I am new to working on 555 timer. I am running it in monostable mode. I am triggering it using a button on trigger pin. It works just fine. What I want is the LED connected to the out pin 3 to switch off when I press the trigger button again. If I don't press the button, LED will switch off after the specified time duration by the RC circuit. Is it possible? Thanks in advance. :)
IC1 and its associated components are just a switch debouncer. C2 & R2 trigger IC2 on the falling (trailing) edge of the pulse coming from IC1. IC3a (a positive edge triggered D-Type flip flop) holds IC2 either in reset or enable dependent upon the circuit's output state at the time of the rising (leading) edge of the pulse coming from IC1. A transistor is used to drive the LED to ensure that IC3a's D input sees a sufficiently high logic 1 level voltage. In this edit I have added a power-on-reset circuit to the asynchronous set pin (S) of IC3a.
I have built and tested the circuit, it works well.
Yes it's possible using logic gates: It will reset only if the LED is ON and you press the trigger button again.
Note: The extra inverters and the AND gate are for rising edge detection (When you release the trigger button). D flipflop to get the Previous state of the output.