Create trigger pulses from falling ramp??

Started by StephenGiles, August 26, 2006, 06:20:42 PM

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StephenGiles

During our 3 1/2 hour return flight from Madeira this afternoon, I jotted down some ideas - as well as yelling at the hideous child sitting in the row behind who insisted on kicking the back of my seat for the first 3 hours. Nothing very interesting remained not crossed out, except for a big question mark against this problem - how to extract a trigger pulse at preselected points during a falling ramp voltage? That is to say, a ramp falling from a peak of say +15v, and to extract trigger pulses when it passes 12, 9, 6 and 3 volts for instance, and what task could these trigger pulses be utilised to perform?
"I want my meat burned, like St Joan. Bring me pickles and vicious mustards to pierce the tongue like Cardigan's Lancers.".

The Tone God

First thing that comes to mind is use a comparator/opamp with one input set to the voltage you want to trigger at and other input the ramp signal. You can tack a pulse detector on the output if you just want a pulse when the voltage is hit. As for what you would want to do with it I don't know. Trigger a bunch of preselected filter settings ?

Andrew

R.G.

The simple way is with an LM3914 watching a falling ramp. In dot mode, one output is high at each of the voltage ranges.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

The Tone God

Quote from: R.G. on August 26, 2006, 09:34:30 PM
The simple way is with an LM3914 watching a falling ramp. In dot mode, one output is high at each of the voltage ranges.

Be aware that when in "dot" mode there is some overlap between outputs, about 1mV worth IIRC, so depending on the load being driven you many get multiple simultaneous outputs.

Andrew

StephenGiles

"I want my meat burned, like St Joan. Bring me pickles and vicious mustards to pierce the tongue like Cardigan's Lancers.".