highaltitude.log.20100921

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[10:14] <Laurenceb> hi
[10:15] <Laurenceb> SpeedEvil, Randomskketc, I'm going to order some lsm303dlh sensors
[10:15] <Laurenceb> anyone wantsome?
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[10:51] <Stratisphere> ooo
[10:51] <Stratisphere> neat
[10:51] <Stratisphere> we're putting the same kinda thing in but using two seperate packages
[10:59] <SpeedEvil> yes, put me down for one.
[10:59] <SpeedEvil> thanks!
[11:00] <earthshine> morning
[11:00] <Randomskk> Laurenceb: will take two if that's okay, cheers!
[11:01] <earthshine> Laurenceb: How much pls ?
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[11:54] <Laurenceb> $13 or so
[11:56] <Laurenceb> just asec
[12:00] <Laurenceb> £12.13
[12:00] <Laurenceb> each
[12:00] <SpeedEvil> sounds reasonable.
[12:00] <Laurenceb> from polish webstore
[12:00] <Laurenceb> onlyplace that has any
[12:01] <Laurenceb> there are samples,but you can only get two maximum
[12:01] <Laurenceb> cometo think of it i should reallyenquire with st before spending any money
[12:03] <SpeedEvil> ah - same here - I'll ping them.
[12:08] <earthshine> Are they the raw modules or do they have breakouts?
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[12:13] <Laurenceb> LGA28
[12:13] <Laurenceb> ooh you can order stm32 samples from st.comtho
[12:25] <m1x10> I bought an assembled RG176 coax but on the wire it does not write 'rg176'
[12:26] <m1x10> the bulk rg176 I bought some months ago it had the 'rg176' along the whole cable
[12:27] <m1x10> strange
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[13:24] <juxta_> ping rjharrison
[13:33] <m1x10> shit! i was searching for greek companies that print PCBs and I found one next to my neighborhood !!!! Thats crazy !
[13:38] <griffonbot> @nearsys: The radios art in the mail. Soon i'll have the NearSpace UltraLight flight computer ready for retail. #ARHAB [http://twitter.com/nearsys/status/25119186053]
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[14:23] <juxta_> did you end up getting your design sorted out m1x10?
[14:26] <m1x10> juxta_, I finished the small radio breakout. Now that Ive learned a bit about PCB software I started designing a whole arduino shield
[14:26] <m1x10> and i will put there everything
[14:26] <juxta_> great :)
[14:26] <m1x10> hehe
[14:26] <juxta_> if your design is simple you could make it at home quite easily
[14:26] <m1x10> I remember you, warning me, about the breadboards :)
[14:27] <m1x10> I finished the schematic and now Im trying to place the whole stuff on the PCB editor.
[14:28] <m1x10> designing is a very kool thing :)
[14:29] <juxta_> flying a breadboard would be a bad idea I think ;)
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[14:31] <m1x10> sure, but I didnt have any other choice back then :)
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[14:32] <m1x10> pcb makes it less heavy and takes up less space
[14:47] <Darkside> hehe
[14:47] <Darkside> my transmitter is currently a piece of veroboard, and another box
[14:47] <Darkside> and puts out 40mW
[14:48] <SpeedEvil> I've done 1200W class D on breadboard.
[14:48] <SpeedEvil> It did not immediately explode.
[14:48] <Randomskk> fcvo immediately?
[14:49] <Darkside> SpeedEvil: 1200W?
[14:49] <Darkside> also how did you generate the FET drive signal?
[14:50] <Darkside> i'm having trouble finding a comparator that will work at RF frequencies
[14:53] <SpeedEvil> Darkside: Pulse transformer
[14:53] <SpeedEvil> RF?
[14:53] <Darkside> 40m - 7MHz
[14:53] <SpeedEvil> maxim-ic.com - for one - there are thousands.
[14:53] <SpeedEvil> why?
[14:54] <Darkside> comparate a sine wave
[14:54] <Darkside> to get a square wave
[14:54] <Darkside> and hence drive the FET
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[14:54] <Darkside> (through a buffer)
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[15:04] <Laurenceb> hi
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[15:05] <SpeedEvil> Hi again.
[15:12] Action: Laurenceb is looking for anti vibration mounts
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[15:17] Action: SpeedEvil passes Laurenceb 1023 cubic yards of readymixed concrete.
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[15:21] <timbobel> evening
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[15:26] <johnnyfive|work> mornin!
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[15:51] <timbobel> i know i can say:
[15:51] <timbobel> int getPct(void) {
[15:52] <timbobel> or
[15:52] <timbobel> long getDpi(void) {
[15:52] <timbobel> or
[15:52] <timbobel> char getDpi(void) {
[15:52] <timbobel> but how do i tell it it's a char array
[15:55] <timbobel> no-one?
[16:10] <timbobel> ping everyon
[16:10] <SpeedEvil> http://www.st.com/mcu/contentid-133-110-STM32VLDISCOVERY.html?wt.mc_id=enews_sep2010_STM32discovery $10 32 bit processor dev kit with USB
[16:10] <SpeedEvil> Is this C/
[16:11] <SpeedEvil> you generally cannot return arrays
[16:11] <Randomskk> timbobel: char*
[16:11] <Randomskk> will return a pointer to a char
[16:12] <Randomskk> if you allocate memory, that is the same as an array
[16:13] <timbobel> i tried
[16:13] <timbobel> oh well
[16:14] <timbobel> incompatible types of char* to char[20]
[16:15] <SpeedEvil> you can't do that.
[16:15] <SpeedEvil> you need to allocate the storage first.
[16:15] <timbobel> speedevil: looks like a unpretty version of the leaf maple :)
[16:15] <SpeedEvil> static char array[20]
[16:15] <SpeedEvil> or example.
[16:15] <timbobel> yeah i do
[16:15] <SpeedEvil> In main()
[16:15] <timbobel> char user[20];
[16:16] <SpeedEvil> Or user=malloc(20)
[16:16] <SpeedEvil> However - in genreal for embedded stuf you should never use malloc - but manage the memory yourself.
[16:16] <Randomskk> also you may have to cast to use it as an array
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[16:38] <timbobel> i figured it out
[16:39] <timbobel> so.. how do i put a "%" logo in here : sprintf(buffer, "%lddpi %d%", dpi, pct);
[16:39] <timbobel> since % is used as an operator
[16:39] <SpeedEvil> %%
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[16:42] <timbobel> you are the man.
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[17:00] <EI5GTB> ohi
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[17:38] <timbobel> oh hi
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[19:18] <Laurenceb> http://i.imgur.com/rANe9.png
[19:18] <Laurenceb> ^dongle finished XD
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[19:19] <Randomskk> Laurenceb: that was quick work :P
[19:19] <jcoxon> evening
[19:19] <Laurenceb> yeah i have some more practice now
[19:19] <Laurenceb> needs a little neatening up but basically thats done
[19:21] <Laurenceb> http://uk.farnell.com/lumberg/2410-07/plug-usb-type-a/dp/1308875?Ntt=lumberg+2410-07 <- using that plug
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[19:54] <SpeedEvil> :)
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[20:40] <chris_99> hi guys, has anyone used hydrogen before with weather balloons
[20:40] <SpeedEvil> I have not, however I plan on doing a launch with natural gas.
[20:41] <chris_99> what do you mean by natural gas?
[20:41] <SpeedEvil> largely methane
[20:41] <SpeedEvil> Anyway.
[20:41] <SpeedEvil> Hydrogen is largely fairly benign.
[20:41] <chris_99> benign?
[20:42] <SpeedEvil> As long as you start out with the balloon with no air at all in it, then the absolute worst-case is basically a balloon diameter bonfire lasting maybe 2s, with a flaming lump of plastic thrown a few metres.
[20:42] <chris_99> aha, rather than a rather big explosion
[20:43] <chris_99> yeah thats what i'm kind of worried about
[20:43] <SpeedEvil> See http://www.youtube.com/watch?v=AQwHU8vhXY8
[20:43] <SpeedEvil> err - not that
[20:44] <SpeedEvil> Sigh.
[20:44] <SpeedEvil> I seem to have misplaced my youtube link which had someone demonstrating this.
[20:45] <chris_99> no worries, i saw a video yesterday where people where making hydrogen with aluminium + acid
[20:45] <chris_99> and they lit it
[20:45] <chris_99> also i found some interesting devices with cars, (while being completely pointless for a car) are supposed to produce 1l / minute
[20:46] <SpeedEvil> http://www.youtube.com/watch?v=cQvpK9cl0No
[20:46] <SpeedEvil> aha
[20:46] <chris_99> of hho
[20:46] <SpeedEvil> you can see - it's rather boring
[20:46] <SpeedEvil> hho is _DANGEROUS_
[20:46] <SpeedEvil> In a balloon.
[20:46] <SpeedEvil> The above commens do not apply.
[20:47] <chris_99> yeah, i would modify to only take the hydrogen
[20:47] <SpeedEvil> With a wearther balloon sized volume of HHO, or impure hydrogen with >2% oxygen, you risk explosions with at best severe hearing damage
[20:47] <chris_99> and discard the oxygen somehow
[20:47] <SpeedEvil> hydrogen is inexpensive to purchase
[20:47] <SpeedEvil> Also - zinc + acid is cheap and easy
[20:48] <chris_99> ah is that another metal you can use to make it?
[20:48] <SpeedEvil> yes
[20:48] <SpeedEvil> Ir's available moderartely cheaply on ebay.
[20:48] <chris_99> that might be better to do it that way, to avoid the oxygen entirely
[20:50] <chris_99> have you used this site before btw http://habhub.org/predict/
[20:50] <chris_99> to predict landing point
[20:53] <SpeedEvil> It's commonly used.
[20:53] <SpeedEvil> I've not launched anything yet.
[20:55] <chris_99> aha, me neither it sounds a really cool hobby though, i enjoy electronics + photography so it seemed like a fun thing to do
[20:56] <SpeedEvil> :)
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[21:06] <chris_99> i like this wikipedia article http://en.wikipedia.org/wiki/Lighter_than_air on the bottom the 'Vacuum balloon'
[21:06] <Laurenceb> easiest way to make hydrogen is al + NaOH
[21:06] <Laurenceb> bbl
[21:07] <chris_99> thanks Laurenceb
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[21:26] <natrium42> Laurenceb, what about electrolysis?
[21:35] <jcoxon> hey natrium42
[21:35] <natrium42> hi james
[21:35] <jcoxon> how everything?
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[21:38] <natrium42> pretty good, my back hurts a bit :S
[21:38] <natrium42> how are you?
[21:41] <jcoxon> good thanks
[21:41] <jcoxon> just working on a circuit to keep the ntx2 crystal warm
[21:42] <natrium42> oh cool
[21:42] <chris_99> i've found you can wire up 7805's to go 'hot'
[21:42] <natrium42> i want to launch the ntx2 soon
[21:42] <natrium42> jcoxon, so is a moxon antenna enough?
[21:42] <natrium42> or even a whip?
[21:42] <jcoxon> a whip is enough really
[21:42] <jcoxon> a moxon is a bit better
[21:42] <jcoxon> and then of course the yagi
[21:43] <natrium42> it's going to be just me tracking, most likely
[21:43] <jcoxon> pah we can recruit someone else
[21:43] <natrium42> i mean, for local latex launch
[21:43] <jcoxon> is va3sie near to you?
[21:43] <natrium42> i am keen on getting started simple first
[21:43] <natrium42> yes
[21:43] <jcoxon> i'm sure he'd help out
[21:43] <natrium42> alright, cool
[21:44] <jcoxon> natrium42, i'm about to send off my new flight board to seedstudio
[21:44] <jcoxon> want one?
[21:44] <natrium42> what does it have?
[21:44] <jcoxon> arduino, ntx2 and power reg
[21:44] <jcoxon> thats all
[21:44] <jcoxon> serial port access for gps
[21:45] <jcoxon> but no onboard gps
[21:45] <jcoxon> might be quicker to make your own
[21:45] <jcoxon> or of course just use the atlantichalo flight computer
[21:45] <natrium42> yeah, i think i will just put something together quickly
[21:45] <jcoxon> thats probably more sensible
[21:45] <natrium42> i am too impatient to wait :D
[21:45] <jcoxon> yeah get it up in the air
[21:46] <jcoxon> we need to get on with this project!
[21:46] <natrium42> :D
[21:47] <chris_99> how much does it cost roughly for seeed studio to make PCBs btw jcoxon?
[21:48] <natrium42> jcoxon, might test SPOT2
[21:48] <jcoxon> 2 layers 5cm x 5cm is 20 dollars iirc
[21:48] <jcoxon> natrium42, yeah that would be good
[21:49] <chris_99> wow, that could work out rather expensive imo
[21:49] <jcoxon> oh for 10
[21:49] <jcoxon> sorry
[21:49] <jcoxon> missed that bit
[21:50] <chris_99> oh cool :) they can do bigger than 5x5 i assume?
[21:50] <jcoxon> yeah
[21:50] <chris_99> cool, i might check that out, i was thinking of making some UV PCBs, but that seems pretty cheap too
[21:51] <jcoxon> postage takes a while
[21:52] <chris_99> ah, might go the acid etching way, i want to send something up asap heh
[21:53] <jcoxon> cool, i've got my temp sensor to stay nicely at 30 deg C
[21:53] <natrium42> chris_99, where are you located?
[21:53] <chris_99> lancaster, UK
[21:54] <natrium42> ah, ok
[21:54] <chris_99> you in the US?
[21:54] <natrium42> there is some cheap 1 day pcb service in the US
[21:54] <natrium42> no, canada here
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[21:55] <chris_99> aha, i'll have to see if theres anyone in the UK that might do that
[21:55] <chris_99> i've used seeed before once for their logic analyser and it did take rather a while
[21:56] <jcoxon> hmmm i'm going to do a fridge test
[21:56] <jcoxon> need some way of recording/communicating the info
[21:56] <jcoxon> thoughts?
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[21:57] <jcoxon> doubt 10mW of radio will get through
[21:57] <chris_99> you could see if the aerial might fit through the door if it doesnt
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[21:58] <natrium42> jcoxon, is there a transparent window?
[21:58] <DanielRichman> I put the nim2 (10mW) in the freezer and sat upstairs getting data
[21:58] <natrium42> i recommend optical
[21:58] <chris_99> you could also write to the EEPROM of your microcontroller
[22:00] <jcoxon> chris_99, that might be easier
[22:00] <jcoxon> eventually will need to rig the radio
[22:00] <jcoxon> but not tonight
[22:01] <chris_99> what kind of battery are you using btw?
[22:01] <jcoxon> on the balloon? energizer lithiums
[22:01] <chris_99> yeah
[22:01] <chris_99> does lithium work ok when its cold then?
[22:02] <jcoxon> yes
[22:02] <chris_99> cool, i bought a few radiosondes recently and they come with 'water' batteries which i'd never seen before
[22:02] <chris_99> so i might try using some of those with my own circuit
[22:03] <jcoxon> i recommend the lithiums
[22:03] <jcoxon> never failed me yet
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[22:03] <chris_99> cool :) any particular one?
[22:03] <jcoxon> energizer lithiums AAs
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[22:04] <chris_99> oh nice, should be able to get those easily
[22:04] <jcoxon> yeah
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[22:04] <earthshine> hi jcoxon
[22:05] <jcoxon> hey earthshine
[22:05] <RocketBoy> for inception lovers http://www.youtube.com/watch?v=ZrYPJ4Yc31g
[22:05] <earthshine> lol
[22:06] <chris_99> haha
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[23:33] <chris_99> these look pretty fun http://www.modelballoon.com/balloondesign.html
[23:33] <chris_99> i'm curious whether if you held onto them, they'd take you up too
[23:36] <SpeedEvil> no
[23:36] <SpeedEvil> 3500 cubic feet
[23:36] <SpeedEvil> that's 400m^3
[23:37] <SpeedEvil> at sea level - the air in that will weigh about 600Kg
[23:37] <SpeedEvil> If you raise the temp 10C, you get 60Kg of lift.
[23:37] <SpeedEvil> hmm
[23:37] <SpeedEvil> err
[23:37] <SpeedEvil> 27c
[23:37] <Randomskk> you'd need a lightweight person, no significant ballast and an almost zero mass basket
[23:38] <chris_99> heh, interesting
[23:38] <chris_99> wheres that calculation come from SpeedEvil
[23:38] <chris_99> i'm rather curious
[23:39] <SpeedEvil> ideal gas laws.
[23:39] <SpeedEvil> P1V1/T1=P2V2/T2
[23:39] <SpeedEvil> Or something like that
[23:40] <chris_99> cheers, i remember doing some of those calculations in physics now
[23:40] <Randomskk> physics is great for this kind of stuff
[23:41] <Randomskk> SpeedEvil: is electronic beam forming still really hard these days?
[23:41] <Randomskk> I was wondering if you could use it, given a balloon's GPS and magno, to beam at a receiver
[23:41] <chris_99> i'd like to look into how the prediction websites work too, i imagine thats pretty cool too
[23:41] <Randomskk> chris_99: simpler than you'd imagine
[23:41] <Randomskk> we get wind velocity data at pressure levels and latitude/longitudes from the US weather supercomputers
[23:42] <Randomskk> then, we assume the balloon travels at wind velocity with no inertia
[23:42] <Randomskk> then we give it a constant ascent rate and follow the wind velocity as it goes up
[23:42] <SpeedEvil> Randomskk: It depends what you mean by 'really hard'.
[23:42] <Randomskk> then it follows a formula for descent based on atmospheric density and its drag, again following wind velocity
[23:43] <Randomskk> SpeedEvil: achievable by someone without formal education in the subject, on a reasonable time and money budget but not an R&D department
[23:43] <SpeedEvil> Randomskk: For example, from memory, you can get AD 4-quadrant multipliers trhat go DC-2.4GHz for $3 or so.
[23:43] <chris_99> so you're taking account of the multiple directions of the wind too i guess, by looking at the patterns of cloud movement from the sat data
[23:43] <SpeedEvil> Randomskk: In principle, you could rtake 16 of these, a master transmitter, and generate an arbitrary phase from it.
[23:44] <Randomskk> chris_99: well we have a multidimensional array of wind velocity data. each data point gives the wind direction as an (x, y) vector for a given pressure (maps to altitude), latitude, longitude and time
[23:44] <SpeedEvil> Randomskk: So you hten have 16 antennas you can change phase on at random.
[23:44] <Randomskk> we just run through them, ascending.
[23:44] <chris_99> thats really cool :)
[23:44] <Randomskk> SpeedEvil: doing the maths for the phasing is how hard?
[23:44] <SpeedEvil> Randomskk: umm.
[23:46] <Randomskk> "very"?
[23:47] <SpeedEvil> For example, if you want the beam to go north. You start out at the origin with 0 phase, and then go to +90 degrees 1/4 of a wavelength northwards of the origin, and -90 1/4 south
[23:47] <SpeedEvil> I'm not sure if this is optimal.
[23:48] <Randomskk> is that harder than it sounds or..?
[23:48] <SpeedEvil> I suppose you'd be wanting a circular array of antennas arranged horizontally.
[23:48] <Randomskk> I mean, making 16 antennas wouldn't be super easy, but not really all that awful. you could rig them to a balloon.
[23:48] <SpeedEvil> It's not harder than it sounds.
[23:48] <SpeedEvil> But I'm unsure how to calculate it.
[23:48] <Randomskk> at microwaves it'd be easier, but even at 434 it seems like it would be doable
[23:49] <Randomskk> in terms of fitting antennas
[23:49] <Randomskk> microwaves get more complicated with legalities and driving it and all that I guess
[23:49] <Randomskk> but a directed beam microwave link seems like it'd let you up the baud rate really significantly
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[23:49] <SpeedEvil> Yeah.
[23:50] <Randomskk> even fairly crude beam forming would make a big difference, but you know the direction you need it to go fairly precisely
[23:50] <Randomskk> tell it the receiver (or multiple receivers and scan between them) before flight, it has GPS, it can have a magno and accel to compensate for some tilt
[23:50] <SpeedEvil> Going from omni to +10dB or so is a reasonable improvement.
[23:50] <Randomskk> I guess beamforming in 3d is harder so you probably couldn't do much about the tilt
[23:51] <Randomskk> but making a basic rigging that held 16 antennas on 434 wouldn't be hard
[23:51] <Randomskk> just the driving them that seems difficult
[23:51] <Randomskk> I imagine the information on how to do so is out there
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[00:00] --- Wed Sep 22 2010