I am trying to determine the optimum arrangment for multiple LED's powered by a 12V battery/alternator system on a motor vehicle.
I could mate each LED with a 500 ohm resistor, which is how they came from the HK eBay vendor. This will waste 2/3 of the energy consumed and might create a heat problem if I pot the electronics in epoxy.
I could put three LED's in series with a 150 ohm resistor, but they would significantly brighten and dim as the vehicle's voltage ranged between 12.5 volts (engine off) and 15 volts (alternator charging).
I am leaning toward using one 7808 regulator feeding multiple clusters, with each cluster containing two LED's in series and a 50 ohm resistor. This would put most of the energy loss in the regulator, which I can put in a protected spot with a heat sink. The constant 8V would solve the variable brightness. The regulator, rated at 2.2 amps, could in this fashion illuminate over 200 LED's, which is more than enough.