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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi all.
Just bought a few of these sky lanterns for £4.50 each.
Main advantage is that they can lift about the same weight as a box of matches (better than a helium balloon) and they are also somewhat predictable.
My plan is to use an RGB LED on a tether to send back data sequentially (i.e. red for temperature, green for pressure and blue for humidity) and then use an automated tracker and video camera to record the data stream.
I was also looking into recording cosmic radiation as my extensive collection of spare parts includes some very lightweight Geiger tubes.
Registered Member #816
Joined: Sun Jun 03 2007, 07:29PM
Location:
Posts: 156
Hi,
Right If get what your trying to do is like make a simple small radio sonde? I think I rembember little more than a crystal oscillator module those in the retangular metal cans, and an LC lowpass filter ( as these things give out square wave). Could make a cheap and lightweight transmitter when used with a peice of long wire as an antenna. Clearly you could only switch it on or off with your data. Of course it would be sensable to pick a frequancy around one of the bands used for remote control toys like 27 or 49Mhz.
I have to say I haven't tryed this so wouldn't know what to expect in terms or range ect. The use of an l.e.d is a novel idea though, and no doubt would work, trying to automate the receive part does sound complex though, unless you were prepaired to stand there and manually count the coloured flashes while watching it go up.
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
I have tried to turn those oscillators on and off quickly and it doesn't make a very nice signal. I would use a 2N2222 or similar to act as a switch to the antenna and feed your signal into the base.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Managed to get some helium and launched 6 illuminated test balloons. as expected they can lift around 3-4 grams, depending on the amount of helium I use.
Interestingly over-inflation causes problems as the density increases, resulting in less lift increase and wasted gas.
Next step, write PIC code and attach it to 4 balloons (12 grams total lift capacity)
Altitude hold anyone? might be able to use a pager motor and small fan for this or possibly a rotating vane to steer it in a particular direction.
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Sky lantern weather station?
