Make A Dual LED Flasher Using Arduino

Dual LED Flasher (1)

A two transistor circuit that flashes two LEDs on and off alternately.

Dual LED Flasher (1)


Complete tutorial two – Transistor Timer before attempting this tutorial.


In addition to an electronic breadboard, wire links, a 9V battery and a battery clip, you will need:

2 22k resistors (red – red – orange) R2, R3 1/4W, 5% or better Resistors
2 470 ohm resistors (yellow – violet – brown) R1, R4
2 100uF C1, C2 Electrolytic capacitors, 16V or more 

Try using 47uF or 33uF capacitors to speed up the rate at which the LEDs flash

2 KSP2222 or PN2222 Q1, Q2 NPN transistors 

2N2222, BC107, BC108 or BC109 transistors can be used in the circuit, but have a different case to the KSP2222 / 2N2222

2 5mm red LED D1, D2 Or similar LED


The required parts are shown below:

Circuit Diagram

Dual LED Flasher Schematic (1)

Building the Circuit

Insert the two transistors into the breadboard with the flat face pointing down as shown in the photo. Use wire links to connect the emitter of each transistor to the bottom rail. Get the two LEDs and the two 470 ohm resistors ready.

Connect one end of a 470 ohm resistor to the collector of each transistor. Connect the other end of the resistor to a tie point on the other side of the breadboard center channel.

Connect an LED to each resistor as shown below. The anode of each LED is to be connected to the top rail of the breadboard.

Get the two 22k ohm resistors and two wire links ready.

Connect the two 22k resistors across the middle channel of the breadboard. Connect the top lead of each 22k resistor to the top rail of the breadboard using a wire link.

Get the two 100uF capacitors ready.


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