oltmann

With the 5K v-led interior lights I selected, I was getting an annoying flickering from the PWM that generates the theater lighting effect.

I added a 2200µf cap across the circuit, and it eliminated the flickering at the cost of the dimming effect.

I was wondering if by selecting the right values, one could use an RC filter to restore the dimming effect. I don't have a scope handy right now, so was wondering if anyone has tried this.

A bit obsessive, but as much as I love these LEDs, I'm rather sensitive to intense light.

paimon.soror

iTrader: (15)

It's not exactly that simple, you need to remember that a "dimming effect" is generally just the driver cutting off the start of half cycle by a variable timer, which in turn (on a filiment bulb) provides just enough power to light the filament at a lowered current.

LED's are far more sensitive to their drivers. As suspected, our car's circuitry isn't designed for LED lighting, which is why you see flickering, after installing LED's in the door and map lights, when the lights are dimming after closing a door.

What PWM are you using to light your system? You will need one with at least a 12 bit resolution when working with LED's to allow seamless dimming. And yes, a capacitor will also render the dimmer useless as it will restore the first cycle to proper operation. If you are going to use a capacitor, I would only use one to filter out any noise through your theater system.

oltmann

I assumed that the built in dimming effect was achieved by a PWM in the keyless control module. I suppose I add a separate LED dimmer circuit, but I wasn't planning that.

http://www.makingthings.com/wiki/analog-output

Therum

It isn't nessesary to make your own dimmer. The key is using the correct value capacitor. 2200uf is obviously to high. Maybe around 500uf. There is a formula to finding the correct cap based on the frequency of the pulse width.

oltmann

I know how to find the RC time constant, but I'm lazy. :P I guess I'll try to borrow a scope.