highaltitude.log.20090222

[00:31] <natrium42> jcoxon, here's an idea for redundant valves --> http://www.pegasushabproject.org.uk/wiki/doku.php/private:cross:ballast
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[00:32] <jcoxon> natrium42, tis a lot of valves :-p
[00:32] <natrium42> yeah, 1 more than you plan :P
[00:32] <natrium42> but it's one tank instead of 2
[00:32] <natrium42> dunno, just an idea
[00:33] <jcoxon> yeah i liked the idea of 2 tanks as it balances the payload a little
[00:40] <jcoxon> well i'll get as many valves i can :-p
[00:40] <natrium42> bbl
[00:40] <natrium42> hehe
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[01:30] <Laurenceb> jcoxon: still up?
[01:35] <jcoxon> yes
[01:35] <Laurenceb> I'm just working on the level sensor
[01:35] <jcoxon> okay cool
[01:35] <Laurenceb> theres about 30cm of coax from the board to the sensor
[01:36] <Laurenceb> senor is about 25cm long
[01:36] <Laurenceb> ok?
[01:36] <jcoxon> okay so we mount the ballast tanks direct to the payload
[01:36] <Laurenceb> yeah, on the side was my idea
[01:37] <jcoxon> cool
[01:43] <Laurenceb> you can trim the sensor down if youre careful not to damage the wires inside
[01:44] <jcoxon> so how is the sensor read? adc or i2c
[01:44] <Laurenceb> i2c
[01:44] <Laurenceb> AD7746 on an i2c bus
[01:45] <Laurenceb> I'm just about to solder it in...
[01:45] <jcoxon> okay
[01:45] <Laurenceb> just checking everythings ok with my cap meter
[01:46] <Laurenceb> theres a teemperature sensor on the 7746 as well
[01:46] <jcoxon> okay thats good
[01:47] <Laurenceb> so we can use that for internal temperature
[01:48] <Laurenceb> it has 4aF resolution
[01:48] <jcoxon> so might be best to go for 1 ballast tank
[01:48] <Laurenceb> we'll get ballast height to a few uM :P
[01:48] <jcoxon> as you've sorted the sensor
[01:49] <Laurenceb> unfortunately of course theres going to be slosh
[01:49] <jcoxon> perhaps an average then over a time period
[01:49] <Laurenceb> yeah
[01:50] <Laurenceb> we want to add some sort of ionic solute to the ballast
[01:50] <Laurenceb> so we can check the valve is working/jammed with electrodes
[01:50] <jcoxon> even with ethanol
[01:50] <Laurenceb> NaCl is soluble in ethanol
[01:54] <Laurenceb> I'll put a humidity sensor on as well
[01:55] <Laurenceb> annoyingly I'm out of coax
[01:57] <Laurenceb> I may stick the humid sensor on about 5cm of wire
[01:58] <Laurenceb> so it can be mounted in the side of the foam enclosure or something
[01:58] <jcoxon> yeah thats a good idea
[01:58] <Laurenceb> if we wanted it more than ~10cm away itd need coax
[01:59] <Laurenceb> I used rg-174 for the level sensor
[01:59] <Laurenceb> *rg-178
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[02:07] <Laurenceb> this should be cool, humidity, internal temp and ballast all off one IC :P
[02:11] <jcoxon> :-)
[02:11] <jcoxon> things are coming together
[02:12] <jcoxon> just need these damn valves
[02:13] <Laurenceb> I'll see if I can make the sensors unpluggable
[02:18] <jcoxon> right night Laurenceb
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[02:32] <fergusnoble> Laurenceb: you there?
[02:32] <fergusnoble> want to see something awesome and mysterious?
[02:32] <Laurenceb> yeah
[02:32] <Laurenceb> :-S
[02:32] <Laurenceb> maybe
[02:32] <Laurenceb> as long as its not a part of your body :P
[02:33] <fergusnoble> http://imagebin.org/38997
[02:33] <Laurenceb> whats that?
[02:33] <fergusnoble> hallam and i just took this image trying to characterise the noise of the camera on the star tracker
[02:34] <Laurenceb> ah ok
[02:34] <fergusnoble> thats a 4sec exposure with the lens cap on
[02:34] <fergusnoble> can you guess what it is?
[02:34] <fergusnoble> hint: its not the lens cap or lens
[02:34] <Laurenceb> something to do with the lithography?
[02:34] <fergusnoble> (we tried rotating the lens assy and the pattern didnt rotate)
[02:35] <fergusnoble> not exactly
[02:35] <Laurenceb> what camera?
[02:35] <fergusnoble> OV9655
[02:36] <Laurenceb> what do you think it is?
[02:36] <fergusnoble> do you give up?
[02:36] <Laurenceb> yes
[02:36] <fergusnoble> its the bga balls and their bonding wires
[02:37] <fergusnoble> not sure how its being imaged but the pitch matches exactly
[02:37] <fergusnoble> im guessing its thermal
[02:37] <Laurenceb> oh yeah
[02:37] <Laurenceb> or maybe stress
[02:38] <Laurenceb> how are you controlling it?
[02:38] <Laurenceb> blackfin library?
[02:38] <fergusnoble> with great difficulty
[02:39] <fergusnoble> we've spent all night trying to work out what all the registers do as the datasheet is really bad
[02:39] <fergusnoble> its controlled through i2c and a parallel data iface
[02:39] <Laurenceb> couldnt you modify the blackfn lib?
[02:40] <fergusnoble> there is no blackfin lib
[02:40] <fergusnoble> this isnt an issue as we never do 4 sec exposures on full gain with the lens cap on
[02:40] <Laurenceb> oh, its the the surveyor cam?
[02:40] <fergusnoble> its just interesting
[02:40] <fergusnoble> yeah
[02:41] <Laurenceb> why not sure the surveyor cam?
[02:41] <fergusnoble> ?
[02:42] <Laurenceb> the one with the surveyor board
[02:42] <fergusnoble> we are using that
[02:43] <Laurenceb> oh ok sorry
[02:43] <Laurenceb> so isnt there a libaray for controlling it?
[02:43] <fergusnoble> no
[02:43] <Laurenceb> sucks
[02:44] <fergusnoble> there was some example code but it doesnt do waht we need
[02:49] <Laurenceb> are you actually going to be doing star tracking then?
[02:49] <fergusnoble> not for the rocket or anything, its for henry's 4th year project
[02:49] <fergusnoble> im just helping out a bit
[02:49] <Laurenceb> ah ok
[02:51] <Laurenceb> sounds cool
[03:48] <Laurenceb> right ballast/temp/humi sensor is finished :P
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[09:07] <Laurenceb> morning guys
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[09:52] <jcoxon> morning all
[09:52] <jcoxon> ping natrium42
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[10:57] <jcoxon> hey Laurenceb you around?
[11:22] <jcoxon> Laurenceb, http://www.gidenstam.org/FlightGear/JSBSim-LTA/
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[14:12] <edmoore> greetings everyone
[14:12] <jcoxon> hello edmoore
[14:12] <edmoore> hi jimbo. all well?
[14:13] <jcoxon> yes, thanks - you?
[14:13] <edmoore> fergusnoble: if you can face a rabble, loughy and I are doing a joint b-day drinks/food thing at the castle tonight, 7.30
[14:13] <edmoore> I'm good thanks jcoxon, just popped home today for a birthday lunch
[14:13] <jcoxon> oh cool
[14:14] <jcoxon> happy birthday - for a couple of days ago
[14:14] <jcoxon> :-D
[14:15] <shellevil> Me too - if I diddn't say.
[14:16] <edmoore> hapy bday shellevil !!
[14:16] <edmoore> oh no wait
[14:16] <edmoore> i get it
[14:17] <shellevil> http://www.cypress.com/products/?gid=12&fid=208
[14:18] <shellevil> interesting cameras - I don't know if they are readily available though - used to be before cypress bought them - even 'B' grade ones with defects cheap
[14:20] <shellevil> Interesting as they can readout while integrating.
[14:21] <shellevil> And some of them are even pixel addressable
[14:21] <edmoore> oh....
[14:21] <edmoore> reading out while integrating is very interesting indeed
[14:21] <shellevil> so you can - forex - readout the array every Hz, and at the same time read 4*4 pixels at 1MHz
[14:22] <edmoore> you see why i might be interested then :)
[14:23] <shellevil> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CYIL1SM0300AA-QDC-ND
[14:25] <edmoore> sod that
[14:27] <jcoxon> hehe
[14:30] <SpeedEvil> yes, it's a bit more.
[14:30] <SpeedEvil> But 450fps!
[14:50] <SpeedEvil> I think that's a magnitude 6 star being about equivalent to thermal noise with a 12mm F/1.2 lens or so.
[14:51] <SpeedEvil> And maybe a magnitude 5 star at 450fps.
[14:53] <SpeedEvil> Hmm. That violates the lens angle recommendations tho.
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[15:21] <SpeedEvil> http://focus.ti.com/docs/prod/folders/print/tx285spd-31.html I wish were readily available.
[15:21] <SpeedEvil> (the TI 'impactron' solid state amplified CCD)
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[15:27] <sYx66> these sensors are sick :D
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[17:01] <SpeedEvil> mirk: yeah - completely random numbers generally
[17:01] <SpeedEvil> oops
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[17:21] <Xenion> Hallo alle miteinander / Good Evening ! :-)
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[18:07] <hallam> hey all
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[18:49] <Laurenceb> hello
[18:49] <Laurenceb> http://www.walkingclub.org.uk/
[18:49] <Laurenceb> ^ scrollable os maps :P
[19:04] <SpeedEvil> leave it
[19:04] <SpeedEvil> oops
[19:04] <SpeedEvil> possibly not legally.
[19:05] <SpeedEvil> Oh.
[19:05] <SpeedEvil> I see - they've taken an innovative solution to avoiding problems with copyright.
[19:05] <SpeedEvil> Take over 75 years to load.
[19:05] <Laurenceb> hehe
[19:05] Action: Laurenceb just walked to Dorking
[19:06] <Laurenceb> ~15 miles
[19:06] <SpeedEvil> :)
[19:06] <sYx66> why do you need a book to go on a walk?
[19:06] <Laurenceb> a book?
[19:06] <Laurenceb> oh that site
[19:07] <Laurenceb> hehe yeah I just thought it was good for the maps
[19:11] <sYx66> yeah
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[21:27] <jcoxon> evening all
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[21:47] <natrium42> hi jcoxon
[21:47] <jcoxon> hey natrium42
[21:50] <jcoxon> how are things?
[21:51] <natrium42> pretty good, how are you?
[21:52] <jcoxon> yeah, might have been in the pub for the past 6 hrs
[21:52] <jcoxon> had to leave as we might have been a little rowdy
[21:53] <jcoxon> :-p
[21:53] <jcoxon> oh well
[21:53] <natrium42> hehe
[21:53] <jcoxon> they didn't throw us out so we can go back again perhaps in a weeks time
[21:53] <jcoxon> you?
[21:53] <natrium42> bbl coffee time
[21:53] <jcoxon> np
[21:54] <natrium42> about to start writing a small usb driver
[21:54] <natrium42> for business
[21:54] <jcoxon> oh okay
[21:54] <natrium42> bbl, sorry
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[22:55] <jcoxon> hey henry
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[23:05] <hallam> hey
[23:06] <hallam> http://www.mibbit.com/up/Idc86Gxx.jpg
[23:10] <jcoxon> oooo it works!
[23:15] <Laurenceb> hallam: v nice
[23:16] <Laurenceb> hallam: whats the aperture of the lens and exposure?
[23:17] <jcoxon> hey Laurenceb did you see my link earlier today?
[23:17] <Laurenceb> yeah interesting
[23:17] <jcoxon> possibly helpful in modelling
[23:17] <Laurenceb> I've been trying to get the level sensor working... theres some annoying problems atm
[23:18] <Laurenceb> hmm I hardly need a gui
[23:18] <jcoxon> oh?
[23:18] <jcoxon> the oh is for the problems
[23:19] <Laurenceb> just some code to simulate envelope heating ect
[23:20] <jcoxon> what are the problems with sensor
[23:21] <Laurenceb> the cap to digital convertor seems to have infinite sensitivity
[23:21] <Laurenceb> it flips from 0xFFFFFF to 0x000000
[23:26] <jcoxon> strange
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[23:42] <Laurenceb> no cant get it to do anyting :-/
[23:42] <Laurenceb> the temp sensor has a perminent busy status as well
[23:43] <hallam> Laurenceb: it was about 4 sec exposure, 16mm focal length, f/1.2
[23:43] <Laurenceb> if I turn off the oscillator so the convertor is just getting noise then theres noisy values
[23:43] <Laurenceb> hallam : cool
[23:43] <Laurenceb> I'm thinking mybe it got damaged somehow :-(
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[23:46] <Laurenceb> but I only ordered one of them :-(
[23:48] <Laurenceb> hallam: whats the basic algorythm for finding your attitude from a starfield?
[23:49] <hallam> 1. detect stars (isolate them from noise, find their positions in the frame and optionally magnitudes)
[23:49] <hallam> 2. identify which stars they are
[23:49] <hallam> 3. do coordinate transform to get attitude
[23:50] <hallam> 4. track them as they move across the frame rather than having to reacquire them each frame
[23:50] <Laurenceb> its part 2 that confuses me
[23:50] <hallam> there are a bunch of ways
[23:50] <hallam> some just use the angular distance between pairs of stars
[23:51] <hallam> some also use the shape information (the angle between sides of a triangle)
[23:53] <Laurenceb> ok
[23:53] <Laurenceb> brightness?
[23:53] <hallam> algorithms that I'm aware of don't use it
[23:53] <hallam> but in principle you could
[23:54] <hallam> there are issues with sensor/lens degradation and stuff that make it kind of hard to accurately determine the magnitude of an observed star
[23:55] <Laurenceb> yeah, but you could use relative
[23:58] <hallam> yeah
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[23:58] <hallam> there are only like 4000 stars below mag 5 anyway so it's not that critical
[23:58] <Laurenceb> ok
[23:59] <Laurenceb> hmm guess it would never be fast enoug for running with an IMU?
[00:00] --- Mon Feb 23 2009