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PWM question (Duncan, your name is written all over this one)

CowboyBilly9Mile

Charter Member
7,118
442
USA
If a 12V low amperage output PWM unit (automotive dash and LCD display illumination) unit is left on and with no load applied or a very small, in fact, tiny load is applied, can/will this damage the unit?
 

DNFXDLI

The Token Canadian
Staff member
Shouldn't....it's like an idle amplifier...things that should cause unhappiness would be overloading output, feeding with modified square wave, peeing on it etc.
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
Lol, it's behind the face of the dash so peeing on it won't be happening (but of course, I could reach so I'll be careful peeing on the the side of the road at night) and besides, my luck there wold be a capacitor in there and I'd get zapped.

Isn't it less than desirable to leave an amp on, even with the volume off, when there is no speaker attached? Bear in mind, what I'm doing here is not mission critical, but rather, reliability long term is the concern.
 
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DNFXDLI

The Token Canadian
Staff member
Not at all.....idle is idle....no speaker attached is offering an infinite impedance...aka load....so it couldn't care less...quiescent current is a function of the circuit design....perhaps a circuit might fail from heat at idle at a time, but that will be dependent upon what the design specs called for.
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
Ok, that makes sense, and thanks!

FWIW, I've got some LED's that won't dim with the usual variable resistor dash/interior light dimmer so I'm toying with the idea of experimenting with the PWM unit out of an Explorer. Bad news on those is, new, they cost $130 new but thanks to little Tijuana/little Moscow, I've acquired three of them with no visible wear for $2 each. Spares are worth having around. :D
 

DNFXDLI

The Token Canadian
Staff member
Anytime Bill....remember though, I'm just a dumbass electrician with a couple of semesters of Electrical Eng. Tech. under my belt..so I might just be baffling you with BS.....:p

Post up your results please.
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
Anytime Bill....remember though, I'm just a dumbass electrician with a couple of semesters of Electrical Eng. Tech. under my belt..so I might just be baffling you with BS.....:p

Post up your results please.

Which part of the results? I've got about 12 *things* happening in one big swoop and I'm wrapping up the exterior LED's on Monday when the mailman delivers.

*That homelink on the visor is nice!
 

DNFXDLI

The Token Canadian
Staff member
Which part of the results? I've got about 12 *things* happening in one big swoop and I'm wrapping up the exterior LED's on Monday when the mailman delivers.

*That homelink on the visor is nice!

An entire writeup would be cool if you have time and desire...good info on LED transplanting is hard to come by, especially by a capable Engineer.

Homelink is cool...OL has it on the Lincoln.
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
Boy, that is/is not exactly a simple one. This because there are so many different LED's to chose from, the controller in the LED's (if existent), so many different vehicles, it depends what bulb is being replaced with an LED, and there is trail and error involved. I've found that probably 95% of the work is in studying the existing lap fixture, maybe looking at vehicle schematics, shop till you drop on ebay to learn what options are out there, buy them, install and see if they work, and if they do, finish the job (or back to the drawing board) by going out somewhere dark and doing a visual.

For example, I know that here in WA the law says the front/back park/tail/turn and brake lights must be visible between 50 - 1000 feet under "normal atmospheric conditions". Guess what? I do three tests, park light, 4-way, and 4-way and park lights, and walk the 2,000 foot round trip for each test. Yeah, a little over a mile. I stop and look at ~100 feet, 250 feet, 500 feet and on the way back. All this, and bearing in mind that FMVSS108 also has requirement about light output, in candlepower, at various angles left/right and up/down, and both together for lighting. BTW, this is my trump card if a cop were to give me a ticket, make the state prove I don't comply..........because they can't f*cking succeed in doing so, lol!

Upshot is, it's I don't think it's possible to do a one size fits all write up but I can show what I've done for my particular vehicle and answer questions on what I thnk about and look for when converting. Some people say it's not safe to swap LED's in for incandescent exterior lighting; I disagree. I think it's only unsafe when done by an idiot that thinks the job is plug-and-play, buys LED's installs and does nothing more. This, and especially those lame early LED's from maybe five years ago, the kind that have a bunch of 5mm LED's in them. Two words for those: dim and directional. Dangerous if not tested, and the cops should give that drive a ticket.
 

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