Metal Halide Lights, Another Green Solution!




About: No more fun than demolition, designing, building, experimenting! I like making things on a really low budget , so most people in this world, who are poor, might benefit from my ideas

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...).



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    8 Discussions


    8 years ago on Step 3

    iv used these lights be for and they can run very hot if left on for to long 1 hour brake in 24 hour should be enough but they do have a safety feature in the circuit to protect against the light being switched off and then back on when the bulb is to hot
    i know of some 1 that had the light running all the time in the end the transformer just melted not the best of ideas and could be very dangerous


    9 years ago on Introduction

    um yea
    when i saw 'green' and 'metal halide' i thought this was going to be a pot growing instructable =p
    metal halide is the best light for it, that and HPS ;)

    1 reply

    Reply 9 years ago on Introduction

    HPS, high pressure sodium, is very similar: high voltage, high temperature strips the metal vapor of many electrons. HPS, as well as many metal halide lights have a cool (like half of the sun's surface) color temperature: 'warm colors'.
    A high color temperature (think of a welding torch: 2X the sun's surface temp) looks cold to us; interesting paradox!

    Some plants use their internal clock (days after germination), others use day length (strawberries vs. chrysanthemums), and some seem to use color temperature as a signal to flower. Most likely: clear days in early summer: white sunlight; dusty days in late summer: reddish light, all in the countries of origin. Look at some press photos of Afghanistan to see what I mean


    Reply 9 years ago on Introduction

    Beamers (video projectors) use a metal halide lamp as a light source. The color temperature is higher (more bluish white) than most common display lights.

    The socket will probably not fit, but if it can be replaced, it should work great!

    But please take the time to check for overheating!!!


    9 years ago on Introduction

    You are obviously a very experienced & well qualified Dumpster Diver.
    I scored one of these & the damn bulb was broken. As I recall there was a ballast & a thing called an igniter. I have thee bits but no bulb. All the components are very expensive so if you are't lucky it may not be worth hanging on to the other bits.
    Any Dumpster Diving hints would be well appreciated, most of the Dumpsters around here get locked to stop people disposing of trash & filling up the Dumpster.

    1 reply

    Reply 9 years ago on Introduction

    The same thing is happening in Holland, and it is very enraging!!! I have seen perfectly intact tropical hardwood window sills being cut up so they could be fit into the dumpster. True, when a dumpster stands for a long time, people tend to put  stuff in it which the city does not take, like bricks, etc. But now, nothing gets taken out anymore, and due to the now confined space, more air pockets remain. It is very anti recycling and re-use, and should be forbidden.

    I wish I had a portable welder!!!! The only thing I do now is leave lots of trash on top of the locked containers.

    Nowadays, when I need parts, I take some minor leftovers from a disassembly project to the city waste disposal and hope to find what I'm looking for (and/ or other useful stuff). 

    But like you say, I am very experienced, took stuff from the trash since i was 5 years old (in 1958...). This trend discourages recycling!


    9 years ago on Introduction

    Nice 'ible. I do belive the metal disk is some form of thermal cutout, but i could be wrong.