Trigger signal generator

Aug 29, 2005 5 Replies
A

Hi all.



I want to synchronize a laser pulse with an AC current (only about 1kHz) source that unfortunately doesn't have a sync output. For the laser pulse I need a good trigger signal, which up to now I have generated with an oscilloscope that has a trigger output. But this signal is not very good, probably it's 'cause the scope is not the best one.



So my question is, how do I generate a good trigger signal from a sine signal with an amplitude about 10V-50V? It seems a pretty simple task, but up to now I haven't found any device that does this job. Neither in google, nor at the major test equipment suppliers. I am also not very good at soldering, though if the circuit is very simple and the risk to screw it is not very high I might try it.



Thanks for your help! Alex


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Take a low voltage sample of your sine wave by either a voltage divider or a transformer. Send that to the input of a zero detecting IC. The output can be delayed, if necessary, with a 555 timer.

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C

Use a Comparator to convert it to a square wave. Set one input to 0V and feed the sinewave in on the other. Give the comparator just enough hysterysis to make it immune to any any noise on the sinewave.

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A

Am Tue, 30 Aug 2005 15:09:44 +0200 schrieb CWatters :

Thanks, I'll try this one. It seemed to me that this was a pretty simple and common task and I just thought that there should be plenty of little gadgets out there that do this job.

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C

Just one follow up... The output from a comparator will be a square wave ok but it will swing between the power rails (eg -VCC to +VCC). The device you are trying to trigger may need a logic level signal (eg 0-5V) square wave. You can fix this several ways but let us know if you need help with that.

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C

ok

you

I lied.. another follow up....

If you want to be able to adjust the circuit so that the trig point varies you can wire up the comparator so that instead of switching at a fixed 0V it switches at a variable point on the waveform. Instead of connecting one input of the comparator to 0V connect it to a potential divider.

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