low priced HPS ballasts

[Me2!]

Hi Guy,

I was surpised to hear you using the ushio. As one of the experts here i always figured you'd have some fancy small arc setup. This new purchase is for testing or is it your standard setup? I seem to remember the spectral pattern on that lamp is weak in the red. The pics ive seen also look greenish. Does the OSD let you compensate? Does compansation = lowering the light transmission on the other colors? There is no doubt the price is good and with that many lumens who cares if some are blocked. Is that the approach you took with it?

What do you think of 400w vs 250w vs 150w?

Thanks in advance.

[Guy Grotke]

I am using the Ushio retrofit lamps because they fit my basic philosphy about DIY projection: It only makes sense if you can make something usable for much less than the price of a commercial projector. If a big fresnel lens and a cardboard box over your TV worked well enough, then I would use that!

We could make projectors that are incrementally better by using short-arc lamps, elliptical reflectors, process lenses, dichroic beam splitters with three monochrome LCDs, etc. But then they would cost more to build than buying a new commercial projector.

Actually, I see DIY projection beinng squeezed by the new low-cost commercial projectors that have appeared during the last year. The only advantage we have is that most of the low-end commercial products are stuck at 800 by 600 native resolution.

The other huge advantage we have is that we can use lamps that cost $38 and run for 15000-20000 hours. If we switched to short-arc lamps that cost $250 and run for 2500 hours, then we might as well just get a used commercial projector that uses those lamps. Buying a used commercial projector on eBay and modifying it to use a cheaper lamp may not be such a bad idea...

Regarding the Ushio retrofit lamps: I think the emission spectrum in the lamp data sheet may be a bit misleading. It looks like the lamps make a lot more blue and green than red. But what matters is the total energy integrated over the wavelengths that are perceived as red (and get through the red color filters in the LCD). The highest peak is an orange that will get through the red filters. I think the red area, green area, and blue area are pretty well matched. That is why the Color Rendering index is around 90. (That is better than most MH lamps.) The color temperature is 5200 K. If you include a dichroic IR filter, that will push the color temp up by about 300. 5500 K is the color temp of most LCD backlights, so you end up with very good colors without using any adjustments. (I don't need any.)

I watch DVDs and satellite video on my one and only projector, because I think the "proof is in the pudding". (If you can't watch it, then some technical "enhancement" is worthless.) Every new IR filter, fresnel, lens, mirror, etc. that I try goes into that projector.

Regarding lamp wattage: I have been using 250 Watts for a 95" image, and it is not as bright as I would like. If you want an image that large or larger, then I would suggest you use a 400 Watt lamp. The total amount of light gets spread out over whatever size image you make, so doubling the diagonal image size cuts the brightness by 4. Don't try to make a huge image, or you will only be able to watch it in total darkness.

[qytum]

Could anyone post a pic of how you wired this ballast?

This is what I have so far:

1. I have my 120v wire connected to black in the outlet, and the one common to the white. There was an extra common but i just placed a wire nut on it. I also put nuts on all the extra volt wires (seperate).

2. The capacitor: I connect one cap wire from the ballast to one side the of capacitor. The other cap wire I connect to the other side of the capacitor. Thats it.

3. Ignitor?? (CD14): The red wire coming from the ignitor is plugged into the the red of the ballast. The blue is connected to the blue of the ballast. The white is connected to the Common wire of the outlet along with the ballast common.

4. Mogul Socket: The hot is connected to the red ballast and red ignitor. The common is connected to the same ballast and ignitor common.

Is this all right? Just looking for some confirmation before I plug this thing in.

[gabel87]

Yes, I believe this is correct. My pj is put away in the shed and it's cold and snowy so I can't go out and check my wiring. But I think you've got it right. They give you an extra common so you don't have to nut soo many wires together.

[TheBigMastodon]

Would this be good for a 15" enclosed projector? I want the screen to be 120" wide, mainly to be used for sporting events and video games.

[Guy Grotke]

That would make a 90" tall by 120" wide image with a diagonal size of 150". That will have 2.25 times the area of a 100" diagonal image. If you really need to do that, then maybe you DO need to build a 1000 Watt projector!

But are you sure about that size? You would need to have an enormous room for that, since you should sit back from the screen at least 1.5 times the diagonal distance size. (2 times is more comfortable.) If you sit closer than about 19 feet from such a screen, your eyes and neck would get very tired from moving around so much. Like sitting it the front row of a movie theatre.

With that kind of screen size, you also need to plan very carefully where you will sit, relative to the projector. It does you no good to have a floor to ceiling image if you have to sit behind the projector!

[TheBigMastodon]

lol Thanks Guy, Well maybe not 120" but I want it pretty big. 150" Would be kind of rediculous as my 80" right now looks HUGE. I bought that 400w ballast on ebay that was posted eariler in this thread and I'm going to mount it in my OHP. Its a pretty nice OHP but its only 2000 lumens so I gutted it. I'm gonna see what my Telex Magnabyte looks like with the 400w and I'll just go from there and decide if I'm going to build an enclosed one with a 15" panel.

[kinglikeprince]

TheBigMastodon, How long did your shipping take?

[TheBigMastodon]

It hasnt shipped yet. I still have to contact to seller for shipping info. It should be around 12 bucks since I live in New York. Guy Grotke lives farther from the shipper. than I do and his was only 12 bucks. I'm not in a hurry right now as I still need to build my box. Brainchild sent me the free lumenlab guide today so I plan on building the LL one to the exact.

[TheBigMastodon]

Okay mine came today. It was 40 bucks total to ship to New York, it took 3 days. Guy Grotke can you please post a picture of how you wired this? It would be appreciated. Thank you.