I'm an electrical engineer student and I'm trying to make an LED Flasher circuit using a 555 Timer.

When I simulated the circuit in Proteus simulator, it's not working! But in Icircuit simulator it works perfectly! It's an identical circuit.

The question is: Why is the circuit not working in Proteus?

Circuit in Icircuit:

enter image description here

Circuit in Proteus:

enter image description here

  • \$\begingroup\$ The polarity of TRIG and R seem to be opposite between the two. \$\endgroup\$
    – Eugene Sh.
    Commented Jul 26, 2019 at 15:01
  • \$\begingroup\$ Check the models. \$\endgroup\$
    – Andy aka
    Commented Jul 26, 2019 at 18:09
  • \$\begingroup\$ I imagine you have ALL the signals available to you. Post some traces from Threshold, Trigger, and Q, and let's see if we can figure it out. \$\endgroup\$ Commented Jul 26, 2019 at 18:35

1 Answer 1


Your circuit is working, believe it or not. How do I know? I created your exact circuit on my copy of Proteus. However, I did it with one small difference.

If you go to the "System" tab, then "Set Animation Options" you can tick the box that says "Show Logic State of Pins?"

enter image description here

What this will do is show blue and red boxes at certain points in the circuit:

enter image description here

So, you will see that your output is indeed toggling, but the LEDs aren't turning on. Why is this? Well, the properties of the standard LEDs in proteus need a minimum current to turn on. You just don't have enough. Change the value of resistors R3 and R4 and you'll find the LEDs turn on fine.

enter image description here enter image description here

If you find this doesn't solve your problem, I would move R4 and double check that it is indeed connected to the rest of the circuit. Putting the ends of components together on Proteus doesn't physically join them. You need to make the connection first, then move the part.


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