highaltitude.log.20090315

[00:01] Action: natrium42 brings out the whip
[00:07] Action: SpeedEvil ponders GPS guided whips.
[00:13] <Laurenceb> ok breadboard setup s done
[00:13] <Laurenceb> usb- serial - atmega168 -i2C - AD7746 - cap sensor in glass of water
[00:16] <SpeedEvil> :)
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[00:18] <Laurenceb> treble check the pinouts time :P
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[00:26] <SpeedEvil> you're not overvolting the ad7...?
[00:31] <Laurenceb> it can take up to 5.5v
[00:32] <SpeedEvil> you are doing the antistatic environemnt thing?
[00:32] Action: SpeedEvil passes Laurenceb a can of apple-scented ani-static pledge.
[00:32] <Laurenceb> well I dont have an antistatic work area
[00:32] <Laurenceb> but I try to be careful
[00:32] <Laurenceb> keep myself grounded ect
[00:33] <SpeedEvil> the above suggestion isn't actually silly
[00:33] <Laurenceb> yeah sure
[00:33] <SpeedEvil> works well
[00:33] <SpeedEvil> though IIRC you had same problems replacing the chip didnd't yoiu
[00:33] <Laurenceb> yeah identical
[01:00] <Laurenceb> hmm after reading the datasheet I suspect something may be wrong with my I2C timing
[01:00] <Laurenceb> as the timing specs change with supply voltage
[01:00] <Laurenceb> and it only works at all at 5V
[01:01] <Laurenceb> I'm using a usb-i2c convertor atm and its poorly documented
[01:01] <SpeedEvil> :)
[01:02] <Laurenceb> at 3.3v it doesnt respond to its address byte
[01:06] <Laurenceb> my usb-i2c is probably 400Khz or something
[01:06] <Laurenceb> grr i need a scope
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[02:11] Action: shellevil would offer, but you're a bit far.
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[04:46] <Laurenceb> muhahah
[04:47] <Laurenceb> cap sensor is working
[04:48] <natrium42> Laurenceb, ooh, awesome
[04:48] <natrium42> what was wrong?
[04:48] <Laurenceb> my usb to i2c thingy had weird timing
[04:49] <Laurenceb> I'm wring some groovy code now to give water level and stuff
[04:49] <Laurenceb> I'll try and put together a library you can use on the payload
[04:49] <natrium42> coolz
[04:49] <natrium42> good job
[04:50] <natrium42> i just soldered one of those venus + sarantel pcbs
[04:50] <Laurenceb> should have ballast level, humidity and temperature
[04:50] <Laurenceb> neat
[04:50] <natrium42> it's receiving position inside the house
[04:50] <Laurenceb> hey wow
[04:50] <natrium42> although at the window
[04:50] <Laurenceb> how long to lock?
[04:50] <natrium42> let me check if it works further away
[04:50] <natrium42> 10 mins to lock
[04:51] <Laurenceb> ok... its hard to come up with a good test
[04:51] <Laurenceb> my lassen iq can sometimes get a lock at the window
[04:51] <Laurenceb> but they are so vulnerable to EMI
[04:51] <Laurenceb> have you tried 10Hz update?
[04:52] <natrium42> yeah, still getting a fix away from window
[04:52] <Laurenceb> neat
[04:52] <natrium42> no, that's the old rom version i got for free
[04:52] <Laurenceb> try 10Hz :P
[04:52] <Laurenceb> oh ok
[04:52] <natrium42> it's 1Hz only
[04:52] <Laurenceb> yeah
[04:53] <natrium42> but 25 pieces free, can't complain :P
[04:53] <Laurenceb> it'll be interesting to see how the noise goes up
[04:53] <Laurenceb> yeah
[04:53] <natrium42> do you want to wait for the 10Hz version?
[04:53] <Laurenceb> I just spent ages kicking avr studio into gear :-/
[04:53] <Laurenceb> yes
[04:53] <natrium42> k
[04:53] <Laurenceb> it was linking to the wrong libraries :-S
[04:54] <natrium42> haha
[04:54] <Laurenceb> sometimes having a gui just makes things more complex
[04:54] <natrium42> happens
[04:54] <natrium42> yeah, i am considering switching away from avr studio
[04:54] <natrium42> it has debugging, but i don't really like the editor
[04:54] <Laurenceb> yeah ubuntu makes it easy
[04:54] <natrium42> and rarely use debugging
[04:54] <Laurenceb> me neither
[04:55] <natrium42> printfing to serial port is where it's at :P
[04:55] <Laurenceb> but my programmer is windows only
[04:55] <Laurenceb> its how they do it with satellite hardware :P
[04:55] <Laurenceb> so must be the way to go
[04:55] <natrium42> haha, they do?
[04:55] <natrium42> in iran?
[04:55] <Laurenceb> yeah rs232 or CAN for everything
[04:56] <Laurenceb> no here
[04:56] <natrium42> :P
[04:56] <natrium42> rs232 is nice
[04:56] <Laurenceb> the gps receivers use a ripoff of TSIP
[04:57] <Laurenceb> although the guy who wrote the interface denied it
[04:57] <natrium42> wait, they use gps receivers on satellites?
[04:57] <Laurenceb> yes
[04:57] <natrium42> cool
[04:57] <Laurenceb> thats what my phd involves
[04:57] <natrium42> what if the satellite is above gps satellites?
[04:58] <natrium42> i guess you can still triangulate
[04:58] <Laurenceb> yeah
[04:58] <Laurenceb> even up to geostationary
[04:58] <natrium42> i didn't know they used gps navigation for sats too, pretty cool
[04:59] <Laurenceb> http://www.sstl.co.uk/assets/Downloads/SGR-10%20v7_08.pdf
[04:59] <Laurenceb> thats what I'm using
[04:59] <Laurenceb> for collecting data atm
[04:59] <natrium42> neat
[04:59] <natrium42> does it still have to conform to US limits? :P
[04:59] <Laurenceb> nope
[05:00] <Laurenceb> hence why its so expensive
[05:00] <Laurenceb> and outdated :P
[05:00] <natrium42> as long as ti works
[05:00] <natrium42> *it
[05:01] <Laurenceb> runs on 29V O_o
[05:02] <natrium42> weird
[05:02] <Laurenceb> most sat stuff does
[05:02] <Laurenceb> so it can connect directly to the battery
[05:03] <Laurenceb> theres no central power system in most designs I dont think... guess it improves reliability
[05:03] <Laurenceb> the flight computer just commands stuff to turn onto standby
[05:08] <natrium42> sts launch today :)
[05:09] <natrium42> Laurenceb, are you using any i2c library for avr?
[05:09] <natrium42> i am about to play with those i2c temp sensors i put onto the pcb
[05:13] <Laurenceb> theres code on the wiki
[05:14] <Laurenceb> under code i2ceeprom
[05:14] <Laurenceb> but theres a couple of ; after while loops
[05:14] <shellevil> stswhen?
[05:14] <Laurenceb> need to delete them
[05:14] <Laurenceb> http://wiki.ukhas.org.uk/code:i2c_eeprom
[05:15] <natrium42> shellevil, http://spaceflightnow.com/shuttle/sts119/fdf/119flightplan.html
[05:15] <Laurenceb> just fixed it
[05:16] <Laurenceb> /----------General I2C functions--
[05:16] <Laurenceb> should do the job
[05:16] <natrium42> cool
[05:21] <Laurenceb> http://www.mibbit.com/pb/QtvhzL
[05:21] <Laurenceb> my extremely scrappy ad7746 code
[05:22] <natrium42> looks good
[05:23] <Laurenceb> thats just to test everything works
[05:25] <natrium42> ok, i2c code seems to compile with some changes
[05:26] <natrium42> now i need to write code to talk to the MCP9800 temp sensor
[05:52] <Laurenceb> what sensors are onboard?
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[06:05] <Laurenceb> arg this code is going into a reset loop
[06:06] <natrium42> Laurenceb, just a temp sensor
[06:06] <natrium42> but i could connect other external sensors
[06:06] <natrium42> brb, reboot
[06:06] <Laurenceb> http://www.mibbit.com/pb/UQunuo
[06:06] <Laurenceb> k
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[06:11] <natrium42> nice, it got 10 satellites inside the house
[06:12] <Laurenceb> sweet
[06:12] <Laurenceb> good as my lassen out in the open
[06:12] <natrium42> :)
[06:13] <Laurenceb> hmf I cant solve this reset loop :-/
[06:13] <natrium42> helix antennas are nice too
[06:13] <Laurenceb> http://www.mibbit.com/pb/UQunuo
[06:13] <Laurenceb> its just saying hello world over and over
[06:13] <natrium42> watchdog is off?
[06:13] <Laurenceb> havent touched the watchdog
[06:13] <natrium42> you need to switch it off
[06:14] <Laurenceb> no
[06:14] <natrium42> wdt_disable();
[06:14] <Laurenceb> its fine it its nver turned on
[06:14] <Laurenceb> thats not the problem
[06:14] <natrium42> dunno, some avrs seem to have it on by default
[06:16] <Laurenceb> hmm I'll add tons of comments
[06:16] <Laurenceb> still think theres a problem with libraries
[06:16] <Laurenceb> wish I had a programmer running on ubuntu, I feel so much more confident its working properly on ubuntu
[06:17] <natrium42> :S
[06:17] <Laurenceb> hmm as I¬ thought
[06:17] <Laurenceb> humidity+=(float)(((unsigned long)i2cread(_AK_))<<(8*(n-1)))/1.67e8;
[06:18] <Laurenceb> resets the uC
[06:18] <natrium42> are you using the newest winavr?
[06:18] <Laurenceb> erm think so
[06:18] <Laurenceb> at least the newest non beta
[06:19] <Laurenceb> but my installation of avr studio is from 2007
[06:19] <Laurenceb> so I'm linking to the new libraries
[06:19] <Laurenceb> and its a pain to setup
[06:20] <Laurenceb> I deleted the old ones and replaced them with the new libraries
[06:20] <Laurenceb> but for some reason thats not enough
[06:20] <natrium42> weird
[06:20] <Laurenceb> I dont understand
[06:20] <Laurenceb> I'm so tempted to format c
[06:21] <Laurenceb> would probably save time in the long run
[06:21] <Laurenceb> its a tip on here
[06:21] <Laurenceb> anyway... whats wrong with that line of code?
[06:24] <natrium42> looks good to me
[06:25] <Laurenceb> hmm something wrong with the floating point lib maybe
[06:29] <natrium42> they had problems with it in the past
[06:29] <natrium42> Laurenceb, getting I2Cerr == 0x02
[06:29] <natrium42> :S
[06:30] <Laurenceb> no ack
[06:31] <Laurenceb> pull up resistors in place?
[06:31] <natrium42> yeah
[06:31] <Laurenceb> slower clock?
[06:32] <Laurenceb> correct address? :P
[06:32] <natrium42> address is sent without problems and it's straight from datasheet
[06:33] <natrium42> it chokes on the 2nd byte sent
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[06:54] <natrium42> ah, i am an idiot
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[06:58] <Laurenceb> lol
[07:01] <natrium42> still one weird thing remains
[07:01] <natrium42> getting 1001011 instead of 10010110
[07:01] <natrium42> it's shifted by 1 bit
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[07:06] Action: natrium42 removes printfs between i2c transactions
[07:06] <natrium42> nope, still same problem
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[07:16] <Laurenceb> I cant believe how windows manages to suck so much
[07:16] <Laurenceb> it now bluescreens each time I connect my board
[07:17] <Laurenceb> something is seriously wrong here :-/
[07:19] <natrium42> lol
[07:19] <natrium42> you should reinstall..
[07:19] <Laurenceb> guess it would make a neat prack usb stick
[07:19] <Laurenceb> *prank
[07:19] <Laurenceb> the bluestick
[07:24] <natrium42> XD
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[07:28] <Laurenceb> hello
[07:28] Action: Laurenceb gave up
[07:28] <Laurenceb> ubuntu time
[07:28] <Laurenceb> apparently its possible to use my programmer from ubuntu
[07:31] <natrium42> :)
[07:31] <natrium42> did you ever see received bytes shifted by one?
[07:32] <natrium42> as if last bit is not received?
[07:32] <Laurenceb> hmm
[07:32] <Laurenceb> maybe you need a stop and start or something
[07:33] <natrium42> not according to docs
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[07:56] <Laurenceb> sweet
[07:56] <Laurenceb> got it working under ubuntu
[07:56] <Laurenceb> well the programmer anyway
[07:57] <Laurenceb> just have to run the makefile and it compiles and flashes :D
[07:59] <natrium42> cool
[07:59] <Laurenceb> screw avr studio
[07:59] <natrium42> bah, damn i2c
[07:59] <natrium42> maybe it's a hardware problem
[07:59] <natrium42> in the 2560
[08:00] <natrium42> i could always use software i2c...
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[08:08] <Laurenceb> damn even ubuntu isnt safe
[08:09] <natrium42> what happened?
[08:09] <Laurenceb> X hung
[08:15] <Laurenceb> hmm this is looking good
[08:16] <Laurenceb> right... need to decrease the ADC clock and average a lot of samples
[08:16] <Laurenceb> then make a refreshing terminal display
[08:17] <Laurenceb> how can I move the curser to the top of the terminal in linux?
[08:17] <Laurenceb> putchar(12); ?
[08:19] <natrium42> use ansi escape sequence
[08:23] <Laurenceb> whats that?
[08:29] <natrium42> http://en.wikipedia.org/wiki/ANSI_escape_code
[08:29] <natrium42> you can control the cursor with special codes
[08:41] <natrium42> meh, it works
[08:45] Action: natrium42 zzz
[08:46] Action: Laurenceb has level in cm
[08:46] <Laurenceb> sweet dreamz
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[09:55] <jcoxon> morning all
[10:09] <Laurenceb> hi jcoxon
[10:09] <Laurenceb> I've got the sensor working
[10:10] <jcoxon> amazing
[10:10] <jcoxon> thats really good news
[10:10] <jcoxon> ready to be sent over?
[10:10] <Laurenceb> almost
[10:11] <Laurenceb> its talking ok, but I'm still not sure about the performance
[10:11] <Laurenceb> I'm hoping theres electrolytic effects
[10:11] <Laurenceb> as the ends of the wires arent sealed yet
[10:11] <jcoxon> okay
[10:11] <Laurenceb> temperature and humidity works
[10:11] <jcoxon> thats good
[10:12] <jcoxon> Laurenceb, well we also record time that ballast valve has been open and roughly approximate how much has been dumped
[10:12] <Laurenceb> yeah
[10:12] <jcoxon> just in case
[10:13] <Laurenceb> 24C here
[10:16] <jcoxon> temp?
[10:16] <Laurenceb> yes
[10:16] <Laurenceb> aha
[10:16] <Laurenceb> I just shook some water droplets of the ends of the wires
[10:16] <Laurenceb> and the capacitance changed by miles
[10:17] <Laurenceb> I'll have to seal them with epoxy
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[10:17] <jcoxon> Laurenceb, great
[10:17] <Laurenceb> then I'll do another test, but I'm pretty sure it'll work
[10:18] <jcoxon> how long is the sensor?
[10:18] <Laurenceb> 31cm
[10:19] <jcoxon> okay
[10:19] <jcoxon> and it sits inside the tank
[10:19] <Laurenceb> yeah
[10:20] <Laurenceb> theres coax out the top
[10:20] <Laurenceb> 27cm of coax
[10:24] <jcoxon> so does it go sensor---coax---ADxxxx---Flight 'puter?
[10:25] <Laurenceb> yep
[10:26] <jcoxon> and the temp sensor is next to ADxxxx
[10:26] <Laurenceb> its no the ic
[10:27] <jcoxon> okay
[10:27] <jcoxon> wondering if it would be worth putting a temp sensor into the ballast tank itself?
[10:27] <jcoxon> as that sort of info would be helpful to solve any problems we might encounter
[10:30] <Laurenceb> dont think so
[10:33] <Laurenceb> just epoxying...
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[10:45] <MOTEK> mornin all
[10:45] <MOTEK> jcoxon: where are you geographically?
[10:46] <jcoxon> hey MOTEK
[10:46] <jcoxon> i'm in S London
[10:47] <jcoxon> Canada Water
[10:47] <MOTEK> cool
[10:47] <MOTEK> what's there?
[10:48] <jcoxon> as in?
[10:49] <jcoxon> there are shops, cinema and bowling alley
[10:49] <MOTEK> what's taking you to that bit of lond?
[10:49] <jcoxon> its where i live
[10:50] <MOTEK> ah right
[10:50] <MOTEK> thatt's a good answer
[10:50] <jcoxon> :-)
[10:50] <Laurenceb> back
[10:50] <Laurenceb> ok this is weird
[10:50] <Laurenceb> its fluctuating all over the place
[10:51] <Laurenceb> maybe bubble formation or something
[10:51] <Laurenceb> there lots of chlorine coming out on the electrodes :-/
[10:52] <Laurenceb> I'm going to see if it stabilises then add about 1cm of water
[10:52] <Laurenceb> I'd be interesting to plot this...
[10:52] <jcoxon> MOTEK, from the looks of your IP you aren't in cam or at home home...
[10:52] <MOTEK> nope
[10:52] <MOTEK> at tess's
[10:52] <MOTEK> E15
[10:53] <jcoxon> nice
[10:53] <MOTEK> can see the dome and wharf
[10:53] <jcoxon> se16
[10:53] <MOTEK> beautiful morning
[10:53] <jcoxon> so can I
[10:53] <MOTEK> you're like the mirror image of me relative to the thames
[10:54] <jcoxon> tis a nice day
[10:56] <MOTEK> we should beer some time
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[10:57] <jcoxon> yeah, there is a pub near me which is nice to sit in
[10:57] <jcoxon> especially in the summer as it has a deck onto the thames
[10:58] <MOTEK> aweso e
[10:58] <MOTEK> m
[10:58] <jcoxon> how often are you down in londinium?
[10:58] <MOTEK> eee keyboard means typos sorry
[10:58] <MOTEK> increasingly so
[10:58] <MOTEK> especially this holiday
[10:58] <MOTEK> probs weekly at least
[10:59] <jcoxon> oh cool
[10:59] <jcoxon> well i'm around and about
[10:59] <MOTEK> cool
[10:59] <jcoxon> got exams in 2 weeks but apart from that...
[10:59] <MOTEK> need to get natrium42 over
[10:59] <jcoxon> hehe
[10:59] <jcoxon> he is busy sending balloons to us!
[10:59] <MOTEK> natrium42: fancy a visit to london?
[11:01] <jcoxon> MOTEK, did you get the invite to the atlantic-halo mailing list thingy?
[11:01] <Laurenceb> hes asleep
[11:01] <MOTEK> timezone schminezon e
[11:01] <MOTEK> right, now i can soend a few weeks doing balloontastic stuff
[11:03] <Laurenceb> hmm this doesnt exactly work well
[11:03] <jcoxon> :-)
[11:03] <Laurenceb> jcoxon: its not really working
[11:03] <jcoxon> crap
[11:03] <Laurenceb> think its partly the chlorine
[11:04] <Laurenceb> it might be better with alcohol
[11:04] <jcoxon> hmmmmm,
[11:04] <jcoxon> is it going to be reliable?
[11:04] <Laurenceb> dont know
[11:04] <jcoxon> shall i have a play with a range sensor? as an alternative idea
[11:04] <Laurenceb> theres also a meniscus between the two wires
[11:05] <Laurenceb> that should be less severe with alcohol right?
[11:05] <jcoxon> not sure
[11:07] <Laurenceb> medics should know all about the effects of alcohol
[11:07] <jcoxon> yeah but not on the meniscus between 2 wires
[11:07] <Laurenceb> :P
[11:07] <jcoxon> the effects on the cerebellum yes
[11:09] <gordonjcp> and I suppose if you've got alcohol *and* two wires in your cerebellum then you've basically got enough to worry about already
[11:10] <jcoxon> hehe
[11:10] <jcoxon> its true the meniscus is just a detail to the larger issue at hand
[11:10] <Laurenceb> http://macro.lsu.edu/howto/solvents/Surface%20Tension.htm
[11:11] <jcoxon> Laurenceb, so there will be a larger meniscus
[11:11] <jcoxon> oh wait
[11:11] <jcoxon> smaller sorry
[11:11] <Laurenceb> so for methanol is 1/2.5 times as high
[11:12] <Laurenceb> - density is slightly lower as well
[11:12] <Laurenceb> ok... its stable at 5.03pF with no water
[11:13] <Laurenceb> 4.7
[11:13] <Laurenceb> with 5cm
[11:13] <Laurenceb> but its straignth away gone up to 5.2
[11:14] <Laurenceb> it just gets stuck at 5.2
[11:14] <jcoxon> hmmm
[11:15] <jcoxon> not good
[11:15] <Laurenceb> I've now added 10cm of water
[11:16] <Laurenceb> if I blow down the tube nothing changes
[11:17] <Laurenceb> I suspect theres a mensicus between the two wires most of the way up, and due to the v high permittivity of water that saturating it
[11:18] <Laurenceb> there are small changes, but its all in the noise
[11:18] <Laurenceb> think theres lots of noise due to chlorine bubbles
[11:18] <jcoxon> got any alcohol to hand? e.g. white spirit?
[11:18] <Laurenceb> fraid not
[11:19] <Laurenceb> ooh I do have some distilled water
[11:19] <jcoxon> oh wait white spririt isn't alcohol
[11:19] <jcoxon> oops
[11:24] <Laurenceb> oh well
[11:24] <Laurenceb> the humidity sensor can detect my breath :P
[11:24] <jcoxon> i'll have a play later with a range sensor
[11:27] <Laurenceb> ir ?
[11:27] <Laurenceb> I'll see if I can find some meths
[11:27] <jcoxon> Laurenceb, yeah
[11:35] <jcoxon> bbl
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[11:53] <Laurenceb> me too
[11:53] Laurenceb (n=laurence@dyres221-35.surrey.ac.uk) left irc: "The day microsoft make something that doesnt suck is the day they make a vacuum cleaner"
[11:54] <gordonjcp> bah, they've both left
[11:55] <gordonjcp> tape head cleaning fluid would have worked
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[12:41] <MOTEK> what about one of those IR range sensors?
[12:41] <MOTEK> they're cool
[12:42] <MOTEK> and a float
[12:48] <jcoxon> MOTEK, just connecting one to my arduino
[12:48] <jcoxon> as we speak
[12:48] <MOTEK> the sharp thingamies?
[12:48] <jcoxon> yeah
[12:48] <jcoxon> i've got a GP2D12
[12:49] <MOTEK> cool
[12:49] <MOTEK> they're nice
[12:51] <MOTEK> i want to build something which uses an array of them
[12:51] <MOTEK> not sure what though
[12:52] <jcoxon> haha
[12:54] <MOTEK> can't use two at once i presume
[12:54] <MOTEK> in the same direction
[12:55] <jcoxon> i assume not
[12:58] <jcoxon> hmmm ship in a bottle situation
[12:58] <jcoxon> need to get a float into this 2L bottle
[12:58] <jcoxon> though don't really want to cut it open
[13:00] <MOTEK> expandi9ng foam?
[13:01] <MOTEK> bbl
[13:01] <MOTEK> back to cam
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[14:16] <Laurenceb> hello
[14:16] Action: Laurenceb has meths
[14:17] Action: Laurenceb drinks the meths
[14:17] <Laurenceb> mmmm refreshing
[14:22] <Hiena> Grrrr...
[14:23] <Hiena> Well, the telemetry works, but the GPS speedup isn't.
[14:23] <Laurenceb> what are you doing?
[14:24] <Hiena> I hopes it's just a minor sofware versioning error.
[14:24] <Hiena> UAV.
[14:24] <Laurenceb> nice
[14:24] <Laurenceb> is there a webpage?
[14:24] <Hiena> Small scale.
[14:24] <Hiena> Nope.
[14:24] <Laurenceb> what are you doing for guidance?
[14:25] <Hiena> GPS, accelerometers, AA and slip sensors, pressure sensors and a serial telemetry hooked to a ATMEGA32.
[14:26] <Laurenceb> nice
[14:26] <Laurenceb> AA and slip sensors are fins?
[14:26] <Hiena> Jup, with magnetic angle sensors.
[14:26] <Laurenceb> I see
[14:26] <Laurenceb> thats interesting
[14:27] <Laurenceb> lots of autopilots go for an IMU and little/no airflow sensing
[14:27] <Laurenceb> how many accelerometers?
[14:27] <Hiena> Two three axis.
[14:28] <Laurenceb> ok, at either end of the fusalage?
[14:28] <Hiena> Fuselage and the wingtip.
[14:28] <Laurenceb> hmm... ok....
[14:28] <Hiena> I want to measure the wing deformation.
[14:29] <Laurenceb> right
[14:29] <Laurenceb> so this isnt designed just with guidance in mind?
[14:29] <Laurenceb> you dont need all these sensors just to fly right?
[14:29] <Hiena> The system main purpose not making a wrking UAV rather a "poor man wind tunnel".
[14:30] <Laurenceb> right
[14:30] <Laurenceb> hmm
[14:30] <Laurenceb> so what is your plan for guidance using these sensors?
[14:30] <Laurenceb> from what I've seen trying to make an autopilot with just accelerometers is very hard
[14:31] <Laurenceb> and gps is laggy/slow/noisy
[14:32] <Hiena> Well, the GPS is keeping the heading, and the pressure sensor keeping the programmed altitude, the AA sensor will be looped to the elevator keeping the AA in bay.
[14:33] <Laurenceb> hmm ok
[14:33] <Hiena> The accelerometers is the safety until i could get a gyro.
[14:33] <Laurenceb> I've tried using gps for heading hold and it wasnt fast enough
[14:33] <Laurenceb> what update rate on the gps?
[14:34] <Hiena> 1 second at this moment.
[14:34] <Laurenceb> hmm which chip?
[14:35] <Hiena> PGM-248 gps.
[14:35] <Laurenceb> not sure it will work, but using AA for pitch control sounds like a nice idea
[14:35] <Laurenceb> not heard of it
[14:36] <Hiena> Will work because it will be connected to the visual horisont and mapping.
[14:36] <Laurenceb> sure
[14:36] <Laurenceb> but it has to be responsive enough to control the plane
[14:37] <Hiena> But it will run on the ground unit because the need of the computing power for the image recognition.
[14:40] <Hiena> As i wrote, i needn't a full working UAV system rather a data aquisition validating the calculated and the wind tunnel datas. My tunnel will be limited at the lower Re numbers, that means i have to check it at higher speeds.
[14:42] <Hiena> (If i not sell the wind tunnel frame as rabbit cage as i done with the previous one.)
[14:45] <jcoxon> hey Laurenceb
[14:45] <jcoxon> rigged up a Sharp IR sensor
[14:46] <jcoxon> with a plastic float in the bottle
[14:46] <Laurenceb> interesting
[14:46] <jcoxon> works okay - not very precise and at the mercy of splashing
[14:46] <Laurenceb> does it work?
[14:46] <Laurenceb> yeah but you can average readings
[14:46] <jcoxon> sure
[14:47] <jcoxon> top of the tank reads about 500
[14:47] <jcoxon> bottom of the tank 280
[14:47] <Laurenceb> ok
[14:47] <jcoxon> certainly could give a rough estimate say 1/10ths of a tank
[14:50] <Laurenceb> hmm apparead epoxy doesnt like meths :-/
[14:50] <Laurenceb> hmmm could we use wider pipe
[14:50] <jcoxon> hmmm interesting
[14:50] <Laurenceb> say 10mm microbore?
[14:50] <jcoxon> need new valves
[14:56] <jcoxon> what is your thinking with wider pipes?
[14:57] <Laurenceb> less problems with it soaking up the middle
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[14:58] <jcoxon> not sure what you mean
[15:01] <Laurenceb> the meniscus problem
[15:01] <jcoxon> oh right
[15:02] <jcoxon> not the pipe that connect to the valve
[15:02] shea|up (n=shea@pool-71-164-88-29.albyny.fios.verizon.net) joined #highaltitude.
[15:03] <shea|up> cool, hi
[15:03] <jcoxon> hi shea|up
[15:03] <SpeedEvil> Laurenceb: you're getting hte pipe internally filled with liquid, and it's not coming out due to surface tension?
[15:04] <shea|up> I'm going to start a high-altitude balloon project. I have no idea what I'm doing. Expect stupid questions in the future :)
[15:04] <SpeedEvil> so it's 'sitcking' ?
[15:04] <shea|up> (post-google of course)
[15:04] <Laurenceb> yeah
[15:04] <jcoxon> shea|up, no problem, fire away with questions
[15:04] <SpeedEvil> shea|up: the balloon should be filled with something lighter than the surrounding air. :)
[15:04] <jcoxon> shea|up, the most important question is where are you based :-D
[15:04] <shea|up> drats i quit!
[15:04] <SpeedEvil> Laurenceb: wind up the diameter, till it doesn't do that.
[15:04] <jcoxon> as that'll dictate a lot of your options
[15:04] <shea|up> albany NY (usa)
[15:04] <SpeedEvil> Laurenceb: fairy liquid may help
[15:05] <jcoxon> okay cool, that makes it easier
[15:05] <SpeedEvil> Laurenceb: you're still trying with water?
[15:05] <SpeedEvil> jcoxon: as long as he doesn't look foreign.
[15:05] <shea|up> the country?
[15:05] <SpeedEvil> shea|up: regulations vary dramatically with country
[15:05] <shea|up> neat
[15:05] <Laurenceb> no meths
[15:06] <SpeedEvil> Laurenceb: wha'ts the diameter?
[15:06] <SpeedEvil> Laurenceb: you've got two coaxial popes?
[15:06] <Laurenceb> 2.5mm
[15:06] <Laurenceb> no one pipe with two wires down the mibble
[15:06] <Laurenceb> pipe is grounded
[15:06] <Laurenceb> I measure capacitance between the wires
[15:07] <Laurenceb> I'm beginning to suspect it may be the seal around the end of the wires
[15:08] <shea|up> i guess my biggest question at this point is -- which rf band should I use? seems like 700-900MHz would do nicely
[15:08] <shea|up> but i have no idea.
[15:08] <SpeedEvil> shea|up: regulatory dependant too
[15:08] <SpeedEvil> shea|up: do you have any radio licenses?
[15:08] <shea|up> no
[15:08] <SpeedEvil> Laurenceb: first and most obvious would be to go to 10mm dia tubing I guess
[15:09] <Laurenceb> the way the capacitance drift around
[15:09] <jcoxon> 700-900 is good though the range isn't great without quite a bit of power
[15:09] <SpeedEvil> Laurenceb: for the outer shield
[15:09] <Laurenceb> it just doesnt make sense
[15:09] <shea|up> yeah i'm mainly worried about power
[15:09] <jcoxon> lots of people in the US use 144Mhz as they have a radio licence
[15:09] <Laurenceb> it drifts over timescales of ~5 minutes
[15:09] <shea|up> (and the fcc)
[15:09] <jcoxon> which works really well
[15:09] <SpeedEvil> shea|up: a few milliwatts will get you _long_ ways
[15:09] <SpeedEvil> shea|up: at low baud rates
[15:09] <SpeedEvil> shea|up: 50bps or so
[15:09] <shea|up> 9600 or so?
[15:09] <shea|up> oh :(
[15:09] <shea|up> well i suppose that's fine really
[15:09] <SpeedEvil> shea|up: if you want video, it gets lots more complex
[15:10] <shea|up> i'm ok with recording video locally
[15:10] <SpeedEvil> 50 is fine for 'longitude=x, latotude=y, alt=z, longitude=...'
[15:10] <shea|up> i would definitely like some part of the gps sentence though, every minute or two
[15:10] <shea|up> yeah, cool
[15:10] <jcoxon> shea|up, i recommend looking into getting a radio licence
[15:10] <SpeedEvil> as in over a couple of hundred miles have been gotten on 10mW 433MHz here
[15:10] <SpeedEvil> (Uk)
[15:11] <shea|up> jcoxon, couldn't hurt
[15:11] <jcoxon> and then you can use the APRS system to track your balloon
[15:11] <shea|up> neat
[15:11] <shea|up> SpeedEvil, very cool
[15:11] <jcoxon> shea|up, i recently got mine and it was good fun, learnt loads about electronics and radios
[15:11] <shea|up> i'll go for it, thanks :)
[15:11] <SpeedEvil> There are also wacky alternatives - 'spot' - for example, which may not be _that_ ruinous for a sat tracker
[15:12] <jcoxon> SpeedEvil, spot is still in development :-p
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[15:12] <SpeedEvil> http://www.findmespot.eu/en/explorespot/index.php?cid=110
[15:12] <Laurenceb> hmm it seems to work
[15:12] <SpeedEvil> jcoxon: yes - but in principle, you could just glue one to a payload and press the 'on' button before launch
[15:12] <Laurenceb> I used blue tack to seal the ends of the wires
[15:12] <Laurenceb> for some reason its inverted
[15:13] <Laurenceb> so capacitance decreases with depth
[15:13] <shea|up> i already have a nice little gps module though :) costs seem to be *cough* ballooning
[15:13] <Laurenceb> SpeedEvil: any idea how to seal the ends of the wires?
[15:13] <jcoxon> shea|up, whats teh module?
[15:14] <shea|up> em-408
[15:14] <shea|up> i had it long before i decided to do this, hopefully it will suffice
[15:14] <jcoxon> i'm sorry to say...
[15:14] <shea|up> craps!
[15:14] <jcoxon> its a SIRF III gps module
[15:14] <jcoxon> they break at about 24km altitude
[15:14] <shea|up> indeed, oh
[15:14] <shea|up> well that's annoying
[15:15] <jcoxon> apart from that they are great modules :-D
[15:15] <shea|up> so which chipset doesn't break? :)
[15:15] <jcoxon> here we are big fans of Lassen IQs and ubloxs
[15:15] <shea|up> alrighty
[15:15] <jcoxon> and perhaps soon venus modules
[15:15] <jcoxon> http://www.sparkfun.com/commerce/product_info.php?products_id=163
[15:16] <jcoxon> http://www.sparkfun.com/commerce/product_info.php?products_id=8889
[15:16] <Laurenceb> the cleft of venus
[15:16] <jcoxon> Laurenceb!
[15:17] <jcoxon> Laurenceb, language
[15:17] <Laurenceb> :P
[15:17] <shea|up> i don't think i need 5Hz, so the lassen iq it is
[15:17] <shea|up> (do i)
[15:18] <jcoxon> 1Hz is just fine
[15:18] <shea|up> hooray
[15:18] <jcoxon> now another big question is what are you going to use as your flight computer?
[15:19] <shea|up> that is a question
[15:19] <shea|up> i have lots of micros i could use, and a beagle board. i don't really know what the flight computer needs to *do*
[15:20] <shea|up> other than read serial data, transmit
[15:20] Action: shea|up thinks
[15:20] <jcoxon> well at the basic jsut grab the gps and send it over some sort of communication system
[15:20] <shea|up> alright
[15:20] <jcoxon> AVRs are very popular
[15:20] <jcoxon> as our arduinos
[15:20] <jcoxon> are*
[15:20] <shea|up> i guess i'll go with an atmega168,
[15:21] <shea|up> (since that's what i have on hand)
[15:21] <jcoxon> cool
[15:21] <shea|up> so they're ok at crazy low temperature? :)
[15:22] Action: shea|up grabs the spec sheet
[15:22] <jcoxon> yeah, no problems with temp, and we insulate the payload
[15:22] <jcoxon> so they don't get too cold
[15:22] <shea|up> great then.
[15:22] <shea|up> -40C to 85C
[15:23] <shea|up> another thing i had trouble finding clear info on -- how do you guys deploy chutes?
[15:24] <shea|up> both detecting freefall (accelerometer?) and the release mechanism
[15:24] <jcoxon> often we have them predepolyed
[15:24] <shea|up> oh dur :)
[15:24] <jcoxon> so you have a main line from payload to balloon which runs through the spill hole on the chute
[15:25] <shea|up> that a bit easier
[15:25] <jcoxon> and on this is a bottle top of bit of card which the parachute rests on slightly loose
[15:25] <jcoxon> when the balloon bursts the main line goes slack and the parachute inflates
[15:26] <Laurenceb> you can detect burst by a decrease in altitude
[15:26] <shea|up> i feel better already
[15:26] <Laurenceb> - useful for changing telmetery ect
[15:26] <Laurenceb> but you dont need it for chutes
[15:26] <shea|up> cool
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[15:27] <shea|up> so the gps's z coord is generally as accurate as the x & y?
[15:27] <jcoxon> no, its not as good
[15:28] <shea|up> okay
[15:28] <jcoxon> but it does the job
[15:29] <shea|up> and, so, the fcc requires two methods of terminating flight, and two methods of detaching the payload, right? triggerable remotely?
[15:29] <shea|up> er heh, faa
[15:29] <shea|up> the regulations kind of confused me in some places
[15:33] <jcoxon> yeah, i'm not too familiar with the regs in the US
[15:33] <jcoxon> i think the balloon bursting counds as one of your methods
[15:33] <jcoxon> counts*
[15:33] <shea|up> oh, sweet.
[15:33] <shea|up> sorry i assumed you were in the US too (how american of me)
[15:34] <jcoxon> hehe, lots of people on here are based in the UK
[15:34] <jcoxon> no worries, the US rules are a lot better then those in the UK
[15:34] <jcoxon> http://www.eoss.org/pubs/far_annotated.htm
[15:35] <jcoxon> yeah, the fact that i'll burst counts as one of the termination methods
[15:35] <jcoxon> so you'll want a cutdown device as well
[15:36] <jcoxon> perhaps nichrome wire or perhaps an explosive tube
[15:36] <shea|up> any popular rigging mechanisms?
[15:36] <shea|up> oh :)
[15:37] <jcoxon> one idea:
[15:37] <jcoxon> http://wiki.ukhas.org.uk/ideas:flight_support#pyrotechnic_cutdown_device
[15:44] <shea|up> hey i like that
[15:46] <SpeedEvil> I think I prefer resistor + plastic tape
[15:47] <SpeedEvil> as it's easy to test
[15:47] <SpeedEvil> 3W or so resistor, rated to 250C temperature, with a plastic tape over it, holding the payload
[15:48] Action: Laurenceb uses 0.125W
[15:48] <Laurenceb> with 7 watts dissapation :P
[15:48] <shea|up> haha :)
[15:49] <SpeedEvil> yeah - the whole testable thing though :)
[15:49] <Laurenceb> you have to be careful not to go to far or they explode without burning the tie
[15:49] <SpeedEvil> there are resistors ideal for this stuff that are actually rated to quite adequate temps
[15:56] <Laurenceb> hmm looking at the datasheet I need about 1Gohm between the two wires
[15:56] <Laurenceb> may explain why it was screwing up
[15:56] <Laurenceb> I've tried to seal them using heat shrink now
[15:56] <Laurenceb> its fluctuating, but seems to be stabilising
[15:57] <Laurenceb> hopefully the gunk will "burn" off
[15:57] <Laurenceb> before the heat shrink pops... it seems to be inflating :-/
[16:08] <SpeedEvil> seal the ends?
[16:09] <SpeedEvil> I'd cut the end, grab the 'top' of the wire, and work the insulation down 5mm or so, before heating and squashing
[16:15] <Laurenceb> hmmm
[16:15] <Laurenceb> I put heat shrink between the two
[16:32] <Laurenceb> seems to be stabilising now
[16:32] <Laurenceb> I should rig up the php plotter
[16:36] <Laurenceb> ok this seems to work
[16:36] <Laurenceb> there are some long term drifts over periods of about an hour
[16:36] <Laurenceb> but you can detect ballast drops I think
[16:37] <Laurenceb> hopefully to mm accuracy
[16:38] <Laurenceb> its rather nonlinear as well
[16:42] Action: shellevil ponders screwfix.com
[16:43] <Laurenceb> hmm yeah theres an ~instant response
[16:43] <Laurenceb> then a trailing exponential one
[16:43] <Laurenceb> time constant ~a minute
[16:44] <Laurenceb> the instant response should give you level to <5mm error
[16:44] <shellevil> you have a twisted pair of cables?
[16:44] <Laurenceb> yes
[16:44] <Laurenceb> then coax feeders
[16:44] <shellevil> right
[16:45] <Laurenceb> rg178
[16:45] <Laurenceb> I just immersed it to give a reading of ~1
[16:45] <Laurenceb> its now at 6.3
[16:46] <Laurenceb> previously it was at 6.55
[16:46] <Laurenceb> now 6.33
[16:46] <Laurenceb> ... and so on
[16:46] <Laurenceb> 6.34
[16:46] <jcoxon> Laurenceb, so the instant response is correct
[16:46] <jcoxon> then it drifts off
[16:46] <Laurenceb> no
[16:46] <Laurenceb> the instant response is underestimated
[16:47] <Laurenceb> then it drifts to the correct value
[16:47] <Laurenceb> as the meniscus moves
[16:47] <jcoxon> okay
[16:47] <jcoxon> but it is now working?
[16:47] <Laurenceb> its probably best to calibrate it in the bottle
[16:47] <Laurenceb> sorry natrium42
[16:48] <Laurenceb> yes pretty much as planned now :P
[16:49] <jcoxon> good
[16:51] <Laurenceb> I dont understand why its -ive
[16:51] <Laurenceb> capacitance decreases with depth
[16:53] <Laurenceb> must be some phase effect due to the conductivity
[16:54] <Laurenceb> at 6.46 now
[16:57] <Laurenceb> 6.55
[16:58] <Laurenceb> hmm it overshot :-/
[16:59] <Laurenceb> I suspect maybe this thing need running for ages
[16:59] <Laurenceb> to "burn it in"
[17:02] <shellevil> Laurenceb: you've got three capacitors? Wire A-B, A->shield, and B-> shield? And the wiring capacitance - which shouldn't change?
[17:02] <shellevil> Laurenceb: A->B will increase, but A-> shield and b->shield will too - when you fill it up
[17:02] <Laurenceb> sure
[17:02] <shellevil> how good is the differential mode, and might that be the problem?
[17:02] <Laurenceb> but that AD7746 doesnt mide
[17:02] <Laurenceb> nope
[17:02] <Laurenceb> it can handle a couple of hundered pf
[17:03] <Laurenceb> what it really cant handle is conductive gunk on the electrodes on pcb
[17:03] <Laurenceb> <1G ohm starts to screw things up
[17:04] <shellevil> conformal coat to avoid possible icing I guess
[17:05] <Laurenceb> I want to make a capacitance tomography scanner
[17:06] <Laurenceb> use a motating electrode mount
[17:07] <Laurenceb> then read in capacitance values at hundereds or thousands of positions
[17:07] <shellevil> I want one for my walls.
[17:08] <shellevil> Attach two drawing pins at corner of walls
[17:08] <shellevil> hook up the two strings for the device
[17:09] <shellevil> it moves over the wall in 5cm increments spraypainting with some colour that will evaporate in 24 hours different densities
[17:09] <Laurenceb> what
[17:09] <Laurenceb> crazy
[17:10] <shellevil> none of this 'where is the beam' stuff - it's all right there.
[17:10] <Laurenceb> hmm methanol/ethanol vapour is going to have a different density to air right
[17:11] <Laurenceb> I think I worked this out - previously I did the test horizontally
[17:11] <Laurenceb> now its vertical
[17:11] <shellevil> should do, I think
[17:11] <Laurenceb> I guess the inside is drying out more easily
[17:11] <shellevil> I'd be surprised if the dielectric constant is noticable though
[17:11] <shellevil> oh
[17:11] <Laurenceb> the vapour sets up convection currents
[17:12] <shellevil> yeah I was surprised similar to that.
[17:12] <shellevil> I'd setup a 4cm dia 2m glass tube vertically, filled with water
[17:12] <shellevil> and a 20W bulb at the bottom
[17:12] <shellevil> when the bulb was on, bubbles came from it.
[17:13] <shellevil> Drove me crazy, till I realised convection was drawing dissolved gas-rich colder water from the top, which was then coming out of solution as it hit the hot bulb
[17:15] <Laurenceb> getting images from a capt scanner isnt easy
[17:15] <Laurenceb> I was thinking have a forward model then try sucessive approximation techniques
[17:15] <shellevil> why not?
[17:16] <shellevil> Oh - I diddn't mean anything about inferring deeper structure
[17:16] <shellevil> only the first order image
[17:16] <shellevil> of capacitance between two probes 5cm apart or so
[17:16] <Laurenceb> 3D :P
[17:21] <Laurenceb> hmm from wikipedia An N-electrode system can only provide N(N-1)/2 independent measurements. This means that the technique is limited to producing very low resolution images of approximate slices
[17:21] <Laurenceb> not if you move the electrodes :P
[17:22] <shellevil> SAR...
[17:23] <Laurenceb> http://www.tomography.manchester.ac.uk/flame.shtml
[17:23] <shellevil> then it's all noise limits and how much CPU you're willing to throw at it
[17:23] <Laurenceb> something like a 3D capacitor mesh
[17:24] <Laurenceb> then find the capacitance between the electrodes
[17:24] <Laurenceb> thats your forward model, then use monte carlo or somethnig to invert
[17:24] <shellevil> yeah
[17:25] <shellevil> it's all nice and 'easy' if you know that you've got two materials in there
[17:25] <shellevil> with known and different properties
[17:28] <Laurenceb> http://www.tomography.manchester.ac.uk/captom.shtml
[17:28] <Laurenceb> hmm this behavoiur is pretty odd now... its like damped oscillation
[17:29] <Laurenceb> it was at 6.55 before the immersion
[17:29] <Laurenceb> then it shot up from 0.27 full immersion to 7.1
[17:29] <Laurenceb> then down to 6.85
[17:29] <Laurenceb> now its up to 6.9
[17:30] <shellevil> the really nice thuing about capacitive tomography for medical use is in principle it could be very cheap
[17:30] <Laurenceb> yeah
[17:30] <shellevil> whereas MRI, CT, ... are really quite hard to get to say $50
[17:30] <Laurenceb> from what I've seen the image reconstruction techniques used so far are very simple
[17:32] <Laurenceb> just first order approximations using matrices
[17:33] <shellevil> capacitance scanning, IR, thermography, ultrasound all in principle could be cheap.
[17:33] <shellevil> sensor fusion is where teh sexy is though.
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[17:39] <Xenion> Guten Abend / Good evening :-)
[17:51] <Laurenceb> hmm it seems to have stabilised now at 6.8
[17:52] <Laurenceb> I suspect in a ballast tank it may be more stable as its not going to be drying out unevenly
[17:55] <natrium42> hi
[17:56] <Laurenceb> hi natrium42
[17:56] <Laurenceb> got the ballast sensor working
[17:56] <Laurenceb> unfortunately
[17:56] <Laurenceb> your going to have to calibrate it
[17:57] <Laurenceb> in the tanl
[17:57] <natrium42> so read the min and max values?
[17:57] <Laurenceb> nope
[17:57] <Laurenceb> leave it for a week...
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[17:57] <Laurenceb> then test it at lots of different vlues
[17:57] <natrium42> :S
[17:57] <Laurenceb> and test the response time
[17:57] <Laurenceb> and transients
[17:58] <natrium42> sounds a bit dodgy
[17:58] <Laurenceb> ok not that bad but its a bit of a pain
[17:58] <Laurenceb> yeah
[17:58] <Laurenceb> it can give you cm resolution easily I think
[17:58] <Laurenceb> but if you want mm or less you have to take out the nonlinearity and response weirdness
[17:59] <Laurenceb> e.g. it oscillates over a period of around an hour
[17:59] <natrium42> hrm
[17:59] <natrium42> but is it going to be reliable after calibration?
[18:00] <Laurenceb> I think so
[18:00] <Laurenceb> I could have a go at rebuilding the sensor
[18:01] <Laurenceb> with wider diamter tube
[18:01] <natrium42> yeah, week of calibration doesn't sound too appealing i must say
[18:01] <Laurenceb> :P
[18:01] <natrium42> have you considered resistance instead of capacitance?
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[18:01] <natrium42> maybe it's more stable?
[18:02] <Laurenceb> yeah... oh well its built now
[18:02] <Laurenceb> I havent come up with a new design yet...
[18:02] <Laurenceb> not sure what materials are meths safe
[18:03] <natrium42> bbl, need to pick up my parents
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[19:05] <jcoxon> evening all
[19:05] <SpeedEvil> Evening.
[19:08] <jcoxon> 4hrs 35 before STS-119 launch
[19:08] <jcoxon> :-p
[19:10] Action: SpeedEvil has wondered occasionally about parasitic payloads.
[19:10] <SpeedEvil> Little automated helicopter gluing a payload onto STS.
[19:11] <jcoxon> hehe, remote controlled bird 'plants' a nano payload
[19:12] <SpeedEvil> problem is that if you want orbit, you really need to be on the shuttle
[19:13] <SpeedEvil> http://encyclopediadramatica.com/Image:Death_Longcat.jpg :)
[19:16] <Laurenceb> hmm
[19:16] <Laurenceb> I've increased the voltage to the CDC
[19:16] <Laurenceb> it seems to be more stable
[19:16] <Laurenceb> its now using +-0.5Vdd
[19:16] <Laurenceb> not +-0.125Vdd
[19:19] <natrium42> back
[19:23] <jcoxon> hey natrium42
[19:24] <jcoxon> will you be around this evening for the 'meeting'?
[19:24] <Laurenceb> SpeedEvil: lol@ the adverts on that site
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[19:30] <natrium42> hi jcoxon
[19:30] <natrium42> yes, i will be
[19:30] <jcoxon> cool cool
[19:33] <SpeedEvil> Laurenceb: http://images.clickbangpop.com/4chan_girls_adv.gif
[19:33] <SpeedEvil> Laurenceb: cdc?
[19:33] <SpeedEvil> Laurenceb: oh
[19:33] <Laurenceb> oh god
[19:33] <SpeedEvil> (link to a dating site)
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[19:41] <SpeedEvil> http://www.mauve.plus.com/bedroom-wall.jpg - insulation on, cable duct in.
[19:41] <SpeedEvil> and underfloor void cleared and almost ready to put insulation in.
[19:41] <SpeedEvil> :)
[19:41] <natrium42> did you remember to add network cabling?
[19:42] <natrium42> jcoxon:
[19:42] <natrium42> http://www.natrium42.com/gallery2/v/balloon/transatlantic/venus-gps-soldered.jpg.html
[19:42] <natrium42> http://www.natrium42.com/gallery2/v/balloon/transatlantic/venus-gps-soldered2.jpg.html
[19:42] <SpeedEvil> natrium42: 1-wire, cat5, ...
[19:42] <natrium42> works inside the house
[19:42] <jcoxon> amazing
[19:42] <natrium42> picked up 10 satellites inside
[19:42] <SpeedEvil> natrium42: I'm implementing a 1-wire bus over the house - ~50 temp sensors and control nodes.
[19:42] <natrium42> SpeedEvil, fiber!
[19:42] <SpeedEvil> natrium42: great!
[19:43] <natrium42> thx
[19:43] <Laurenceb> speedevil: neat
[19:43] <natrium42> SpeedEvil, how many of the old and new gps chips do you want?
[19:43] <SpeedEvil> Laurenceb: lots of temp sensors to track airflow, and wall temp, and ...
[19:43] <Laurenceb> cool
[19:43] <Laurenceb> what are you using as nodes?
[19:43] <SpeedEvil> natrium42: 5 at least of the new.
[19:43] <Laurenceb> natrium42: yum yum yum
[19:44] <natrium42> SpeedEvil, do you want any of the old verison?
[19:44] <SpeedEvil> natrium42: sure - another couple at least for prototyping.
[19:44] <natrium42> k
[19:44] <SpeedEvil> Case of oopses
[19:44] <natrium42> lol
[19:44] <edmoore> Laurenceb: there was a website of a guy who had a very impressive prototpying technique - glueing chips to kapton onto proto board, then meticulously soldering enamled wires on each pin for the routing. it was in chinese with english translations. he'd one lots of cool project. Do you rmeember what it was?
[19:44] <natrium42> i can ship them separately if you want
[19:45] <Laurenceb> elm-chan
[19:45] <natrium42> since i have no idea when the new ones will ship
[19:45] <SpeedEvil> Laurenceb: ds18b20's as temp sensors - 10 bits or so
[19:45] <SpeedEvil> natrium42: no hurry alas. See above pic :/
[19:45] <natrium42> the elm-chan dude is crazy
[19:45] <natrium42> SpeedEvil, kk
[19:45] <edmoore> that's the one
[19:45] <Laurenceb> http://elm-chan.org/
[19:45] <edmoore> ta
[19:45] <SpeedEvil> Laurenceb: some 4 channel A/Ds for current sensing and power control.
[19:46] <Laurenceb> ah cool
[19:46] <SpeedEvil> Laurenceb: found a source of the a/ds at $2.22 per
[19:46] <SpeedEvil> Also interestingly, the A/Ds can be used when the open drain FET for GPIO is on.
[19:46] <natrium42> jcoxon, also hot glued the spot so that wires don't detach
[19:47] <SpeedEvil> Laurenceb: this lets you measure resistances.
[19:47] <natrium42> jcoxon, 80 grams without top plastic, 120 with
[19:47] <jcoxon> natrium42, thats a really smart gps
[19:47] <jcoxon> sell them to sparkfun!
[19:47] <natrium42> haha
[19:47] <jcoxon> they'd take them up and would sell out in seconds
[19:47] <natrium42> those antennas are not being made anymore
[19:47] <natrium42> i should order some
[19:48] <natrium42> before they are gone
[19:48] <Laurenceb> SpeedEvil: use pcharts to stick the temperature logs online
[19:48] <SpeedEvil> natrium42: have you got any more details of the logging to flash mode?
[19:48] <natrium42> now they have only the active antenna with the black radome
[19:48] <SpeedEvil> Laurenceb: possibly
[19:48] <natrium42> the passives are without radomes
[19:49] <natrium42> SpeedEvil, check sparkfun page, they put up a doc describing it
[19:49] <SpeedEvil> oh - neat
[19:50] <edmoore> natrium42: nice gps units!
[19:50] <edmoore> have you fired one up?
[19:50] <natrium42> yeah, got 10 sats from inside the house
[19:51] <SpeedEvil> a valid position?
[19:51] <natrium42> yep
[19:51] <natrium42> now i need to check if it actually works at altitude as they claim
[19:51] <Laurenceb> how far out?
[19:51] <Laurenceb> was the position?
[19:52] <natrium42> 1.5 m from window
[19:52] <Laurenceb> error?
[19:52] <natrium42> i didn't map it
[19:52] <natrium42> i could test again
[19:52] <natrium42> it's connected to a usb-to-serial converter atm
[19:53] <Laurenceb> cool
[19:53] <Laurenceb> does the led flash?
[19:54] <edmoore> right, bbl
[19:55] <natrium42> yep
[19:55] <natrium42> so if anybody need a pcb and/or venus chip, let me know
[19:55] <natrium42> i got dozens of either one
[20:00] <jcoxon> is it 3.3v TTL?
[20:00] <Laurenceb> I'll take 2 :P
[20:01] <natrium42> jcoxon, yeah
[20:02] <jcoxon> its a really nice module now, just got to check those alt limits
[20:02] <natrium42> also low power
[20:02] <Laurenceb> how much current?
[20:03] <natrium42> " Under low power acquisition mode, most used hot-start and warm start
[20:03] <natrium42> has acquisition current of ~50mA, once having fix the average tracking
[20:03] <natrium42> current is ~25mA, if all available satellites are tracked then current is
[20:03] <natrium42> ~23mA. Out of box first time cold start acquisition current is ~70mA."
[20:04] <SpeedEvil> @3.3?
[20:05] <Laurenceb> not bad
[20:06] <natrium42> yep
[20:07] <natrium42> very good for a 65 channel chip :P
[20:08] <Laurenceb> doesnt the datasheet imply it works at altitude?
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[20:09] <rjharrison_> Hi jcoxon I'm not going to be arround at nine
[20:09] <jcoxon> rjharrison_, no worries
[20:09] <natrium42> Laurenceb, yes, but you never know...
[20:09] <natrium42> anyway, going to test it rather soon
[20:09] <rjharrison_> Will be happy to commit to having the remote tracker in place for wednesday
[20:10] <jcoxon> rjharrison_, great
[20:10] <rjharrison_> It's npt much more work to do to be honnest
[20:10] <Laurenceb> remote tracker?
[20:10] <rjharrison_> Is there any thing extra to code for than we have done before
[20:10] <rjharrison_> Listener sorry!
[20:11] <rjharrison_> http://wiki.ukhas.org.uk/projects:dlistener
[20:11] <jcoxon> rjharrison_, i don't think so, i'll go over it with you sometime this week
[20:26] <natrium42> Laurenceb, http://rafb.net/p/3sPJlv16.html
[20:27] <Laurenceb> hello there
[20:27] <natrium42> it's a bit off
[20:28] <natrium42> but it's because the antenna is inside
[20:29] <Laurenceb> http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=43+29.9780%27+N,+80+28.6830%27+W&sll=43.675818,-8.481445&sspn=7.18272,19.775391&ie=UTF8&ll=43.499713,-80.477981&spn=0.000879,0.002414&t=h&z=19&iwloc=addr
[20:30] <Laurenceb> that your house?
[20:30] <natrium42> no
[20:31] <natrium42> http://maps.google.co.uk/maps?saddr=%2B43%C2%B0+29%27+58.68%22,+-80%C2%B0+28%27+40.98%22+(43.499633,+-80.478050)&geocode=&dirflg=&daddr=409+falconridge+dr&f=d&hl=en&sll=43.49934,-80.478137&sspn=0.001734,0.001636&ie=UTF8&ll=43.499262,-80.478019&spn=0.001734,0.001636&t=h&z=19
[20:31] <natrium42> B is my house
[20:32] <Laurenceb> hmm ~50m off
[20:33] <jcoxon> that said google earth is often off
[20:33] <Laurenceb> beten by the Se4120
[20:33] <Laurenceb> not these days
[20:33] <jcoxon> i found that especially in africa
[20:33] <Laurenceb> they've made it a lot neater
[20:33] <jcoxon> not that canada is in africa
[20:33] <jcoxon> :-p
[20:33] <natrium42> canada is pretty precise
[20:33] <Laurenceb> I'd say <2m probably
[20:34] <SpeedEvil> If canada is in aftica, that's unusually bad imagery :)
[20:35] <Laurenceb> rightI'm off, bbl
[20:35] <jcoxon> haha
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[20:57] <natrium42> sprintf(temp, "%f", (double) tempC); is not working
[20:57] <natrium42> getting '?'
[20:58] <natrium42> :S
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[20:59] <natrium42> do i need to add libprintf_flt.a?
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[21:01] <natrium42> oh, lib math
[21:03] <natrium42> nah, still the same
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[21:30] <natrium42> hi Ikarus
[21:34] <shellevil> Ikarus is wondering how kalman filters work, and how to implement them - for flying stuff in the future.
[21:35] <natrium42> Laurenceb loves kalman filters
[21:36] <Laurenceb> hmm kalman
[21:37] <natrium42> kalman is *the* man
[21:37] <natrium42> Laurenceb, agree?
[21:37] <Laurenceb> yep
[21:37] <Laurenceb> unscented kalman filter is where its at
[21:39] <Ikarus> So what do I want to read so I actually know what really goes in, comes out and how the hell it works :) assume I have no prior knowledge to such systems
[21:39] <Laurenceb> wikipedia is good
[21:39] <Laurenceb> what are you wanting to do?
[21:40] <Ikarus> Laurenceb: basic INS and GPS integration stuff, determine position and attitude of a platform, moving at low speeds (at a later date, higher speeds)
[21:41] <Laurenceb> so attitude as well as position?
[21:41] <Ikarus> attitude is very significant, yes
[21:41] <Ikarus> hence using both accelerometer as magnetic sensors
[21:41] <Laurenceb> and full attitude or some approximation, e.g. heading and roll only say
[21:42] <Ikarus> full
[21:42] <Laurenceb> hmm thats a deal harder
[21:42] <Laurenceb> if you want to do it properly you need at least an accel and three gyros
[21:42] <Laurenceb> alongside your gps
[21:43] <Ikarus> yup
[21:43] <Laurenceb> http://wiki.ukhas.org.uk/code:4_state_extended_kalman_filter_in_matlab
[21:44] <Laurenceb> looks like you want that :P
[21:44] <Ikarus> actually I was planning on more sensors
[21:45] <Laurenceb> ok you obviously have money to burn
[21:45] <Ikarus> In the future :) currently actually working on simulated data
[21:46] <Laurenceb> you can actually do it pretty with with that - on a fixed wing at least
[21:46] <Ikarus> actually the magnetic sensors are dirt cheap to add and provide a very unambigious reference
[21:46] <Laurenceb> hmmm
[21:46] <Laurenceb> unless you have any motors nearby
[21:46] <Ikarus> actually those motors have to be quite nearby to influence them
[21:47] <Ikarus> well, influence them more then a simple metal mass (which you easily compensate)
[21:47] <Laurenceb> yeah
[21:47] <Laurenceb> hmm ok
[21:48] <Laurenceb> well you can stick a magnotometer in in a similar facion to the accel
[21:48] <Ikarus> I was thinking of GPS + accelerometers + rate gyros + magnetometers (total parts cost 200 euro if I did my shopping well)
[21:48] <Laurenceb> yeah
[21:48] <Laurenceb> ok... what micro?
[21:49] <Ikarus> Laurenceb: no exact pick yet
[21:49] <Ikarus> probably throwing some ARM 7 or 9 at it
[21:49] <Laurenceb> yeah you'll need it
[21:49] <Laurenceb> on a breakoput board of some sort?
[21:50] <Ikarus> Laurenceb: nah, I'll be baking a few boards of my own most likely
[21:50] <Laurenceb> nice
[21:50] <natrium42> mmh, baked pcbs
[21:51] <Laurenceb> you can go with bias tracking....
[21:51] <Laurenceb> but I'd use an ovenised IMU personally
[21:52] <Ikarus> Laurenceb: bias tracking ? ovenised ?
[21:52] <Laurenceb> the components drift with temperature
[21:52] <Ikarus> aah, yes
[21:53] <Ikarus> ovenised is probably a bit too expensive and erm, heavy
[21:53] <Laurenceb> not really
[21:53] <Ikarus> Laurenceb: argue that at a cost of 10 euro for things like the gyros :P
[21:53] <shellevil> some foam, and a resistor
[21:53] <Laurenceb> IDG300, ADLX330, 2axis magno, and an mlx90609
[21:54] <shellevil> 10 euro?
[21:54] <shellevil> where are you getting gyros at 10 euro?
[21:54] <Laurenceb> erm more like 50
[21:54] <Ikarus> shellevil: rate gyros
[21:54] <shellevil> yes, I'm not aware of any at 10.
[21:54] <Ikarus> I spotted them in the catalog at work, seemed to match the requirements
[21:54] <shellevil> which catalog?
[21:54] <Laurenceb> hmmm....
[21:55] <Laurenceb> you need very decent part sfor this
[21:55] <Laurenceb> so anyway... everything on a pcb with copper sheet ontop
[21:55] <Laurenceb> thermal paste between
[21:55] <Laurenceb> then some resistors glued onto copper with thermally conductive epoxy
[21:56] <Ikarus> Laurenceb: they only need to provide data when the angle between the acceleration and magnetic sensor is too small due to acceleration (or flying near the magnetic north :P)
[21:56] <Laurenceb> sure
[21:56] <Laurenceb> but its a pain to do in software
[21:57] <Laurenceb> and eats up tons more cpu as you have to extend the state vector
[21:57] <Ikarus> Laurenceb: well, I already implemented determining attitude using those 2 datas
[21:57] <Laurenceb> unless you fundge things
[21:57] <Laurenceb> whats your state vector?
[21:58] <Ikarus> ?
[21:58] <Laurenceb> for you filter?
[21:58] <Laurenceb> at the moment
[21:59] <Ikarus> ah, didn't do it with a filter, this is just a pure get data from (virtual) sensors and output attitude
[22:00] <Ikarus> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-8230-ND this one seems similair (though not exactly the same model nr)
[22:00] <Laurenceb> hmm
[22:01] <Laurenceb> ADLX330, MLX90609, IDG300
[22:06] <Ikarus> you aren't yet convincing me which parameter of it is so bad I need to use a more then twice as expensive gyro (per axis more expensive for devices like the IDG300)
[22:07] <Laurenceb> the noise
[22:07] <natrium42> hmm, is "Dust-Off" liquid conductive?
[22:07] <Laurenceb> also the bias drift with temperature
[22:07] <natrium42> i want to test temp sensor at low temp
[22:07] <shellevil> natrium42: I think it's just propanol
[22:07] <shellevil> nat: look at the side of the can
[22:08] <natrium42> doesn't say
[22:08] <shellevil> website should then
[22:08] <Laurenceb> ikarus: if your going to build this thing, you may as well not shoot yourself in the foot by using cheap parts
[22:08] <Laurenceb> may as well use the best mems parts you can easily get
[22:09] <Ikarus> Laurenceb: erm, the bias drift is HIGHER on the IDG300
[22:09] <Laurenceb> makes it so much easier
[22:09] <natrium42> http://en.wikipedia.org/wiki/Dust-Off
[22:09] <Laurenceb> yeah, thats why its ovenised
[22:09] <Laurenceb> but its a balance still...
[22:09] <Laurenceb> you could go with two mlx90609
[22:10] <Laurenceb> if you really want to burn money
[22:10] <Ikarus> noise is okay, 6x better on the IDG300
[22:10] <Ikarus> but only 6x
[22:10] <Ikarus> Laurenceb: if I wanted to burn money I would be buying a normal gyro, not a rate gyro (though those can suffer from lock)
[22:10] <Laurenceb> yeah, with some half decent temperature control, you can avoid the drift on the IDG300
[22:11] <Laurenceb> well... its just the way I'd do it
[22:12] <Laurenceb> theres a point where you want to stop faffing with firmware
[22:12] <Ikarus> Laurenceb: let's see, spend 80 euro on a pair of IDG300s, which only need to be accurate enough to cover gaps in my attitude measurement via absolute sources, or 30 euro on a triplet of LISY300AL, heh
[22:13] <Laurenceb> fair enough
[22:13] <natrium42> SpeedEvil, ok, i tried it & it worked :(
[22:13] <natrium42> *:)
[22:13] <Ikarus> yeah, but remember, the way I look at it, I don't suffer too badly from the noise as I am constantly callibrating it vs the two other attitude sensors
[22:13] <Laurenceb> but I's still ovenise it... just cuz you can :P
[22:13] <natrium42> SpeedEvil, -32C O_O
[22:13] <Laurenceb> and it makes it so much nicer
[22:14] <Ikarus> no idea what filters I need to use though to actually get it to work efficiently though :)
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[22:14] <Laurenceb> well an extended kalman like the one i linked should get you <0.5 degree errors on all axes
[22:15] <Laurenceb> with an ovenised imu
[22:15] <Ikarus> oh, that is perfectly acceptable
[22:15] <Laurenceb> if you want to do drift tracking and insulate the sensors against sudden temperature chifts, you could get similar performance
[22:15] <Laurenceb> but it would be move complex and use more clock cycles
[22:16] <Laurenceb> do you want to have position in the filter as well as attitude?
[22:17] <Ikarus> Laurenceb: would it help ? (I think so, but not sure)
[22:17] <Laurenceb> depends what you want to do
[22:17] <Laurenceb> you dont need it to fly a plane
[22:18] <Laurenceb> complexity goes up with n!n^3 where n is the size of your state vector
[22:18] <Laurenceb> so that code uses a quaternion and has n=4
[22:18] <Laurenceb> if you added position and velocity n=10
[22:18] <Laurenceb> if you add gyro bias as well n=13
[22:18] <Laurenceb> accel bias ontop and n=16
[22:19] <Laurenceb> you soon get beyond the limits of an ARM
[22:19] <Ikarus> I think I'll have to determine that experimentally :)
[22:19] <Laurenceb> well yes you can go for fixed point ect
[22:20] <Laurenceb> but its a headache... guess it depends what tyou want to do
[22:20] <Laurenceb> if its a one off, use the best hardware you can afford
[22:20] <Ikarus> Laurenceb: I was thinking of ARM 9 just because I can get them with either vector unit or even a DSP tied on to do this number crunching
[22:21] <Laurenceb> hmm ok
[22:21] <Laurenceb> yeah you could do some serious stuff with an ARM9
[22:21] <Laurenceb> position and velocity probably poss
[22:22] <Ikarus> I guess I'll go extend my virtualised version of the instruments with some more accurately modelled errors
[22:23] <Laurenceb> if you ask on the sparkfun forum someone may help record some data for you
[22:23] <Ikarus> yeah, given their http://www.sparkfun.com/commerce/product_info.php?products_id=8454 + a GPS is essentially what I am building
[22:24] <Ikarus> http://www.sparkfun.com/commerce/product_info.php?products_id=8726 or well morer accuratle
[22:24] <Ikarus> ty
[22:25] <Laurenceb> yeah...
[22:25] <Ikarus> But I tied virtual sensors into flightgear so I could get an idea of possible data
[22:25] <Laurenceb> never use dthat
[22:25] <Laurenceb> I just asked on the forums
[22:25] <Laurenceb> and someone kindly recorded some data with the v6
[22:25] <Ikarus> well, originally I planned to toss this on an airplane
[22:25] <Laurenceb> why not buy one of their units?
[22:26] <Ikarus> Laurenceb: $350 + import taxes == around 500 euro
[22:26] <Laurenceb> that sucks
[22:26] <Laurenceb> not so high here in UK
[22:26] <Ikarus> how much would you guess it was in the UK
[22:27] <Ikarus> if it is significantly lower I'll import it via the UK (because I don't pay any taxes on UK -> NL)
[22:27] <Laurenceb> £330 maybe
[22:27] <Laurenceb> depends if it gets causght by customs
[22:27] <Laurenceb> to be honest I'm not sure
[22:27] <Ikarus> anyway, my own stuff, including the GPS came to 200 euro, though that is with some cheaper parts as said
[22:28] <Laurenceb> yeah
[22:28] <Laurenceb> I'd still but theirs unless I really needed ARM9
[22:28] <Laurenceb> easier
[22:28] <Laurenceb> saves reinventing the wheel
[22:28] <Ikarus> but I want a tweel
[22:28] <Laurenceb> :P
[22:29] <Ikarus> actually mainly I want to see if I can do it significantly cheaper while still getting usable data
[22:29] <Laurenceb> hmm I see where you're going
[22:29] <Ikarus> the ARM 9's I am considering are, on a break out board, 40 euro a piece, including debug HW and the like
[22:29] <Laurenceb> so you want really cheap but usable
[22:29] <Ikarus> yup
[22:29] <Laurenceb> hmm ok
[22:30] <Ikarus> I can afford the sparkfun board if I really needed it
[22:30] <Laurenceb> in which case yeah go for ARM9
[22:30] <Laurenceb> then you can do a huge state vector
[22:30] <Ikarus> but it is mainly a learning experience for me
[22:30] <Laurenceb> and try and filter out bias drift ect
[22:30] <Laurenceb> anyway I'm off, cya
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[23:15] <Laurenceb> Ikarus: hi again
[23:15] <Laurenceb> your idea is interesting
[23:15] <Laurenceb> thinking about it a bit more, I think you'll need to add some sort of sensor bias tracking
[23:16] <Ikarus> yeah, I just re-did the numbers, it's even cheaper ...
[23:16] <Laurenceb> cool
[23:16] <Laurenceb> I'm not sure how the maths works...
[23:16] <Ikarus> Sparkfun's $350 is seriously 80% profit
[23:16] <Laurenceb> yeah
[23:17] <Laurenceb> basically you compare two consecutive iterations to try and estimate the sensor bias values
[23:17] <Laurenceb> is how it seems to work
[23:17] <natrium42> yes, they have been overpricing things lately...
[23:17] <natrium42> maybe time for some competition!
[23:17] <Laurenceb> 5DOF IMU went up to $110
[23:17] <Ikarus> natrium42: it's more fun when you compare with some of their sources that also sell to individuals
[23:17] <Ikarus> natrium42: like olimex
[23:17] <Laurenceb> yeah
[23:18] <Ikarus> Sparkfun needs a European competitor atleast
[23:18] <Ikarus> to cut short on the tax mess we currently face
[23:18] <Laurenceb> where are you based?
[23:18] <Ikarus> The Netherlands
[23:18] <Laurenceb> ah cool
[23:18] <Laurenceb> not too far :P
[23:19] <Laurenceb> bias tracking confuses me as I always thought the kalman filter was based around individual descreet time steps
[23:20] <Ikarus> I am totally not in the know :)
[23:20] <Laurenceb> as they model Markov chains
[23:20] <Laurenceb> determining sensor bias requires examining previous timesteps
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[23:23] <natrium42> Ikarus, seriously, the venus gps chip they sell for $40
[23:23] <Ikarus> Laurenceb: no, you can include it as a running update in your model
[23:23] <Ikarus> natrium42: yup
[23:23] <natrium42> i got it for $8.50 a piece for 250 pieces
[23:23] <Ikarus> natrium42: heck, you can ger a half decent GPS receiver for 15 euro
[23:23] <natrium42> usually retail is 30-40%
[23:23] <natrium42> if you are just reselling a part
[23:23] <Laurenceb> hmm I've seen it done with bias values in the state vector
[23:23] <Ikarus> I just came to a total of 100 euro, using the same parts as Sparkfun, except for the gyros
[23:24] <natrium42> and i do sell my own devices
[23:24] <Ikarus> oh and adding a GPS receiver
[23:24] <Ikarus> and that is including rape you taxes, etc
[23:24] <Laurenceb> but I'm sure it can be made to work well with some "external" algorythm
[23:24] <Ikarus> so that is at worst, what, a 100% markup for Sparkfun
[23:24] <Laurenceb> to find the biases
[23:24] <natrium42> i could do a complete PCB with that chip and an antenna for $50 or so
[23:25] <natrium42> seriously considering it...
[23:25] <Ikarus> Laurenceb: yeah, take the output of the model then reinput that into a dedicated model for providing bias correction
[23:25] <Laurenceb> yeah I think we're thinking the same thing
[23:25] <Ikarus> natrium42: hrm, I've seen modules around that price, though possibly based on simpeler GPS chips
[23:25] <Laurenceb> run kalman filter giving position and attitude, then take that data and compare to the sensor readings to get biases
[23:26] <Ikarus> yup
[23:26] <natrium42> Ikarus, http://www.natrium42.com/gallery2/v/balloon/transatlantic/
[23:26] <Laurenceb> the good news is bias changes slowly
[23:26] <natrium42> see the last two pics
[23:26] <Laurenceb> if you were clever you could have an RTOS with completely seperate processes :P
[23:26] <Ikarus> Laurenceb: probably will
[23:26] <Laurenceb> e.g. high priority task running filter and control loops
[23:26] <natrium42> chip is $9, antenna is $12, pcb is like $3
[23:26] <Ikarus> Laurenceb: yeah, as said, the chip I looked at provides actually better temperature change then the ones Sparkfun uses, but only 300 degrees per second instead of 500
[23:27] <Laurenceb> then say something to track biases, and something to do navigation
[23:27] <natrium42> so $40 retail is doable
[23:27] <Ikarus> natrium42: sounds about sane
[23:27] <natrium42> but $50 is more realistic
[23:27] <Laurenceb> hopefully you wont be spinning that fast
[23:27] <natrium42> same with the accel sensors they sell :P
[23:27] <Laurenceb> you could sell opensource imus :P
[23:28] <Laurenceb> or closed source take your pick
[23:28] <Ikarus> Laurenceb: which unlike theirs provide complete fixes
[23:28] <Ikarus> both position and attitude
[23:28] <natrium42> Ikarus, could build an IMU out of http://www.electrobee.com/motion-card-p-24.html
[23:28] <Ikarus> natrium42: I love your power budget :P
[23:28] <Laurenceb> yeah they seriously need to write some code for their imu
[23:28] <natrium42> it got 3 axis accel and 1 axis gyro
[23:29] <Laurenceb> I fear they are too dumb to manage it :p
[23:29] <natrium42> i should probably lower the price, since they don't sell too well
[23:29] <Ikarus> natrium42: yes, except in parts it is 20 euro for the same
[23:29] <Laurenceb> shuttle launch comin gup
[23:29] <natrium42> yeah
[23:29] <Laurenceb> that epsom gyro isnt actually that bad
[23:30] <Laurenceb> people have been using similar for quadcopters
[23:31] <Ikarus> Laurenceb: it is all dependent on how long you need stability
[23:31] <Laurenceb> yeah
[23:31] <Laurenceb> and if you have a human to control it
[23:31] <Ikarus> I only need it as long as the jerk is larger then 0
[23:31] <Laurenceb> or if its autonomous
[23:32] <Ikarus> and even if jerk is larger then 0 only in a few border line cases do I really absolutely need it
[23:32] <Laurenceb> the pilot can step in to fly it
[23:32] <Laurenceb> its really an augmentation system on quadcopters
[23:32] <Ikarus> Laurenceb: and it is on my INS platform aswell
[23:33] <Laurenceb> they dont even use proper filters, just badly fudged euler angle calculations
[23:33] <Ikarus> it is only relevant when the vector of the accelerometer platform and magnetic platform are too close together
[23:33] <Laurenceb> hmm when you take a corner its going to knock the g vector off
[23:34] <Ikarus> oh and possibly because it can be faster for immediate corrections
[23:34] <Laurenceb> or do any other manover
[23:34] <Laurenceb> if you look at my results with no magnetometer, the heading drifted only ~ 20 degrees over several minutes
[23:35] <Laurenceb> quite nice :D
[23:35] <Ikarus> Laurenceb: yes, but I only need it for the duration of any maneuver, once the speed is constant I don't need it because then the magnetic and gravity sensors are always well differentiated, unless I fly close to the magnetic poles
[23:35] <Laurenceb> yeah sure
[23:36] <Laurenceb> if you have a wind vector, then you can just use accel and three gyros
[23:36] <Laurenceb> then use the airvector to adjust heading
[23:36] <Laurenceb> airvector=gps_groundvector-wind_vector
[23:37] <Ikarus> yeah, you can also use multiple GPS points to correct for any drift/bias in the accelerometer sensors
[23:37] <Laurenceb> then heading=atan2(airvector_x,airvector_y);
[23:37] <Laurenceb> that as well
[23:38] <Ikarus> will be fun to write an actually working system for this
[23:38] <Laurenceb> so for fixed wind, 3 axis accel and gyro, and gps is all you need
[23:38] <Ikarus> yup
[23:38] <Laurenceb> load wind vectors off a weather model
[23:38] <Laurenceb> or if you are clever, plot the ground vectors over last ~30s
[23:38] <Laurenceb> then fit a circle to then
[23:39] <Laurenceb> center of the circle is the wind vector
[23:39] <Ikarus> I wouldn't dare run it here though
[23:39] <Ikarus> bloody wind shifts
[23:39] <Laurenceb> well it only has to be rough
[23:39] <natrium42> 4 mins left
[23:40] <Laurenceb> if your gyro is good, gusts can be filtered out
[23:40] <Ikarus> It is such a shame there is no other easy to do in small scale devices attitude reference other then gravity and magnetic north
[23:40] <Ikarus> wind being only a reasonable one
[23:40] <Laurenceb> well your reference here is gps
[23:41] <Laurenceb> and the fact you fly forwards
[23:41] <Laurenceb> however wind means thats not 100% correct
[23:41] <Laurenceb> so you have to correct
[23:42] <Laurenceb> ooh engine gymbal
[23:42] <Laurenceb> wow it gets dark fast there
[23:42] <Ikarus> heh
[23:43] <Laurenceb> in like 10miutes
[23:43] <Laurenceb> what the....
[23:43] <Laurenceb> the clock ~3 minutes ago it was practically sunny
[23:43] <Laurenceb> looks like midnight now
[23:44] <Laurenceb> must be as its so far south
[23:46] <Ikarus> hmz, I am heading to bed, the beer is getting to me
[23:47] <Laurenceb> cya
[00:00] --- Mon Mar 16 2009