Good morning,

I'm attempting my first projector build using a PSONE screen and a light source scrounged from a 3M 9550 OHP. However, I'm having trouble getting my light source powered. Initially, I gave it WAY too much power by hooking it directly to 120VAC (just to see what would happen) and supernova'ed the bulb.

Now that my sight has returned, I can see that the socket for the bulb is labeled "50V". Has anyone here devised a manner to power a similar type of light source successfully? I'd rather not go out and build a 50V power supply, as it would likely take up all the remaining space in the enclosure. Also, the transformer from the overhead projector is too large to fit in the enclosure as well.

Thanks,
Lucas

I assume its 50v ac, If thats the case go get a house/wall dimmer switch and with your DMM set it to the level you want. You may find that keeping it at 40v or so will be bright enugh for you and should give you a bit more life out of the bulb.

Brian kc0kfg

Thanks for the input. I went to Home Depot and got a Trimatron Single Pole 120VAC rotary dimmer and attempted to hook it up tonight to measure the voltage with my DMM. Refering to the wiring diagram below, I hooked the rotary dimmer up to 120VAC and measured between the black line of the dimmer and the white line of the wall plug. Grounds were tied together. With the rotary dimmer off, no voltage is measured (as would be expected). When the rotary dimmer is turned on, the voltage measures 120VAC no matter what position the dimmer is in. Is this dimmer merely acting as a current limiter, or do I have something incorrect in the hookup?
Click to view attachment

Your meter is right it is 120v but the waveform is all choped up so it will make less power. Use a shop light to see the power output. You should make some kind of stop to stop you from turning up the power too much.

You can't go by the socket rated maximum voltage to determine the lamp voltage. That OHP projector uses ANSI lamp #EVD rated at 400 watts running at 36 volts.

http://www3.3m.com/catalog/us/en001/office...ler/output_html

Another method of obtaining 36 volts would be to use a variac, and with that you could actually measure the voltage and current as it doesn't muck up the waveform.

I agree, The dimmer needs to have a load on it to work and keep it way below 50v to start.

Brian kc0kfg

I would find a way to fit the transformer in some how. It's the right part for the job.