# Pulse calculated resistor circuit?

Discussion in 'The Projects Forum' started by ryndeclark, Mar 6, 2013.

1. ### ryndeclark Thread Starter New Member

Mar 6, 2013
1
0
I have a device that is adjusted with a 10K ohm variable resistor. I want to replace this resistor with a circuit that does the following:

Receives a timed pulse from a N.O. manual switch (I will handle the switch)

Converts the time into a resistance value and recalcs with each set of pulses (current and previous pulse only, no averaging).

As an example:

I want to produce the same resistance as my resistor set at 99% by sending a set of pulses that are .1 seconds apart. If I send pulses that are .5 seconds apart, the resistor would be at 95% and so on (.1sec=1% change). I would also need a manual adjustment or trim to control the relationship so that a .1 second pulse could equal 92% and a .5 could equal 60% (.1sec=8% change) and so on. If the calc exceeds the 10K range, it would need to be ignored. The pulse would range from 0.1 sec to 2.0 seconds.

The real life application is this:
I have a guitar effect pedal that can have any knob controlled with an expression pedal (a rocking foot pedal that adjusts a 10k pot). Rather than rock the pedal back and forth, I would rather tap a switch to the beat of the music and have it calculate a resistor setting that would synchronize it with the music. This is commonly refered to as tap tempo, but my unit does not support it and I don't know any other way to get there.

if anyone can help it would be greatly appreciated!

Thanks.

2. ### crutschow Expert

Mar 14, 2008
20,283
5,739
I think the simplest way to do that is to detect the pulse timing with a microprocessor which is programmed to set the value of a digital pot accordingly.