[simpits-chat] Altimeter Question

Brian Sikkema hangr18 at hotmail.com
Mon Nov 3 17:37:23 PST 2003

Hey Guys,

I've got a question, not about an aircraft altimeter, but one I'm thinking of building for model rocket use.

For those of you into the hobby, you know that even the most basic altimeter good for data logging and, most importantly to me, ejection charge timing, can be very expensive (cheapest I've found to do what I need is about $120). But I've found what seems to be a very nice setup online, here:


I'm confident I could build this altimeter and get it working, I know enough to do that, but I'm not quite experienced enough to modify it to what I need it to do (blow an ejection charge). This setup is just a data-logger. What I need is for it to trip a relay at some pre-specified altitude or time after apogee which would blow the ejection charge. This is pretty important, because the launchsite we use up here is very narrow, flanked by a dense forrest on one side and Lake Superior on the other. It's nice and long, but if you drift to the side you're screwed! I lost two rockets to the trees on our last launch, and I would have lost my prized V2 to the Lake had the parachutes not come off on the last flight (thats a funny story in and of itself - I'll tell it later ;) 

So anyway, long story short, anyone here have experience with PICs and whatnot, who could take a look at the circuit and code and give me some ideas on modding it to trip a relay? I'd be VERY appreciative! :)

If we can modify this circuit, it could be used for all sorts of useful things, including staging. My mouth waters with the possibilities! :)

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