Electronic circuits that use the 555 Timer

555 Timer Circuits

555 Timers are fun and a great way to start learning electronics


This circuit flashes the left LEDs 3 times then the right LEDs 3 times, then repeats.


This circuit uses a 555 timer which is setup to both runn in an Astable operating mode. This generates a continuous output via Pin 3 in the form of a square wave. When the timer's output changes to a high state this triggers the a cycle on the 4017 4017 decade counter telling it to output the next sequential output high. The outputs of the 4017 are connected to the LEDs turning them on and off.


Police Lights Circuit


This video walks you through building this circuit using a breadboard.

Parts List

1x - NE555 Bipolar Timer
1x - 4017 Decoded Decade
6x - 1N4148 Diode
1x - 1K Resistor (1/4W)
1x - 22K Resistor (1/4W)
2x - 4.7K Resistor (1/4W)
6x - 470 Resistor (1/4W)
1x - 2.2�F Electrolytic Capacitor (16V)
2x - BC547 NPN Transistor
2x - LED (Blue)
2x - LED (Red)
1x - 9V Voltage Battery

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