A-man930

iTrader: (2)

I had red LEDs under the dash of my Skylark at one time, and I noticed that they didn't dim with the rest of the dash lights very much at all. Is this a common thing with LEDs? I want to replace the factory incandecent guage cluster/dash lights with some LEDs (still red) and put some under the dash and under the seats. (also those little ones in the door) I still want to be able to dim the lights for those dark roads (and romantic nights out ) Any suggestions on where to get mine would be appreciated! Thanks

A-man930

iTrader: (2)

bump...

kraaazymike

iTrader: (2)

to my understanding LED's typically only operate under a specific voltage range. If they dont get the minimun voltage they just turn off. So when you dim the lights and lower the voltage, the LED's just turn off.

JohnnyBs98WS6Rag

iTrader: (1)

LEDs, even if they are properly biased (w/ a series resistor) for 12V operation, are not nearly as "linear" as incandencent bulbs in their brightness vs. voltage (dimmer setting). So when you connect LEDs + resistor in parallel w/ dimmed incandencents, they won't track brightness very well. However, if you replace ALL of the incandescents w/ LEDs (same types, biased the same way), they will track in brightness much better.

A-man930

iTrader: (2)

So as long as all the lights on the curcuit are all LEDs (what exactly makes them "same types" by the way?) and they are properly resisted, my dimmer switch should work pretty well?

JohnnyBs98WS6Rag

iTrader: (1)

By "same types", in general I meant that if you compare a high-efficiency green LED and a low-efficiency red LED, their brightness might not track each other very well as a function of the current through them. Best way to find out is to experiment w/ the LEDs you intend to use before actually installing them. Some low efficiency types need 10-20mA to appear "bright", while some high efficiency types only need 3-5mA.

LED Forward Current = (Volts applied - LED Forward Voltage) / Series Resistance

The LED Forward Voltage will be around 1.7V, but will vary slightly with LED Forward Current.

A-man930

iTrader: (2)

Ok, so make sure that the LEDs I buy are all high-efficiency and test them out before I put them in... sounds doable. Would any modifications to the dimmer be helpfull?

ScrapMaker

FYI you can't really 'dim' LEDs... you will never get the result you are looking for without some sort of micro-controller.

It's easily done with PWM... what you basically do is run the LED at a higher voltage than what it's rated for, (it's actually got a rating for PWM,) so you can get a higher brightness from each LED, and you use the controller to pulse them. The more time between the pulses, the darker the LEDs appear.... all of this happens faster than your eyes can see, therefore it just appears to dim...

but basically... lets say you run the LED directly off the 3.3 volts, or whatever it needs... you can get 12,000 MCD... okay, well now if you essentially run the LED at 40FPS, it's running a minimal load... so you can run closer to 5 volts to it... it will be brighter and last longer as well... maybe 20,000 MCD... just guessing...

but yeah, that's really the only way to 'dim' an LED...

A-man930

iTrader: (2)

PWM... acronym I'm assuming? Are these do-dads hard to find?

A-man930

iTrader: (2)

And MCD...?

ScrapMaker

Pulse-Width Modulation...

and MCD is the brightness of an LED... if you've ever purchased any, you know that the "Super-Bright" ones go anywhere from 10,000MCD to 20,000MCD...

if you run full direct-current 3.3v, you get 12,000MCD or so, but if you pulse the power, you can run them at like 5v, giving you a much higher light output...

and I think you can purchase these controllers... but I would just make my own...

A-man930

iTrader: (2)

So at 5v or so with the pulse-width modulator, you can reach the 10,000 - 20,000 MCD level (with the right LEDs)?

Where can I get the controllers? or how do I make my own? What role would the factory dimmer play in this all? (assuming ALL the lights normally controlled by the dimmer were all LEDs of the same color and MCD) Now you say that all this happens faster than what you're eye can see... so the pulses are faster than 50Hz or so even at a pretty low setting? The last thing I need is an annoying flicker.

I'm sure there's been plenty of people wondering about doing this for awhile, thanks for the info!
Alan

A-man930

iTrader: (2)

bump...

ScrapMaker

well basically you can use ANY microcontroller... the trick is being able to program it the way you want... do you or anyone you know have the ability to program one? if not you may be able to find someone who can do it cheap for you.

basically what you will do is, take the 12v output from the dimmer wheel, read that number, and change the pulse based on the information.

and yes, you can dim it to like 30%... much lower and you will see flicker..

the way you overcome that is by having different grids of LEDs... if you want to reach the 1-30% dimming-mark, then you will basically have to shut off 75% of the LEDs, then proceed to pulse the remaining...


it would be pretty tight if you had a show car and you made all the lights in your car flash with the music, or light strobe lights or something...

someday I'll get around to it, but my goal right now is to build custom front turn signals, as mine keep getting destroyed by moisture since the bulbs mount so strangely...

I'm still deciding on the design though... I'm thinking for the DRL/Turn it's gonna be full output, and then for parking/headlights, it will be either the classic trans am Bird logo, or 'WS6' or something interesting...

I will probably do it based on darkness with a sensor... because I drive with my fogs on always, and it would be pretty neat to have just the fogs and the WS6 logo right before dark...

plus when I lock/unlock the doors, the WS6 logo would pulse...

possibilities are endless...

A-man930

iTrader: (2)

I can't really think of anyone off the top of my head who would be able to do that for me... if worse comes to worse I guess I could learn how myself.
So this makes sense to me, but I don't know how practical this would be behind the dash... know what I mean?
So how difficult would it be to program the microcontroller to only use the 30%-100% pulsing range? (this is assuming I couldn't do the grid idea)

I'm not looking for too fancy of a setup in all reality. I just want an all-LED interior light setup that works and looks like it could've come from the factory like that.

ScrapMaker

if you don't do the grid setup, you may be able to get to 30%, but it's hard to say... but you need to know how to program a microcontroller... it's not as simple as just changing a setting... do you know any C++?

A-man930

iTrader: (2)

now that you mention that, I DO know someone... is there any other way I could get any lower than 30%?

ScrapMaker

well TECHNICALLY... you can do ANY percentage you want... but when you get to a point, below like 35FPS, you will see flickering... that would distract me beyond belief

if you know someone who can program a microcontroller, it should NOT be hard to make like 75% of the LEDs turn off and just have specifically-placed LEDs to evenly light through 0-30%...

personally, I'd be happy with 30-100% really... you can do 0, or 30-100...

also, don't quote me on the 30%, because every LED/setup is different.... you may only get 50% but that's still pretty dark...

A-man930

iTrader: (2)

That's what I'm thinking... less trouble and that's probably dark enough.

yea, I know it wouldn't be difficult to program that in, what I'm thinking would be hard is fitting that many bulbs behind the dash for the guage cluster... I don't want 25% of my guages lit up... see what I mean? I'll probably just go with the more straight forward approach. Awesome!