The article discusses the construction details of the popular "knight rider" chaser circuit incorporating LEDs as well as mains operated bulbs through triacs. The proposed circuit is transformerless and is thus a lot compact and light weight.
The Circuit Concept
It's basically a light chaser or a running light effect generator circuit, quite resembling the effect produced over the popular "knight rider" car.
The circuit mainly comprises of IC 555 and the IC 4017 for implementing the required functions. The IC 555 is used to generate the clock pulses which is fed to the clock input of the IC 4017.
These clock pulses received from the IC555 is translated into a sequencing or chasing effect over the LEDs connected across the various outputs of the IC 4017.
In its normal mode the IC 4017 would have generated a simple start to end sequencing of the LEDs wherein the LEDs would have lit up and shut off one after the other in a sequencing pattern with a rate determined by the IC555 cock frequency, this would repeat continuously as long as the unit stays powered.
However in the proposed knight rider LED light chaser circuit, the output of the IC4017 is configured in a special way using a group of diodes which enable the output sequencing to produce a to and fro chasing of the connected LEDs, albiet through 6 LEDs only in contrast to 10 LEDs as in the normal mode.
How it Works
As can be seen in the first circuit diagram, the design produces a reverse forward moving effect of the LEDs in response to the clocks generated by the IC555 which is basically wired as an astable.
The frequency of this astable can be varied by adjusting the associated 500k pot which in turn influences the LED sequencing speed.
The entire circuit is powered via a compact transformerless power supply circuit thus avoiding the need of bulky transformers or costly SMPS.
This circuit can be also modified for illuminating mains operated bulbs by incorporating a few triacs in conjunction with the LEDs present at the outputs.
The second figure shows the complete arrangement where we can see 6 triacs being rigged across the output LED ends via 1 K resistors.
Again, this mains operated knight rider light chaser does not depend on bulky power supply stages rather employs a simple capacitive power supply for implementing the proposed running light or chasing LeD effect.
WARNING: THE CIRCUIT IS NOT ISOLATED FROM MAINS AC SUPPLY, THEREFORE IS EXTREMELY DANGEROUS TO TOUCH IN POWERED AND UNCOVERED CONDITION.
Knight Rider Circuit using 220V Mains Lamps
Knight Rider Chaser using 12V Bulbs
The above circuit can be also as effectively used for car installation by doing the following modifications to the above circuit. The circuit shows how the design can be used for illuminating 12V car automotive lamps.