highaltitude.log.20060728

[00:00] <phatmonkey> hmm, too much mindless irc chatter
[00:00] <kc0wys> lol
[00:00] <kc0wys> yeah my (former) teacher stopped by today
[00:00] malgar (n=malgar@adsl-ull-164-217.47-151.net24.it) left irc: "*** E' solo l'urto con un iceberg, che vuoi che sia, questa è una nave inaffondabile. *** 75$/barile"
[00:00] <kc0wys> we strapped the payload to the top of the car and he drove around while i received the data at home
[00:00] <kc0wys> it was funny the faces we got on camera :)
[00:01] <kc0wys> there was one ups truck that drove by with the door open
[00:01] <kc0wys> the guy was staring at the car
[00:01] <phatmonkey> hahaha
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[00:01] <phatmonkey> do you have any backup systems if the radio fails?
[00:02] <phatmonkey> well, i suppose you can find the signal if the communication fails
[00:02] <phatmonkey> phone or something?
[00:03] <kc0wys> no
[00:03] <kc0wys> :/
[00:03] <kc0wys> oh well
[00:03] <kc0wys> the voltage regulator is well-cooled
[00:03] <kc0wys> in fact, over-cooled
[00:04] <kc0wys> it's got a cpu heatsink and fan :P
[00:04] <kc0wys> do you know if james has temperature logs of pegasus 1 and 3 on his site?
[00:05] <phatmonkey> he didn't have any temperature sensors
[00:05] <kc0wys> oh really?
[00:05] <kc0wys> huh.
[00:06] <phatmonkey> i really need to hook up some, hmm
[00:06] <phatmonkey> i can probably just get some thermistors on the ADCs
[00:07] <kc0wys> ya, or even transistors are cheap too
[00:07] <kc0wys> i'm using lm335's
[00:07] <kc0wys> just fyi
[00:07] <LaurenceB> I'm using a 1-wire sensor DS1820 I think
[00:09] <phatmonkey> can those be hooked up to GPIOs?
[00:09] <phatmonkey> probably easier than calibrating it myself
[00:09] <LaurenceB> Not sure about gumsticks I'm using a microcontroller
[00:10] <kc0wys> gpio is just an i/o port, right?
[00:10] <kc0wys> can you can read/write bits to and from it?
[00:10] <phatmonkey> general purpose digital i/o, yes
[00:11] <phatmonkey> pretty much it
[00:11] <LaurenceB> I've got to go see you ;-)
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[00:15] <phatmonkey> holy crap
[00:15] <phatmonkey> http://wiki.ukhas.org.uk/code#bash_script_to_rotate_and_gzip_log_files
[00:15] <phatmonkey> whoops
[00:16] <phatmonkey> wrong link
[00:16] <phatmonkey> http://www.thefintels.com/bbs/viewtopic.php?t=96
[00:16] <phatmonkey> that is awesome :D
[00:16] <phatmonkey> and he links to james' balloon...
[00:18] <phatmonkey> i'd better get some sleep, night all
[00:18] <kc0wys> alright
[00:18] <kc0wys> cya
[00:58] <kc0wys> woo camera's mounted
[00:58] <kc0wys> and that's it for the hardware ;)
[00:58] <kc0wys> now to finalize the software...
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[02:33] <kc0wys> well this is my first time shorting a camera's flash capacitor
[02:33] <kc0wys> that was scary
[02:33] <kc0wys> :/
[02:34] <Tiger^> ok so what's the lesson?
[02:34] <Tiger^> don't try it out before disassembly ;>
[02:34] <Tiger^> (it's easy for me to say, my cameras didn't have flash ;>)
[02:38] <kc0wys> oh i just shorted it on the broken camera
[02:38] <kc0wys> no way would i do something stupid with one that works :)
[02:38] <Tiger^> ah, right ;>
[02:38] <kc0wys> i think it's still good, though
[02:38] <kc0wys> not sure
[02:38] <kc0wys> just lots of sparks
[02:38] <kc0wys> i mean the capacitor
[02:38] <kc0wys> i'm sure the camera's shot
[02:39] <Tiger^> hm
[02:40] <kc0wys> okee i drilled four small holes in the plexiglass
[02:41] <kc0wys> that *should* let in some cold air and prevent it from fogging
[02:41] <kc0wys> 'tis what they do on planes
[02:41] <kc0wys> *shrugs*
[02:42] <Tiger^> no that's not true! one small hole in the window and things start being sucked out of the plane! even at low altitudes!
[02:42] <Tiger^> ;>
[02:42] <kc0wys> no they do
[02:42] <kc0wys> there are two panes in the boeing jets i've been in, and the outside panes have a hole at the bottom of each
[02:43] <Tiger^> i was joking ;P
[02:43] <kc0wys> or maybe that was the inside pane
[02:43] <kc0wys> o ok
[02:43] <Tiger^> it is like that in the movies ;)
[02:47] <kc0wys> hehe
[02:47] <kc0wys> whoosh
[02:47] <kc0wys> woops there goes billy!
[02:51] <kc0wys> hmm what should my note to the person who finds my balloon say?
[02:51] <kc0wys> "Harmless Civilian Bomb"?
[02:51] <kc0wys> :P
[02:51] <kc0wys> er I mean "Harmless Civilian Experiment"
[02:51] <kc0wys> hehe
[03:12] <Tiger^> hmm
[03:13] <Tiger^> i wrote "Harmless meteorological experiment, if found please call xxxxx"
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[04:16] <kc0wys> yea i put "Harmless Meteorological Balloon" then a little description of it (including "It is completely SAFE and NOT HAZARDOUS") and then my phone number and email
[04:26] <Tiger^> "look, mister, junior here dropped it on his foot... and twas supposed to be SAFE!"
[04:26] <Tiger^> ;)
[04:46] <kc0wys> hehe
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[11:42] <jcoxon> morning all
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[13:33] <phatmonkey> kc0wys, make sure you say there is a reward available
[13:34] <phatmonkey> that'll encourage most people to ring you instead of pinching it
[15:01] <kc0wys> but i'm a cheap guy! :P
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[16:10] <kc0wys> yay the helium is here
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[16:56] <phatmonkey> kc0wys, even just giving them £25 or so as a thank you is worth it to get your stuff back!
[16:58] <LaurenceB> I've added a few photos on UKHAS wiki :-)
[17:00] <phatmonkey> ooh, nice
[17:01] <phatmonkey> what sort of hardware did you use?
[17:03] <LaurenceB> ATmel AVR mega8 from active robots
[17:03] <LaurenceB> and bascom compiler (demo compiles 4k of machine code)
[17:04] <LaurenceB> Camera is a 300K pixel webcam think with internal memory
[17:06] <phatmonkey> ah right
[17:07] <phatmonkey> i've been considering condensing my code to fit on a little microcontroller
[17:07] <phatmonkey> to make tiny little gliders
[17:08] <phatmonkey> the robostix is a atmel mega128, that would do the job i suppose
[17:08] <LaurenceB> is robostix from gumstix
[17:09] <kc0wys> that's 50 bucks!!
[17:12] <phatmonkey> kc0wys, would you rather lose your stuff or pay 50 bucks?
[17:12] <phatmonkey> LaurenceB, yeah
[17:13] <LaurenceB> Tiny gliders is a good idea, you could use a smart ant and maybe a diy radio like james coxons 437MHz thing
[17:13] <phatmonkey> yeah, exactly
[17:13] <phatmonkey> nice thing with the little microcontrollers is they use practically no power
[17:13] <LaurenceB> www.active-robots.co.uk is the site I think
[17:14] <phatmonkey> i'll get the big one done first though :D
[17:15] <LaurenceB> they sell these microcontroller boards with ISP ports which are handy
[17:15] <phatmonkey> yeah
[17:15] <phatmonkey> it's terribly easy to program the robostix
[17:15] <LaurenceB> rather like Basic stamp but way cheaper and more powerful
[17:16] <LaurenceB> Yes I might give linux a go
[17:16] <phatmonkey> i wonder how much current my robostix draws... one sec
[17:16] <kc0wys> damn faa says i need to choose a new launch location
[17:16] <phatmonkey> the robostix is a gumstix expansion with a atmel mega128 processor
[17:16] <phatmonkey> damn
[17:16] <kc0wys> in the neighboring state!
[17:17] <phatmonkey> http://docwiki.gumstix.org/Robostix
[17:17] <kc0wys> so i gotta cross the missouri-illinois border and launch somewhere in the middle of nowhere
[17:17] <kc0wys> this sucks
[17:17] <phatmonkey> http://docwiki.gumstix.org/Image:Robostix-Top.jpg
[17:17] <phatmonkey> handy little thing for I/O
[17:17] <phatmonkey> damn
[17:17] <phatmonkey> can't you change the date?
[17:17] <kc0wys> no it's all because of the local international airport
[17:18] <LaurenceB> Hard luck Kc0wys
[17:18] <phatmonkey> ah
[17:18] <kc0wys> i'd be flying right by 747 trans-atlantic flights
[17:18] <kc0wys> in fact, there was a close call over in kansas city i heard from the guys at the faa
[17:18] <kc0wys> some guy in a private jet almost hit a weather balloon
[17:19] <kc0wys> had to maneuver around it
[17:19] <kc0wys> :
[17:19] <LaurenceB> Any ideas how to interface a camera with a gumstix?
[17:19] <kc0wys> npn transistor?
[17:19] <kc0wys> would probably work
[17:19] <phatmonkey> there are some old serial digital cams about
[17:20] <LaurenceB> year I'm talking so you can copy the pictures over
[17:20] <kc0wys> oh
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[17:21] <LaurenceB> You could have a satellite phone and copy them over from anywhere in the world
[17:21] <kc0wys> and also pay a fortune
[17:21] <kc0wys> :)
[17:21] <LaurenceB> Well you'd look at thumbnails
[17:22] <kc0wys> have you seen the price of satellite phones? not to mention the service!
[17:22] <Tiger^> and weight
[17:22] <kc0wys> well they have gotten smaller over the years, but still heavier than normal cell phones
[17:23] <kc0wys> but seriously some serial cams do send thumbnails
[17:23] <kc0wys> mine does
[17:23] <LaurenceB> You can pick them up on ebay for approx £200, so it would be feasible to build a round the word balloon with one if you could solve the ballest problems
[17:23] <phatmonkey> robostix on its own draws about 70mah
[17:23] <phatmonkey> ma rather
[17:24] <LaurenceB> not bad
[17:24] <kc0wys> and the policial problems ;)
[17:24] <kc0wys> i've had enough trouble just trying to launch locally
[17:24] <phatmonkey> the US have satellites spying on everybody... why would this make much of a difference?
[17:24] <LaurenceB> airspace is uncontrolled over 60,00 feet
[17:25] <Tiger^> phatmonkey: he's a civilian.
[17:25] <kc0wys> because you're a civilian without a huge military to back you up ;)
[17:25] <Tiger^> :]
[17:25] <kc0wys> righto
[17:25] <LaurenceB> 60,000 rather
[17:25] <phatmonkey> i wouldn't quite call it an aircraft up there...!
[17:25] <Tiger^> you have to get permission from every country the balloon flies over
[17:25] <phatmonkey> above 60k ft... is that completely uncontrolled?
[17:25] <phatmonkey> treated as space?
[17:26] <phatmonkey> could transmit pirate radio from up there :]
[17:26] <kc0wys> ya it is uncontrolled
[17:26] <kc0wys> at least here
[17:26] <kc0wys> maybe it depends on the country
[17:26] <Tiger^> it may be uncontrolled
[17:26] <LaurenceB> I heard it was internationally uncontrolled
[17:26] <Tiger^> the problem is, the regulations don't state clearly
[17:27] <Tiger^> you can do anything you like with a balloon there
[17:27] <Tiger^> if*
[17:27] <kc0wys> how would one recover it, though? that would be tough
[17:27] <kc0wys> if not impossible
[17:28] <LaurenceB> The problem for long duration high alt flights is ballast
[17:28] <Tiger^> kc0wys: you wouldn't
[17:28] <Tiger^> you'd get the pictures and telemetry via sat phone
[17:28] <kc0wys> you could put solar panels on it and leave it up indefinitely!
[17:28] <kc0wys> hehe
[17:28] <Tiger^> hehe
[17:28] <phatmonkey> wait until it comes nearish home then use a glider ;)
[17:29] <kc0wys> the first permanent civilian satellite
[17:29] <kc0wys> cool!
[17:29] <LaurenceB> you need some system like a phase change of some liquid for ballast
[17:29] <LaurenceB> for unlimited duration
[17:29] <Tiger^> next flyby over home: 2 years, 6 months, 11 days, 12 hours and 16 minutes
[17:29] <Tiger^> ;>
[17:29] <kc0wys> oooh idea!
[17:29] <Tiger^> ...if the winds don't change ;)
[17:29] <kc0wys> dehumidifier!
[17:29] <kc0wys> then dump the water when you want to go up
[17:29] <kc0wys> and make more when you want to go down
[17:30] <LaurenceB> I've been thinking about it for ages but haven't worked anything out
[17:30] <kc0wys> hehehe
[17:30] <phatmonkey> some sort of decent sealed airship maybe
[17:30] <phatmonkey> like those ones that have been in the news
[17:30] <LaurenceB> I was thinking butane gas and a compressor to turn it into liquid
[17:31] <LaurenceB> a second envelope would store the butane
[17:31] <kc0wys> matter cannot be created nor destroyed
[17:31] <kc0wys> so how would it increase in mass?
[17:31] <phatmonkey> if it were properly sealed, surely we wouldn't have much of a problem with loads of ballast?
[17:32] <LaurenceB> butane gas> less ballast liquid> more
[17:34] <LaurenceB> alternatively you could go with a solar balloon CNES managed 90 days with one
[17:35] <LaurenceB> that's the french people
[17:40] <phatmonkey> LaurenceB, what GPS did you use?
[17:40] <phatmonkey> i'm trying to find somebody who used the SiRF II chipset, hmm
[17:40] <LaurenceB> holux gm-80 I think, it has SiRF II chipset
[17:51] <phatmonkey> ah, so did james'
[17:52] <LaurenceB> don't know any commands for it tho
[17:52] <LaurenceB> I just used the factory settings
[17:54] <LaurenceB> Got to do some printing at the local internet cafe! brb
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[17:55] <kc0wys> wow this is fun
[17:55] <kc0wys> looking for public parks in an unfamiliar state
[17:55] <kc0wys> on google maps
[17:55] <kc0wys> hehe
[18:01] <phatmonkey> hehe
[18:01] <phatmonkey> hmm, i'm looking for a new gps
[18:02] <phatmonkey> http://www.sparkfun.com/commerce/product_info.php?products_id=576
[18:02] <phatmonkey> that looks ideal, but it says a max of 60k ft
[18:04] <phatmonkey> i'm wondering if that's the chip or the board
[18:05] <kc0wys> there's a law that says gps units are to shut down if they go above 60,000ft AND travel at >999knots
[18:05] <kc0wys> however some manufacturers interpret that as an OR function and shut off at 60,000ft regardless of speed
[18:05] <phatmonkey> yeah, i know
[18:05] <kc0wys> ok
[18:05] <phatmonkey> ah
[18:05] <phatmonkey> if it's the chip, it'll be fine
[18:05] <phatmonkey> because james used it
[18:05] <kc0wys> oh ok
[18:06] <phatmonkey> i wonder what gps james used exactly, i'll see if their datasheet says somethign similar
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[18:13] <phatmonkey> http://www.flickr.com/photos/phatmonkey/200395857/
[18:13] <kc0wys> well i've changed the launch date to monday
[18:13] <kc0wys> weather will be more favorable, anyway
[18:13] <phatmonkey> ah righty, because of the new site?
[18:13] <kc0wys> yea
[18:14] <phatmonkey> more testing time too! :)
[18:14] <kc0wys> i have to go more than 20 miles (!!)
[18:14] <kc0wys> ya
[18:14] <phatmonkey> ^ that's why i want to put my software on a little microcontroller...
[18:15] <phatmonkey> all the algorithms will be a copy and paste job, it's just a matter of getting everything into a single process
[18:15] <phatmonkey> hmm, and storage
[18:15] <phatmonkey> wonder if i can easily hook up some storage
[18:15] <phatmonkey> or just hope that the radio link will be reliable and log it on the ground
[18:17] <kc0wys> sounds like a bad idea
[18:17] <kc0wys> better to have logs onboard
[18:19] <phatmonkey> yeah
[18:19] <kc0wys> i'm probably the only high altitude ballooner using heavy duty batteries :P
[18:19] <phatmonkey> i'll have to ask somebody who knows more about microcontrollers...
[18:20] <kc0wys> they're for the servo, which doesnt take much power
[18:20] <kc0wys> they're lighter than alkalines, and certainly cheaper than lithiums ;)
[18:21] <phatmonkey> yeah
[18:21] <phatmonkey> i'm pretty much forced to use some sort of lithium because of weight
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[19:58] <henryhallam> evening
[20:27] <phatmonkey> evening!
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[21:45] <kc0wys> test pictures:
[21:45] <kc0wys> http://macfreak4.homeunix.com/projects/ensure/test-pics/TEST%20IMAGES/index.html
[21:46] <phatmonkey> cool
[21:48] <henryhallam> neat
[21:48] <henryhallam> is that the one based on a disassembled laptop?
[21:49] <kc0wys> ya
[21:50] <kc0wys> i'll post the received pictures as well in a sec
[21:58] <kc0wys> here are the transmitted images:
[21:58] <kc0wys> http://macfreak4.homeunix.com/projects/ensure/test-pics/TRANSMITTED%20IMAGES/index.html
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[22:04] <henryhallam> Hi Steve
[22:07] <phatmonkey> hey steve
[22:07] <phatmonkey> i have a challenge for you!
[22:07] <henryhallam> I had a play with the Circuit Design transmitter, could receive it at approx 1km through a whole lot of buildings
[22:07] <rocketboy> hi
[22:07] <phatmonkey> http://www.flickr.com/photos/phatmonkey/200395857/ - a 434mhz antenna for something like that ;)
[22:07] <phatmonkey> that's a foot rule
[22:08] <phatmonkey> nice stuff kc0wys
[22:08] <kc0wys> thx
[22:08] <rocketboy> henry - thats becuse its through a whole lot of buildings - there us a massive difference between that and free space (line of seight)
[22:09] <henryhallam> yep I was pretty impressed
[22:09] <henryhallam> I'm not convinced that we're using the right receiver for the job, or using it in the right mode though
[22:10] <kc0wys> what kind of transmitter is this?
[22:10] <henryhallam> 10mW 434MHz narrowband
[22:10] <rocketboy> sounds like your doing it right
[22:11] <henryhallam> the SSB filter on the receiver has 3kHz bandwidth
[22:12] <henryhallam> am I right in thinking that if I tune the receiver exactly to the frequency being transmitted then I won't hear anything? (either in USB, LSB or "CW" mode)
[22:12] <rocketboy> - yes use that if you want to get the most from it
[22:12] <rocketboy> correct
[22:12] <henryhallam> so when I hear a tone it must be a kHz or so off from the right frequency
[22:12] <rocketboy> the SSB filter is set up so any carrier is cut off - and that is re-inserted locally
[22:13] <rocketboy> yes - you need to be off by about 300Hz to start to hear anything
[22:13] <henryhallam> but will that cause it to not get the best possible range? (compared to tuning the exact freq and somehow measuring signal strength)
[22:13] <henryhallam> what do you mean by the carrier being cut off?
[22:14] <rocketboy> oh no - dont worry about that
[22:15] <rocketboy> when you have the transmitter signal in the passband then it will get the best signal strength
[22:15] <rocketboy> thats when you get the tone
[22:16] <rocketboy> if the carrier is anywhere inside the passband yu will get the maximum signal strength
[22:16] <henryhallam> ah right ok
[22:16] <henryhallam> thanks
[22:17] <rocketboy> I have been playing with the radiometrix transmitters - they are much bigger (x4)
[22:17] <henryhallam> any ideas roughly how much better a receiver like yours is compared to the AR2800?
[22:17] <henryhallam> oh.. do they gain anything from the size? ;)
[22:17] <rocketboy> but they seem to be better for frequency stability (not that the CD is that bad)
[22:17] <henryhallam> ok
[22:17] <rocketboy> not a lot
[22:18] <henryhallam> can you just retune the receiver to correct for drift in the transmitter?
[22:18] <rocketboy> possibly a couple of dBs s/n - perhaps about 20% in terms of distance
[22:18] <henryhallam> right
[22:19] <rocketboy> yes no probs - most have a 100Hz step (thats about 30 steps across the passband)
[22:20] <henryhallam> we were planning to launch the new lighter balloon without insurance but Carl seems to have changed his mind on that, there is some progress on getting the insurance though so I'm hopeful for a launch next weekend or the sometime the following week
[22:20] <henryhallam> it's certainly dragged on long enough :(
[22:20] <henryhallam> would you be interested in testing your data radio gadget then?
[22:21] <rocketboy> OK excellent - I offered tom make Carl a radio modem
[22:21] <henryhallam> we'll fly the circuit design one as well, sending GPS position as morse
[22:21] <henryhallam> cool :)
[22:21] <rocketboy> good idea - the more methods of tracking the better
[22:21] <henryhallam> will there be any problems with having the two transmitters so close together?
[22:21] <rocketboy> I'll see what I can put together over the weekend
[22:22] <rocketboy> shouldn't be aproblem if the antennas are monthed on opposite sides of the payload box
[22:22] <henryhallam> ok
[22:23] <henryhallam> that fits with the configuration we have at the moment of GPS tracker on one side and "science payload" on the other
[22:23] <rocketboy> it would be a good idea for them to be on different frequencies though - what frequency CD Tx did you get
[22:23] <henryhallam> 434.075
[22:23] <henryhallam> having an antenna on each side is convenient if it lands on one of them
[22:23] <rocketboy> ok no probs the radiometrix module is 434.650
[22:23] <henryhallam> ok
[22:23] <henryhallam> miles apart :P
[22:24] <rocketboy> the only thing i did discover is that 434.650 is in use by the local Hams for the loacl radio repeater input
[22:24] <rocketboy> - shouldn't be a problem over by cambridge
[22:24] <henryhallam> well if it has 1000km range...
[22:25] <henryhallam> or would it be drowned out by the repeaters in your local area
[22:25] <rocketboy> humm - well its very weak - its more of a problem from them (which will be masked by the earth)
[22:26] <henryhallam> ok
[22:27] <rocketboy> no fortunatly its on the input (uplink) frequency - so its only the local hams that are sending to it that are the problem - the output is 1.6MHz away
[22:28] <rocketboy> Its going to need a bit of software integration
[22:28] <rocketboy> not too difficult
[22:30] <henryhallam> oh I just noticed your email
[22:30] <henryhallam> one sec, I'll read it and then ask you what all the words mean :)
[22:31] <rocketboy> yeh - all the right words but not necessarily in the right order
[22:35] <henryhallam> thanks very much, this is useful info
[22:35] <henryhallam> from the picture the TNC-X looks pretty big though, about 3 times the size of the existing tracker PCB
[22:36] <henryhallam> do you think it's reasonable to try and do it in software on the main PIC?
[22:36] <rocketboy> yes - its all DIP components
[22:36] <henryhallam> (there are a lot of cycles free at the moment)
[22:37] <henryhallam> that way I could keep everything on 3.3V as well
[22:37] <rocketboy> yes if you can construct morse - then its much simpler to send to the TNC
[22:37] <rocketboy> Ah - do you mean do a TNC on the tracker you have built
[22:37] <henryhallam> I meant replacing the TNC with software so my PIC would talk directly to the radio
[22:37] <henryhallam> yeah
[22:37] <rocketboy> ?
[22:38] <rocketboy> It can be done - but its a bit more complex
[22:38] <rocketboy> quite a bit
[22:38] <henryhallam> ok
[22:39] <rocketboy> I'm hacking some PIC code at the moment to do just that
[22:39] <rocketboy> its going to take me a couple of days yet
[22:40] <rocketboy> I was planning on making a 300 (or possibly 600) baud system
[22:40] <henryhallam> I'm doing some fairly complex stuff with the PIC (wind prediction, cutdown decisions based on predicted flightpath and a map of "danger zones" + the coast) but there is a lot of flash space and CPU cycles still available
[22:40] <henryhallam> presumably slower is better for reception
[22:41] <rocketboy> with direct FSK (Frequency Shift Keeying) - rather than the AFSK (Audio FSK) that the TNC-X uses
[22:41] <henryhallam> ah
[22:41] <henryhallam> ok
[22:42] <henryhallam> so what does the TNC do exactly?
[22:42] <rocketboy> yes - slower is better for 2 reasons - 1) bandwidths are narrower 2) there is longer to integrate each bit over
[22:42] <henryhallam> I understand it has to recode the data stream so that there are no long periods of a single bit state
[22:42] <henryhallam> does it also put it into packets?
[22:43] <rocketboy> its just a packetizer - it takes a packet, encodes it into a format sutable for transmission - encoding like bit stuffing (to stop long runs of data) - to reduce low frequency compinents
[22:44] <rocketboy> also NRZI or manchester coding is normally used - a TNC normally adds a CRC
[22:45] <henryhallam> yeah why do you need to reduce the low frequency components? the morse sounded fine and that was up to 600ms of a single state... is it to make sure you can recover the clock at the receiver? (like any asynchronous serial link)
[22:45] <henryhallam> ok
[22:45] <henryhallam> NRZI is similar to the coding used on most RS232 connections right?
[22:46] LaurenceB (n=laurence@host86-141-239-39.range86-141.btcentralplus.com) joined #highaltitude.
[22:46] <henryhallam> hi Laurence
[22:47] <LaurenceB> I've just fried my camera! anyway hi henry :-)
[22:47] <rocketboy> NRZI is a bit different - again its about frequency components - NRZI encodes a 0 as no change and 1 as a change in (one of 2 frequencies)
[22:47] <henryhallam> it's ok we've destroyed two so far :)
[22:47] <henryhallam> ok thanks I'll look it up
[22:47] <rocketboy> removing low frequency components is only really important for AFSK
[22:48] <LaurenceB> I plugged in the wrong usb cable, it's not completely busted, I think a SD card reader will solve the problem
[22:48] malgar (n=malgar@adsl-ull-155-235.47-151.net24.it) joined #highaltitude.
[22:48] <rocketboy> are you guys using opto-couplers for the camera
[22:48] <LaurenceB> I'm using mini relay switches
[22:49] <rocketboy> that should be OK
[22:49] <henryhallam> just a MOSFET to save space, we used an optocoupler on the first one
[22:49] <rocketboy> sorry I was thinking that the fring was due to direct connections
[22:50] <henryhallam> the cameras destroyed so far have both been by Carl pulling a ribbon cable out of one of those sockets without pushing the thingy in to release it
[22:50] <rocketboy> ahg
[22:50] <phatmonkey> is there a simple way to hook up storage (flash I guess) to a small microcontroller like the atmel megas?
[22:50] <henryhallam> he isn't allowed to take things apart any more
[22:50] <henryhallam> yes
[22:50] <henryhallam> SD card
[22:50] <LaurenceB> Yes my mistake was nothing to do with the camera modifications
[22:50] <henryhallam> or MMC card, they're pretty much interchangable
[22:51] <phatmonkey> can you get interfaces for it then?
[22:51] <henryhallam> they support a connection using an SPI interface which most microcontrollers have built in, or if not it's very easy to bit-bang in software
[22:51] <henryhallam> that's the "low level" interface, then you have to do a bit of software to send the card commands to initialise it and read/write data
[22:52] <henryhallam> it's not too hard, I can give you some C code for PICs which works an would be easily translated to Atmel or whatever
[22:52] <LaurenceB> Hey rocketboy, is there any chance we could put one of your radios on MiHAB 2
[22:52] <phatmonkey> ok
[22:52] <phatmonkey> it's not that urgent, just wondering if it was possible!
[22:52] <rocketboy> sure
[22:52] <henryhallam> beware a bunch of webpages/forum posts which say it's very hard or give broken code :P
[22:52] <phatmonkey> interesting anyway, i'll start thinking about porting my software to a small microcontroller
[22:52] <phatmonkey> hokay
[22:53] <rocketboy> drop me a line @ steve@btinternet.com
[22:53] <henryhallam> brb
[22:53] <henryhallam> you have a good email address btw :)
[22:53] <LaurenceB> I was thinking of sending position data via radio
[22:53] <phatmonkey> rocketboy, would we be able to get a 434mhz antenna small/efficient enough to fit on something like http://www.flickr.com/photos/phatmonkey/200395857/ ?
[22:54] <rocketboy> just looking
[22:54] <henryhallam> back
[22:55] <rocketboy> oodles of room - put a dipole in the wing
[22:56] <rocketboy> two elements 16.5cm each - one in each wing - comming together in the main body
[22:57] <rocketboy> or down the length of the body
[22:57] <LaurenceB> Could I send data in and the transmitter say generate different tones for 0 and 1 ?
[22:57] <rocketboy> yep
[22:57] <henryhallam> Laurence, the Circuit Design transmitter does that out of the box
[22:57] <rocketboy> I have been doing some experiments
[22:57] <henryhallam> it has 4 pins... ground, power, data in and radio out
[22:58] <rocketboy> i did the equivelent of over 20Km with 10mW - I expect to get much further
[22:58] <rocketboy> with a bit more effort going into the encoding
[22:59] <LaurenceB> Cool, MiHAB 2 is almost complete apart from communications, I could just connect the wires to the phone to the transmitter instead and recode
[23:01] <rocketboy> I have a bit more investigation to do - to see if I can come up with somthing simpler/better
[23:01] <LaurenceB> Did pegasus 3 just use one of these radio modules you can pick up off loads of sites then?
[23:01] <henryhallam> one of those plus Steve's genius and a pic :)
[23:02] <LaurenceB> Cool you can pick them up for approx £20
[23:02] <rocketboy> correct
[23:02] <rocketboy> but then you need to use them in a special way
[23:03] <rocketboy> not exactly the way they were intended to be used - you will normally see that they have a range of 500m
[23:04] <henryhallam> hm
[23:04] <henryhallam> would there be anything wrong with just plugging in say 300 baud RS232-style data, with a CRC after each packet?
[23:04] <henryhallam> since the frequency components don't matter with plain FSK and the start+stop bits handle synchronisation
[23:05] <rocketboy> The problem with using them as they stand is that the frequency shift is like +/- 3KHz
[23:05] <henryhallam> the receiver would need a little more work but not all that much more, just a tone detector plugged into a UART
[23:05] <rocketboy> which puts them outside of the passabnd of SSB
[23:06] <rocketboy> the passband of FM is about 25KHz - but a) you need to remove DC component b) it takes in a lot more radio noise and therfore reduces the range
[23:07] <LaurenceB> Sorry I'm not very hot on fm, wHAT'S FSK
[23:08] <henryhallam> frequency-shift keying, you move the frequency one way or the other by 3kHz
[23:08] <rocketboy> you need to drive the modules with a much smaller siganl than usual - so they shift +/- 100Hz and therfore stay inside the SSB passband - also the sugnals become tones - so there is no need to remove DC components
[23:08] <henryhallam> ohh
[23:09] <henryhallam> I had been giving the module the full digital signal
[23:09] <henryhallam> and tuning the receiver to hear either one tone or nothing at all, not one tone or the other
[23:09] <rocketboy> the SSB passband is about 3KHz - i.e. about 1/8 of FM - which gets about 3x the distance
[23:10] <phatmonkey> rocketboy, are dipoles pretty omnidirectional?
[23:10] <LaurenceB> So it made a tone as you were putting in 010101010101
[23:10] <rocketboy> henry - yes thats one way to do it - however thats not much good for anything other than morse
[23:11] <henryhallam> right, because you can't tell the difference between sending 0 and not sending at all
[23:11] <rocketboy> dipoles are quite good omni except end on
[23:12] <rocketboy> so if it was across the wings and the wing tip was pointing at you the signal would be weak
[23:13] <phatmonkey> ok
[23:13] <henryhallam> if the wingtip is pointing at the ground you may have other issues
[23:14] <rocketboy> henry - yes you relly need two conditions (not just signal and no signal) for reliable communication
[23:15] <rocketboy> oh - yes and if the whole lots smashed into the ground it doesn't work either =:-(
[23:17] <rocketboy> henry - I'll drop you a line over the weekend - I think I could do somthing smaller/simpler than the TNC
[23:18] <rocketboy> but i think it will have to use the radiometrix module
[23:18] <henryhallam> ok... thanks, would be good to have a chat
[23:18] <henryhallam> why is that, freq stability?
[23:18] <rocketboy> becuse the frequency shift is easier to control than the CD ones
[23:19] <henryhallam> ok
[23:19] <henryhallam> I was thinking of something like a potential divider to put around 1V on the data in pin, with a transistor that can short out part of the potential divider to change it slightly
[23:19] <rocketboy> I need to do the odd test over the weekend
[23:20] <rocketboy> yes thats the way to do it
[23:20] <rocketboy> the radiometrix modules have a near linear frequency shft with input voltage
[23:20] <rocketboy> the CD ones are much more digital
[23:21] <henryhallam> oh I see
[23:21] <henryhallam> makes sense
[23:22] <henryhallam> it's really 4x the size? :/
[23:22] <rocketboy> to shift +/- 100Hz you need about a +/- 0.1V shift - at about 1.5V - so 1.6V to 1.4V
[23:22] <rocketboy> well about 3x
[23:22] <rocketboy> - but its actually a lot better technically
[23:23] <rocketboy> the CD ones shift quite a bit when the antenna wips about
[23:23] <henryhallam> heh
[23:23] <henryhallam> ok
[23:23] <rocketboy> the radiomenrix ones don't
[23:23] <henryhallam> actually the CD is so small that 3x the size isn't too big a deal
[23:23] <rocketboy> true
[23:23] <henryhallam> do you know what its power consumption is like?
[23:24] <rocketboy> about the same (18mA)
[23:24] <rocketboy> at 3V
[23:24] <henryhallam> ok
[23:24] <henryhallam> yeah that's even better than the CD I think, it was 22mA IIRC
[23:24] <henryhallam> and transmission power doesn't suffer from running it at 3V?
[23:24] <rocketboy> also the radiometrix ones have an enable pin
[23:25] <henryhallam> handy
[23:25] <rocketboy> you can turn them off - even though they are still connected to power
[23:25] <rocketboy> consumption drops down to 0.5mA
[23:25] <henryhallam> not bad
[23:26] <henryhallam> I'll see if I can rip the radiometrix module out of the Traxa rocket beacon we have
[23:26] <rocketboy> good for power saving - and they come back on again in 5mS
[23:26] <rocketboy> yes it should be the same
[23:26] <henryhallam> anyway I'm heading off now, goodnight and thanks very much for all your help
[23:27] <rocketboy> I'll try to sort ot the recieve end over the weekend
[23:27] <henryhallam> talk to you later this w/e
[23:27] <henryhallam> great! :)
[23:27] Nick change: henryhallam -> henry|sleep
[23:27] <rocketboy> noprobs - gotta go to bed too
[23:28] rocketboy (n=steve@217.47.75.184) left irc: "Leaving"
[23:50] <LaurenceB> Updated MiHAB 2 page on UKHAS wiki
[00:00] --- Sat Jul 29 2006