Introduction: Pulsating LED Using a 555 Timer and Potentiometers


In this instructable, we will be showing you how to construct a LED Dimmer circuit that runs on an adjustable timed loop using a potentiometer, a 555 timer and other basic circuit components. We first obtained the idea for this project from another instructable that made an LED strip controlled by a dimmer switch, found here: This project was incredibly helpful in understanding how the potentiometer could work as a dimmer switch. For our purposes, however, we want to set up the potentiometer as a timer switch that automatically controls the length of time it takes for the LED strip to fade in and out. Hope you find this helpful!

Step 1: Acquire Your Components.

555 Timer


R1 560 Ohm resistor

R2 10 kOhm potentiometer

R3 10 kOhm potentiometer

R4 82 kOhm resistor

R5 1 kOhm resistor

R6 100 kOhm potentiometer

R7 100 kOhm potentiometer

R8 22 kOhm resistor

R9 1 kOhm resistor

R10 100 kOhm resistor


C1 470 uF capacitor

C2 470 uF capacitor

C3 470 uF capacitor

C4 1000 uF capacitor

C5 .01 uF capacitor


D1 1N4148 switching diode


T1 P2N2 NPN transistor

T2 N-channel mosfet

Step 2: Set Up the Circuit on a Breadboard

Step 3: Test the Circuit Using an Oscilloscope

When the circuit is finished and all put together, you should connect your circuit to an oscilloscope to see that the output wave is similar to the one shown above. Connecting one lead of the oscilloscope to ground and the other to the positive output terminal the LED strip will be connected to in the next step.

R2 adjusts the fade out time of the wave.

R3 adjusts the fade in time of the wave.

R7 adjusts the oscillation amplitude of wave, affecting the range of brightness of the circuit.

R6 adjusts the DC offset, alternating the range of voltage passing through the LED strip.

Step 4: Connect LED to Circuit and See the Magic