Comment Nitpicking: Not a rheostat per se, (Score 1) 1074
"Rheostat" would mean that you have a variable resistor in front of the load. Dimmer switches use a potentiometer connected to a triac, which controls the duty cycle of the voltage supplied to the load. Inane nitpicking I know, but it's slashdot... what do you expect? LEDs are a little more complicated because they don't run directly off line AC power (or, not usually). Neither do CFLs, by the way... most new ones have an electronic ballast, and the old ones have a magnetic ballast.
However, LED dimming is really easy. LED power supplies rectify the AC, then convert the resulting DC voltage into a controlled DC current output. (If your LED power supply has a voltage output, you're either inefficent or you're going to run into lots of problems). LED power supply controllers come on really cheap chips that have a connection for a dimmer control. Unfortunately, most of them dim the LEDs by producing PWM current output rather than simply reducing the current output, causing the LEDs to flicker when dimmed. This can be mitigated if the frequency is high enough, as the LEDs have a little bit of capacitance.
However, LED dimming is really easy. LED power supplies rectify the AC, then convert the resulting DC voltage into a controlled DC current output. (If your LED power supply has a voltage output, you're either inefficent or you're going to run into lots of problems). LED power supply controllers come on really cheap chips that have a connection for a dimmer control. Unfortunately, most of them dim the LEDs by producing PWM current output rather than simply reducing the current output, causing the LEDs to flicker when dimmed. This can be mitigated if the frequency is high enough, as the LEDs have a little bit of capacitance.
