LED Dome Lights

80083r

New Member
Poodles;1948796 said:
They're not going to dim nearly as well as it's not the proper way to dim LEDs (which is PWM, and there's ways to retrofit it)

Ok, had to look up PWM (basically flicker really fast, with longer off to make dimmer, right?)

The problem with dimming by voltage (normal) as I read it is that the extra voltage gets absorbed by the regulator and converted to heat - is there some way to shunt different levels of voltage to some dummy load instead? Like a small heater (useless for heating anything...) or something? so instead of the regulator absorbing the extra voltage, it just redirects to a heatsink type arrangment?

Please be gentle - I'm an electrical idiot, but I'm trying to learn.
 

Dan_Gyoba

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Aug 9, 2007
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I was more or less curious if the dimmer function actually worked, or if it just hit a threshhold and shut off. I've done enough LED circuits to do PWM stuff, though I've never done it from something like the integration relay. Another method that works is current control. If you restrict current through an LED, you can dim them that way before. I've done it using an LM317 circuit in current regulator mode. With a log pot, you can get a pretty smooth limit from full brightness to off. The nice thing is that with a current limiter, you can arrange it so that you never kill the LED with overcurrent. (A couple of my dashboard LEDs are now dead/dying from overcurrent issues.)

I thought that it was using a current limiter that the factory CC module uses to dim the indicator LEDs when the lights are on.

As far as offloading the load to a different device, that's where you would use a regulator. The regulator would restrict either voltage or current such that the LED device(s) would only see power that they could use, so less heat buildup. The 194 replacement LEDs that I have in my dash just use a simple resistor, so they are vulnerable to failure during an overvolt event. (Probably why I've got a couple that are dying.) I should probably just put another resistor in-line with the lamp circuit before I replace them, which I want to do soon...
 

57trimMKIII

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Jul 14, 2010
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Dan_Gyoba;1948823 said:
I was more or less curious if the dimmer function actually worked, or if it just hit a threshhold and shut off.

My LED dome lights do not dim, however they have a slight flicker before turning off.

I assume the slight flicker is caused by decreasing voltage.
 

Doat

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Feb 6, 2012
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Mine dim but flicker a little bit as they dim then suddenly shut off they dim for a total of about 5 seconds max before they suddenly shut off.