Help on closing a circuit for an instant during powerup..

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Hi all,

I'm working on a variant of the CMOS aliaser that was posted here
http://www.diystompboxes.com/smfforum/index.php?topic=53536.0
Thank you, by the way, those who made it possible!

Right now it's just breadboarded so I'm still trying stuff with it. I've noticed I get far less bleedthrough if I simply remove R2! The bleed falls off in a plesant way after each sound/note without the resistor. The sound of the overall effect is a bit smoother to my ears as well.  However it looks like the resistor needs to be in place the moment I'm turning the thing on. I would like to have the resistor contact closed only at the moment I stomp the unit on (3PDT), but I'm still learning and I'm unsure how to go about it.

[R.G.]

Here's one way I have used before to good results.

I use a schmitt trigger CMOS inverter, CD40106 or CD4585, or 74C14.  I tie the input to +V through a resistor and to ground through a capacitor. At power on, the capacitor is discharged to 0V. When power comes on, it starts ramping up through the resistor.

The inverter output comes up a little ways as the rising supply voltage makes the transistors start being active, then blips to fully high. The output stays high as long as the capacitor remains below the positive threshold of the inverter. When the capacitor voltage ramps above the threshold, the output goes low and stays low. You adjust this time by choosing R and C to be big enough.

You may want a reverse biased diode from the top of the capacitor to +V to discharge C rapidly when the power supply drops. This resets the circuit quickly.

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hmmm, that's a little more complex that I was hoping, but I'll still give it a try, thank you very much!

( at least I have plenty of excess 40106's)