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Homemade avionics


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Many of you may have noticed the page that is linked to in the ADSB thread,

 

http://lea.hamradio.si/%7Es53mv/avionics/avionics.html

 

This is very interesting, and I will try to make some of the gadgets here.

 

I was wondering how many others out there have soldered up very cheap electronics into effective things.

 

I want to try to make a CO detector from some Jaycar parts I have seen for cheap as chips.

 

Anyone else have any ideas?

 

 

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I have made a CO meter using the sensor module from Farnell, a digital voltmeter module and a bridge circuit to set the zero and calibration.

 

CO alarms are now available for less than what the parts would cost me at our local aero supplies however being designed for homes they do seem cumbersome and ugly in the cockpit. Another thing to watch is sensor life usually about 3 yrs.

 

For aircraft I use the 18 month type spots I have had one go dark once in the rear of a C150A and that is why I built the meter so I could find the source - the meter is much quicker response and The CO was getting in the rudder cable slots and coming thru the rear cabin headliner.

 

Ralph

 

 

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CO sensor should be pretty easy. I havn't seen the sensors jaycar has to offer, but the ones at http://www.futurlec.com/Gas_Sensors.shtml are pretty cheap, and should interface to a small microcontroller well (pic or similair).

 

If your making the radios/transponders from that site be aware that in aus radios & transponders need to be CASA approved.

 

 

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I read somewhere that the colour type sensors are a bit useless in as much as CO affects colour vision first, so I want something that buzzes.

 

Also with the radio/ transponder, if they are not certified, can anyone tell from the signal? Or would they have to inspect it?

 

 

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Being able to tell if they are certified or not probably depends on your build quality. If your IF, Mixer and Final stages are not "clean" enough you'll get a fair amount of interferance happening which would no doubt result in a call from ATC saying "get your transponder fixed", or "bring your transponder in for checking".

 

As for the radio, if you don't get it right your range will be crap, you'll be difficult to understand and your transmission will be spread across the surrounding frequencies.

 

I guess the point is, the guy who built that had all sorts of test equipment (oscilliscope, frequency counter and maybe a spectrum analyser), so he can make sure the signal is very clean.

 

I'm not sure what the fine for operating an authorised transmitter in the Aircraft band is, but its probably pretty steep. It may be possible to get a permit for operating experimental gear...

 

I'd stick with some of the other gear hes got, like the TCAS system, or the digital directional gyro (slaved to digital compass) - though with that one i'd change it to use a different display, probably a nokia 3510i screen or similair, so it looks similair to your normal DG.

 

Anyway, the CO sensor that Jaycar sells looks the same as the one from that other site I listed, and it looks like i was completly wrong about the voltage output (damn it). Anyway, i'm looking for some examples of how to use the things now.

 

*edit* yup, i was wrong, it was the CO2 sensor that was a simple voltage change. Looks like the CO sensor is a change in resistance? should be fairly easy to measure..

 

 

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