Impact sensor ideas

If I remember correctly a lot of the older/cheaper photo flash unit (like that in a disposable camera) work as follows:

A push button (shutter button) short circuits a capacitor through a pulse transformer that produces a high voltage impulse incident on the xenon flash tube. This ionizes the gas, allowing it to rapidly discharge a high energy capacitor, all the while producing a bright flash.

If you simply replace the the shutter button with your automotive shock sensor then this might be the only change in existing circuitry you need to make.

So to make this more clear, assuming your shock sensor has two terminals, one that would normally be tied to Vcc and the other ground, just attach these leads in parallel with the shutter switch. Don't worry about having one end tied to ground, as your shock sensor is just acting as a mechanical switch and it doesn't care what potential you have on what end.

jta said:

If I remember correctly a lot of the older/cheaper photo flash unit (like that in a disposable camera) work as follows:

A push button (shutter button) short circuits a capacitor through a pulse transformer that produces a high voltage impulse incident on the xenon flash tube. This ionizes the gas, allowing it to rapidly discharge a high energy capacitor, all the while producing a bright flash.

If you simply replace the the shutter button with your automotive shock sensor then this might be the only change in existing circuitry you need to make.

Click to expand...

Somehting like this is definitely in my plans, but I think I need some kind of trigger first.

I just can't figure out how to use the sensor I have with a Mosfet.

Maybe I should just try it with a relay and see if it's fast enough.

jta said:

<SNIP>

So to make this more clear, assuming your shock sensor has two terminals, one that would normally be tied to Vcc and the other ground, just attach these leads in parallel with the shutter switch. Don't worry about having one end tied to ground, as your shock sensor is just acting as a mechanical switch and it doesn't care what potential you have on what end.

Click to expand...

HMMM, I will look into that. Thanks

turbid said:

mneary,

Thank you for taking the time to actually draw that up, but I'm still stuck on the fact that all the sensor trigger will do is ground the gate on impact.

Click to expand...

The sensor will ground the gate of the first transistor, allowing the second transistor's gate to rise to Vcc.

mneary said:

The sensor will ground the gate of the first transistor, allowing the second transistor's gate to rise to Vcc.

Click to expand...

Ah, That makes complete sense. Thanks

OK, I have a trigger working using a transistor and a relay, but I have another problem.

The sensor has a tendency to bounce a bit. It may just be because I have the sensitivity to low so I can just set it off by tapping it. But I figure I need to start looking into a cure for it now.

I know you want to use the sensor you already have, but here is a cheap simple circuit for a simple vibration sensor with no moving parts. Perhaps someone here can adapt it for you to energize your flash.

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DSGarcia said:

I know you want to use the sensor you already have, but here is a cheap simple circuit for a simple vibration sensor with no moving parts. Perhaps someone here can adapt it for you to energize your flash.

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Click to expand...

I'm not really locked into what I have, it's just what I have and so I'm messing with it to get some ideas and to refresh my memory on this stuff. It's been a couple years since I really sat down with a project like this so I'm having to re-learn some stuff.

I've looked into all the suggestions here and may end up using one of those.

The link you posted is actually very helpful. I have a piezo vibration sensor coming and that circuit may be a big help to me. In fact that circuit might even help with my current problem.