About Dimming LED Instrument Lights

[porwolf]

I am very interested in upgrading my instrument lights to LED's. What is holding me back is that I would like to be able to dim the LED's to almost complete darkness for night driving on very dark Country roads. I can see the road so much better with no instrument lights glaring at me. I found a rennlist thread that deals with exactly that situation and someone built an after market dimming box for 928 cars that is controlled by the Porsche factory rheostat. That seems to be the ideal solution and should also work on 911 instruments because I think that setup must be very similar to the 928's:

PWM dimmer for instrument backlighting after upgrading to LEDs - Rennlist Discussion Forums

And here is where you can order the dimmer as a complete unit or parts kit for do your own:

Protizmo AILD-1 Information

[Jack Stands]

If you do get this installed, please post a video of the dimming as there are many that love LEDs, but the dimming is not always very linear when replacing the factory bulbs.

[porwolf]

Originally Posted by Jack Stands

If you do get this installed, please post a video of the dimming as there are many that love LEDs, but the dimming is not always very linear when replacing the factory bulbs.

From the rennlist thread:



Looks pretty linear to me. And the author's circuit is micro controller base to adjust for non linearities. Though the LEDs don't seem to go completely dark, but that should be solvable. And the YouTube is just his very first breadboard approach.

I will post my experiences if and when I decide to go LED. But I certainly will make sure that I can dim them to practically complete darkness.

[Tremelune]

I don't see the value in linear dimming, but I'm very interested in LEDs that can go near-dark. I never even have the stock bulbs at max. There are times when I want a black dash at night for the novelty. Bonus project: Put the brights/fogs indicator on the circuit...

[jstobo]

I installed blue LED's in my 928 with a kit from garage 9. With the kit they sent a potentiometer so you could dim the LED's. Because of the low current draw of the LED's the stock potentiometer even at its lowest setting supplies enough current to keep the LED's fully bright. I ended up not installing it though because the light was so soft it doesn't effect my night vision at all. A pic.

[wwest]

Complex problem. LEDs will always produce some light, however minor, as long as the source voltage is above the LED's minimum conductive voltage, typically 1.2 volts.

Incandescent bulbs do not produce light as linear function so why bother to get LEDs to work that way?

[porwolf]

Originally Posted by wwest

Complex problem. LEDs will always produce some light, however minor, as long as the source voltage is above the LED's minimum conductive voltage, typically 1.2 volts.

Incandescent bulbs do not produce light as linear function so why bother to get LEDs to work that way?

The circuit used in:

PWM dimmer for instrument backlighting after upgrading to LEDs - Rennlist Discussion Forums

is microprocessor based. It should be possible to program it that at zero Porsche rheostat settings the LED's go completely dark.

[ClickClickBoom]

Found this on eBay:
PWM Dimmer Switch for 12V DC LED and Panel Lights 6 Amp 72 Watts Capacity | eBay

Price was right, I needed another project on the pile!