555 Toggle Switch

By using the SR latch inside the 555, something similar to a toggle switch can be made. Setting (turning on) To set the latch pin 2 and the comparator its connected to is used. When the button isnt pressed, pin 2 is at Vcc voltage. When the button is pressed, pin 2 is grounded; because ground is 0v and that is lower than 1/3 Vcc the comparator is turned on. Because the comparator's output is connected to the SR Latch's set pin, the latch is set and pin 3 is high. Resetting (turning off) Attaching pin 6 to ground ensures that the first comparator stays off which makes resetting the SR latch from here impossible. Instead, resetting is done using pin 4 which is an inverted input that goes directly into the SR latch. When the button isnt pressed pin 4 is at Vcc voltage and because pin 4 is an inverted input the SR latch isnt reset. When the button is pressed its pulled to ground which resets the latch.

published 3 years ago