Friday, February 8, 2019

Push button ON/OFF + Soft start v.3

This is a revamping of an old project: "Two versions of soft sart". There were reports in the comments that the circuit doesn't always work. I have tried myself on a breadboard and indeed - the schematic works with chips from Nexperia and doesn't work with chips from other manufacturers. The problem is in the input stage of the schematic - the push button.  There is a capacitor in parallel to smooth the bouncing of the contacts but the pulse gets too long and is registered by 4027 clock input as more than 1 impulse. Without the capacitor schematic will work if the push button is high quality, otherwise, again the 4027 will detect more than 1 input signals. To combat this problem I tried different methods an here I present two of them.