LED driven tail/brake Light Cluster

Constant current circuitry

12V Battery operation

Circuit diagram:

Tail/Brake Light Cluster


R1______________10K  1/4W Resistor
R2______________33R  1/4W Resistor (See Notes)
R3______________15R  1/4W Resistor (See Notes)

D1___________1N5819   40V 1A Schottky-barrier Diode (See Notes)
D2--D13________LEDs   High brightness, high efficiency red types (See Notes)

Q1____________BC547   45V 100mA NPN Transistor
Q2____________BC337   45V 800mA NPN Transistor

SW1____________SPST   Tail Light Switch
SW2____________SPST   Brake Light Switch


This circuit was designed on request to drive a Light-cluster formed by several LEDs that can be mounted in the vehicle as a tail and brake light.
When SW1 is on, the cluster will illuminate at medium brightness. When brakes are operated, SW2 will be closed and the cluster will shine at maximum brightness.
These two brightness levels of the cluster are obtained by a constant current source drive formed by Q1 and Q2. The two constant current levels are set by R2 and R3 values.