highaltitude.log.20070622

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[09:53] <edwardmoore> hi jcoxon
[09:55] <edwardmoore> are you well?
[10:07] <jcoxon> hey edwardmoore
[10:07] <jcoxon> yes, much refreshed
[10:07] <edwardmoore> good
[10:08] <edwardmoore> the order is, according to the net, in uk customs
[10:08] <jcoxon> right
[10:08] <jcoxon> cool
[10:08] <edwardmoore> i hadn't reckoned with that... that could hurt
[10:08] <jcoxon> well i'm happy to make up any differnence
[10:09] <edwardmoore> nah it's ok
[10:09] <edwardmoore> i don't think they shout tax student projects :(
[10:09] <jcoxon> its VAT though
[10:09] <jcoxon> sadly we don't get let off it
[10:09] <jcoxon> right
[10:10] <jcoxon> so what shall I start work on first?
[10:10] <edwardmoore> what are the options?
[10:10] <jcoxon> (oh steve's stuff is here)
[10:10] <jcoxon> i was thinking perhaps we should work in order
[10:10] <jcoxon> of operation
[10:11] <jcoxon> I guess the first step would be a gps parser
[10:11] <edwardmoore> how have you parsed previously?
[10:11] <jcoxon> I have one in perl which logs to a file which could hten be read by the c program
[10:11] <jcoxon> or i could get one in C
[10:11] <edwardmoore> we could jsut do it in C too
[10:11] <jcoxon> (or write one)
[10:11] <edwardmoore> (easy :p)
[10:11] <jcoxon> yuk strings in C
[10:12] <jcoxon> i'll have a look for one :-D
[10:12] <jcoxon> i'll start there
[10:12] <edwardmoore> it'll be wierd writing a gps parser in C with no real computation pressure
[10:12] <edwardmoore> i have written them before, it's ok
[10:12] <jcoxon> in regards to the cinema - i'll text my friend in a sec to see if she is actually awake
[10:13] <edwardmoore> ok
[10:13] <edwardmoore> actually i guess we may aswell copy one as it's not like the processor is under pressure
[10:13] <jcoxon> yup
[10:13] <jcoxon> the limiting factor will be waiting for hte string
[10:14] <jcoxon> in some ways thats the whole limiting factor in the whole system
[10:14] <edwardmoore> the one i did for an avr turned the ascii into ints in a time-saving way which iw as quite proud of
[10:14] <edwardmoore> can you not do it on interrupts?
[10:14] <jcoxon> well i sort of meant actually waiting for the gps to produce the nmea
[10:15] <edwardmoore> guess so
[10:16] <edwardmoore> one of the packets does speed in x,y,z components doesn't it?
[10:17] <jcoxon> http://www.gpsinformation.org/dale/nmea.htm#nmea
[10:19] <edwardmoore> ta. i've just grabbed the sirf manual too
[10:19] <edwardmoore> as that's what we got
[10:21] <edwardmoore> ok so back to the list, first we need a parser
[10:23] <jcoxon> then i guess we need to calculate distances, angles etc - so all the maths
[10:23] <edwardmoore> ok well that's just some c-bashing too
[10:24] <edwardmoore> actually, which distances and angles do we actually want?
[10:24] <jcoxon> i guess first we need angle we are travelling, angle we should be travelling
[10:24] <edwardmoore> ok
[10:24] <jcoxon> therefore direction that correction needs to be in
[10:24] <edwardmoore> so angle we are travelling is vtg
[10:24] <jcoxon> i reckon range would also be helpful
[10:25] <edwardmoore> range from take-off site?
[10:25] <jcoxon> sorry i meant distance to landing site
[10:25] <edwardmoore> ok.... how are we going to decide on a landing site for the first one?
[10:26] <jcoxon> predetermined?
[10:26] <jcoxon> down wind
[10:26] <jcoxon> i'm not sure
[10:26] <edwardmoore> if it's a calm day i'd be half inclined to tell it to land at ears
[10:26] <edwardmoore> and just see how close we can get
[10:27] <jcoxon> it'll have to be down wind
[10:27] <jcoxon> or not?
[10:27] <edwardmoore> afterall for the initial flight we just want to see if this even has a slight hope of working
[10:27] <edwardmoore> yes.... but now
[10:27] <edwardmoore> no*
[10:27] <edwardmoore> well yes actually i guess :)
[10:28] <edwardmoore> it depends on how ground winds relate to jet stream
[10:28] <jcoxon> true
[10:28] <edwardmoore> but if we're within 30km of ears at apogee then i'd be inclined to tell it jsut to try and come back and see what happens
[10:29] <jcoxon> fair enough
[10:29] <edwardmoore> that we mean at 45 degree descent rate which is conservative
[10:30] <jcoxon> after the calculations
[10:31] <jcoxon> i guess we then need to convert the info into servo commands
[10:31] <jcoxon> and then move the servo
[10:31] <edwardmoore> yeah that'll be the trickier bit
[10:31] <edwardmoore> is this a purely gps feedback system?
[10:31] <jcoxon> that was the plan i think
[10:31] <jcoxon> at least for now
[10:32] <edwardmoore> ok
[10:33] <edwardmoore> so we'll move the servo, then we'll want to see how the course over the ground packet compares to the range we need to take
[10:33] <edwardmoore> but we'll want to let the course over the ground settle
[10:33] <jcoxon> well we'll have 1hz i guess
[10:33] <edwardmoore> so maybe take the average of the last 3 packets?
[10:33] <jcoxon> between nmea strings
[10:34] <edwardmoore> just emailed you the sirf manual
[10:34] <jcoxon> so have the parser collect 3 string?
[10:34] <edwardmoore> yeah if that's ok
[10:34] <edwardmoore> or maybe just have course_over_ground[3]
[10:34] <edwardmoore> and then in the parser routine:
[10:35] <edwardmoore> course_over_ground[0] = course_over_ground[1]
[10:35] <edwardmoore> course_over_ground[1] = course_over_ground[2]
[10:36] <edwardmoore> course_over_ground[2] = whats_in_latest_VTG_packet
[10:36] <jcoxon> so basically shift them through an array
[10:36] <edwardmoore> d'ya see?
[10:36] <edwardmoore> yup
[10:36] <edwardmoore> it's only 3 big so it doesn't need to be done cunningly
[10:36] <jcoxon> sure
[10:37] <jcoxon> remember you've got a nice set of C libraries
[10:37] <jcoxon> the joy of using linux
[10:37] <edwardmoore> i have no idea what's in the c library for the most part, so yeah, your knoweledge hear will help
[10:37] <edwardmoore> here*
[10:37] <edwardmoore> infact just ignore my typing
[10:37] <jcoxon> standard stuff
[10:37] <edwardmoore> the string commands will be useful
[10:38] <jcoxon> right i'm thinking that we should use polling rather than interrupts
[10:38] <edwardmoore> i think there's a command for strings that allows you to split it up over a character of your choice
[10:38] <edwardmoore> in our case a comma
[10:38] <jcoxon> as interrupts would require a kernel driver
[10:38] <edwardmoore> so basically it would seperate what's between commas
[10:38] <jcoxon> there is in perl and other languages
[10:38] <jcoxon> not sure in C
[10:38] <jcoxon> definitly in C++
[10:38] <edwardmoore> there is
[10:38] <edwardmoore> in c
[10:38] <edwardmoore> henry uses it
[10:39] <edwardmoore> it's probably the same as the c++ one
[10:39] <jcoxon> http://www.gnu.org/software/libc/manual/html_node/Finding-Tokens-in-a-String.html
[10:40] <edwardmoore> that's the fella
[10:40] <edwardmoore> i remember it was slightly klingon sounding
[10:40] <edwardmoore> oooh good resource
[10:42] <jcoxon> however
[10:43] <jcoxon> we don't have libc
[10:43] <jcoxon> we have uclibc
[10:43] <edwardmoore> :o
[10:44] <jcoxon> which is for embbedded systems
[10:45] <jcoxon> though i'm sure it'll have all the same basic stuff
[10:45] <jcoxon> its just more optimised
[10:48] <jcoxon> http://www.easysw.com/~mike/serial/serial.html#3_1
[10:48] <jcoxon> for serial port stuff
[10:49] <edwardmoore> ok well i hope it can be worked out
[10:50] <jcoxon> np
[10:50] <jcoxon> :-D
[10:50] <jcoxon> i've got some code already lying around
[10:50] <jcoxon> from the parafoil drop test payload
[10:50] <edwardmoore> ok that's good then
[10:51] <jcoxon> cool
[10:51] <jcoxon> right i am going to the cinema at 11.45
[10:52] <jcoxon> so should be finished after 12.30
[10:52] <edwardmoore> what are you seeing?
[10:52] <jcoxon> painted veil
[10:52] <jcoxon> at the picturehouse
[10:53] <jcoxon> a friend of mine who is a linguist is back for a week and wanted to go to the cinema
[10:53] <edwardmoore> ok fair enough
[10:53] <edwardmoore> kinda short tho...
[10:53] <jcoxon> oh
[10:54] <jcoxon> oops that should be 2.30
[10:54] <edwardmoore> i think i'm seeing something equally cultured and high brow today
[10:54] <edwardmoore> fanrtastic 4
[10:54] <jcoxon> haha
[10:54] <jcoxon> sorry ed - finished at 2.30
[10:55] <edwardmoore> i suspected that might be the case :)
[10:56] <edwardmoore> i'm in love with apralells
[10:56] <edwardmoore> parallels too
[10:57] <jcoxon> :-D
[10:58] <edwardmoore> i'm running ubuntu and xp right now. ubuntu for no reason.... but xp is useful
[10:58] Action: jcoxon still has a G4 800mhz iBook
[10:58] <edwardmoore> well if you get round to uprgrading, it's damn good
[10:58] <jcoxon> hehe
[10:58] <jcoxon> it still works fine
[11:02] <jcoxon> okay i'll set up the gumstix stuff
[11:02] <edwardmoore> cool
[11:05] <jcoxon> i've also bought arduino board
[11:05] <edwardmoore> yeah i saw that... what brought that on?
[11:05] <jcoxon> http://www.arduino.cc/
[11:05] <jcoxon> got it from italy
[11:05] <jcoxon> cost 42 euros
[11:07] <jcoxon> want to make a super simple payload
[11:07] <edwardmoore> what is it exactly?
[11:07] <jcoxon> for video triggering
[11:07] <jcoxon> its a atmega168 + breakout board
[11:07] <jcoxon> with usb
[11:07] <jcoxon> and nice IDE
[11:08] <edwardmoore> emphasis on nice ide :p
[11:08] <edwardmoore> it makes you feel like you're not using smelly micros :p
[11:08] <jcoxon> exactly
[11:08] <jcoxon> i've made an LED flash
[11:08] <jcoxon> and also used PWM to make it fade
[11:09] <edwardmoore> i'm giggling
[11:10] <edwardmoore> actually it'd probably make a nice servo driver
[11:12] <jcoxon> i like it
[11:12] <edwardmoore> yeah it is quite neat
[11:12] <jcoxon> its more my sort of thing
[11:12] <edwardmoore> saves faffing with pcbs
[11:12] <jcoxon> exactly
[11:13] <edwardmoore> pcb design sucks you in though
[11:13] <edwardmoore> it's a task... untill you begin to adore it
[11:13] <edwardmoore> it's a matter of pride
[11:16] <edwardmoore> you could run a balloon off it quite nicely actually
[11:16] <edwardmoore> hmm....
[11:16] <jcoxon> yeah that was the plna
[11:16] <jcoxon> plan
[11:17] <edwardmoore> i'm going to do a balloon with my local primary school next year some time.
[11:17] <edwardmoore> this might be perfect
[11:17] <jcoxon> they are very keen for this sort of thing
[11:17] <jcoxon> they have hackadays
[11:17] <jcoxon> where they give them out free
[11:17] <edwardmoore> ooooh
[11:17] <jcoxon> though in of course the USA
[11:17] <edwardmoore> well i might ask them for a freebie
[11:17] <jcoxon> make it so you can plug stuff in
[11:18] <jcoxon> say the gps
[11:18] <jcoxon> radio
[11:18] <jcoxon> etc
[11:18] <jcoxon> the only thing is that is has one serial port
[11:18] <jcoxon> okay code done to open the serial port
[11:19] <edwardmoore> most micros have just the one- what can ya do?
[11:19] <edwardmoore> i got a few multiplexers from SF anyway
[11:19] <edwardmoore> which suddenly means it could have 16 serial ports
[11:20] <jcoxon> that might be enough
[11:20] <edwardmoore> with any luck
[11:22] <edwardmoore> btw james this is the best use of a square wave ever
[11:22] <jcoxon> ?
[11:23] <edwardmoore> http://www.youtube.com/watch?v=3ff_AXVlo9U
[11:24] <jcoxon> yeah i saw that
[11:25] <jcoxon> so when do you think the gps will arrive?
[11:25] <edwardmoore> hrm.. tomorrow if we're lucky
[11:25] <edwardmoore> if not it'll be next week
[11:26] <jcoxon> okay
[11:26] <jcoxon> right i better go
[11:26] <jcoxon> whats the plan for hte day
[11:27] <edwardmoore> text me when you're back
[11:27] <edwardmoore> i'll come down
[11:28] <jcoxon> okay
[11:28] <jcoxon> it'll probably be 2.30
[11:28] <jcoxon> cya te
[11:28] <edwardmoore> cool
[11:28] <jcoxon> then*
[11:28] <edwardmoore> cya
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[13:33] <Max0> hey Laurenceb
[13:50] <Laurenceb> Hi there
[13:50] <Laurenceb> are you working on any balloon projects?
[13:51] <Laurenceb> I've forgotten who half the people on here are :-)
[13:51] <Laurenceb> been away for ages concentrating on finals
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[14:23] <Laurenceb> Hi there
[14:24] <Laurenceb> whats happening with the parafoil?
[14:35] <jcoxon> hey Laurenceb
[14:35] <jcoxon> oh the parafoil is coming along slowly
[14:35] <jcoxon> once hte weather improves we need to do some low altitude drop tests
[14:36] <jcoxon> and we are also looking into controlling and navigation
[14:36] <jcoxon> hows ultrahab
[14:36] <jcoxon> ?
[14:36] <Laurenceb> well..
[14:36] <Laurenceb> I think I need tougdate my compiler
[14:36] <Laurenceb> -update
[14:37] <Laurenceb> the mega2561 is very new
[14:37] <Laurenceb> and the .def file seems to be in error
[14:37] <Laurenceb> I near it has been updated
[14:37] <Laurenceb> I cant get portf to work, and I need that to talk to the phone
[14:38] <Laurenceb> other than that, I have fat32 and a 256mb sd card, camera, temperature sensor and power supply all integrated
[14:39] <Laurenceb> just need to attatch the cut down circuit and gps off the glider and I'm away
[14:39] <Laurenceb> also write the code of course
[14:39] <Laurenceb> but I have all the subroutines off previous missions
[14:40] <jcoxon> yeah its nice when its just a matter of fitting all of it together
[14:40] <jcoxon> so looks like you are nearly done!
[14:40] <Laurenceb> but very fustrating when your code has annoying bugs
[14:40] <Laurenceb> but yes its really just stuff I've done before
[14:41] <Laurenceb> the fat32 was the hard part
[14:41] <Laurenceb> it should be a lot lighter than previous missions
[14:42] <Laurenceb> the other thing is the cutdown code
[14:42] <jcoxon> so are you going for the hook approach?
[14:42] <Laurenceb> I'll use the prediction code of the wiki, and I've written a polygon boundary routine
[14:42] <jcoxon> cool
[14:42] <Laurenceb> yep I've come up with a hook design I'm happy with now
[14:43] <jcoxon> looking forward to seeing it
[14:43] <jcoxon> when do you plan to launch?
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[14:43] <Laurenceb> Yes I need something good to use for the enclosure..
[14:43] <Laurenceb> hopefully 2 weeks
[14:44] <jcoxon> get yourself a hotwire cutter :-D
[14:44] <Laurenceb> my polygon routine is being buggy, need to sort that
[14:44] <Laurenceb> it could be some sort of overflow, I'm testing it with a square, so the sides are parallel
[14:44] <Laurenceb> its all in 32 bit floating point
[14:46] <Laurenceb> also the in system programming port on my board has a bad joint which I cant seem to resolder its very annoying
[14:46] <Laurenceb> anyway I've done it all before now so it shouldnt take too long
[14:48] <jcoxon> so oxford finished then?
[14:48] <Laurenceb> yes finished at the weekend
[14:48] <Laurenceb> exams over :)
[14:49] <jcoxon> did okay?
[14:49] <Laurenceb> welll... could have done better
[14:49] <jcoxon> :)
[14:49] <Laurenceb> generaly went reasonably
[14:49] <Laurenceb> but in past years I've had some good exams some really bed
[14:49] <Laurenceb> -bad
[14:50] <jcoxon> yeah same
[14:50] <jcoxon> glad i'm finished
[14:50] <Laurenceb> 4th year now?
[14:50] <jcoxon> nah
[14:50] <jcoxon> finished my 3rd year
[14:50] <jcoxon> but i graduate as well
[14:50] <jcoxon> off to london for my next 3 years
[14:50] <Laurenceb> ah cool
[14:50] <jcoxon> graduate a week today
[14:51] <Laurenceb> where will you be based?
[14:51] <Laurenceb> - in london
[14:51] <jcoxon> i'm at Kings College
[14:51] <jcoxon> so Guys and Thomas' hospitals
[14:51] <Laurenceb> I see
[14:51] <jcoxon> living in Bermondsey
[14:51] <Laurenceb> thinking of doing biophysics next year
[14:51] <jcoxon> oh right
[14:52] <jcoxon> were these your finals?
[14:52] <Laurenceb> well... depends how you define it
[14:52] <Laurenceb> they call the 4th year exams finals
[14:52] <Laurenceb> but effectively these are my finals
[14:52] <Laurenceb> 4th year is easy
[14:53] <jcoxon> how many years is your course?
[14:53] <Laurenceb> 4
[14:53] <jcoxon> i'm confused
[14:53] <Laurenceb> how so?
[14:53] <jcoxon> 4 year course, now finished - biophysics next year?
[14:53] <Laurenceb> you have a 3 year course and then specialise in the 4th year
[14:53] <jcoxon> masters? phd?
[14:53] <jcoxon> right
[14:54] <Laurenceb> masters
[14:54] <Laurenceb> mphys to be precise
[14:55] <jcoxon> cool
[14:55] <Laurenceb> anyway, what is the plan for the parafoil
[14:55] <jcoxon> i get a BA this year
[14:55] <jcoxon> ummm
[14:55] <Laurenceb> ie control wise
[14:55] <jcoxon> going for GPS based
[14:55] <Laurenceb> $GPRMC
[14:55] <Laurenceb> ?
[14:55] <jcoxon> ummm
[14:55] <jcoxon> VTG
[14:56] <Laurenceb> erm whats that one?
[14:56] <jcoxon> not really sure yet
[14:56] <jcoxon> http://www.gpsinformation.org/dale/nmea.htm#VTG
[14:56] <jcoxon> will know more later
[14:56] <Laurenceb> edwardmoore said he had got a 5 axis imu off sparkfun
[14:56] <jcoxon> once Ed and I have done some coding
[14:56] <jcoxon> yeah i don't think thats for this though
[14:56] <jcoxon> his own project it think
[14:56] <Laurenceb> what sort of algorythm?
[14:57] <Laurenceb> accelerometer and gps?
[14:57] <jcoxon> hehe
[14:57] <jcoxon> not srue
[14:57] <jcoxon> just started writing code
[14:57] <jcoxon> to access and parse the gps!
[14:57] <Laurenceb> I'v been trying to work out how to do it best
[14:57] <jcoxon> we'll get back to you then
[14:58] <Laurenceb> was thinking of gps + compass + rate gyro
[14:58] <Laurenceb> that would have you sorted
[14:59] <Laurenceb> I was thinking of making a stand alone unit with compass + rate gyro and a serial input for the gumstix to give it a heading
[14:59] <Laurenceb> it could be used on all sorts of other projects as well e.g. boats
[15:00] <jcoxon> oh right
[15:00] <Laurenceb> someone on #electronics said to try an accelerometer at the apex of the parafoil
[15:00] <Laurenceb> with the cut down electronics
[15:01] <Laurenceb> as the accel vector in the payload will always be pointing to the bottom of the payload
[15:01] <Laurenceb> but at the parafoil apex it will go from side to side if your turning
[15:01] <Laurenceb> use an i2c bus the talk to the accel + cutdown up at the top
[15:05] <jcoxon> good idea
[15:06] <Laurenceb> its a lot cheaper
[15:06] <Laurenceb> but it wouldnt be very sensitive
[15:06] <Laurenceb> and if the accel wasnt parallel with the parafoil it wouldnt work
[15:07] <Laurenceb> although that could be filtered out in software... arggg
[15:08] <Laurenceb> that would start to get complicated
[15:08] <jcoxon> :-D
[15:09] <Laurenceb> I prefer the compass as its pretty invincible
[15:09] <Laurenceb> all the electronics is in the nice warm enclosure as well
[15:09] <Laurenceb> only thing that would mess that up is if the payload in hanging 20degrees or so off horizontal
[15:10] <Laurenceb> that would much up the compass
[15:10] <Laurenceb> but thats just a matter of checking the rigging
[15:10] <jcoxon> yeah but checking the rigging at 20km is a tough one :-d
[15:10] <jcoxon> the big issue with a parafoil
[15:11] <Laurenceb> well if its okay at launch the lines arent going to go anywhere :)
[15:11] <jcoxon> they are going around each other :-D
[15:11] <Laurenceb> it it tangles we're ***ed anyway
[15:11] <jcoxon> hehe
[15:12] <jcoxon> i'm also working on a payload to start testing hte deployment system
[15:12] <Laurenceb> hmmm
[15:12] <Laurenceb> I'd say try using the parafoil like a normal chute
[15:12] <Laurenceb> to start with
[15:12] <jcoxon> of certainly
[15:12] <Laurenceb> less to go wrong
[15:12] <jcoxon> oh*
[15:15] <Laurenceb> when your manovering the payload will temporarily go off horizontal
[15:15] <Laurenceb> but if you kalman filter the compass + rate gyro
[15:15] <Laurenceb> it should be okay, especially if the rate gyro is temperature compensated
[15:16] <Laurenceb> - as non horizontal payload muchs up compass heading by 1.7 times the of horizontal angle
[15:17] <Laurenceb> - thats the worse case over east anglia at 67 degrees inclination
[15:18] <jcoxon> hmmm indeed
[15:18] <Laurenceb> just worked that out :)
[15:18] <Laurenceb> 3d trig
[15:20] <Laurenceb> http://cosmos.ssol.iastate.edu/RGS/
[15:21] <Laurenceb> this appears to just use a compass
[15:21] <Laurenceb> but not updated recently
[15:24] <jcoxon> yeah seen that site
[15:25] <Laurenceb> doesnt appear to glide very well
[15:25] <Laurenceb> perhaps they didnt get the trim right
[15:37] <Laurenceb> I'm off cya
[15:37] <jcoxon> cya
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[16:31] <edwardmoore> hello
[16:31] <edwardmoore> jcoxon
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[20:45] <max0_> hey guys
[20:45] <max0_> my wifi router came today and ive got openwrt installed :)
[20:46] <max0_> and irssi ;)
[20:49] <icez> woohoo
[20:50] <max0_> yeah im quite happy seemed to work ok
[20:50] <max0_> ive got a rockwell gps and nokia to add to it now
[20:52] <icez> gps to a router?
[20:52] <icez> oh it's for a balloon
[20:52] <icez> :P
[20:53] <max0_> maybe
[20:53] <max0_> im more intresed in the computing side
[20:53] <max0_> :)
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[22:14] <mc-> anyone around?
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[22:23] <Laurenceb> Hi all
[22:23] <Laurenceb> loads of people
[22:24] <Laurenceb> just got ultrahab texting me :)
[22:24] <phatmonkey> hey guys
[22:24] <phatmonkey> hey jcoxon
[22:24] <Laurenceb> hi there
[22:25] <Laurenceb> anything happening with your glider?
[22:25] <phatmonkey> i have holidays now, yay, time to do some balloon stuff
[22:25] <phatmonkey> nope, not at all
[22:25] <phatmonkey> hehe
[22:25] <Laurenceb> can I ask you where you got thermopiles from?
[22:25] <phatmonkey> i'm planning to help with the glidery parafoily things james is doing, but haven't really kept up to date
[22:25] <phatmonkey> eermm, one sec
[22:26] <phatmonkey> hmm
[22:26] <phatmonkey> forgotten the site
[22:26] <Laurenceb> I'm vaugely thinking of making a thermopile gided glider
[22:26] <Laurenceb> fma direct?
[22:26] <phatmonkey> no
[22:26] <phatmonkey> somewhere else....
[22:27] <Laurenceb> well they are quite cheap
[22:27] <phatmonkey> http://uavs.net/
[22:27] <Laurenceb> but dont sell individual z axis sensors
[22:27] <phatmonkey> http://scalerobotics.com/store/catalog/
[22:27] <phatmonkey> that's it
[22:27] <Laurenceb> looking..
[22:28] <Laurenceb> erm cant see it
[22:28] <phatmonkey> hmm
[22:28] <Laurenceb> that rcap thing is not going to work
[22:28] <phatmonkey> well it used to be there!
[22:28] <phatmonkey> maybe try emailing the guy
[22:28] <Laurenceb> oh well
[22:29] <Laurenceb> the rcap is 0.5hz proportional control
[22:29] <Laurenceb> with no wind compensation
[22:29] <Laurenceb> not going to work !
[22:30] <mc-> I emailed the guy on scalerobots and he doesn't sell thermopiles any more
[22:30] <Laurenceb> I'll go fma then
[22:30] <mc-> would pyroelectric sensors work? they are cheap
[22:30] <mc-> and I've got some
[22:31] <Laurenceb> they are not dc coupled
[22:31] <Laurenceb> probably a bad idea
[22:31] <mc-> are you sure?
[22:31] <Laurenceb> I'm sure they're ac coupled
[22:31] <mc-> I thought the difference was that it has an amp inside
[22:31] <Laurenceb> nope
[22:31] <mc-> ok
[22:32] <Laurenceb> its a pyroelectriccrystal
[22:32] <Laurenceb> thermopiles are a mems thermopile
[22:32] <Laurenceb> I was working on some thermopile wafers at work last summer
[22:32] <mc-> I tried pointing the pyro out of the window, and it showed a change
[22:33] <Laurenceb> it would as its ac coupled :)
[22:33] <Laurenceb> but leave it for 30 seconds and itd go back to 0
[22:34] <Laurenceb> Just been trying to derive a function to turn thermopile temperature difference into roll or pitch
[22:34] <Laurenceb> its a bit tricky
[22:35] <Laurenceb> I'm assuming a circular aparture and square sensing surface
[22:35] <mc-> how about using the sun as a reference, around midday it's pretty high in the sky.
[22:35] <Laurenceb> then parallel planes for the ground and sky
[22:35] <Laurenceb> tricky
[22:36] <Laurenceb> easy to pick up, but its nice to have a vertical vector
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[22:36] <Laurenceb> it you have a vertical vector then you can get roll and pitch straight away
[22:36] <Laurenceb> longwave IR flux is a vertical vector, as is gravity
[22:37] <Laurenceb> IMUs use gravity, but the acceleration of the vehicle mucks this up on the short term, so you use gyros
[22:37] <Laurenceb> as well
[22:37] <mc-> I forgot about gravity because I've been assuming it's a rocket
[22:37] <Laurenceb> well I'm only interested in gliders at the moment :)
[22:38] <mc-> how about a combined sun and gravity sensor
[22:38] <mc-> use the sun when there's some violent turns, and then switch over to a gravity sensor
[22:38] <Laurenceb> easier to have a combined compass + accelerometer
[22:39] <Laurenceb> hmmm you need at least two vectors at all times
[22:39] <mc-> a 2 axis accelerometer is a nice gravity sensor
[22:39] <Laurenceb> unless you have gyros as well
[22:39] <mc-> I like cheap and cheerful
[22:39] <mc-> and gyros drift
[22:40] <Laurenceb> a cheap and cheerfull idea for parafoils is to have an accelerometer at the parafoil apex
[22:40] <Laurenceb> you can then detect the roll
[22:40] <Laurenceb> and use it for steering
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[22:41] <edwardmoore> wow
[22:41] <mc-> I guess the apex is the CoG of the parafoil
[22:41] <Laurenceb> wow?
[22:41] <mc-> or CoP
[22:41] <edwardmoore> it's rammed in here
[22:41] <Laurenceb> erm cop yes
[22:41] <Laurenceb> deosnt make a grate deal of difference
[22:42] <Laurenceb> as long as its away from the payload
[22:42] <mc-> but accelerometer would give bad results when doing sharp rolls/pitches etc
[22:42] <Laurenceb> yes
[22:42] <Laurenceb> but good enough in that configurtion for parafoil guidance
[22:43] <Laurenceb> a guy on #electronics built that arrangement
[22:43] <mc-> I bought a toy motorized parafoil which flies
[22:43] <Laurenceb> cool
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[22:43] <mc-> don't know how much payload it can carry
[22:43] <mc-> it not RC controlled
[22:44] <mc-> might remove the motor and put in some servos
[22:45] <mc-> must sleep
[22:45] <mc-> cya
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[22:49] <Laurenceb> edwardmoore, what hav you got planned parafoil guidance wise?
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[22:52] <msweeney> evening all
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[23:15] <Laurenceb> lots of people:)
[23:15] <Laurenceb> ultrahab is texting me :)
[23:29] <Laurenceb> cya all
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[00:00] --- Sat Jun 23 2007