About cheap Ebay leds. They don't stop working,
How can you have a ground on the scope AND measure the difference between points A & B?
Btw, if place a rectifier diode between +12 V and point A on my picture to cut the negative halfwave, would that be any help for LEDs (they would not be exposed to reverse voltage)? Price of a voltage drop due to diode forward voltage is acceptable. Do I miss some other drawbacks?