X10 Brake Light Repeater

HIS IS A TAIL LIGHT & BRAKE LIGHT REPEATER based on a cheap car DRL kit, each lamp having 16 LED's. The white LED's were replaced with red, with which two levels of brightness can be achieved, and where a microcontroller based circuit senses the brake light wire going positive and switch the LED's to high brightness.

The main purpose of using a microcontroller however, was to also be able to introduce an inital short sequence of flashing of the brake light mode, in order to better get attention of drivers behind. This is in vogue with the introduction of similar behaviour of brake lights as are becoming fitted to some new cars. At the moment the sequence is set for two flashes, then steady on. Available range is no flashes, to a maximum of three.

There are add-on flashing brake light kits you can buy, but it occurred to me that repeated flashing every time the brakes are used could quickly become annoying, or at best look like overkill. So the idea occurred to me for an initial couple of flashes, and thereafter lamp just increases brightness on repeated brake applications.

After the initial flashing, and after the brake switch is released, the microcontroller begins a 15 seconds time-out period, during which it will not flash the LED's again if the brakes are applied again, but merely increase the brightness. Also the timer is restarted from the beginning when brake next is released. In other words, before the controller will flash the LED's again, there has to be no further brake switching until 15 seconds have elapsed.

My previous blue X10 is shown here, which was later crashed, but the rear carrier with lamp and controller were moved to the white X10.

The rear facing lamp is mounted under the rear carrier:

The second prototype controller was built on stripboard, and comprises a PIC 16F505 microcontroller and a ULN2003A 7 transistor switch array, plus a 5V regulator. The supply is from one of the X10 tail light wires, which are always powered. The other two wires are ground, and brake light wire, all spliced and soldered into the X10 tail lamp wiring. On the right, the wire pair to the actual lamp.

Later, copies of the module were redone on proper manufactured PCB's. (The board was designed for various applications of the 16F505 and driver chips, not just this one.)

The new PCB installed in the rear carrier – and which incidentally is waterproofed with PCB lacquer:

Hiding the wiring inside the lefthand arm of the rear carrier – the 2-way plugs were later replaced by a single 3-way one, and ends up hidden inside the bodywork:

The first prototype board possibly looks simpler, and actually had a variable current source to feed the LED's, but was twice the size, and using the ULN2003 transistor switch array chip instead of discrete transistors simplifies things a lot as well as providing more possibilities.

Circuit diagram here:
Brake Light Controller-V2.pdf