So, a few years after version 1, I have now completed my 4th iteration of this idea.
Version 2, was more 5mm LED’s like the 1st, but was unreliable. Version 3 used the same LED’s as version 4 but with a 556 timer as in version 1. Version 3 got very hot – so hot in fact it started to smoke.
This version is an interim version as it still gets too hot on full brightness. Fortunately, the brake light only requires a fraction of the maximum output, so is perfectly useable for long periods of time.
New for version IV is the 12F675 PIC Micro Controller. This was my first dabble with Micro controllers and I am hooked. The reason for the change is that the PIC can do PWM like the 556 timer, but with less circuitry. It also enables me to modify the brightness of the output without the need for me to take the cover off and adjust variable resistors (and it can also do 0-100% duty cycle). This is the source code for the PWM and the control on the 675 chip. Todo: Add watchdog timer support and maybe add option to reduce brightness steps. Having looked at some PWM code on the net, I decided to create my PWM code from scratch. I did try a 2 timer approach, but found that a single timer worked better for me.