Multisim circuit breaks when a 555 square generator is just present in the circuit

Thread Starter

Abdi Rahman

Joined Apr 23, 2018
5
Hi, I have a pretty bizarre problem with Multisim. I have a larger circuit which works perfectly when the inbuilt square wave generator for Multsim is used. I wish to replace the square wave generator with my own.

I have a 555 square generator circuit which works perfectly when I test it by itself, the moment I recreate that circuit in the main circuit and connect it to a 5V source the output of the main circuit just stops after a few milliseconds. This only occurs when the square wave generator is connected to a source without even connecting it to the rest of the circuit, when I remove the 5V source the circuit simulates for a few seconds and then just stops the only way to get the correct waveform is to completely remove the 555 square wave circuit.

The circuit is supposed to count up until the green wave form reaches the red and then it resets and starts again.

Circuit with the square wave generator in the bottom left hand corner
output when the 555 timer is disconnected from the circuit but the 5V source is connected

output when the 555 timer is connected

The correct waveform and what I am trying to achieve. My multsim file is here
 

Thread Starter

Abdi Rahman

Joined Apr 23, 2018
5
@crutschow My apologies I thought I had posted it, I have narrowed the problem down to the 555 timer refusing to work with the staircase circuit so the file I am posting now contains only those two, if you connect a pulse generator circuit to the staircase circuit and disconnect VCC you should see the staircase circuit works as intended. @Alec_t I thought VCC was a source? The square wave circuit works when it is on a page of its own.

Edit: Link https://drive.google.com/open?id=1Kp5WKkvYNn1vQQMidgy2ckx2hL-ejScr
 
Top