highaltitude.log.20100423

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[08:09] <earthshine> morning
[08:11] <juxta> hey Mike
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[08:17] <jonsowman> morning world
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[08:19] <jonsowman> http://www.srcf.ucam.org/~cuspaceflight/hourly-predictions
[08:19] <jonsowman> looking better
[08:20] <jonsowman> anyone know if rob is still planning to launch on sat?
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[08:23] <earthshine> morning
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[11:38] <rharrison> Saurday is off for launch. Will be at ears the following w/e with kids if wx is good there will be a launch
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[11:57] <earthshine> Nice
[12:00] <earthshine> yeah i can see it's landing in the drink this weekend
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[15:37] <edmoore> is anything going up this w/e?
[15:38] <russss> I think rharrison has delayed till next weekend
[15:38] <edmoore> h'ok
[15:39] <rharrison> Yep this is true
[15:39] <russss> I think I'm going to try and get a receiver by then
[15:39] <rharrison> Stuggeling to get and XYL pass
[15:39] <rharrison> an XYL
[15:39] <rharrison> = wife
[15:40] <russss> I'm still tossing up whether to get a scanner or a transceiver
[15:40] <rharrison> lol just looked up what XYL means Ex Young Lady :)
[15:40] <edmoore> yes indeed
[15:40] <rharrison> I'm thinking of getting an alinco rx
[15:40] <rharrison> Wide band
[15:40] <edmoore> I am resolutely YL only for a few years yet
[15:41] <rharrison> I'm wishing I was too :)
[15:41] <rharrison> Perhaps a trade in :)
[15:41] <edmoore> handheld?
[15:41] <rharrison> Yep
[15:41] <edmoore> I have used a DJ-G7 for a month or two
[15:42] <edmoore> don't bother - the intermodulation makes the multi-bandness basically unusable
[15:42] <edmoore> so whilst you think it'll get you on AO-51, it won't
[15:48] <edmoore> which were you thinking of getting?
[15:48] <rharrison> edmoore, ok cool
[15:51] <edmoore> yeah, I think the G7 was one of those cases where if it looks too good to be true, it probably is
[16:06] <rharrison> What I really want is a muti mode rx SSB for testing on 800+ MHz
[16:07] <edmoore> something like the DJ-X10T?
[16:07] <edmoore> we've one in the lab
[16:07] <edmoore> nice but deaf
[16:08] <rharrison> Ok good to know
[16:08] <rharrison> I'll abandon that purchase
[16:08] <edmoore> oh it's not bad
[16:08] <edmoore> but it'll never be as sensitive as a proper rig
[16:09] <edmoore> the whole way those scanners work is different, electrically
[16:09] <rharrison> No but then pay peanuts ...
[16:10] <edmoore> sensitivity 30-1000MHz = 0.5uV
[16:10] <edmoore> vs 0.11 for my yeasu
[16:10] <edmoore> so say 7dB
[16:11] <rharrison> humm so usable for bench testing
[16:11] <rharrison> but not so good in the filed
[16:11] <rharrison> field
[16:11] <edmoore> yup
[16:12] <rharrison> BTW I have come up with a replacement idea for the moxon shiled for tha parachute
[16:12] <rharrison> the
[16:12] <edmoore> moxon shield for a parachute?
[16:12] <rharrison> That bit of card to hold it in place
[16:13] <edmoore> just have the parachute inline
[16:13] <edmoore> works better
[16:13] <rharrison> With drag on the way up?
[16:13] <edmoore> the drag should be 0
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[16:14] <edmoore> the parachute becomes load-bearing
[16:14] <rharrison> I just used a small loop in the line to hold the para in place tied to the hole in the centre of the cute
[16:15] <edmoore> you've got to be careful if doing that
[16:15] <rharrison> Ahh with you and yep that is basically what happens
[16:15] <edmoore> as you could affect the inflation shape of the chute
[16:15] <edmoore> which isn't a huge deal if you just want it to come down in one piece, granted
[16:16] <rharrison> But surely you have the same problem inline when the balloon comes back with the payload it must pull at the top of the chute or am I missing something here?
[16:17] <edmoore> I think the most robust method for this is to have a line up to the parachute's base (the confluence point) from the payload. Then a line from the parachute apex up to the balloon
[16:17] <edmoore> that's no different to the current methods
[16:17] <rharrison> Nicely put edmoore I like the word confluence
[16:17] <edmoore> you can still have the balloon shard fall back down over the chute if its ballistic coefficient is greater than the parachute+payload
[16:18] <edmoore> it's the term in the parachute industry, doncha know
[16:20] <rharrison> Of course pyro cut is cleaner for descent
[16:20] <edmoore> fo sho
[16:22] <rharrison> You going to get pyro working on gyros. Should it be possible to detect burst fast enough to trigger pyro by gyro?
[16:22] <edmoore> accelerometer is a better bet than gyros
[16:22] <edmoore> and yes
[16:22] <edmoore> easy enough with accelerometers
[16:22] <rharrison> Does it matter which plane
[16:22] <edmoore> it wants to be a 3-axis accel
[16:23] <edmoore> then just take thge magnitude of the vector
[16:23] <edmoore> that way the payload can roll all over the place chaotically
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[16:23] <edmoore> in ascent it should feel 1g (gravity)
[16:23] <edmoore> so just wait for it to be, say, <0.2g for 200ms (numbers very rough) as a freefall indicator
[16:24] <rharrison> So the trick will be distinguishing turbulance from burst though the latter will be a more violent event
[16:24] <edmoore> it would be worth logging, but i doubt turbulence would cause an acceleration profile that would be too difficult to discriminate with freefall
[16:25] <edmoore> and you can always arm it in software
[16:25] <rharrison> Any 3 axis acc. on badger2 or cub?
[16:25] <edmoore> i.e. wait till above 20km or something
[16:25] <edmoore> of course!
[16:25] <rharrison> Cool R U going to have a free ish summer?
[16:26] <edmoore> the current setup has 2 x 3 axis accels and a 2-axis accel, 3 axis of gyro, 3 axis of mag
[16:26] <edmoore> I don't know about summer yet. I have something of a job offer on a research project, but not sure if I'm taking it
[16:26] <rharrison> I assume you're not getting a job yet and phd beckoning
[16:26] <edmoore> I think there's going to be lots of rocket activity
[16:26] <edmoore> rockoons are where it's at
[16:26] <rharrison> You need a break from all this studying
[16:27] <edmoore> and all our focus atm is rockety
[16:27] <edmoore> badger2 is really a rocket flight computer
[16:27] <rharrison> + CUSF has been v quiet this year so far
[16:27] <edmoore> well, quiet on balloons
[16:27] <rharrison> Yep
[16:28] <edmoore> but the balloon side of things is easier than the rocket side, and there's a great deal of rocketry bumph to get working before getting something into space
[16:30] <edmoore> we'll be making good use of forthcoming EARS weekends, that's for sure :)
[16:31] <edmoore> and we've nearly finished a 5 degree of freedom rocket motor test stand, which we'll be using to test our carbon fibre rocket motors to see quite what off-axis thrusts we have to deal with
[16:32] <russss> sounds fun
[16:32] <edmoore> will get that up on the wiki as soon as everyone's finished with zams
[16:33] <edmoore> it's quiet atm, fergus and I both have 'finals' and Iain is writing papers for a conference - his first year of PhD is going well!
[16:33] <SpeedEvil> edmoore: the missing axes is roll?
[16:33] <edmoore> yep
[16:34] <edmoore> it measure's axial thrust as usual (z) and x and y at the front and back
[16:34] <edmoore> infact I can fling a pdf up on our site if you guys want to see the cad model
[16:34] <rharrison> http://www.st.com//stonline/products/literature/ds/12726/lis302dl.pdf Might chuck one of these on icarus IV
[16:35] <SpeedEvil> I could see residual roll might be interesting - I can't imagine it being large though
[16:35] <SpeedEvil> And would be hard to measure, as it's so small
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[16:36] <edmoore> i think the roll 'noise power' from the motor would be small compared to fin missalignment
[16:37] <edmoore> right, have found the renderings that Iain and John made up of the rig
[16:37] <edmoore> just uploading
[16:38] <SpeedEvil> I think so too
[16:38] <edmoore> http://www.srcf.ucam.org/~cuspaceflight/testrig.pdf
[16:38] <SpeedEvil> It's a third or fourth order effect
[16:38] <edmoore> it's mechanically more or less complete, just need to make the telemetry/data-logging box
[16:39] <edmoore> that bosch aluminium extrustion is *brilliant*. the suppliers cut it to length for you
[16:39] <edmoore> so our rig arrived pretty much as a flat-pack kit
[16:40] <SpeedEvil> Looks neat.
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[16:40] <edmoore> can't wait to fire something!
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[16:41] <SpeedEvil> you're hybrid?
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[16:41] <edmoore> solid
[16:41] <SpeedEvil> ah
[16:41] <edmoore> need the ISP
[16:41] <SpeedEvil> using commercial propellant?
[16:41] <edmoore> yep
[16:42] <edmoore> but our own case
[16:42] <edmoore> pre-preg carbon fibre pressure vessel lined with a ceramic
[16:42] <edmoore> much lighter than the off the shelf ali
[16:42] <SpeedEvil> Pity regulations make solids annoying.
[16:42] <edmoore> yeah it is a bit
[16:43] <edmoore> trying right now infact to get an explosives store in the eng department
[16:43] <edmoore> for the motors we're about to start burning
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[16:43] <edmoore> right, gtg
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[16:44] <edmoore> Neil seems to be having issues
[16:44] <edmoore> !
[16:44] Nick change: edmoore -> edmoore|away
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[16:49] <futurity> Hi, sorry about all the connection attempts
[16:50] <SpeedEvil> np
[16:50] <futurity> is rharrison still launching tomorrow?
[16:50] <russss> nope, next weekend hopefully
[16:51] <SpeedEvil> (11:38:49 AM) rharrison: Saurday is off for launch. Will be at ears the following w/e with kids if wx is good there will be a launch
[16:51] <futurity> cool
[16:51] <futurity> i couldn't make this weekend and wanted to help out if possible
[16:55] <futurity> looks like that weekend in the Big EARS rocket event
[17:05] <earthshine> What rocket event ?
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[17:18] <futurity> let me find the link
[17:19] <futurity> http://www.ears.org.uk/launches/bigears/index.shtml
[17:30] <DanielRichman> the predictor is hovering just off the coast, taunting us
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[17:42] <earthshine> futurity: thanks
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[17:44] <earthshine> that event looks cool
[17:44] <earthshine> Who is going
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[18:01] <futurity> Well it looks like rharrison is
[18:01] <futurity> not sure which day
[18:02] <futurity> i'm planning to go, not bothered which day so will hopefully try to go when he does
[18:02] <futurity> you never know, we could get everyone together
[18:02] <futurity> at the same launch
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[18:11] <edmoore|away> we might go
[18:11] <edmoore|away> big ears is alwaysd fun
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[20:30] <Lunar_Lander> hello people, I'm not bobby brown, but actually I got my parachute today
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[20:46] <Laurenceb> hi all
[20:47] <Lunar_Lander> hello Laurenceb
[20:47] <Lunar_Lander> how's life?
[20:50] <Laurenceb> not so bad thanks
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[20:51] <Laurenceb> been repairing/cataloguing old staircase parts...
[20:51] <Lunar_Lander> yea
[20:51] <DanielRichman> With an op-amp do bad things happen if the p.d between + and - is greater than that between the opamp's supply lines Vcc and GND?
[20:51] <Lunar_Lander> I had to get my parachute from customs
[20:51] <Lunar_Lander> but now it is here
[20:51] <Lunar_Lander> white-neon yellow-neon orange
[20:51] <Laurenceb> not sure if its worth it... guess if I can assemble the entire thing its worth a few hundered
[20:52] <Lunar_Lander> yes
[20:52] <Lunar_Lander> wanna have something funny?
[20:53] <Laurenceb> maybe...?
[20:54] <jonsowman> DanielRichman: it might do weird things
[20:54] <Lunar_Lander> http://www.youtube.com/watch?v=_hcTrf7WEh8
[20:54] <jonsowman> you'd be unlikely to damage it I think, theyre quite tough
[20:54] <jonsowman> also some will have internal clamping diodes
[20:54] <DanielRichman> OK
[20:55] <SpeedEvil> most have internal clamping diodes
[20:55] <jonsowman> i would avoid it if possible
[20:55] <DanielRichman> I plan to
[20:55] <SpeedEvil> if you drag the inputs outside the rail by >0.6V - expect bad stuff to happen
[20:55] <SpeedEvil> Especially if you supply any current
[20:55] <DanielRichman> got it
[20:57] <DanielRichman> Building a AF str/level indicator & AF amp for Intermediate practical - the signal strength indicator currently is run by a massive (9 diode) potential divider (logarithmically increasing values chosen) with op amps taking the p div's vout into (-); the AF connected to (+) after a cap
[20:58] <DanielRichman> I think I will be amplifying from a 3.5mm jack (0-5v) through an op amp to 0-9v
[20:58] <DanielRichman> from a pp3; was just worried about it running low and busting all the op amps
[20:59] <SpeedEvil> add a 10K resistor on the input
[20:59] <SpeedEvil> problem - largely solved.
[21:00] <DanielRichman> The output of the amplification stage will be the input to the signal strengh meter bit (unless this is a bad idea)
[21:00] <DanielRichman> should I put a 10k before the amp?
[21:01] <DanielRichman> Also: Before measuring sig. str I thought it might be a good idea to put a cap in there to smooth it out a bit; or not necessary; if so would a diode before the cap protect the real amplified signal from being smoothed?
[21:02] <DanielRichman> or should I just use the one left over op-amp (after 10 measuring str & 1 amp on quad chips) as a voltage buffer?
[21:02] <SpeedEvil> Do you have a diagram we can look at?
[21:02] <DanielRichman> I'm making it now
[21:02] <DanielRichman> probably was a good idea to do before asking Qs :P
[21:03] <SpeedEvil> also - why not use the lmwhatever vu-meter chip?
[21:03] <DanielRichman> because there's a tray full of quad op amp chips at school
[21:03] <SpeedEvil> http://www.national.com/pf/LM/LM3915.html
[21:03] <SpeedEvil> ah
[21:03] <SpeedEvil> fair enough
[21:03] <DanielRichman> they looked a bit lonely
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[21:40] <DanielRichman> SpeedEvil, do you prefer PDF PNG or the SCH file?
[21:40] <SpeedEvil> png
[21:40] <SpeedEvil> generally
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[21:45] <DanielRichman> SpeedEvil, http://lh3.ggpht.com/__lkz-FOKbO8/S9IGU4PlgZI/AAAAAAAAAFc/KmdFJ9JkC9s/s800/audio-ampstr.png
[21:46] <SpeedEvil> Ok - as stuff occurs.
[21:47] <SpeedEvil> The integration cap needs a resistor across it, so it decays after 1s or so.
[21:47] <SpeedEvil> you probably want a cap on the af out/in
[21:48] <DanielRichman> on or between af out/in and gnd?
[21:48] <SpeedEvil> between af out, and the actual af out
[21:49] <SpeedEvil> in series with ic3c output
[21:49] <DanielRichman> OK, will do that, thank you
[21:49] <SpeedEvil> The loading of D1/C1 will affect the audio signal a bit (or a lot, depending on their value)
[21:49] <SpeedEvil> Also - what is the power supply on this?
[21:50] <DanielRichman> I will probably use a 9V batt; not ideal
[21:50] <DanielRichman> Is 10uf + 100R OK? for C1 & its Resistor?
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[21:50] <DanielRichman> SpeedEvil, there will be an op amp spare (IC3D; should I use it as a voltage buffer from AF out into C1?)
[21:51] <SpeedEvil> Ah - right. You need in that case to put '0V' at 4.5V
[21:51] <SpeedEvil> no
[21:51] <SpeedEvil> a couple of resistors from 0V to 9V - which = 4.5. A small cap across them to bypass this, then the remaining opamp as a buffer from this.
[21:51] <SpeedEvil> This provides a virtual ground
[21:51] <SpeedEvil> at 4.5V
[21:52] <DanielRichman> I thought that a 3.5mm jack was meant to be a signal centred around 2.5V (is that the reason for the 3-way-power?)
[21:52] <SpeedEvil> Otherwise, the amp can't do 'negative' outputs. Also - the 324 can only source a few mA
[21:52] <SpeedEvil> so a 100R resistor is way too small - 100K and 10uF will have a time constant of around a second
[21:53] <SpeedEvil> is this just a 3.5mm mono jack?
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[21:53] <SpeedEvil> it's generally accepted that you have to decouple the input and output, as the level may vary
[21:53] <DanielRichman> Sorry; must have thought I had 10mF caps (:X); Yes it's just a 3.5mm jack
[21:53] <DanielRichman> well that's easiest
[21:53] <DanielRichman> (I think).
[21:54] <SpeedEvil> Oh - the LED negatives goes to the battery negative - yes.
[21:54] <SpeedEvil> Other than that, all the '0v' should go to a virtual ground at 4.5v
[21:55] <DanielRichman> Will it not (without the virtual ground) just amplify the input signal centred around 2.5V (0-5V) to a 5V centred (0-10V; clipping at 9V) signal?
[21:56] <SpeedEvil> http://www.analog.com/static/imported-files/tutorials/MT-035.pdf
[21:56] <SpeedEvil> skim that
[21:56] <SpeedEvil> there is no centre around 2.5
[21:56] <SpeedEvil> at least - as the general case
[21:57] <SpeedEvil> the DC level is either undefined, or about 0
[21:58] <SpeedEvil> sorry - afk - see #electronics too
[21:58] <DanielRichman> don't worry; thank you for help
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[22:12] <DanielRichman> Hmm I can't remember where I read that 3.5mm jack audio was centred around 2.5V rather than ground
[22:12] <DanielRichman> I guess I made it up
[22:23] Nick change: guysoft422 -> guysoft4
[22:23] Nick change: guysoft4 -> guysoft442
[22:23] Nick change: guysoft442 -> guysoft42
[22:25] <earthshine> yo
[22:27] <Lunar_Lander> hello
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[23:05] <DanielRichman> "Release Candidate:" http://lh6.ggpht.com/__lkz-FOKbO8/S9IZlznMOrI/AAAAAAAAAFo/bv6omo7cRNo/audio-ampstr.png
[23:07] <Lunar_Lander> DanielRichman what is this device?
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[23:07] <DanielRichman> my Intermediate License "project" (we have to make something to prove we can solder; I wanted something not *too* boring (hence it has 10 LEDs) but that can be quickly made using parts lying around in our Tech Department)
[23:08] <DanielRichman> It's an Audio Amplifier + signal strength meter
[23:08] <Lunar_Lander> ah ok
[23:08] <Lunar_Lander> cool!
[23:08] <Lunar_Lander> looks good, I hope your instructor thinks like me
[23:08] <Lunar_Lander> :)
[23:09] <DanielRichman> IC3C (providing I'm not Doin it wrong) amplifies the signal by just under 2; the abuse of op amps on the right hand side lights up the leds as the power increases
[23:09] <DanielRichman> the instructor is fine with it :)
[23:09] <Lunar_Lander> yeah :)
[23:10] <DanielRichman> I now require SpeedEvil's blessing as to whether it will work or not ;)
[23:11] <Lunar_Lander> yes
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[00:00] --- Sat Apr 24 2010