Create trigger pulses from falling ramp??

[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?

[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.

[The Tone God]

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]

Thanks for that.