NAND Gate Bistable Using SN74HC00N IC

This NAND gate bistable is a free running multivibrator circuit that blinks / flashes LEDs. It is very similar to a transistor flip-flop circuit, except we can achieve the same thing with a pair of NAND gates. In this circuit, the LEDs are connected to the positive voltage rail, and therefore a logic 0 output, which is 0 V, provides the ground for the current to sink, thereby lighting the LED.

This simple GCSE type project circuit will operate at 4.5 V using three AA batteries, or perhaps 6 V using four batteries. If your breadboard can supply 5 V, then that will work too.

For this circuit, we will be using the commonly available SN74HC00N IC, which has quad 2-input NAND gates. I have marked out the gates to use for this project.