highaltitude.log.20081211

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[00:06] <akawaka> slr would be pretty heavy though, right?
[00:06] <akawaka> you could get a real astrophotography ccd
[00:06] <edmoore> ish
[00:07] <akawaka> i guess it would be a pretty heavy rig anyway
[00:07] <akawaka> i've been thinking of buying a scope
[00:07] <akawaka> i keep telling myself i don't need a fancy eq mount
[00:07] <akawaka> i then i keep pretending i'm going to do fancy photography
[00:19] <edmoore> hallam: I guess a moon tracker would be pretty straight forward?
[00:20] <edmoore> if just for orientation in 3 axes
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[00:38] <edmoore> bloody americans
[00:38] <edmoore> moments of inertia in this paper are 'slug-foot^2'
[00:38] <edmoore> what the hell kind of a unit is that
[00:39] <natrium42> that's english units
[00:40] <natrium42> :D
[00:40] <natrium42> not american
[00:40] <edmoore> imperial units
[00:40] <natrium42> http://en.wikipedia.org/wiki/Slug_%28mass%29
[00:40] <edmoore> english units are a euphamism
[00:40] <edmoore> like freedom fries
[00:40] <natrium42> hehe
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[06:11] <natrium42> if anybody is still awake
[06:11] <natrium42> http://natrium42.com/balloon/nova9/
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[08:28] <jcoxon> morning all
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[12:01] <Laurenceb> hello
[12:03] edmoore (n=edmoore@88-212-167-121.rdns.as8401.net) joined #highaltitude.
[12:04] <Laurenceb> hi edmoore
[12:05] <edmoore> hi Laurenceb
[12:05] <edmoore> long time no see
[12:05] <edmoore> all well?
[12:05] <Laurenceb> yeah thanks
[12:06] <edmoore> sorry gtg
[12:06] <edmoore> bbl
[12:07] <edmoore> ps - the Hobble Near-Space Telescope
[12:07] <edmoore> my new project :D
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[17:43] <rjharrison_> hi natrium42
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[17:51] <natrium42> hey
[17:51] <natrium42> oh, he left
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[19:10] <edmoore> yo all
[19:16] <gordonjcp> 'sup chan?
[19:16] <edmoore> nowt
[19:17] <edmoore> bought a piano today
[19:17] <edmoore> that was exciting
[19:17] <edmoore> thought about yaw control on balloons more
[19:20] <gordonjcp> cool
[19:20] <gordonjcp> I wish I had both the room and skill for a proper piano
[19:21] <edmoore> working on the skill bit...
[19:21] <gordonjcp> I did buy an old Ensoniq VFX recently
[19:22] <edmoore> awesome :)
[19:24] <gordonjcp> yeah, lovely gritty 90s digital sounds
[19:29] <natrium42> edmoore, http://natrium42.com/balloon/nova9/
[19:32] <edmoore> natrium42: awesome - tis downloading
[19:32] <natrium42> let me know if you want it in a different format
[19:32] <natrium42> raw video is about 250MB
[19:57] <edmoore> natrium42: five have bloody not landed in the north sea!?!?!?!
[19:57] <natrium42> edmoore, reporters...
[19:57] <edmoore> only nova 2 did
[19:58] <edmoore> and that was because of the worlds worst idea - some kind of knot that would pull apart on cutdown and release it
[19:58] <edmoore> we sacked that guy shortly after
[19:58] <natrium42> haha
[19:59] <natrium42> but it was a good interview
[19:59] <natrium42> they keep referring to it as space instead of near-space too
[19:59] <natrium42> but i guess that's also reporting :)
[20:00] <edmoore> :)
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[20:14] <rjharrison> Hi all
[20:14] <edmoore> g'evening sir
[20:14] <rjharrison> Any one care for a quick discussion on PWM
[20:14] <edmoore> fire away
[20:15] <rjharrison> PWM is basically on and off very quickly and the on part compared to the off part gives you an average voltage
[20:15] <edmoore> yep
[20:15] <rjharrison> 0 - 5 volts with a 80% duty cycle would give ~4v
[20:16] <edmoore> yep
[20:16] <rjharrison> Is that ok for the tx on a radio metrix. Would it see the on and off or is it so fucking quick it sees 4v
[20:16] <rjharrison> I know the radiometix is 3v
[20:17] <edmoore> i would really strongly advice a LPF
[20:17] <rjharrison> 2.3 - 2.5 say for the radiometrix
[20:17] <rjharrison> PWM + LPF
[20:17] <edmoore> so the radiometrix has its own lpf but i think its cutoff freq might be a bit high for this
[20:17] <edmoore> PWM + LPF = rock and roll
[20:17] <edmoore> laurenceB did this for his radio
[20:18] <rjharrison> Just thought I would try and see how it goes compared to the dac
[20:18] <rjharrison> Plus I'm waiting for tha dac and PWM is on there
[20:18] <edmoore> :)
[20:19] <rjharrison> 2 secs kids 2 bed
[20:24] <rjharrison> LPF just a cap and resistor?
[20:24] <edmoore> yep, that'll do it
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[20:41] <rjharrison> Are the values easy to work out for the filter or is that going to be a bit of work
[20:41] <edmoore> super trivial
[20:41] <rjharrison> Great
[20:42] <edmoore> you want it to block all the pwm-ness, but let through the whatever-baud rtty
[20:42] <edmoore> swo pick the cutoff frq between the two
[20:42] <edmoore> so*
[20:43] <rjharrison> Ie only let through 2.4 2.6 v
[20:43] <rjharrison> will that be smooth?
[20:43] <edmoore> hrm
[20:43] <edmoore> don't think in terms of voltages
[20:43] <rjharrison> Or should I step the voltage up
[20:43] <edmoore> just freq
[20:44] <rjharrison> Ok
[20:44] <edmoore> duty cycle sets the voltage
[20:44] <rjharrison> Yep
[20:44] <edmoore> lpf won't change that
[20:44] <rjharrison> ok
[20:44] <edmoore> but you want it to smoother out the pwm, so the pwm freq needs to but a fair bit above the pwm cutoff freq
[20:45] <edmoore> sorry, the pwm freq needs to be a fair bit above the lpf cutoff freq
[20:45] <rjharrison> Ok
[20:45] <edmoore> so the actual pulses get smudged out and you just get the DC component
[20:46] <rjharrison> Ok that makes sense I think
[20:46] <rjharrison> Sort of holds the voltage up when the signals off
[20:47] <edmoore> yep
[20:47] <edmoore> think of it as a pulsed hose going into a bucket (the cap) with a small hole in the bottom (resistor)
[20:48] <rjharrison> And the output comes out the bottom >
[20:48] <rjharrison> Ish
[20:48] <edmoore> the bucket just holds the pulsed splashes and lets them trickle out of the hole
[20:48] <rjharrison> Regulated
[20:48] <edmoore> yeah
[20:48] <rjharrison> Cool
[20:50] <rjharrison> Right I'll have a go I guess it doesn't really matter what type of PWM I use
[20:51] <edmoore> an oscilloscope is coming up on the horizon of robert purchases, btw
[20:51] <rjharrison> yep
[20:52] <rjharrison> only 1k :(
[20:52] <rjharrison> ebay
[20:52] <rjharrison> 100 quid
[20:52] <rjharrison> ?
[20:52] <edmoore> ebay!
[20:52] <edmoore> well, the best you can afford is the usual answer
[20:52] <edmoore> but yeah
[20:52] <rjharrison> min spec 20Mhz?
[20:52] <edmoore> def
[20:53] <rjharrison> bit better 40Mhz?
[20:54] <edmoore> well, you'll not need it 99% of the time
[20:54] <rjharrison> You know what I'm going if i run an avr at 16Mhz I guess 20Mhz is going to be ok
[20:54] <rjharrison> I may be wrong
[20:55] <rjharrison> going = doing
[20:55] <edmoore> yep
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[22:06] <edmoore> all - without googling, does the name 'Michael Covington' ring any bells?
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[22:06] <edmoore> I know who he is via google, and have his book from about 7 years ago, but since forgot who he was. however I'm sure someone was talking about him recently
[22:08] <epictetus> no.
[23:17] Laurenceb (n=laurence@host86-133-67-102.range86-133.btcentralplus.com) joined #highaltitude.
[23:17] <Laurenceb> hello
[23:20] <EI5GTB> OHAI
[23:20] <Laurenceb> whats new?
[23:21] <edmoore> rjharrison: ping
[23:22] <Laurenceb> hi edmoore
[23:23] <EI5GTB> not much
[23:27] <Laurenceb> working on the antenna mount still?
[23:28] <rjharrison> pong
[23:31] <edmoore> oh
[23:31] <edmoore> yes
[23:31] <edmoore> Laurenceb is the man to ask about pwm and radio
[23:31] <Laurenceb> hello
[23:31] <Laurenceb> well...
[23:31] <rjharrison> Hi
[23:31] <Laurenceb> I still need an icom
[23:31] <rjharrison> You're the man :)
[23:32] <edmoore> i need an icom too
[23:32] <edmoore> we all need icoms
[23:32] <rjharrison> Me too
[23:33] <Laurenceb> hehe
[23:33] <Laurenceb> well with my usb SDR your problems will be solved
[23:33] <rjharrison> Well I'm going to give PWM a go with LPF
[23:34] <Laurenceb> whats the easiest/cheapest way to do 4 layer pcb design?
[23:35] <Laurenceb> rjharrison: youre welcome to the eagle files for my radio if you want
[23:35] <rjharrison> Ooh I have a dodgy set up here
[23:36] <Laurenceb> you could do it on stripboard
[23:36] <rjharrison> Just going to set up PWM and get it to drive the radiometrix
[23:36] <Laurenceb> the code is on the wiki
[23:36] <rjharrison> via a LPF
[23:36] <Laurenceb> yeah
[23:36] <Laurenceb> sounds like a plan
[23:36] <rjharrison> I guess I want to step up and down the voltage using the PWM to step the vlotage
[23:37] <rjharrison> Does that make sense save the typo
[23:37] <Laurenceb> yeah
[23:37] <Laurenceb> http://wiki.ukhas.org.uk/code:radio
[23:38] <Laurenceb> I've forgotten which pwm channel that uses
[23:38] <Laurenceb> but it takes 9600 baud 8O1
[23:40] <rjharrison> Nice code
[23:40] <rjharrison> 9600 baud 8N1 or 8 odd 1
[23:41] <rjharrison> That's going some I hope to do 300 and that would be fantastic
[23:43] <Laurenceb> sorry thats what you give it
[23:43] <Laurenceb> over RX, it transmits at 300 baud
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[23:55] <Laurenceb> gtg, cya all
[23:56] Laurenceb (n=laurence@host86-133-67-102.range86-133.btcentralplus.com) left irc: "The day microsoft make something that doesnt suck is the day they make a vacuum cleaner"
[00:00] --- Fri Dec 12 2008