site
[13:15] <G7PMO_Kev> thanks guys
[13:16] <eroomde> G7PMO_Kev: i hate tooting my own trumpet in an appeal-to-authority way (I usually do it strictly on the merits of the arguement) but i do have a bit of experience with parachute systems in general and for high altitude applications. see my ukhas talk on oyutube from last year where i talked about some testing we did for mars parachutes at 25km alt
[13:17] <G7PMO_Kev> cool :)
[13:17] <eroomde> where we were testing high performance parachutes whose performance we had to model and measure very carefully
[13:17] <eroomde> for the uropean space agency
[13:17] <costyn> I'm all for tooting if it's justified :)
[13:18] <eroomde> my philosophy is always, if sources like internet say confusing things, go back to funademantals and work it out
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[13:19] <eroomde> costyn: piccy coming up
[13:20] <eroomde> but it makes sense if you think about it
[13:20] <eroomde> Cd tells you how much drag you get for a sort of nominal parachute diameter
[13:20] <eroomde> if that parachute is cruciform, there's obviously a lot more gaps in the virtual circle that it sits inside than if it is a solid sheet of the same diameter
[13:20] <eroomde> generally, one sacrifices Cd and gains stability
[13:21] <eroomde> up to a point
[13:21] <eroomde> by building in porosity
[13:21] <eroomde> the most stable chutes have about 22% (by area) geometric porosity in their design
[13:21] <eroomde> so this is why chutes have spill holes at the top, for example
[13:21] <costyn> interesting
[13:21] <eroomde> that increases stability
[13:21] <costyn> yea
[13:21] <eroomde> however even better is if the porosity is evenly distrubuted
[13:22] <costyn> why would one choose round chute with a hole over cruciform or the other way around?
[13:22] <eroomde> have a look at this video for an example of a v good parachute
[13:22] <eroomde> http://www.youtube.com/watch?v=mzEcSO6oDcY
[13:22] <eroomde> this is 10 times slower than real life
[13:22] <eroomde> it is stable at about 2 mins
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[13:22] <eroomde> you can see it is a series of ribbons and slots
[13:23] <eroomde> infact it is called a ringslot parachute
[13:23] <eroomde> costyn: yes sometimes
[13:23] <eroomde> it depends on your design constraints
[13:23] <eroomde> do you need stability, descent rate, low cost?
[13:24] <eroomde> it's a tradeoff against all these thigns are more
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[13:24] <costyn> I see.. a ringslot is difficult to construct where a cruciform gets you more strenght I imagine
[13:24] <eroomde> for example, if you are designing a planetary entry probe, you want high stability so that instruments like cameras on the way down can get sensible stable shots
[13:24] <eroomde> for a hab you might no care though
[13:24] <eroomde> yea, cruciforms are super cheap and easy
[13:24] <eroomde> and their stability is not bad, if you get the propertions right
[13:25] <costyn> whats the metallic plate dangling half way bwteen chute and camera in the video?
[13:25] <eroomde> 3:1 on the strips is not very stable
[13:25] <eroomde> but 3.x (i forget x) is pretty stable
[13:25] <eroomde> costyn: lens cap
[13:25] <eroomde> it's plastic
[13:25] <costyn> I see
[13:25] <eroomde> it is the high speed camera's lens cap
[13:25] <costyn> cool
[13:25] <eroomde> you can see the balloon we deployed away from in the background
[13:26] <eroomde> using one of those plastic link explosives
[13:26] <costyn> cool
[13:26] <eroomde> if you look at this video around 30 mins
[13:26] <eroomde> http://www.youtube.com/watch?v=DVRx7En7tRY
[13:26] <eroomde> you can see how stable everything is
[13:27] <eroomde> this is still at hab-type altitudes, where we used to seeing everything being thrown around and descending into hell violently
[13:27] <costyn> hehe
[13:27] <eroomde> but with the right chute and harness configuration, it can be very smooth indeed
[13:28] <eroomde> quality of this cameraphone pic is a bit shit sorry
[13:28] <eroomde> but u will get the idea
[13:28] <costyn> sure
[13:28] <eroomde> http://i.imgur.com/gwPen.jpg
[13:29] <eroomde> it's quite a useful table
[13:31] <costyn> so how flat or tall a hemispherical chute will be isnt that relevant?
[13:31] <costyn> (profile view)
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[13:39] <costyn> eroomde: why does it say hemispherical chutes are obsolete? :)
[13:46] <navrac> ru there laurenceb ?
[13:52] <eroomde> costyn: :)
[13:52] <eroomde> old tech
[13:52] <eroomde> better ways of doing things
[13:52] <costyn> eroomde: ok, but aren't the ones we usually use hemispherical?
[13:52] <costyn> or are those "good enough" for what we ned
[13:52] <costyn> need
[13:52] <eroomde> hemispherical is contant radius in profile
[13:53] <eroomde> so it can;t be flatter or shorter
[13:53] <eroomde> costyn: yeah - they're good enough
[13:53] <eroomde> hobby rocket chutes are very crude
[13:53] <eroomde> compared to the state of the art
[13:53] <eroomde> but cheap to make and 'good enough' and or customers don;t know or care
[13:53] <costyn> right
[13:54] <eroomde> aeroconn systems is good though
[13:54] <eroomde> they have military surplus
[13:54] <eroomde> often decent quality
[13:54] <eroomde> sometimes not
[13:54] <eroomde> but worth keeping an eye on
[13:54] <eroomde> we used one of their cruciforms as the reserve parachute on the esa parachute test vehicle
[13:55] <eroomde> http://aeroconsystems.com/cart/
[13:55] <eroomde> lots of goddies there for hab and rocket people
[13:55] <eroomde> goodies*
[13:55] <eroomde> the 73" yellow is what we sued
[13:55] <eroomde> used*
[13:56] <costyn> eroomde: the x-form one?
[13:58] <eroomde> yeah
[13:58] <eroomde> you can see it deploy in this low-altitude full-sequence test
[13:58] <eroomde> http://www.youtube.com/watch?v=TOfwDgcKpMY
[14:00] <eroomde> they all come with decent deployment bags too
[14:01] <G7PMO_Kev> (sorry, had a work call)
[14:02] <G7PMO_Kev> some cool videos
[14:02] <G7PMO_Kev> and some fun testing :)
[14:02] <costyn> eroomde: cool... that's a lotta parachutes :)
[14:02] <costyn> (in the video)
[14:02] <eroomde> yep
[14:02] <eroomde> i like prachutes
[14:03] <costyn> so what do you think about ram-air chutes? or are you more of a 'round' chute guy
[14:05] <eroomde> i don;t know as much about them
[14:05] <eroomde> but i am interested in them
[14:05] <eroomde> especially flying something back from a balloon
[14:06] <eroomde> they're quite sensitive to wrigging, i think ensuring you get that right is the big thing
[14:06] <eroomde> in terms of geometry of angle of attack, line tensions and centre of gravity
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[14:07] <eroomde> i think jgrahamc expressed an interest in tacking autonomous return with a parafoil for GAGA-3
[14:07] <costyn> eroomde: yea me too; i know quite a bit about square chutes (1100 skydives must be good for something ;) but there hasn't been much overlap with HAB yet
[14:07] <eroomde> oh wow
[14:07] <eroomde> right well i totally defer to you in ram-air know-how
[14:08] <eroomde> i think it would be awesome if someone had a go
[14:08] <costyn> eroomde: the packing sequence is paramount of course, to get the opening sequence just right
[14:08] <costyn> problem with a ram-air chute is that they're not very good when flying into the wind
[14:09] <costyn> you need a high wing load to get any penetration, which you can do with increase weight or decrease wing area
[14:09] <eroomde> that's my worry too
[14:09] <costyn> but smaller wing areas make the chute more sensitive to input and imbalances in the center of gravity of the payload beneath it
[14:09] <eroomde> at our scale you might get piss-all compared to typical wind speeds
[14:09] <costyn> indeed
[14:10] <eroomde> but it would be fun to try regardless
[14:10] <costyn> which why the rogallo Laurenceb is always tooting about might be better
[14:10] <costyn> it's more of a hang glider which is easier to deploy, gets more forward speed and is easier to control
[14:11] <costyn> the thing with ram air chutes is they are made to slow one down from 200km/h and fit into a small backpack; HAB doesn't have those requirements
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[14:11] <eroomde> yeah
[14:12] <eroomde> although my interest for them is as much rocket stage recovery
[14:12] <eroomde> which does have those requirements :)
[14:12] <costyn> so a homing HAB payload is not a good place for a ram air chute
[14:12] <costyn> eroomde: ah yes, there it is a lot more applicable
[14:13] <eroomde> i agree with you technically
[14:13] <eroomde> glider would be the thing
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[14:13] <eroomde> but fixed wing or even semi-rigid is a bit dodgy legally
[14:13] <costyn> mmmm yea there's that
[14:14] <costyn> steerable chute is a gray area :)
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[14:16] <costyn> eroomde: we were thinking of doing something stearable for our 3rd launch but my team isn't very productive/active (I'm the one doing nearly everything) so not sure how that's going to go :)
[14:17] <eroomde> indeed
[14:17] <eroomde> would be fun to just throw something up and see what happens
[14:17] <costyn> in any case it would require the 2 payload configuration with the top one cutting down the bottom one
[14:17] <eroomde> a servo arm and an arduliot or something
[14:17] <eroomde> yes, that's what we did with laurence's various things
[14:18] <eroomde> gave him a tow to some predetermined altitude then cut him away
[14:18] <costyn> i haven't looked at ardupilot, but is that something that works out of the box?
[14:18] <eroomde> pretty much
[14:18] <eroomde> would need a bit of tuning to an airframe i think
[14:18] <eroomde> but nothing too major
[14:18] <costyn> hmm
[14:19] <costyn> was thinking of just a styrofoam ball for the lower payload
[14:20] <eroomde> they do seem to be the fashional thing
[14:20] <eroomde> fashionable*
[14:20] <costyn> yea, not too much drag and not too complicated
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[14:25] <eroomde> G7PMO_Kev: i should mention also, obviously the payload box has some drag too
[14:25] <eroomde> so the actual speed will be a bit lower because the payload itself will add a bit of drag
[14:26] <costyn> eroomde: what equation would you use to calculate drag for that? should be simple right?
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[14:30] <eroomde> well, i don;t want to have to guess the Cd of arbitrarily shaped payload boxes :)
[14:30] <eroomde> but it will be v small compared to the chute
[14:30] <eroomde> usually ignore it
[14:30] <costyn> ok
[14:33] <radim_OM2AMR> costyn, I'm'also thinking about something steerable, like glider with ardupilot :-) but my team position is like your's
[14:33] <costyn> radim_OM2AMR: hehe :)
[14:34] <costyn> radim_OM2AMR: and I have a family as well, which takes up unimaginably massive amounts of my free time
[14:34] <radim_OM2AMR> that's other exact attribute, me to ;-)
[14:35] <chris_99> has anyone used the barometric formula per chance?
[14:36] <eroomde> yes
[14:36] <radim_OM2AMR> we used in our flight - formula from BMP085 datasheet
[14:36] <eroomde> this one is better
[14:36] <eroomde> http://www.grc.nasa.gov/WWW/k-12/airplane/atmosmet.html
[14:37] <radim_OM2AMR> eroomde, did you try it with BMP0850 in HAB ?
[14:38] <chris_99> i'm just looking on the one on wikipedia http://en.wikipedia.org/wiki/Barometric_formula
[14:38] <chris_99> im confused how you'd know which static pressure
[14:38] <chris_99> to use
[14:38] <eroomde> radim_OM2AMR: have never used the bmp0850 specifically
[14:39] <eroomde> chris_99: the nasa one is better - it splits the atmosphere into three layers, broadly according the the temperature profile. it's more accuract
[14:39] <eroomde> chris_99: ok
[14:39] <radim_OM2AMR> BMP085 is not worth to use, as down pressure limit is 300 hPa
[14:39] <eroomde> specifically what is your undertsanding of static pressure and what bit on the wikipedia page is causing the confusion?
[14:40] <chris_99> well if i rearrange the formula, so that i get height from pressure right, how do i know what static pressure
[14:40] <chris_99> to use
[14:40] <eroomde> there is only 1 isn't there?
[14:41] <radim_OM2AMR> good sensor and good formula is a basic ;-) there is GPS and pressure altitude from our flight http://stsproject.net/wp-content/uploads/2012/09/Screen-Shot-2012-09-13-at-17.56.30.png
[14:42] <chris_99> eroomde, theres different static pressures for different layers
[14:42] <chris_99> as far as i can see
[14:42] <eroomde> in the wikipedia model?
[14:42] <chris_99> yeah
[14:44] <eroomde> ah i was confused sorry, the wikipedia model is the same as the nasa model
[14:44] <eroomde> at hab altitudes
[14:44] <eroomde> roughly
[14:45] <eroomde> yes, you would have to know your altitude already to know which layer you are in
[14:45] <chris_99> yeah that's what i don't get
[14:45] <eroomde> but i suspect you can also figure it out from the pressure sensor reading
[14:45] <eroomde> radim_OM2AMR: ouch!
[14:45] <radim_OM2AMR> little bit recursive...
[14:46] <eroomde> chris_99: i suspect that the mapping of alt to pressure is basically monotonic. so if you were to put all this info into excel now, and get a plot of alt vs pressure, it would be a curve
[14:47] <chris_99> hmm, yeah could be
[14:47] <eroomde> and you could be able to make statements like 'if the sensor says i'm between 101kPa and 50kPa, i am in layer 0'
[14:47] <eroomde> so you would then implement that as a lookup table on your micro
[14:47] <chris_99> do you guys also use a thermoter then too
[14:48] <chris_99> to get an accurate value
[14:49] <radim_OM2AMR> eroomde, that's good way to do it ;-) so no such recursion like last altitude verifying I though
[14:49] <radim_OM2AMR> chris_99, we compared temp values from meteosonde and our payload
[14:49] <radim_OM2AMR> meteosonde was 30 meters under our payload box
[14:50] <eroomde> chris_99: yes, knowing temperature is quite useful too
[14:50] <eroomde> measuring temperature is quite hard though
[14:50] <costyn> radim_OM2AMR: weren't the ds18b20s inaccurate too?
[14:50] <chris_99> hmm why's it hard, calibration?
[14:50] <radim_OM2AMR> DS18B20 is unusable costyn
[14:50] <costyn> haha
[14:51] <costyn> too bad
[14:51] <costyn> they're convenient
[14:51] <radim_OM2AMR> due to -55 degrees limit
[14:51] <eroomde> that and that it's difficult to measure the temperature of the air
[14:51] <eroomde> when it is thin
[14:51] <costyn> radim_OM2AMR: have you found anything that might replace it?
[14:51] <radim_OM2AMR> and we found some strange deviation in temp measurement in low pressures too! ;-)
[14:51] <eroomde> but it is very easy to measure the temperature of the thermoemeter
[14:52] <radim_OM2AMR> costyn, maybe something based on PT100, I know, it''s true analog
[14:52] <eroomde> and the thermometer temperature doesn't necessarily have anything to do with the air temperature
[14:52] <eroomde> it might be measuring the temperture of a black body in bright sunlight
[14:52] <chris_99> ah, hmm
[14:52] <eroomde> radim_OM2AMR: i use PT100x stuff, definitely better resolution and accuracy
[14:53] <eroomde> but you've still got the job of measuring air temp
[14:53] <eroomde> rather than thermometer temp
[14:53] <chris_99> the PT100 is a three prong device isn't it
[14:53] <costyn> eroomde: yea i thought of this too, the sun warming the thermometer would give a nicely false reading
[14:53] <radim_OM2AMR> costyn - orange curve is DS18B20, blue is Vaisala thermosensor http://stsproject.net/wp-content/uploads/2012/09/Screen-Shot-2012-09-18-at-17.12.09.png
[14:53] <eroomde> usually 2 or 4 chris_99
[14:53] <eroomde> though the 4 pin will be internall connected like a 2 pin
[14:54] <costyn> radim_OM2AMR: pffff... funny how it is no longer accurate after its' been to -55
[14:54] <costyn> strange
[14:54] <costyn> although that might be problem with the sun heating the ds18b20
[14:55] <radim_OM2AMR> costyn, yes, but difference is higher above 10 km
[14:55] <radim_OM2AMR> costyn, good point, it should be
[14:56] <costyn> radim_OM2AMR: well thats what I mean, after 13km it reaches coldest point, but then as it gets warmer it doesnt match up any more even though youre going below the -55 limit of the DS19
[14:56] <costyn> ds18
[14:56] <eroomde> Dan-K2VOL is probably a good guy to ask about accuracte air temp measurement
[14:56] <radim_OM2AMR> Vaisala is using some microwire based on Pt
[14:58] <radim_OM2AMR> but as far as I remember, it's capacitance sensor
[14:59] <radim_OM2AMR> costyn, exactly, we though about potential pressure effect, but we forgot sun :-)
[15:00] <costyn> radim_OM2AMR: :) so but the vaisala is obviously correct right?
[15:02] <radim_OM2AMR> costyn, yes, we trusted it ;-) I saw sometimes that it's meassured temp below - 65 (not in our flight)
[15:02] <costyn> radim_OM2AMR: do the vaisala's usually go that high too?
[15:03] <costyn> I mean when the met-office sends them up?
[15:03] <radim_OM2AMR> as we observing, they flight to 33 - 38 km's depending balloon filling
[15:04] <radim_OM2AMR> yes, we're chasing it (and monitoring it of course ) ;-)
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[15:07] <radim_OM2AMR> costyn, if you will be quick enough, you can see it in our tracker here http://katanganet.dyndns.org/trackme/test2.html for example meteo sonde from Vienna 34 km
[15:08] <radim_OM2AMR> that tracker is cleared, that's the note about your speed ;-) these are last today's flights
[15:09] <costyn> radim_OM2AMR: interesting
[15:09] <costyn> radim_OM2AMR: and so then you chase them to where they land and pick them up?
[15:09] <costyn> radim_OM2AMR: and then you get to keep it?
[15:10] <radim_OM2AMR> yes, we can use own software decoding or this tracker (it's simillar principle lige spacenear.us)
[15:11] <fsphil> met sonde chasing?
[15:12] <radim_OM2AMR> and then we are chasing it with yagi antennas, and yes, we can keep it, as there is note about eco trashing ;-)
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[15:12] <radim_OM2AMR> fsphil, yes :-) it was out training to HAB chace ;-)
[15:12] <fsphil> the winds here are rubbish atm for those, all landing in scotland
[15:12] <fsphil> http://habhub.org/predict/#!/uuid=12a9bc354d4e44013b858ebde8f719a5f7fc3b2d
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[15:16] <radim_OM2AMR> as I'm living about 150 km from Vienna, I'm also having met sonde chase seldom ;-) depends on the winds
[15:16] <costyn> right :)
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[15:16] <costyn> anwyays, I have to go
[15:16] <costyn> ttyl!
[15:16] <fsphil> yea it's unlikely they'll land near me most weeks
[15:17] <fsphil> but I'm keeping an eye out
[15:17] <fsphil> a few have flown directly overhead
[15:17] <fsphil> but the landed in a small mountain range
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[15:18] <radim_OM2AMR> I never seen it flying ;-) youre lucky man :-)
[15:19] <radim_OM2AMR> except one case, when I was im met office during the launch :-D
[15:19] <fsphil> eye out as in the predictor
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[15:20] <fsphil> although there's no reason why I couldn't see them on a clear day
[15:20] <fsphil> must try that :)
[15:20] <radim_OM2AMR> I said, lucky man, predictions are something out of date ;-)
[15:22] <radim_OM2AMR> ok, I have to go too, bye
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[15:49] <navrac> ping laurenceb
[15:55] <Laurenceb_> hi
[15:56] <Laurenceb_> navrac
[15:56] <navrac> thought id let you know my humbe ulox max6 seems happy to give out 3.75mhz
[15:57] <navrac> rather more than the 1khz datasheet
[15:57] <Laurenceb_> O_o
[15:57] <Laurenceb_> wow
[15:57] <Laurenceb_> how did you manage that?
[15:57] <kokey> he overclocked it
[15:57] <Laurenceb_> lol
[15:57] <navrac> so a simple /8 as built in to some chips would give us 30meg
[15:57] <navrac> no just poked into the timepulse registers
[15:58] <navrac> and it just obeyed
[15:58] <Laurenceb_> amazing
[15:58] <UpuWork> you can change that in the uCenter
[15:58] <Laurenceb_> yeah
[15:58] <UpuWork> you mean the PPS output
[15:58] <UpuWork> ?
[15:58] <navrac> lazy mans way...
[15:58] <navrac> yep
[15:58] <Laurenceb_> can you get a nice frequency like 3MHz or so?
[15:58] <UpuWork> The Timing modules do 10Mhz
[15:58] <navrac> seems to like anything <10mhz
[15:58] <UpuWork> NEO6T
[15:59] <Laurenceb_> interesting
[15:59] <UpuWork> yep
[15:59] <navrac> more expensive...
[15:59] <UpuWork> about £10 a module more
[15:59] <UpuWork> for the NEO-6T
[15:59] <Laurenceb_> hmm but its not 30mhz
[15:59] <UpuWork> vs NEO-6Q
[15:59] <UpuWork> anyway home time bbl
[15:59] <Laurenceb_> navrac: you could use a clock synthesiser then
[15:59] <navrac> i did 3.75mhz as a pll with a x8 would give 30mhz
[15:59] <Laurenceb_> ah
[15:59] <navrac> yep 1 chip
[16:00] <kokey> should make it do 434mhz
[16:00] <Laurenceb_> hehe
[16:00] <navrac> and no drift using the standard upu module#
[16:00] <Laurenceb_> i was looking at the Ti stuff yesterday evening
[16:00] <Laurenceb_> kokey: you can slave the rfm22b off it
[16:00] <Laurenceb_> and get 434 nicely that way
[16:01] <kokey> rfm takes a clock input?
[16:01] <Laurenceb_> well with 8x pll in the middle
[16:01] <Laurenceb_> yes
[16:01] <navrac> 673m has av built in /8
[16:01] <kokey> now that's interesting
[16:01] <Laurenceb_> also output to run the processor
[16:01] <kokey> got a ublox max6 and rfm22b
[16:01] <navrac> so with just a couple of caps and an R givesd us 30meg for the rfm
[16:01] <kokey> was going to play with the rfm22b tonight anyway
[16:02] <navrac> was going to keep the processor seperate as the 1hz output on the ublox on power up may take a time to run the initialsiation routines on the processor....
[16:02] <Laurenceb_> hehe
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[16:03] <Laurenceb_> yeah pity about the clk options on avr
[16:03] <Laurenceb_> i use stm32 for everything these days
[16:03] <kokey> how power hungry is the stm32?
[16:04] <Laurenceb_> depends on clock speed
[16:04] <Laurenceb_> at avr speeds its much less than avr
[16:04] <Laurenceb_> about 45ma at 168mhz
[16:04] <navrac> so for an extra £5 upu hint hint could do an rfm breakout with the space for the chip on it and with one lead from the ublox chip (pin4) we could have drift free txing
[16:05] <Laurenceb_> more if you start doing crazy stuff with peripherals
[16:05] <Laurenceb_> hmm the 673m is a little power hungry
[16:05] <Laurenceb_> wonder if theres anything nicer
[16:05] <Laurenceb_> the Ti stuff seems overkill
[16:06] <navrac> 15mA at 40mhz
[16:06] <Laurenceb_> yeah, nast
[16:06] <Laurenceb_> *nasty
[16:06] <Laurenceb_> of course this is easy with an stm32
[16:06] <Laurenceb_> theres one or two spare plls to use
[16:07] <Laurenceb_> and clkout pins
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[16:07] <Laurenceb_> http://uk.farnell.com/jsp/search/browse.jsp?N=2031+203063&Ntk=gensearch&Ntt=stm32f107&Ntx=mode+matchallpartial
[16:07] <Laurenceb_> ^those have 3 plls
[16:08] <navrac> and far too many legs for my poor eyesight to consider soldering them
[16:08] <Laurenceb_> heh
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[16:25] <UpuHome> hey navrac
[16:25] <navrac> yep
[16:25] <UpuHome> you tell me what you want and I'll design it
[16:25] <daveake> I endorse that plan
[16:25] <UpuHome> I can get the timing modules as well
[16:26] <navrac> its a method of stabilising rfm22's to give zero drift and hopefully the ability to do weitrd modes
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[16:26] <UpuHome> so what is needed an RFM22B with something connected to the PPS output on the GPS
[16:27] <navrac> basically on the rfm22b breakout board add space for a ICS673M which you could feed off the 1pps output of the ublox
[16:27] <navrac> it then generates the 30mhz clock for the rfm22b
[16:27] <navrac> so its locked to the gps
[16:27] <UpuHome> I can do that
[16:27] Nick change: UpuHome -> Upu
[16:28] <Upu> got a circuit diagram ?
[16:28] <navrac> and subject to testing you could program the ublox to change the frequency to give jumps in the order of a few hz
[16:28] <navrac> give me a few days for the bits to arrive and I'll build and test one first
[16:29] <navrac> also looking to find a pll that uses a little less power -
[16:29] <Laurenceb_> where did you find ICS673M ?
[16:29] <Laurenceb_> yeah me too...
[16:29] <navrac> its laurenceb's idea
[16:30] <navrac> but i want to do one the doesnt involve an stm!
[16:31] <Upu> http://i.imgur.com/SfHTg.jpg
[16:31] <navrac> laurenceb_ try http://www.icst.com/products/clocks-timing/clock-generators-synthesizers-and-zero-delay-buffers/general-purpose-clock-generators-synthesizers-and-zero-delay-buffers/673-01-pll-building-block
[16:31] <Upu> with my new drug dealer scales it seems its a little fatter than I originally predicted
[16:31] <Laurenceb_> dedicated stm32...
[16:32] <Laurenceb_> just for the pll
[16:32] <Laurenceb_> :P
[16:32] <navrac> scratch the text off the pcb and you could save a bit - after all 4.5g is soooo heavy
[16:33] <Upu> :)
[16:33] <navrac> or a thyinner pcb
[16:37] <navrac> laurenceb_ sorry link was http://www.icst.com/products/clocks-timing/clock-generators-synthesizers-and-zero-delay-buffers/general-purpose-clock-generators-synthesizers-and-zero-delay-buffers#!/?tis_cck_field__no_of_outputs=%5B0%20TO%2033%5D&tfm_cck_field__output_freq_mhz=%5B0%20TO%2025100%5D&tfm_cck_field__input_freq_mhz=%5B0%20TO%2013%5D&tis_cck_field__no_of_inputs=%5B0%20TO%204%5D&tis_cck_field__no_output_banks=%5B0%20TO%2010%5D&
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[16:44] <navrac> the ic502 looks neat, no programming just an in and an out and a few tied lines
[16:45] <Laurenceb_> hmm
[16:45] <Laurenceb_> i can only find Ti stuff the looks very good
[16:45] <Laurenceb_> but it needs 1.8v supply
[16:48] <Laurenceb_> link?
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[16:49] <Laurenceb_> CDCEL913
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[16:58] <navrac> ICS512 - 9mA ( probably less as its got a clock in not a xtal) 8 pin soic 6x 5mhz in 30mhz out no external caps £2.29 on a one off
[16:58] <eroomde> chapses talking about plling the output of gps and injecting it into radio
[16:58] <navrac> dont spoil it by pointing out a fundamental flaw weve forgotten
[17:00] <navrac> ok , spoil it as long as you do it before i press the order button on the bits
[17:03] <eroomde> ok
[17:03] <eroomde> well, i just think it won't work too well for the reason that stopped me doing exactly this a couple of years ago
[17:03] <eroomde> which is that the gps output is not like a clean oscilaltor output
[17:03] <eroomde> there's an appreciable amount of jitter on the rising edge time
[17:04] <eroomde> and the ppl won;t be able to remove that phase jitter during the multiplying up
[17:04] <eroomde> unless it's like microhertz bandwidth with the best behaved VCO in the hisotry of consumer electronics
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[17:04] <navrac> oh well, ill give it a bash and see what happens - its only going to cost a couple of quid to find out
[17:05] <eroomde> and so you won't be putting a clean clock into the rfm22 so much as an fm-modulated square wave, which will give you an illegally noisy output when multiplied up to 434
[17:05] <eroomde> yeah indeed, just get a decent spectrum analyser on it
[17:05] <eroomde> compare it to a known stable clean clock
[17:06] <Laurenceb_> eroomde: yeah
[17:06] <Laurenceb_> its probably generated by pwm or similar on the ublox
[17:06] <Laurenceb_> but put enough plls in the middle and they will remove the jitter
[17:07] <Laurenceb_> of course a vctcxo adjusted by a micro wouldnt have this issue
[17:07] <navrac> looked half decent on the scope - but thats not saying much
[17:07] <navrac> true
[17:07] <navrac> just found rs stock idt stuff, ive been trawling digikey for the lasty half hour :-(
[17:08] <Laurenceb_> :-/
[17:09] <Laurenceb_> wow thats nice - ICS512
[17:10] <Laurenceb_> better than anything i found on digikey
[17:11] <Laurenceb_> navrac: digital scope?
[17:11] <navrac> yep
[17:11] <navrac> ics511 is slightly better - both stocked by rs
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[17:12] <eroomde> Laurenceb_: i'm not sure the plls would remove the phase noise just inherently
[17:12] <eroomde> unless the pll bandwidth was super tight
[17:12] <Laurenceb_> it might have waveform statistics thingy if you are lucky?
[17:12] <Laurenceb_> eroomde: yeah
[17:12] <navrac> time for tea
[17:13] <eroomde> though of course it's easier to make a low bandiwdth system out of severla progressibely tighter PLLs
[17:13] <eroomde> gah can't type
[17:13] <navrac> hope youve solved the jitter issue by the time I've eaten :-)
[17:13] <Laurenceb_> tho there is another way....
[17:13] <Laurenceb_> but you wont like it
[17:13] <eroomde> it would need a specan to see 15-60ns jitter in the square wave
[17:13] <eroomde> not a scope
[17:13] <navrac> needs an stm?
[17:13] <Laurenceb_> analogue filter and a schmitt trigger
[17:13] <eroomde> aaaargh
[17:13] <Laurenceb_> muhahhaa
[17:13] <eroomde> infact there is a way to do this nicely
[17:14] <Laurenceb_> and a further way of course...
[17:14] <eroomde> which i have a sketch for in my notebook
[17:14] <Laurenceb_> use an stm32
[17:14] <eroomde> which i shall find
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[17:15] <eroomde> but it's just an external oscillator
[17:15] <eroomde> so
[17:16] <eroomde> one can get chips that do clock synchronisation
[17:16] <eroomde> you can abuse them perfectly nicely to solve this problem
[17:16] <eroomde> one input the gps
[17:16] <eroomde> another something with good phase stability, like a tcxo
[17:17] <eroomde> put them both into a clock synchroniser, like the analog devices ad9547
[17:18] <eroomde> one into the 'stable source' input, the other (gps) into the reference input
[17:18] <Laurenceb_> ouch
[17:18] <Laurenceb_> the current draw
[17:18] <Laurenceb_> may as well use vctcxo
[17:19] <eroomde> might not be that much at low freqs
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[17:20] <nosebleedkt> hey
[17:20] <nosebleedkt> im on
[17:20] <nosebleedkt> http://habhub.org//zeusbot/
[17:21] <Laurenceb_> maybe navrac can get some jitter figures using scope
[17:21] <nosebleedkt> how can i search my nickname
[17:21] <nosebleedkt> im trying to find my first post
[17:21] <nosebleedkt> :P
[17:22] <eroomde> my guess would be the link that says 'search the logs'
[17:23] <Laurenceb_> vctcxo can get down to 2ma or so
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[17:23] <Laurenceb_> hard to see that happening with pll
[17:23] <eroomde> yeah
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[17:23] <Laurenceb_> but of course you still need a pll unless you can accept the frequency not being 30mhz
[17:24] <Laurenceb_> as 30mhz vctcxo doesnt exist
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[17:24] <eroomde> stilldavid: congrats on shiny videos
[17:24] <Laurenceb_> but again, stm32 saves the day - pll uses about 3ma or so
[17:24] <Laurenceb_> F4 and F105/7 have spare plls for these sort of problems :P
[17:25] <Laurenceb_> 8,10,12mhz vctcxo is easy to get
[17:26] <eroomde> that's ipressive
[17:26] <eroomde> what do they use them for normally?
[17:26] <Laurenceb_> ethernet, usb etc
[17:27] <Laurenceb_> where you have to have odd frequencies
[17:27] <Laurenceb_> and I2S - outputs for hardcore audio stuff
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[17:28] <Laurenceb_> if you're really smart, youd just use the main systick pll
[17:28] <Laurenceb_> and clk at 60mhz or whatever
[17:29] <Laurenceb_> or even 30 is plenty for a balloon, lower the current draw
[17:32] Nick change: signaleleven -> signaleleven_out
[17:33] <Laurenceb_> in fact i have another idea...
[17:33] <Laurenceb_> if you put two dc blocking caps on one leg of the xtal on the stm32
[17:33] <Laurenceb_> or both legs even... then had a varactor going to the dac
[17:33] <Laurenceb_> diy vcxo
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[17:55] <Broliv> Evening all
[17:55] <stilldavid> eroomde: eh?
[17:55] <stilldavid> awe, shucks. looks like I made the sfe homepage :\
[17:55] <eroomde> there u go
[17:55] <stilldavid> those videos are pretty awful, too.
[17:55] <eroomde> :)
[17:56] <eroomde> i enjoyed the brief flick around them
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[18:01] Action: Laurenceb_ came up with yet another way to do frequency locking
[18:01] <Laurenceb_> stick some varicaps off the rfm22b
[18:01] <Laurenceb_> either side of the xtal
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[18:11] <eroomde> just got an email from someone visitng from the states who is wondering if I might want to 'connect' with him because he is 'vacationing' locally and we can do some 'synamic collaboration' and 'envisioning'
[18:11] <eroomde> why can't amercans just learn to speak english
[18:11] <eroomde> this wierd valley speak, where being social seems to be run as a virtualised process, i cannot be dealing with
[18:11] <Laurenceb_> lol
[18:12] <Laurenceb_> all this clock talk has made me even more insane than is usual
[18:12] <Laurenceb_> mmmmm crystals
[18:12] <eroomde> he hopes I don;t mind him 'reaching out'
[18:12] <Laurenceb_> *drool*
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[18:13] <Laurenceb_> http://i.imgur.com/GEIUA.jpg <- pretty
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[18:14] <eroomde> nice
[18:14] <eroomde> strange URL though
[18:14] <eroomde> some kind of domestic violence conviction avoidance guide
[18:15] <Laurenceb_> apparently hes president of an internet trolling syndicate
[18:17] <stilldavid> I'm going to synergize core competencies so hard.
[18:17] <eroomde> yeah exactly
[18:17] <stilldavid> not even going to know what hit 'em
[18:17] <eroomde> it's wierd
[18:17] <stilldavid> (nice board, btw)
[18:17] <eroomde> it's like you you live near SF and are in your 20s and consider yourself technical, all things have to sound like you're trying to make a printer work
[18:17] <eroomde> 'what's the best way to interface?'
[18:18] <Laurenceb_> im tempted to try http://abusemark.com/store/index.php?main_page=product_info&cPath=1&products_id=30
[18:19] <eroomde> i actually read the following sentence on hacker news recently
[18:19] <eroomde> wait for it
[18:21] <eroomde> " I explained to him how much I loved his presentation and app. We then swapped iPads to compare our Zite interests. We found many similarities. He asked where I hailed from and what I did. I told him I was a tech reporter for Macgasm and lived in Maryland."
[18:21] <eroomde> this is in the context of meeting someone at a conference
[18:21] <eroomde> so first of all you swap an electronics device that enumerates your personality into some bullet points
[18:22] <eroomde> then if these is deemed acceptable, like the dimensions of a cow being sufficient at a meat market, you have decided to 'interface' socially
[18:22] <SpeedEvil> insane
[18:22] <eroomde> heaven knows what happens if their zite interests were not in alignment
[18:23] <eroomde> the ipad explodes and one of them dies or something
[18:23] <eroomde> so they don;t accidently interface again
[18:23] <SpeedEvil> they check if their grindr profiles match.
[18:24] <eroomde> that is weird though right, i'm not just being naive?
[18:24] <eroomde> it's not a cultural reletivism thing?
[18:24] <stilldavid> eroomde: you're what I might call "employable", maybe.
[18:24] <SpeedEvil> he's probably getting paid by the buzzword
[18:25] <Randomskk> eroomde: was this the guy who was really young
[18:25] <eroomde> stilldavid: why thank you
[18:25] <eroomde> Randomskk: yes
[18:25] <Randomskk> yea I read that
[18:25] <eroomde> u read it too huh
[18:25] <Randomskk> I agree with you. it's insane.
[18:25] <Randomskk> incidentally we just bought an iPad
[18:26] <eroomde> yes i have one too
[18:26] <Randomskk> good good
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[18:26] <Randomskk> have you taken a dremel to yours yet?
[18:26] <eroomde> no
[18:26] <Randomskk> http://t.co/ZDlo50Xd etc
[18:26] <eroomde> i use it to read the guardian with my toast in the morning
[18:26] <eroomde> and watch iplayer
[18:26] <eroomde> that's about it
[18:26] <eroomde> what did you write on it?
[18:26] <Randomskk> CUSF.CO.UK
[18:27] <Randomskk> poorly
[18:27] <Randomskk> very entertaining
[18:27] <eroomde> 'hey, you have beautiful eyes. before we go any further, what's your klout score?'
[18:27] <Randomskk> always wanted to do that to something as pristine as a brand-new just-opened iPad
[18:27] <Randomskk> eroomde: "before we go any further"? try harder
[18:29] <eroomde> it would be inefficient to expend more effort if there's a risk we're not compatible
[18:31] <eroomde> Randomskk: Nov the xth, elon musk giving a talk at RAeS
[18:31] <eroomde> if ure interested
[18:31] <Randomskk> cool
[18:33] <eroomde> right, time to leave work time
[18:33] <fsphil> xD
[18:33] <fsphil> but it's not work-o-clock
[18:33] <eroomde> it's badminton o'clock
[18:33] <eroomde> bbl
[18:34] <nigelvh> lunch o'clock for me
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[18:34] <nigelvh> mmmmmmm tuna
[18:34] <fsphil> I always hoped to meet someone called O'Clock .. hasn't happened yet
[18:34] <nigelvh> You could change your name and meet him every day...
[18:35] <fsphil> this is a cunning plan that has no flaws
[18:35] <nigelvh> Then when your phone rings you could say "Oh, hold on, it's Wife O'Clock"
[18:36] <fsphil> and after I'm gone, I can be the late o'clock
[18:37] <nigelvh> Exactly
[18:37] <nigelvh> But in the meantime it's life o'clock
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[18:39] <nigelvh> Then when you and your family go somewhere, your friends can say "Oh look! It's <num_family_members_here> o'clock!"
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[18:40] <nigelvh> Really, if you're not convinced yet, I don't know what will.
[18:42] <SpeedEvil> my fingers are crossed till the 7th - for space
[18:42] <nigelvh> SpeedEvil, what's on the 7th?
[18:42] <fsphil> that'll make it difficult to type
[18:42] <SpeedEvil> launch to kiss
[18:42] <SpeedEvil> iss
[18:42] <nigelvh> The second spacex one?
[18:43] <SpeedEvil> yes
[18:43] <SpeedEvil> 1000lb of cargo up, 700 down
[18:43] <nigelvh> Ah, yes, I read that it was happening soon. Didn't recall the date.
[18:43] <nigelvh> I <3 space.
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[18:47] <Adam012> Good evening. Is there anyone who can offer a little help getting my uBlox6 talking to my Arduino Pro Mini?
[18:49] <nigelvh> 1. Attach speaker to uBlox, 2. Attach microphone to Arduino. 3. Magic.
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[18:50] <nigelvh> Less jokingly though. I haven't worked with the ublox modules, so I don't know.
[18:50] <nigelvh> Are you trying to use i2c or serial?
[18:50] <Adam012> I'm using pins 0 and 1 so I'm assuming that's the hardware setup (i2c)?
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[18:56] <Adam012> I've connected up tx, rx, gnd, vcc from the Arduino to the Ublox Max 6 but I can't figure out the code on ukhas. The hardware code is setup for the use of a level convertor which I don't need.
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[18:58] <G7PMO_Kev> Adam - pins 0 and 1 on the arduinio are hardware serial, they go to the serial pins on the ublox
[18:59] <G7PMO_Kev> then yuo open the serial port at 9600
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[18:59] <G7PMO_Kev> and read in the data
[18:59] <Laurenceb_> navrac / navrac2 :ping
[18:59] <G7PMO_Kev> you will see the default strings being tx'ed every second
[19:00] <jcoxon> evening all
[19:01] <Adam012> That much I have done but all I get is: ub $$ yy ' u u d , U
[19:01] <G7PMO_Kev> hey
[19:01] <G7PMO_Kev> Adam - looks like the rigth string but corrupted
[19:02] <Adam012> That was what I thought but I'm not sure where I am going wrong.
[19:02] <jonsowman> Adam012: are you using delays for timing the RTTY?
[19:02] <G7PMO_Kev> how are you 'seeing' that string
[19:03] <Adam012> I just used the code from ukhas. I see the string in the 'Serial Monitor'
[19:03] <G7PMO_Kev> which code - url?
[19:04] <jonsowman> Adam012: are you using software serial?
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[19:04] <Adam012> http://ukhas.org.uk/guides:ublox6 hardware serial
[19:06] <Adam012> Thank you both for taking the time to help, this is a little beyond my comfort zone but I'm looking for reading/resources.
[19:06] <jonsowman> so is the hardware serial port connected to the GPS?
[19:06] <G7PMO_Kev> ok, and your seeing that string via the software serial output on pins 4 and 5 acroding to that code?
[19:07] <Adam012> @jonsowman - I'm using tx and rx pins 0 and 1 with the hardware code.
[19:07] <jonsowman> Adam012: and those are connected to what?
[19:07] <jonsowman> the GPS?
[19:07] <Adam012> I didn't know how to hook up pins 4 and 5 because I didn't need a level converter
[19:08] <jonsowman> if you've got the serial terminal and GPS both connected to the hardware UART then that's why it's breaking
[19:08] <G7PMO_Kev> that code basically takes what the gps tells it on the hardware serial port, and spits it back out a software serial port
[19:08] <Adam012> Arduino VCC, GND, TX, RX to uBlox VCC, GND, TX, RX respectively
[19:09] <G7PMO_Kev> Adam - yes, but then you also have your serial monitor on the pc connected to the same TX & RX pins
[19:09] <G7PMO_Kev> which is probably why it is breaking...
[19:09] <G7PMO_Kev> you need a FTDI to serial converter attached to pins 4 & 5 to monitor the software serial out with that code
[19:10] <Upu> Adam012 make a new Arduino sketch as follows :
[19:10] <Upu> void setup() {}
[19:10] <Upu> void loop() {}
[19:10] <Upu> program that
[19:11] <Upu> then open the Arduino serial port monitor
[19:11] <Upu> makes your Arduino act like an FTDI
[19:11] <G7PMO_Kev> upu - good call
[19:11] <Adam012> Okay, FTDI for 3.3V?
[19:12] <Upu> Which Arduino do you have ?
[19:12] <Adam012> I've got the Arduino Pro Mini 3.3V 328
[19:12] <Upu> should be fine
[19:13] <Upu> plug the GPS into 0 /1
[19:13] <Upu> RX/TX
[19:14] <Adam012> All done. The problem seems to be that although I have a FTDI to connect the PC to the Arduino I don't have a second FTDI for the Arduino back to the PC
[19:14] <G7PMO_Kev> Adam - yup, hence upu's sugestion for testing to use the Ard' its self as an ftdi
[19:15] <Upu> you don't need one
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[19:15] <Upu> with that code open
[19:15] <Upu> installed, programmed etc
[19:15] <Upu> open the serial monitor
[19:15] <Adam012> Done
[19:15] <Upu> and ?
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[19:16] <Adam012> I get the same corrupt strings over and over again.
[19:16] <Upu> screen shot pls
[19:16] <chris_99> Upu, what's the URL for your shop again?
[19:16] <Upu> http://ava.upuaut.net/store
[19:16] <chris_99> cheers
[19:16] <Upu> nps
[19:18] <chris_99> mind if i just PM you?
[19:18] <Upu> not at all
[19:18] <Adam012> http://img.photobucket.com/albums/v167/cazbuh/Untitled.png
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[19:19] <Adam012> Thanks for the help Upu
[19:20] <Upu> thats odd
[19:20] <Upu> one of my GPS's ?
[19:21] <Adam012> Yes, the uBlox Max6Q on breakout with Sarantel antenna 3.3V
[19:21] <Laurenceb_> parity?
[19:22] <jcoxon> that looks like binary
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[19:22] <Upu> power it all off for 10s and power it back on
[19:23] <Adam012> The code calls for pins 4 and 5 but I wasn't sure what to hook them up to as the only pins spare on the GPS are SCL SDA TIME and VBCK
[19:23] <Adam012> Powered off...
[19:23] <Upu> hang on
[19:24] <Upu> all you should have connected at the moment are
[19:24] <Upu> VCC to VCC
[19:24] <Upu> GND to GND
[19:24] <Upu> GPS RX to Arduino TX (1)
[19:24] <Upu> GPS TX to Arduino RX(0)
[19:24] <Upu> thats all
[19:26] <Adam012> Powered up...
[19:26] <Adam012> No change
[19:27] <Adam012> I'll send a photo of the wiring.
[19:28] <Upu> pls
[19:30] <daveake> Adam012 "Arduino VCC, GND, TX, RX to uBlox VCC, GND, TX, RX respectively" ... did you mean that?
[19:30] <daveake> Should be Rx --> Tx, Tx --> Rx
[19:31] <Adam012> I corrected that when I realised I had them swapped but it made no difference
[19:31] <daveake> It should certainly make /a/ difference
[19:31] <daveake> Are you using the h/w serial on the Arduino to connect to the GPS?
[19:32] <Adam012> I'm using TX0 and RX1 which I assumed where the hardware serial pins?
[19:32] <daveake> Yes
[19:32] <Adam012> http://img.photobucket.com/albums/v167/cazbuh/20121001_202720.jpg
[19:32] <daveake> Tx0 and Rx0 you mean?#
[19:33] <Adam012> There is no RX0
[19:33] <jonsowman> I think he means tx is ardionp pin 0 and rx is 1
[19:33] <jonsowman> can't type
[19:33] <Adam012> That's it!
[19:33] <Upu> that should work
[19:34] <daveake> ok gottit
[19:34] <Adam012> Does the wiring photo help?
[19:34] <Upu> yes ok
[19:34] <daveake> Yes wiring looks fine
[19:34] <daveake> S/w then ... shove the code on pastebin
[19:34] <Upu> pull the Arduino out and just stick that FTDI in its place
[19:34] <Adam012> Okay, 1 minute!
[19:37] <daveake> btw the funny text looks baud-rate-ish
[19:38] <Adam012> Right, FTDI connected.
[19:40] <chris_99> does anyone here use PICs for HAB'ing?
[19:40] <daveake> RocketBoy does; Number10 does
[19:41] <Adam012> The Apex Hab guys use PICs
[19:41] <daveake> Adam012 Have you set the board type in the Arduino IDE?
[19:41] <Upu> ok same deal Adam012
[19:41] <Upu> open the serial monitor
[19:42] <Adam012> @Daveake - yes I set the board and didn't have any problems with the basic led blink script
[19:42] <Adam012> @Upu - Serial monitor is open
[19:42] <chris_99> i'm just wondering if anyones used PIC + SD card?
[19:42] <daveake> And have you set 9600 baud in the source code?
[19:42] <Upu> same output Adam012 ?
[19:43] <Adam012> @Daveake - The code was pulled from UKhas (the ublox 6 tutorial for hardware serial) 9600 seems to be setup in the first few lines and I set the same in the serial monitor
[19:43] <Upu> at the moment the code is irrelevant
[19:44] <Upu> as you should be outputting from the module directly
[19:44] <Adam012> @Upu - no output
[19:44] <Upu> nothing at all ?
[19:44] <Adam012> nothing
[19:44] <Upu> switch RX and TX over
[19:47] <KyleYankan> Sheesh, this APRS is giving me such a hard time
[19:47] <Adam012> I'm getting a lot of scrolling text at the bottom of the Arduino sketch input window but nothing on the serial monitor
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[19:49] <KyleYankan> Has anyone here got a Baofeng UV-5R working with a byonics aprs controller?
[19:50] <Upu> We don't tend to use APRS over here in the UK Kyle
[19:50] <Upu> might be someone whos tried it though
[19:50] <KyleYankan> I've bee fidgeting with it for ~2 weeks now, nd stil lcan't get it to work consistently.
[19:53] <number10> chris_99: you can use SPI sd card breakout from http://proto-pic.co.uk/breakout-board-for-microsd-transflash/ - what processor you use doesnt matter - but PICs go higher ;)
[19:54] <chris_99> sweet hadn't seen that number10. i'm using a PIC32MX250F128B
[19:54] <chris_99> gonna have a USB connection on it probably
[19:56] <Upu> ok Adam012
[19:56] <Upu> remove the GPS
[19:56] <Upu> and go make a sketch that tests the serial port
[19:56] <Upu> one of the example should do it
[19:57] <Adam012> Okay, I'll try it tonight. Got to go now (school closing for the evening)
[19:57] <number10> its nice to see a different mix of hardware platforms and original software chris_99. if everyone did the same it would be dull
[19:57] <Upu> nps Adam012
[19:58] <Adam012> Will the serial port light an led?
[19:58] <chris_99> number10, yeah definitely :)
[19:58] <Upu> its just a digital port Adam012
[19:58] <Upu> make sure you have a resistor on there
[19:59] <Upu> try the sample serial sketches to make sure your serial board isn't damaged or something daft
[19:59] <chris_99> does anyone use LiPo btw?
[20:00] <Upu> no don't
[20:00] <jonsowman> they're a bit rubbish when they're cold
[20:00] <Upu> they freeze and die
[20:00] <chris_99> ah heh, i thought because they can supply a lot of current they may be cool, but didn't think about them freezing
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[20:00] <chris_99> how about LiFe
[20:01] <Upu> fail
[20:01] <Upu> http://ukhas.org.uk/ideas:power_supply?s[]=power&s[]=supplies
[20:01] <chris_99> cheers
[20:02] <chris_99> sweet it looks like LiFe is ok
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[20:02] <chris_99> i found this seller that sells packs of them
[20:02] <chris_99> designed for electric cars
[20:02] <Upu> The AA Ultimate Lithiums work well are light and cheap
[20:02] <Upu> by cheap
[20:02] <Upu> I mean expensive
[20:04] <chris_99> http://www.a123systems.com/prismatic-cell-amp20.htm
[20:04] <chris_99> is what i was looking at
[20:04] <cuddykid> has anyone here worked with the SIM908 module before?
[20:05] <chris_99> probably overkill for HAB mind
[20:08] <navrac2> 715Laurenceb_ sorry hour late pong
[20:08] <navrac2> Laurenceb_ pong
[20:09] <Laurenceb_> hi
[20:09] <Laurenceb_> so i came up with another idea
[20:09] <Laurenceb_> thats very simple
[20:09] <navrac2> i know an stm32.....
[20:09] <Laurenceb_> use two varicaps
[20:09] <Laurenceb_> one either side of the rfm22b xtal
[20:09] <Laurenceb_> then pwm off the avr
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[20:10] <navrac2> leaqves us with getting the reference still
[20:10] <Laurenceb_> sure
[20:10] <Laurenceb_> using timer input capture
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[20:10] <Laurenceb_> so xout on the si4432 goes through a dc bloking cap to xtal
[20:10] <navrac2> well it removes the need for the pll
[20:10] <Laurenceb_> with 100k ohm to gnd
[20:10] <Laurenceb_> and varicap to filtered pwm
[20:11] <Laurenceb_> same at other side of the xtal
[20:11] <Laurenceb_> gpio clkout to timer input, and gps timepulse to input capture
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[20:11] <navrac2> should work
[20:12] <Laurenceb_> BB857 looks ok
[20:12] <Laurenceb_> 19p at RS
[20:13] <Laurenceb_> you could probably improve the performance by setting timepulse to 1khz or so
[20:14] <Laurenceb_> and reducing timer resolution to 14 bits or so
[20:14] <navrac2> 3-7pf over 1 to 3v
[20:14] <navrac2> i had a bright idea but its gone.
[20:15] <navrac2> IIRC th si4432 has a digital tuning cap which from memory was 127pf with 7 bit accuracy and again from memory 1 step pulled the freq by about 250hz
[20:16] <Laurenceb_> yeah
[20:16] <Laurenceb_> but thats loads of spi traffic
[20:16] <navrac2> oh no - i wasnt suggesting using it - it was too course when i tried it
[20:16] <Laurenceb_> to adjust it at 1khz or so and try and keep it coherent
[20:16] <navrac2> was just trying to get an idea of how much you could pull by per pf
[20:16] <Laurenceb_> yeah
[20:18] <navrac2> couldnt see much jitter on the scope when i looked at the timepulse output so im going to try that idea first, but im going to buy enough bits to try every approach!
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[20:20] <Laurenceb_> should be interesting
[20:20] <navrac2> well it would be nice to get a stable tx
[20:20] <navrac2> plus I could use it for calibrating my funcube
[20:20] <Laurenceb_> im not a massive scope guru, but i think you should be able to set the scope to overlay multiple recorded waveforms
[20:20] <Laurenceb_> like an eye diagram, even with a cheap digital scope
[20:21] <Laurenceb_> could give an idea of jitter
[20:21] <Laurenceb_> but varicaps should have the lowest current draw
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[20:21] <navrac2> I was going to set it up against a known good reference that was jitter free and compare
[20:21] <Laurenceb_> virtually no extra current
[20:22] <navrac2> agreed
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[20:22] <navrac2> mind you i havent looked what happens to the clock when i go into low power mode
[20:22] <navrac2> the pps output that is,
[20:23] <navrac2> I currently drop it into low power mode so the draw is 7ma peaking at 20mA and an average about 12mA
[20:24] <navrac2> which seems to make the positioning a little less accurate and I suspect the timepulse output will go similarly off
[20:26] <navrac2> to be honest a really good tcxco would give us pretty good stability
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[20:27] <Laurenceb_> yeah
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[20:40] <navrac2> varicaps are a lot cheaper...
[20:42] <Laurenceb_> what you really want is an allen variance plot of the ublox timepulse
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[20:51] <navrac2> ordering a vctxco plus a pll and some diodes and going to try the various methods
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[21:14] <stilldavid> jonsowman: those hoodies for sale?
[21:14] <jonsowman> stilldavid: soon :) these are samples, but we'll be placing a big order soon
[21:14] <jonsowman> are you after one?
[21:15] <stilldavid> shut up and take my mo^H^H^H yeah, that'd be grand
[21:15] <jonsowman> we'll let you know shortly :)
[21:15] <jonsowman> there are tshirts too
[21:15] <stilldavid> it's getting on towards hoodie weather here, but either would be sweet
[21:17] <jonsowman> hoodies and tshirts have embroidered logo on front: https://dl.dropbox.com/u/62498867/IMG_20121001_221603.jpg
[21:17] <fsphil> it seems to always be hoodie weather here
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[21:18] <fsphil> who designed the logo jonsowman?
[21:19] <jonsowman> fsphil: the university graphics design service
[21:19] <fsphil> they did good
[21:19] <jonsowman> http://www.ucs.cam.ac.uk/media/pandis
[21:19] <jonsowman> yeah we're very pleased with it :D
[21:22] <eroomde> i'm pleased cusf hoodies are becoming a desirable thing
[21:22] <eroomde> you know what they should have actually
[21:23] <eroomde> a hoop in the inside neck
[21:23] <eroomde> and a large strong internal pocket
[21:23] <eroomde> so that you can use it as a ballast bag for balloon filling
[21:23] <eroomde> in a pinch
[21:25] <stilldavid> utilihoodie
[21:25] <eroomde> catchy
[21:25] <eroomde> hug a habber
[21:25] <fsphil> hoodiechute
[21:25] <stilldavid> fsphil: love it
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[21:26] <jonsowman> haha
[21:26] <fsphil> I'd need a winter version, with mittons built in
[21:26] <eroomde> the fingerless gloves built in
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[21:26] <eroomde> with the mitten over-finger bits that you can remove
[21:26] <jonsowman> we did consider one like that
[21:26] <fsphil> ooh perfect
[21:26] <eroomde> for using screwdrivers
[21:27] <eroomde> sow metal thread into the seams to it can be a grand plane
[21:27] <eroomde> and you can wear a dipole on your shoulder like a parrot
[21:27] <eroomde> ground*
[21:28] <fsphil> now you've taken it too far :p
[21:28] <jonsowman> yagi mount on the other shoulder
[21:28] <eroomde> like Predator
[21:28] <jonsowman> lol
[21:29] <fsphil> just thinking that
[21:30] <eroomde> add an attractive pattern
[21:30] <eroomde> eg http://bit.ly/hVrYd
[21:31] <eroomde> receeding hairline optional
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[21:31] <Lunar_Lander> hello
[21:31] <eroomde> no
[21:31] <fsphil> there's still some debate on this subject
[21:32] <eroomde> but, a yagi holster, like a quiver, with flexible elements would be useful
[21:32] <eroomde> always think that when tracking on foot
[21:32] <eroomde> hiking
[21:32] <eroomde> something you can just slide into a thing on your back
[21:32] <jonsowman> so you can whip out the yagi at a moment's notice?
[21:33] <eroomde> yes
[21:33] <fsphil> innuendo proximity warning
[21:33] <jonsowman> actually a flexible yagi would be very cool
[21:34] <eroomde> yes it would
[21:34] <eroomde> that could fit ina poster tube
[21:34] <jonsowman> yes, they're such a pain to get in the car
[21:34] <eroomde> yep
[21:34] <eroomde> might try one
[21:34] <eroomde> tap measure stylee
[21:35] <jonsowman> make th elements from springs
[21:35] <eroomde> oh no, piano wire infact
[21:35] <fsphil> easier to tune?
[21:35] <fsphil> I hate myself
[21:35] <jonsowman> the CUWS yagi on the rotator has extendable elements
[21:35] <jonsowman> it's very cool
[21:35] <jonsowman> fsphil: god that was dreadful
[21:35] <DanielRichman> fsphil: http://i.imgur.com/vqYuG.gif
[21:35] <fsphil> yea, I feel dirty
[21:36] <jonsowman> DanielRichman: i hope you won the pub quiz
[21:36] <DanielRichman> slightly yes, slightly because our table was right by the door so we had 10 people while most had 6...
[21:36] <jonsowman> haha
[21:36] <DanielRichman> I contributed exacltly zero answers (quite common for me in pub quizzes)
[21:37] <DanielRichman> actually it was a tie but we guessed the length of the river cam correct to 1 mile and hence won
[21:37] <jonsowman> nice
[21:37] <jonsowman> good work
[21:37] <jonsowman> :D
[21:38] <eroomde> what is the length of the river cam?
[21:38] <DanielRichman> it started out as "what is the length of the river cam" and quickly became "allow specifics, what's the distance on the wikipedia page"
[21:38] <DanielRichman> which is 40 miles
[21:40] <eroomde> right
[21:40] <Laurenceb_> ambridge university?
[21:40] <Laurenceb_> isnt that on radio 4 ?
[21:40] <jonsowman> yes, they dropped the C recently
[21:41] <eroomde> it is so named because of the bridge
[21:41] <eroomde> the central bridge goes past trinitity and trinity hall
[21:41] <eroomde> it is named orgasm bridge, because it is the steepest
[21:41] <eroomde> and so the noise you make cycling up and then the noise you make coasting down gives it is name
[21:42] <Laurenceb_> lawl
[21:42] <eroomde> this was considered a bit of a mouthfull, and so in the 14th century it was renamed to the slightly more colloquial equivalent that we still have today - came-bridge
[21:42] <eroomde> cambridge
[21:42] <Laurenceb_> oh dear
[21:46] <Laurenceb_> i dont believe eroomde made that one up
[21:46] <eroomde> this is what they tell the japanese tourists on the expensive punt cruises
[21:46] <Laurenceb_> its too good
[21:46] <eroomde> i did actually
[21:46] <Laurenceb_> :P
[21:46] <eroomde> i adlibbed a whole punt schpiel
[21:46] <eroomde> one may week
[21:46] <eroomde> i was ona roll
[21:46] <jonsowman> haha
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[22:08] <chris_99> is the UBLOX classed as BGA to some degree?
[22:08] <eroomde> no
[22:08] <eroomde> because there are no balls
[22:09] <eroomde> and they are not on a grid
[22:09] <chris_99> doh didn't think about the balls. What do you call that type of chip
[22:09] <chris_99> that needs a solder mask
[22:10] <eroomde> it's a module rather than a chip i guess
[22:11] <chris_99> apparently LCC package is it's technical name
[22:15] Action: SpeedEvil loves the word castellated,
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[22:27] <moumou> hello all
[22:30] <moumou> want to buy : DVB-T dongle for a amateur radio receiver, in my balloon, anyone can confirm this is good project http://dx.com/p/mini-dvb-t-digital-tv-usb-2-0-dongle-with-fm-dab-remote-controller-92096?tc=GBP
[22:31] <moumou> It references RTL2832 chipset but I saw RTL2832U referenced (with capital U at the end)... no difference?
[22:35] <eroomde> that one id fine
[22:35] <eroomde> is
[22:36] <moumou> super thanks
[22:37] <m0psi> hi all
[22:37] <m0psi> i'm a newbie to hab, and got a quickie re gas etc
[22:37] <m0psi> what's the story regarding transporting compressed gas in a car
[22:38] <m0psi> do you have to have some sticker on the car?
[22:38] <eroomde> ironic given your callsign
[22:38] <eroomde> in theory you need a sticker
[22:38] <m0psi> :-)
[22:38] <m0psi> y, but do people bother?
[22:38] <eroomde> not really
[22:38] <eroomde> tunnels sometimes have rules
[22:39] <eroomde> eg dartford
[22:39] <m0psi> btw eroomde, nice talk in conf, i saw it on youtube. very cool.
[22:39] <eroomde> oh ta
[22:39] <m0psi> hmm
[22:39] <m0psi> i guess
[22:39] <m0psi> how much of a He gas bottle does it take for a single launch?
[22:40] <eroomde> but for taking a small bottle of helium around, i dont think anyone bothers
[22:40] <m0psi> small == 1meter high?
[22:40] <eroomde> helium is about 1kg of lift (excuse unit abuse) per m^3
[22:40] <eroomde> so about 2-3m^3 is normal for a normal hab
[22:41] <m0psi> ok, and how much is that out of a 1m bottle?
[22:41] <eroomde> i think they're about 4-5m^3 iirc
[22:41] <m0psi> ok, so just over half a bottle for a launch? ish
[22:42] <eroomde> yeah. depends on the bottle
[22:42] <eroomde> see what u can rent
[22:42] <m0psi> ok, so next question, how much pressure is that, and how do you know how much pressure you are putting? gauge on valve?
[22:42] <Randomskk> you'll need a regulator
[22:43] <Randomskk> the bottles are like 400psi order of magnitude and you're discharging to atmospheric
[22:43] <Randomskk> some regulators have gauges on them
[22:43] <eroomde> um, they're more like 3000psi :)
[22:43] <Randomskk> you work out how much gas is in the balloon by measuring the lift -- either with some fish scales or using some known weight ballast
[22:43] <m0psi> ok, so 3m^3 at atmospheric
[22:43] <Randomskk> whatever I was within an order of magnitude
[22:43] <Randomskk> 200bar or so.
[22:44] <SpeedEvil> yeah, there are good reasons for the regs in tunnels.
[22:44] <m0psi> oh, so prior to launch you are literally measuring the upward lift force, live ?
[22:44] <Randomskk> yea.
[22:45] <m0psi> aha, interesting, and simples
[22:45] <SpeedEvil> a regulator blew when someone was transporting a helium cylinder in a car. it was stuck to the top of the tunnel for days,
[22:46] <m0psi> oooh
[22:46] <m0psi> ok, so price and supplier. how much for the 1m bottles (roughly),and from where do i get it, BOC?
[22:47] <SpeedEvil> also, more seriously. hydrogen is not a ridiculous gas to use.
[22:47] <m0psi> i'm doing this as part of a highschool project, so they may have a supplier for the science labs, but i just wanted to know how the hab community does it.
[22:47] <SpeedEvil> as a highschool project, helium will be easier
[22:48] <SpeedEvil> setting fire to school kids is frowned on for some reason.
[22:48] <m0psi> y, don't want to upset the kids for sure
[22:48] <m0psi> y, they don't like it where we are
[22:48] <Laurenceb_> theres a massive helium shortage atm
[22:48] <Laurenceb_> you might not be able to get any
[22:49] <m0psi> oh dear
[22:49] <SpeedEvil> really.
[22:49] <m0psi> that is a bummer
[22:49] <SpeedEvil> even for welding?
[22:49] <Laurenceb_> i havent checked recently
[22:49] <m0psi> someone needs to invent a new atom
[22:49] <Laurenceb_> well it was restricted by BOC to key customers
[22:49] <SpeedEvil> beryllium,
[22:49] <Laurenceb_> no new customers
[22:49] <SpeedEvil> it only works on hot days though.
[22:50] <Laurenceb_> and restrictions to supply
[22:50] <m0psi> cant imagine Be is cheaper that He !
[22:50] <Laurenceb_> this was a few months ago tho
[22:50] <Laurenceb_> when I spoke the BOC then they said supply should be back to normal by October
[22:50] <Laurenceb_> so maybe its ok now, I dont know
[22:50] <m0psi> i used to work in the MRI world
[22:51] <m0psi> so liquid He was a common requirement
[22:51] <Laurenceb_> theres supposed to be a new LNG plant in Quatar apparently, giving lots of He output
[22:51] <m0psi> i found out that they actually mine it in places like Algeria
[22:51] <Laurenceb_> as soon as that starts up He shortage is sorted... for now
[22:51] <BrainDamage> did the us "sell everything" bullshit policy started to impact?
[22:51] <m0psi> and one of the holy grails from a moon mining company is He
[22:51] <Laurenceb_> BrainDamage: yes
[22:51] <SpeedEvil> naah
[22:51] <Laurenceb_> its pretty much out now
[22:51] <SpeedEvil> that's he
[22:51] <SpeedEvil> 3
[22:52] <Laurenceb_> and main Russian plant is out till 2013
[22:52] <SpeedEvil> there is no bulk helium
[22:52] <Laurenceb_> see i was on the phone for like 1 hour
[22:52] <Laurenceb_> talking to someone at BOC who was obsessed with He market :P
[22:53] <SpeedEvil> :-)
[22:53] <SpeedEvil> is He likely to go up then?
[22:53] <Laurenceb_> lol
[22:53] Action: Laurenceb_ zzz
[22:53] <SpeedEvil> night
[22:53] <m0psi> so, how much is a small bottle of He, when you can get it?
[22:56] <SpeedEvil> I've never bought it
[22:56] <m0psi> oh?
[22:56] <SpeedEvil> or used
[22:56] <m0psi> do you he H?
[22:57] <m0psi> do you use H?
[22:57] <SpeedEvil> not personally done launches
[22:57] <m0psi> ah
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[22:57] <chris_99> you need a fancier regulator i hear for hydrogen?
[22:57] <SpeedEvil> have idly looked at both H and natural gas
[22:58] <SpeedEvil> natural gas has half the lift,
[22:58] <m0psi> well, for sure they have different fittings
[22:58] <SpeedEvil> but comes out a tap in the kitchen.
[22:58] <m0psi> to avoid using regs on the wrong bottle, in hospitals etc
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[22:58] <m0psi> natural gas?! never heard that being used. interesting
[22:59] <SpeedEvil> it is not usual.
[22:59] <m0psi> half the lift of H or He?
[22:59] <SpeedEvil> yes, about
[22:59] <SpeedEvil> it's mostly CH4
[22:59] <m0psi> i thought that H is about twice He
[23:00] <SpeedEvil> so half the weight of N2 or O2
[23:01] <SpeedEvil> boiyancy is displaced volume times density difference
[23:02] <moumou> you'll need a heavier baloon for that no? or it will pop too soon with CH4
[23:02] <m0psi> y, makes sense
[23:03] <SpeedEvil> it pops 5km or so lower
[23:03] <SpeedEvil> maybe a little more
[23:03] <m0psi> are there calibration charts for this kind of knowledge?
[23:04] <SpeedEvil> no, understanding the physics of lift
[23:04] <SpeedEvil> balloon bursts at a given diameter, atmospheric density about halves every 5km
[23:05] <m0psi> ok, but the balloon strength comes into 'where / how high it pops'
[23:06] <m0psi> ok, how much would a balloon expand when the atm halves?
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[23:52] <SpeedEvil> balloon volume is proportional to 1/ atmospheric pressure, closely
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[00:00] --- Tue Oct 2 2012