Halogen to Metal Halide

[Daggasalmon]

As a noob, I learnt a lot from this forum and also web searches about lamps e.g. cct, cri, lumens etc... - many thanks to all you helpful diys.
I'm starting my own DIY projector - the current bulb in the OHP is near end of life - I could either replace or change to a HID lamp setup.
I'm thinking of changing my Halogen 400W/36V EVD lamp to a cdm-t 150W (cool white) setup mainly due to the quality of the colour, whiteness, cooler bulb & longer life. Also, the cdm-t is very similar in dimensions to the halogen in my OHP and the probability of seating the HID in exactly the same place is possibly great. (The built in reflector is separate from the bulb.) A few questions.......

1. The projector (bulb?) is rated at 6300 lumen - is this the output from the projector or bulb? (i.e. does the bulb produce lumens >6300 - some of which is lost along the way.)

2. Although the wattage of the HID is much lower, it is rated at producing 12700 lumen. Will this produce superior brightness to the halogen?

3. Halogens produce hot light while halides can have warm to cool light depending on the colour temperature. From the Tom's warehouse projector (my first exposure to DIY projectors), using the standard halogen bulb, it was necessary to include a fan to cool the stage, preventing the LCD sitting on it from being heat damaged. Will this fan be necessary with the cdm-t, rated at 4200K color temp? How cool is 4200K compared to 3000K?

4. I intend getting the electronic ballast. What I've read is contrary to the postings in this forum about flickering bulbs. The electronic ballast is supposed to operate at a higher frequency (400Hz) thereby reducing the 50-60Hz flickering! True/False? Besides, the electronic ballasts are lighter, and there is no need to have separate caps etc. (There is the danger of taking the fun out of DIY!)

5. Lighting (and lenses) seem to be the biggest challenge for the DIY projector. In terms of lighting I'm befuddled with all the options (existing and emerging) one could consider - the cdm-t150 may not be the best option. Could our knowledgeable and experienced collegues perhaps compile a list of the best options for bulbs/lamps based on the various criteria i.e. cct, cri, lumens, ballast availability etc.

Many thanks to this helpful forum!

[18wheeler]

I am not an expert but I will try to answer some of your questions.

Originally posted by Daggasalmon

1. The projector (bulb?) is rated at 6300 lumen - is this the output from the projector or bulb? (i.e. does the bulb produce lumens >6300 - some of which is lost along the way.)

you have to find the rating of EVD bulbs. My guess is that it is the optimal output of the projector.

2. Although the wattage of the HID is much lower, it is rated at producing 12700 lumen. Will this produce superior brightness to the halogen?

theoritically, yes. but it also depends on opticals.

3. Halogens produce hot light while halides can have warm to cool light depending on the colour temperature. From the Tom's warehouse projector (my first exposure to DIY projectors), using the standard halogen bulb, it was necessary to include a fan to cool the stage, preventing the LCD sitting on it from being heat damaged. Will this fan be necessary with the cdm-t, rated at 4200K color temp? How cool is 4200K compared to 3000K?

4200K or 3000K refers to the "color temperature". It has nothing to do with the temperature of the bulb. In term of color temperature, warm light means ~3500K and below (red), cool light means ~6500K and above(blue). around 5500K is considered as 'natual white'.

for your purpose, 150W CDM-T will consume much less energy comparing to 400W halogen, thus the heat will be much reduced too.

4. I intend getting the electronic ballast. What I've read is contrary to the postings in this forum about flickering bulbs. The electronic ballast is supposed to operate at a higher frequency (400Hz) thereby reducing the 50-60Hz flickering! True/False? Besides, the electronic ballasts are lighter, and there is no need to have separate caps etc. (There is the danger of taking the fun out of DIY!)

magnetics are bulkier but more reliable; electronics are more expensive but compact. you better ask someone who has used both.

5. Lighting (and lenses) seem to be the biggest challenge for the DIY projector. In terms of lighting I'm befuddled with all the options (existing and emerging) one could consider - the cdm-t150 may not be the best option.

for now, you should use whatever available in your projector if you are going to continue using it as the enclosure. you can try to use an ellipsoidal reflector as Ace ( check his thread, last 2 pages). in theory and in practice, ellipsoidal reflector is more efficient than spherical and parabol reflectors.

Could our knowledgeable and experienced collegues perhaps compile a list of the best options for bulbs/lamps based on the various criteria i.e. cct, cri, lumens, ballast availability etc.

Many thanks to this helpful forum! [/B]

here you are