How to control LED brightness????????

[Project69]

Is there a way to control an LED brightness?

[Samckitt]

It can be done, but I am not 100% sure how, do you limit the current or voltage? I work at a place with a bunch of electronics engineers, I will find out today & let you know.

[MuscleRodz]

limit voltage

Mike

[Samckitt]

Here is what he told me:

Assuming you have a current-limiting resistor in series with your LED, then by varying the voltage across the circuit, you are varying the current through your LED AND the voltage across it. I can't tell you which of these factors changes the brightness, but it will change the brightness. The other common method is to PWM it.

So I asked what PWM meant:

Pulse Width Modulate. If you're driving it with a CPU, you turn it on and off really fast. Your eyes can't see the flashing, but the LED looks dimmer, the less percentage the LED is on. If you shake an LED clock radio, you can usually see the LEDs flicker.

[Project69]

Well i hooked up blue leds for my gauges and they dont dim when i turn the knob down.

[MonzaRacer]

The resistor in the head light switch is smaller than the one that is inline on the LED(you have to have a resistor inline or a diode goes "pop" when powered up.
See if your light switch has 100 ohms resistance and the resistor inline on the LED 1000 ohms your light switch wont dim them.

[CapSS92]

Try HIDplanet.com under the forums they have a section for LED and a couple of PWM circuits. HTH.

Alex