# Square wave control voltage input

I would like to build a modular synthesiser component (im thinking a step sequencer) However I want this to be driven by an external control voltage clock signal. I have a LFO (in my eurorack modular system http://www.analoguesystems.co.uk/pdf/RS80%20&%20RS85%20manual%20lo-res.pdf) that outputs a square wave that is in the range +/- 5.0V I would like to be able to detect when I get the rising edge to drive a clock.

At first all I want to do is light up an LED to make sure I am getting the correct clock signal. Any thoughts?

I would like to build a modular synthesiser component (im thinking a step sequencer)

outputs a square wave that is in the range +/- 5.0V I would like to be able to detect when I get the rising edge to drive a clock.

Just put the signal through a diode and connect it to a digital input (and, of course, connect the two system grounds together). When the output is +5V the digital input will read high, when it is 0V or -5V it will read low. You may want to also connect a 10k resistor from the digital input to ground to have it turn off faster.

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Just put the signal through a diode and connect it to a digital input (and, of course, connect the two system grounds together). When the output is +5V the digital input will read high, when it is 0V or -5V it will read low. You may want to also connect a 10k resistor from the digital input to ground to have it turn off faster.

Any thoughts on a protection mechanism if the voltage exceeds 5v?

Any thoughts on a protection mechanism if the voltage exceeds 5v?

You can use a circuit like this to limit the voltage to 5V:

http://ruggedcircuits.com/images/sch44.png

The rectifier diode would come before the 1k resistor.

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