1000W Tungsten to 575W HMI Conversion

mattsdni

mattsdni

Active member
I bought a 1K 'as arri' fresnel a few months ago and I began to wonder what the difference was between mine, and an HMI. When the companies on ebay started selling HMI's I thought the difference couldn't be that different. I started my research and started putting together components. I found a 575w HMI bulb that was a G22 socket, which matched my 1K bulb perfectly.
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Now I needed to find a ballast. This is where most of the cost seems to come from. Thanks to a lot of R&D from the folks at lumenlabs forums a lot of time was saved by reading though their research. My conclusion was that a 600W high pressure sodium ballast would serve well as a cheap alternative. Now all I had to do was change that weird looking power plug on the ballast into something I could plug my light into. After cutting off the odd power plug I found out the positive, negative, and ground cables and wired them to a regular power socket that I could plug my light into. After plugging everything in the light ignited properly after a few seconds and began to warm up. I though everything was going perfectly until the light started to flicker. This is caused by the arc becoming unstable (typically due to low voltage). After 1 minute the arc breaks and the lamp goes off. I have been able to sustain a flickering arc for several minutes, but that is still unusable.

I am now stuck. The only option I have at this point is attempting to make the switch to a magnetic ballast where I can replace individual parts as needed to suit the bulbs requirements. This will not be happening soon unfortunately due to the cost of this project. Perhaps in a month or so I will attempt this again with a magnetic ballast, but until then, happy DIY-ing. Here's a video of what it does for those of you who are still interested:


I think I will move on to another project I have been waiting to do. A portable/battery powered 150w metal halide clamp light thingy.
 
Ha I was just thinking about this.... I have 2 1k arri that I wanted to convert, but wasn't sure if this could be done. Not much to offer here, but found this for you (might be worth a read)





I appreciate these opinions and welcome more. Here is another question: Is there a visible difference between an HMI with a magnetic ballast and one with an electronic ballast?

Thanks very much.

Stephen

As long as you are shooting 25 FPS (Pal/50HZ territory) or 30 FPS (NTSC/60HZ) the "look" of magnetic or electronic ballasts should be the same.
However, with the Electronic ballast you can shoot off-speed as they give you a "flicker-free" light output. With magnetic ballast you are limited to certain speeds, which are for film-cameras : 16.66-20-33.33-50-100 for 50Hz , and 60 and 120 fps on 60 Hz (plus some other odd numbers). (180 degrees shutter)
However, this might work different for electronic cameras.
These numbers are also depending on the shutter-angles of the camera.

I would always use electronic ballast, nowadays!

Rob
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I would look into the glass fresnel lens used on HMI'S. I know HMI'S give off harmful radiation IF NOT FILTERED. I'm not saying your glass is any different, but it could be. And therefore worth looking into just to be sure.
 
maranfilms said:
I would look into the glass fresnel lens used on HMI'S. I know HMI'S give off harmful radiation IF NOT FILTERED. I'm not saying your glass is any different, but it could be. And therefore worth looking into just to be sure.
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Yes be very careful to not operate HMI's without the proper safety lens. Eye damage is possible.
 
yep, the fresnel glass is pretty thick glass plus the bulb is G22 so it is double layered. (meaning there is a UV blocker around the "light-making" parts)

I am actually making some progress now. Looks like adding some capacitors could help bring the power levels up high enough. As always, I'll keep you updated.
 
I don't know what you have invested into this project including time and money, but I purchased a set of used 575w HMI lights for a very good price. Just saying!
 
You need UV filtration in place when using an HMI. I would question whether a tungsten fixture's fresnel lens provides adequate UV filtration; maybe, I don't know, but you want to be certain before you point that light at anyone.
 
Agreed. Permanent eye or skin damage is possible without a proper filter. Think of it as very concentrated sunlight.
 
If you don't mind me asking, how much did you get your 575w for? I have seen some cheap ones on craigslist for about $700-1000. I love making things and learning the process, so it's not really about what is cheaper at first, it's more like just learning how all the components work. Although this project is only at $422 so far including the cost of the original 1K fresnel. In the end I think I can build this thing for $400.

I guess I should probably double check the UV filtration properties of the fresnel glass. All glass blocks some amount of UV, it just varies based on the composition. I've got some glass that reacts to UV light that would be a good test. (old transition-lenses:cheesy:)
 
What I really like about this project is that it has the capability to allow one to interchange a light between Tungsten and HMI, something very awesome and unique.
 
UPDATE: The light worked. After a whole lot a hassle with wiring I have a 600w HPS magnetic ballast hooked up. It worked great for about 30 minutes. The lamp got waayyy too hot though and killed the bulb. I think I'm giving up.:cry:

Anybody want to take over for me?
 
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Did you fit the safety interlock? All HMIs have a cutout fitted to prevent you looking at the unfiltered lamp, but also because the striking voltage is somewhat dangerous. From the Tungsten 1K Arris I have memory says that the HMI versions have a different style lampholder to cope with the higher voltage striking, and the cables are thicker and better insulated.
 
I just used stock wiring. The wires are still good. The fresnel still works as a tungsten unit. I tested the hmi bulb at a local rental shop and they said it was dead.
 
So, I found out that I was running too many capacitors in the circuit so the bulb was being overdriven to about 900 watts. So yeah, I think I figured it out now so whenever I get another bulb the light will probably work.
 
I think I've got a brand new extra 575 watt bulb. I live in LA. If I find it you can have it to test.
 
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