Putting lights onto your RC car is a lot of fun and adds realism – plus if your lights are bright enough you can “really” drive in the dark .

You can purchase pre-build lighting sets from a lot of manufactures – which offers an easy way to get you started. Alternatively you can build your own lights for a fraction of the cost and likely with a lot more output and brightness. In my previous post I build headlights for my Tamyia DF03RA Subaru Rally car. The next logical step is to add rear lights and brake lights.

The rear lights are rather straight forward – just get some red LED’s wire 2 (one for the left side and one for the right) in series and add a resistor in series to not fry them when connecting to your rc cars battery. Remember LED’s always need a resistor and the size depends on your LED.

Building brake lights for your RC car is a bit more tricky. Most commercial rc car brake light kits only come on when you are actually pulling the trigger backwards into braking position. This may work for some but not for me (and the rest of our RC Rally Group) who races on nicely flowing backyard rally tracks (we have 4 on Maui/Hawaii  now) where we do not really use the brake but go off the throttle a lot and coast through corners. Slamming on the brakes on a gravel – loose soil track would unsettle the car way too much. Plus the drag of the rc car motor acts as brakes anyway.

My solution to the “brake lights on” when off the throttle and slow coasting is to use a Zener Diode attached to the motor plus lead (important this only works with brushed motors) and to have the breakthrough voltage of the Zener Diode activate a transistor which will essentially offer the electrons a way of less resistance and therefore turn off the brake lights. Or in other words – the rc car brake lights are on when the car is at a stand-still and will remain on until 4 Volts a measured at the Motor Positive lead. The 4 Volts are the breakthrough voltage of the Zener Diode. When I go off the throttle the voltage at the Motor positive lead falls under 4 Volt and the brake lights come on again.

Below is the circuit diagram which makes the brake light switching a little more visual.

Important Notes:

• Works only with Brushed Motor
• Resistor R1 protect the Zener Diode
• Use a bigger (higher Voltage) Zener Diode to have the brake lights come on earlier.
• Resistor R3 needs to be bigger then R2
• Resistor size for R2 and R3 depends on your LED voltage and current

Picture of RC car brake lights on under coasting and when going off the throttle: