Introduction: Metal Halide Lights, Another Green Solution!
Recently, when dumpster diving, I found some spot lights. I went back home to get pliers, because I needed some grounded wires + plugs.
After clipping a few wires, I noticed the bulbs did not look at all familiar. NOW I remember discarding many before. They have a ballast (whatever that is). I have seen this type of thing before, always thought it was for some kind of boring office design fluorescent light, for which I have no use...
This time, I took 2 complete fixtures + 'ballast'. Just checking...
Plugging it in ( only 35 Watt), it turned on weakly, subsequently brightened, tuning bright greenish, then very pink, and then VERY bright warm white. At least as bright as my 250 W building lamp!!!
Some internet research revealed, this is a modification of a high pressure mercury vapor lamp. The mercury does give a nasty, greenish- blue hue white light. High pressure sodium lights give a bright pinkish orange light
This type of light has a high pressure bulb with Argon and Mercury, but also some trace metal salts are added. The metals are rare earths, but due to their very high melting points they are added as ' halides': salts of these metals with Chlorine, Bromine and Iodine. This is easier to evaporate, and the electric equilibrium is less caustic to the quartz bulb @ 1500 degrees C.
Turning it on, looking at the changes, the brightening and color changes, it is caused by increasing temperature, different salts evaporate at different temperatures, etc.
Now the practical side........ These lights can be found everywhere!!!!(Europe). Every supermarket, clothing store or showroom has these fixtures! If they go out of business or do some remodeling, the stuff could end up in the dumpster.....
They do require the' ballast', a switching device, which delivers a brief 5000 V pulse to start the thing, and then controls the proper voltage/ amps. Usually, everything is discarded together. Of the 6 discarded fixtures salvaged, all of them still work!
The mount of this particular light is a 'G12'
Step 1: The Ballast
The ballast is easily opened with a screwdriver. Some transformers and other components are attached to the main circuit board. a bank of 5 transistors (?) on a heat sink and a separate board with smaller components is attached to the main board. The components may or may be not usable for other projects (I do not have the knowledge..).
Step 2: Applications
These lights are usually not available in consumer fixture stores, but easily available on the internet as business 'solutions'.
The fixtures can be used unchanged, by individuals for display of art objects, or in the workshop, as high quality illumination.
'Beamers (video projectors)' have a similar light source, although usually their color temperature is higher (more white, most of these lights in showrooms have a warmer, more cosy color, similar to 3000K or 4200 K. A bluish filter in front of the lens, as used in 35 mm photography, could remedy this, although our eyes easily adapt to this slightly 'warmer' hue.
I think any DIY beamer builder would be thrilled to use these lights...
'Photography and cinematography:' Perhaps almost too bright! No kidding, but with an umbrella or screen, they serve almost all portrait and indoor shooting purposes. Large sheets of plastic/ cellophane filter, to correct indoor light to daylight can be put in front, and can be ordered from professional photo stores, not expensive.
'Grow lights:': The low power requirement could make an ideal supplement to sunlight, to grow a crop out of season at higher latitudes.
Some additional info: The average lifetime of a bulb is 20,000 hrs, and generally, every Watt extra is another 80- 90 lumen...
Step 3: Safety!
Unless you are already familiar installing these lights, please take it easy! If you make an enclosure, check the temperature of different parts repeatedly! Allow hot air to escape, and check if parts around it don't become too hot. If the outer glass bulb breaks, it seems that a large amount of very agressive, ultra short UV rays are emitted, quite similar to a welding torch. Even short time exposure would lead to irreversible eye damage, skin burns, etc.
Electronics: Not my specialty... But anything even briefly using 5 KV should be treated with respect. I invite electronics experts to comment, or even create their own instructable about the parts in the ballast (if they are of any general purpose use...).