Signal to trig converter

[umschmitt]

Hey developers ! Having had hard times to find out how to achieve the conversion from a signal to a triggering pulse, I thought I'd share this handy little circuit with folks around who wonder also how the hell one can do that… Nothing really special, just a tiny tiny stripboard (there could even be one row less at the cost of bending a cap's leg) to take along, with two converters so one uses a full LM324. It runs on 9v and outputs round 5V pulses at 1k. Tweak the trimpots to set a convenient pulse lengths then set the sensitivity pots to achieve successful triggering ! (did I need to explain ?)
Please take note that I didn't build this project as such yet, though I breadboarded a working variation of it. I plan to build it soon, and I'll give more info then. I double checked the layout and think it'is correct, please tell in case you find errors, so I'll edit and update this post. Also give some feedback if you build it !

>>>>>>>>>>from the noobs for the noobs<<<<<<<<<<<

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[inlifeindeath]

awesome! thanks for sharing. let us know what success you have!

[umschmitt]

Thank you ! I'll post it when it's done.
Concerning the circuit, with a non-depleting power supply, one could avoid using those zeners, replacing them with 2k4 resistors, if my maths are Ok.

[JingleJoe]

What exactly does this circuit do? Does it make a pulse when the input signal starts? Or every cycle of the input wave?

I have a circuit for doing something similar, I used an integrator or differentiator (can't remember which) to make pulses when the input voltage changes sharply, even by less than 100mV. So I am interested to hear how your circuit behaves?

[umschmitt]

It's just a stupid piece of circuitry that I needed for a mod in a mutant DS7 project (which you can find somewhere around). The idea is to make possible to trigger things from 'external' devices, like the ouput of your crappy drum machine, your grandma yelling in a microphone, etc… The options are wide.
It converts (sharp attack) signal to pulse, gate to pulse and even… erm, pulse to pulse.It consists of an all out amplifier, then a crude envelope follower, then a cap which lets just the beginning of the previous through, then a comparator to make things binary. Well I think it is so. Anyway it works (at 5V at least). So the pulse comes from signal. But if you have an extreeeemely low frequency signal, I suppose it would trigger at every cycle (like in : aren't pulse trains a kind of signal ?). It'd be interesting to know if the circuit would respond to sudden level changes, but I don't think so, since (I believe) the cap needs its input to be discharged in order to 'trig' again. Lots of guessing here and little certitude.
I'd be very much interested to see what your circuit looks like, perhaps by chance I could understand it…

[fonik]

last year i made myself this comparator, that also creates a trigger pulse:
http://electro-music.com/forum/topic-51470.html

any two voltages are compared, the gate high of the comparator gets converted to a trigger pulse.
however, this circuit is DC coupled. would not work with audio...

[umschmitt]

Thanks for the link ! I've met also this triggering on the falling edge thing ! For the scheduled use, I considered it as a problem, not a feature - eventually solved. Nevertheless, I think one can have it back by setting the trimpot (un)properly !