Today I did a little project and added lights to the car. The orginal idea was to use the "USB" (not really usb...) port on the cars for power, but it does not provide enough mA. So I attached it directly to the batteries (after the switch).
First some planning. The board on the left is a voltage regulator, converting anything between 2.5 and 6V to a constant 5V. This should help keeping the LEDs bright even when the voltage drops for empty batteries. The resistors are based on the V and mA rating of the LEDs ( R= ( V_Battery - V_LED )/ A_LED )
With white frontlights:
Attached in the car:
And then there was a problem... every time the shell was closed and I tried to test the car the sensors didnt work anymore. It just did "Pit Stop...Pit Stop... Pit Stop...", so somthign is wrong, but what?
First I suspected stray light from the LEDs to the sensors, so I added more black tape. Then I supected the voltage regulator (it probably does send some high frequency waves). So I removed it since it is not required to work.
Still no luck. After some searching I found the problem. The soldering joint of the switch is very close to the attachment of the sensor cables on the board. Every time the car was slightly bent with the shell it short circuited the front sensor. After fixing this it worked fine.
I am not totally happy with the light distribution of the front light. I have some other LEDs but right now I am too lazy to change it.