Let Me Debounce That For You!

A project log for WITCH-E Decimal Based Computer

Document and create a modern replica of the Harwell Dekatron computer known as the WITCH

Dave's Dev LabDave's Dev Lab 10/29/2017 at 03:440 Comments

I had hoped that using a schmitt trigger and some large RC (Resistor/Capactor) values would have been enough to debounce the valid data and select signals, but it just wasn't the case. After reviewing the timing on the oscilloscope, I decided to prototype a monostable multivibrator with a 555. Now, I couldn't just use the standard circuit that is usually associated with a monostable 555 that is found on the net. The main issue is that if you have a timer set for 1 second, and you hold the trigger signal low for 2 seconds, the timer expires. What I needed was a timer to start AFTER the trigger is released. Of course, like most things in electronics there hundreds of ways to do this, but this is what I came up with. Now time to update the PCB layout...