dimming hid’s

All the electrical components in the car are gonna "dim" but, Do HIDs use more or less power than halogen bulbs?

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UNLABELED Custom Car Club President

HID use less than halogens - eg 35W compared to 55W.

But I don't think HIDs can be dimmed - not that I'm very knowledgeable on HID technology - but I think they may be damaged or fail if using PWM techniques as used with halogens, LEDs, fluoro tubes etc.

thanks for the reply. But what exactly are PWM techniques? sorry lol

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UNLABELED Custom Car Club President

PWM = Pulse Width Modulation

PWM is a digital technique used to control how much power is sent to a device.  It, in essence, is a duty cycle controller (duty cycle = on / off ratio). 

Say, for instance, you wanted to dim an LED.  You could do it with analog current through a potentiometer or you could do it digitally with PWM by creating a period (say 1khz - 0.0010 seconds) and then controlling how long power is on inside the period.  If you want the LED to be at ~50% brightness you would supply power for the first 0.0005 seconds and then turn the output off for the remaining 0.0005 seconds.  At the end of the period you start over.  For 100%, the on time would be .001 seconds and the off time would be 0.000 seconds, 75% would be .00075s on and 0.00025s off and so on and so on.

PWM can be achieved using a small 8 pin microcontroller and a few lines of code.

Interestingly enough, you can NOT PWM LEDs on a rotational blade.  I found this out the hard way after building a dimmable night blade controller for a remote control hellicopter.  The constant high speed rotating basically turns the pulse width modulated LEDs in to a pie chart that somewhat illustrates the duty cycle.

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Kevin Pierson

KPierson wrote:

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PWM can be achieved using a small 8 pin microcontroller and a few lines of code.

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And that seems to be the norm theses days, but it can also be done with ancient analog components - typically the common 555 timer with some extra components and a pot (potentiometer = variable resistor - like a volume control to adjust brightness) - say ~$5 worth plus a power FET or transistor to drive the load.

Thanks KP for expanding PWM.

And yes - the strobing of LEDs! Not such a problem with slower thermal & discharge lighting, but a disadvantage of fast solid-state LEDs. (So fast they "pulse" this information through fibre-optics to you.)

KPierson wrote:

---

PWM can be achieved using a small 8 pin microcontroller and a few lines of code.

---

And that seems to be the norm theses days, but it can also be done with ancient analog components - typically the common 555 timer with some extra components and a pot (potentiometer = variable resistor - like a volume control to adjust brightness) - say ~$5 worth plus a power FET or transistor to drive the load.

Thanks KP for expanding PWM.

And yes - the strobing of LEDs! Not such a problem with slower thermal & discharge lighting, but a disadvantage of fast solid-state LEDs. (So fast they "pulse" this information through fibre-optics to you.)

Thanks A lot guys. Very appreciated. But just to clear it up, I wasn't planning on trying to make the HIDs dim, I was thinking about them dimming because of a voltage drop due to the stereo system. But either way, I have a lot more information to play with.

Anyone know of a good, cheap micro controller program? I used one last semester in class but don't remember the brand.
Thanks again

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UNLABELED Custom Car Club President

A 555?  What's that?   :)

Years back I got in to Atmel controllers and I've never used anything else.  You can build a parallel port programmer for $3.  You can download the AVR studio program free and you can download PonyProg to flash the chips for free.  You'll spend $2 on a controller.  So, in all, you'll have $5 in "start up" costs.  I doubt you'll find anything cheaper then that.

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Kevin Pierson

Black Civic - I think you should be ok with the HIDs dimming. They use an SMPS (Switched Mode Power Supply) that regulates the lamp voltage from typically a 9V to 16V input range (depending on the manufacturer). This is because the lamp's lifespan is very sensitive to voltage variation.

BTW - Apart from this site's "the Big 3" to avoid audio dips, like many others I am of the opinion that a small battery is far superior to "stiffening capacitors". Suitable batteries might include Yuasa NP7-12 etc, but that's another story....


Kevin - it's probably worth a quick look at https://www.sentex.ca/~mec1995/gadgets/555/555.html
There used to be a "(C) Elektor Electronics" 555 PWM circuit at that site's previous location, but there is an equivalent at https://www.dprg.org/tutorials/2005-11a/index.html

The 555 as a timer has been used for intermittent wipers, sirens etc.
But its versatility has seen it used for car tachometers, Phase Locked Loops (PLLs), Schmidt triggers...

It's old analog technology, but handy for those that aren't into programming PICs & uCs etc, or where they aren't as well suited.

Sorry for the hijack.

Sorry my sarcasm is hard to convey here.  I've used the versitile 555, but not for years now.  I know they used to say that the 555 was one of the most flexible (non programmable) chips ever made and I believe it - I've seen schematic after schematic with different litlte nifty circuits based around a 555 or two.

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Kevin Pierson

Sarcasm from Kevin ?? Noooooooooowayyyyyyyyy

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

That's a relief! I find it a rare lecter that doesn't know of it. (Lecter as in Hannibal as in eLectriker etc.)

I haven't used a 555 for years either except for the dimming of 12V fluoro tubes for camping and 100W halogen headlights instead of wasting money on the so called +50% or super-bright bulbs.

Alas I don't get the sarcasm....
Then again, I never not how people would say (f.ex) solar tracking arrays weren't beneficial, yet I calculated a 10-20 times energy payback.
Then I found out they used uPCs (without even using their sleep/standby state) - they knew of no other technology.
Hopefully now they'll use newer low micro-power chips and devise some wake-up method! (ie, old-tech still has its place)


BTW - being a noob here I do not wish to hijack, though maybe if the original problem is solved/closed....?