MH bulb with Enclosed Luminaires - What do you think?

[rajkumar]

I found this MH bulb with 15 degree beam and am thinking of trying this out. Looks like the bulb has internal reflector and a small condensor like set up on the top which spreads light at 15 degree beam. Unfortunately no other data- physical measurement etc. found on the site. Any suggestions?

Link:
http://www.lighting.philips.com/nam/...hid.php?id=125

[Rolm]

This bulb is huge; 10-7/8" long and 7-1/2" wide:

http://www.donsbulbs.com/cgi-bin/r/b.pl/mh400rsp.html
http://www.lighting.philips.com/nam/...se/pdf/hid.pdf

I'm trying the MH175/RSP. I just got the bulb this week, but my ballast turned out to be bad, so I have to wait another 2 weeks to get a replacement.

[rajkumar]

Yes...its huge I found out when I searched on philips PDF files. I like MH175/RSP that you have..Looks perfect size for my project.

donsbulbs ran out of it do you suggest any other place where I can buy this bulb?

Rajkumar

[Rolm]

http://www.atlantalightbulbs.com/

$89, but that's about as good as you'll get. I know they have them in stock, because they had to order a case to get the one bulb I ordered =)

This is a 16deg lamp. They have a flood version that's $20 cheaper. I went with the 16deg lamp, because I figured a more tightly focused beam would mean more light directed out the apeture. I hope.

[rajkumar]

Thanks for the bulb suggestions. I will order it soon..looks great. Is it true that its rated for 60k lumens!! (on the weblink you gave). Thats really bright so even if we dont capture a whole lot of light we sould be fine..

Which ballast are you using. I am thinking of buying IceCap electronic ballast which can run "any" 175 w bulb at the following for $115 - that the cheapest I found. Any suggestions?

http://www.aquatictech.com/lighting.html


Thx.

[Rolm]

I went with a non-electronic ballast, 'cause it's so much cheaper ($40) :

**/MH0175MT

http://www.1000bulbs.com/

(enter the part # in the search box)

It's a little harder to wire up, and a tiny bit noisier, but I got burned with a bad electronic Magnatek M57 ballast off ebay, so I needed a cheap solution. Esp. after laying out $80 for the bulb.

Not gonna be here til 02DEC, tho...

[Rolm]

Also, AFAIK, the output is, indeed, 60K (peak). There is a pdf on the Philips site listing the bulb properties that supports this. However, there is probably a warm-up time before it gets to peak output. Usually not more than a few minutes.

I've become a little concerned that the 16deg beam may be a little _too_ tight. I've been toying with feeding different lights thru the optics of an OHP, and with a tight beam you lose the sharp edges of the projected image.
This is, of course, speculation until I get the ballast and can test it.

[rajkumar]

I was wondering about the same over the weekend. I found the following formula to measure the distance between the lamp and LCD panel based on the beam angle of the bulb. I am not good at solving these kinds of equations so need some help. Here is the link and the formula. My LCD panel is 10.4 diagonal and considering the 16 degree beam angle I came up with 37 inch distance between LCD and LAMP (if I did the correct math) - Thats too far but I think a frasnel lens can be used - dont know what kind though! Any help appreciated.

http://www.highend.com/news/lightingfaq.html

[Rolm]

My calculator doesnt have an arctan button. You could look at it as half the 16deg triangle and just use

tan(alpha) = OP/ADJ

Since you want ADJ (your 'L' in the diagram),

ADJ = OP/tan(alpha)

or

ADJ = 5.2/0.14054 = 36.9999

So you're right.

A fresnel lens essentially takes light and gets it all moving in the same direction to make a narrower beam:

<img src ="http://www.lanternroom.com/fresnel/_images/fresnel02.jpg">

(the image is of a curved lighthouse fresnel, but you get the idea).

So there may be a problem with this 16deg lamp being too narrow. I don't know about that, tho, because the light source for my OHP passes it's light thru a 1.25" apeture, so there's obviously something else going on.

In any event (for me, anyway), I already have the bulb and am just waiting for the ballast so I can test it. I will post the result as soon as I have it. Worst case is I have to buy the 50deg flood, which, in your case, would reduce your depth to 11.58". This actually sounds much more sane for OHP optics, which is what most of the projectors around here are based on.

[rajkumar]

I am glad my numbers were correct! The problem with MH 175 RFL(Flood) is that its not as bright as the RSP (10 K lumen v.s. 60K) but the beam angle is 65 so the distance I calculated is around 9.16 inch which will work out best sizewise. Since most of the 10K lumens are actually usable I dont think it will be a huge problem for the brightness.

I am planning on cutting the bottom my spare OHP and see if I can mount the lamp upright in a small enclosure before building a custom box.