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August 2009 Randy's Electrical Corner - HID Lights

Posted in How To: Electrical on August 1, 2009
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If you've ever tried lighting a fire with damp wood, you know how hard it can be to get going, but once its going, it's not hard to keep going. Well, the igniter is like the 2 gallons of gas you have to dump on the fire initially. It takes the higher voltage from the ballast, kicks it up more (to around 23,000 volts) in order to get the bulb lit. Once the bulb is lit and running, it gets out of the way and lets the ballast maintain it (like tossing wood on to keep a steady flame while roasting hot dogs).

I have been going on about how much better HID (High Intensity Discharge) lightsare for your Jeeps all this time and it's occurred to me some of you might not know how they work. Heck, some of you younger guys likely take the existence of HIDs in automobiles for granted.

Turn back the clock even just 15 years, and there were no vehicles with HID lighting. HID lighting was something found only in football stadiums and arenas. You see, even back then, we knew how the daytime-like color and intensity of the light was beneficial to reduce eye fatigue and to help our eyes (which work best with daylight-colored light) see what was going on better.

We knew the benefits, we surely had the technology to build HIDs, but the problem was that we didn't have the technology to make it small enough to fit in a motor vehicle. Heck, the first time I saw an aftermarket HID kit, the kit itself cost $3,000 and the ballasts were 12x4x4 inches (each) and weighed a ton. Nowadays, all the HID-related technology fits inside a KC-Daylighter sized light, and while some of us take it for granted, I still find it amazing that they can shrink down a football stadium light that costs thousands of dollars and fit it into a 6-inch light you bolt to your bumper and costs only a couple of hundred dollars.

Anyway, enough about me rambling about my youth. Here is a look at the way an HID works, kind of from an electron's view.

Power comes into the ballast from the relay, which gets mounted somewhere else. The ballast then takes the 12-14 volts from the Jeep and kicks it up to the voltage the bulb needs to burn gas. However, it doesn't actually start the gas burning, it just "tells" the igniter to get to it. Once the bulb is going, it constantly monitors the voltage feeding the bulb to maintain a steady arc and steady light output.

The power from the igniter and ballast ends here at the bulb. Instead of tungsten dental floss that is surrounded by gas (as in Xenon, Halogen, whatever) to simply slow the decay of the metal element, in a HID bulb, there is no free-floating metal dental floss, you are actually igniting the gas itself, and that's where the light comes from.

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