115 volt to 82volt???

[uvodee]

it's another dimmer, black color and good for 1000 watts

i tried it with a 300 watter but the dimmer seemed to get far too hot!

what i did was easy.

I set the dimmer to approx 80 volts and blocked the slider from then on. i used a piece of plastic with super glue and a small screw to make the obstruction.

that was all, i can not remember doing anything else.
two fans, and a parabole from a wal mart work lamp made it good enough for me.


Jean-Pierre

i bought the bulbs in a 12 piece packing, on line and they were very inexpensive, I think they were around $60 per box including shipping each bulb lasts a very long time, when i sold the set up i gave the 10 or so remaining bulbs with the projector.

[modgod]

If your powering from mains which Im guessing is US 120v, WTH is providing the 400W or thereabouts of power needed to run the lamp?

sureley when these are in retail projectors/ohp they use some kind of ballast or PSU.

[uvodee]

i will check at home how i did this, i am sure there was not an issue of ballast...........

[victor-eyd]

I think I get the concept of the dimmer.

Yes, incoming is 110v so at the bottom of the scale one would get 0 volts and at the top end of the scale you would have 110v. That these dimmers could handle 600w or 1000w means that one could light up 10 60w bulbs or 10 100w bulbs to go off one dimmer safely.

That the FXL bulb is rated at 400w means one dimmer could handle this and the trick is simply to measure along the scale where it reaches 82v and stop there.

Can an electrician confirm this theory cuz it sorta makes sense. Now I all I have to figure out is how to use the volt meter without killing myself

[modgod]

So your saying that whatever voltage the bulb draws is supplied no matter what, and the thing your trying to regulate is voltage thus the dimmer must be able to handle that wattage running through it.

Wouldnt wattage change with voltage?

your theory sounds good though, Im no electrician

[DJForce]

Most household dimmers do NOT modify the voltage. The voltage from the wall is a smooth sine wave. The dimmer simply chops part of the wave off. It's exactly equivelant to turning the light on and off VERY rapidly. An analog volt meter sould probably show the effective DC equivelant, since the mass of the needle might smooth out the chopped out AC. Digital multimeters though, no telling how they would respond to a dimmer output. Probably depends on the meter, and might be totally misleading.

[Guy Grotke]

That's the problem with using a dimmer: It would be very difficult to know when you have it adjusted correctly. Too low and you don't get as much light on your screen. Too high and you blow through lamps very quickly. Somebody bumps the dimmer switch knob and "poof", there goes your lamp.

If you have 120 VAC main power, then using a diode gives you a perfect 83 volt lamp supply with no need to adjust anything EVER. This is the circuit that 83 volt AC lamps were designed to work with! The "83" is misleading, because it is the peak level of the half-cycle AC waveform. (Like this: _^_^_^ with no negative half of the sine wave.) If you try to run one of these lamps with 83 volts DC it will expire in minutes.

The basic circuit is just the diode. lamp socket, and switch wired in series. There is no polarity issue: You can wire the diode either way and it will work fine.

A modern silicon rectifier diode won't even get very hot, since it drops about 1 volt in the forward direction and passes no current in the reverse direction. With a 4.4 Amp forward current, the diode would generate 4.4 * 1 = 4.4 Watts. That's about as much as a small Christmas tree lamp. But it's even less than that, since the current only flows half the time, so it's more like 2.2 Watts.

Of course, if you have 240 VAC main power, then you do have to use a transformer or a dimmer switch. But again, the simplest and most reliable circuit would be a 240:120 VAC transformer and a diode.