LED taillights/brake lights

Circuit diagram:

Components:
R1______________10K 1/4W Resistor
R2______________33R 1/4W Resistor (see note)
R3______________15R 1/4W Resistor (see note)
D1___________1N5819 40V 1A Schottky Barrier Diode (see note)
D2--D13________LEDs High Brightness, High Efficiency Red Type (see note)
Q1____________BC547 45V 100mA NPN Transistor
Q2____________BC337 45V 800mA NPN Transistor
SW1____________SPST Taillight Switch
SW2____________SPST Brake Light Switch

Comment:

This circuit is designed to drive a cluster of LEDs that can be mounted on a vehicle as taillights and brake lights. When SW1 is on, the cluster illuminates at medium brightness. When braking is applied, SW2 is off, and the cluster illuminates at maximum brightness. These two brightness levels are achieved by driving the cluster with a constant current source consisting of Q1 and Q2. The two constant current levels are set by the values ​​of R2 and R3.

Notes:
- A cluster of LEDs can consist of up to 12 LEDs, as shown in the circuit diagram. Common cluster types typically range from 5 to 10 LEDs.
- Using the values ​​shown above, the standby current is 1mA; 20mA with SW1 on, 60mA with SW2 on.
- The constant output current value can be adjusted by changing R2 and/or R3. The formula is: R = 0.6/I (unit: amperes).
- Note that the braking current is obtained by paralleling the values ​​of R2 and R3.
- Use a suitable size, high-brightness, high-efficiency red LED type and change the values ​​of R2 and R3 to suit the absolute maximum rating of the LED.
- Any Schottky barrier diode can be used to replace the 1N5819: a BAT46 type would be a very good choice.