LED Chaser Circuits – Knight Rider, Scanner, Reverse-Forward, Cascaded

We also discuss how to modify these into a design popularly known as "knight rider" chaser circuit.

These primarily incorporate LEDs as well as mains operated bulbs through triacs. The proposed circuit is transformerless and is thus a lot compact and light weight.

What is a Light Chaser

Light chasers are decorative lights or LEDs arranged in different moving patterns which create a chasing light or running light kind of effect. These look very interesting and are surely eye catching and that’s why these types of lighting arrangement have gained immense popularity in today’s world.

Though the more complex lighting might need the incorporation of microcontroller ICs, simpler yet very interesting light effects can be generated through ordinary ICs like IC 4017 and IC 555 as shown below. This design requires very few components for the configuration.

Simple LED Chaser Circuit Diagram (The 100K pot can be adjusted to get any desired chasing speed or rate)

Parts List

All resistors are 1/4 watt 5% unless specified

• 1K = 11nos
• 10K = 2nos
• 100K pot = 1no

Capacitors

• 0.01uF ceramic disc
• 10uF/25V electrolytic
• Semiconductors

• LEDs RED, 5mm High Bright or as desired = 11nos
• IC 4017 = 1no
• IC 555 = 1no

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• For learning the pinouts and datasheet of the IC 4017 please refer to this article
• For a detailed explanation regarding IC 555 astable, you can click on this article

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As can be seen in this configuration, in response to the pulses from IC 555, the IC 4017 generates a running or chasing light pattern across the connected 10 output LEDs. The chasing pattern goes on repeating itself from start to finish as long as the IC 555 keeps pulsing pin #14 of the IC 4017.

How to Calculate the Chaser Speed

The chaser speed can be easily adjusted by determining the correct frequency rate of the IC 555, as explained below:

Formula for IC 555 frequency is = 1/T = 1.44 / (R1 + R2 x 2) x C, where R1 is the resistor between pin#7 and the positive line, R2 is the resistor between pin#7 and pin#6/2. C is the capacitor between pin#6/2 and ground, and should be in Farads.