How to Make Car LED Chasing Tail Light, Brake Light Circuit

The circuit explained here is presented in response to a request sent by one of the avid readers of this blog. The proposed circuit is of a sequential LED light driver, especially designed to suit the application of a multipurpose car tail light indicator.
The circuit is integrated to the brake switch and works as a brake light, it’s also connected to the turn signal switches for indicating the turning of the vehicle with chasing light patterns, and the circuit can also be used just as an ordinary tail light warning indicator.

In order to successfully make the proposed car LED chasing tail light, brake light circuit, it will be important to first  understand the circuit functioning in details with the following points:

The CIRCUIT DIAGRAM can be divided into two sections, the first consists of the LED driver stage, where the IC 4017 forms the main LED sequencer and is configured in its usual counter/divider mode.

Only six channels of the IC 4017 have been used to avoid lengthy sequencing patterns and crowding of the LEDs.

Two arrays of LED are taken from the above outputs such that they “run” in opposite directions when switched ON, however both the channels are never run together since they are used for the LEFT, RIGHT turn indicator purpose and therefore only the relevant side is switched ON depending upon the vehicles turning side.

The IC 4060 is configured in its standard mode, as an oscillator and is used for driving the IC 4017 with its clock signals. With every rising peak of the clocks, the outputs of the IC 4017 shift from one pin out to the next in the shown order, making the connected LED illuminate sequentially.

The pot associated with the IC 4060 may be used for adjusting the sequencing speed as desired.

The LED stage consists of the LEDs arranged in a definite sequencing pattern as discussed in above explanation. The LEDs are connected to the IC 4017 outputs so that they are able to perform the intended sequencing or chasing function.

The LEDs are also discretely wired up to the different vehicle controls like the brake switch, the turn signal switches and an optional DIM tail light switch.

When the brake switch is applied, the LEDs light up all together brightly, indiacting the application of the brakes.

When one of the turn signal switches is switched ON, say for example the LEFT turn signal is applied, the LED array positioned on the LEFT portion starts sequencing from center, toward LEFT, indicating the intended moving direction of the vehicle.  

The above function is repeated toward the RIGHT side by the right portion LED array when the right signaling is made with the relevant switch.

A couple of optional switches (S1) may also be included and wired up with the LEDs as shown in the diagram. This provides a feature of operating the LEDs as a dim tail light indicator which stays switched all the time with a relatively lower brightness, however when the brakes are applied the LEDs light up brightly.

The driver circuit is powered through the IC 7812 which is a voltage regulator and provides safe operating stabilized voltage to the circuit, irrespective of the input fluctuations.

In the above position, the turn signals will also work, but is not recommended as the DIM light at the background may affect the signaling. 

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