I was recently attempting to upgrade the parking light on my KTM Duke 200, so I bought a pair of T10 led lamps. These lamps are a cluster of SMD white LED’s.  They are designed to operate on 12v to are a direct replacement for inefficient T10 lamps.  On replacing the lamp this is what it looks like:


However this is still very normal. Throwing in a microcontroller will make it a lot more appealing.  The Idea is to make a breathing lamp like they put on laptops and gadgets these days. The light starts ‘breathing’ when the bike is in neutral and returns to full intensity while it is in gear. The circuit is as follows:

Breathing Parking lamp Circuit

The circuit is powered from the same line as the existing lamp, what is does is that it Pulse width modulates the ground supply to the LED lamp cluster, sweeps the PWM but stops at the highest intensity when the  bike is removed from neutral gear. The neutral position is detected using the line that activates the Neutral light on the cluster.

The PCB is very tiny because of a low component count, The idea was to mount the board right next to the lamp but because of the lack of an SMD device I made it to fit behind the reflectors. This is what it looks like after assembly:




The program is coded in C and is just 59 instructions, an under-kill for a powerful microcontroller. This is because the 12F683 microcontroller has an on board PWM module.There are various examples of a breathing light on the internet, this is however the simplest possible breathing light.

Source Code

This circuit can not directly be fitted on the bike becausehe Headlamps have a common ground, and also cutting or installing any external circuit to the bike voids warranty :( The aim is to install the circuit and the lamp in a way that it can be removed without leaving a trace.  First we must separate lamp ground wire. To do this I removed the negative tin wire that is inserted through the plastic base and soldered a wire directly in the pcb ground. This wire connects directly to our circuit and carries the PWM. This is what the lamp looks like now:


Because the Lamp assembly is water tight, this white wire is pushed through the same opening as the existing lamp wires saving a drill hole. The circuit draws its power from the same connector as the parking lamp. The power wires are inserted from the bottom of the green connector and the wires are bent and inserted into the connector wedge holding them in place. The same is done to the green wire that carries the neutral signal from the console.. This is what the test setup looks like:


Here is a video of it in action:




For Atmel fans: Anool has created a version using the ATTiny with board layout, very neatly done. Check Here

Last Updated:  23.07.2012