SOT: electrical gurus check in..., how to dim LEDs? Options

[dlo914]

So i've retrofitted some LED rings into my daily driver, but i'm only using the LEDs as the running lights and using the filament bulb when brakes are applied. how would i go about using the LEDs for both running and braking light usage? i know i'm suppose to add a resistor to each positive LED wire, but i'm so confused as to what OHM rating or % etc i'm suppose to use. The guys at two radioshacks were useless.

Here's how they look at the moment:
(IMG:http://www.914world.com/bbs2/uploads_offsite/i62.photobucket.com-2697-1354257938.1.jpg)

[Dave_Darling]

All the automotive LED taillights I know of blink. Drives my wife up the wall, because she can see them flicker. (Better eyesight, or maybe just less persistence of vision than many of us.) Vertical bar lights, especially Cadillacs, are the worst. But they all do blink.

If it were as simple as putting a resistor in line with the LEDs, I think they probably would do it. So there is likely a reason they use the blinking circuitry instead. Perhaps the LEDs last longer that way?

--DD

[Spoke]

If it were as simple as putting a resistor in line with the LEDs, I think they probably would do it. So there is likely a reason they use the blinking circuitry instead. Perhaps the LEDs last longer that way?

--DD

The resistor - LED current limiter is the simplest solution and the least efficient as far as power/energy is concerned. The resistor drops voltage and dissipates significant power and heat.

There are a myriad of LED drivers on the market that use a high frequency switching method to efficiently drive the LED. The efficiency can reach 95%. That is 95% of the power is dissipated in the LED.

For the resistor current limiter, it is possible that less than 30% of the power is dissipated in the LED and 70% in the resistors.

The downside of the switching current limiter is complexity and cost. You need an integrated circuit switching converter, inductor, several capacitors, a schottky diode, and some resistors.