DIY Video Projector Part II

[verbose mustafa]

Originally posted by prjctr_builder
the previous post sounded to me like it was written about 2 years ago, when we knew nothing about projection....

my point is... though we did have some progress with learning a thing or two about projection, and some people even had pretty good results, most of us never applied new concepts to their projects. Many people told us which way not to go, but still everyone keeps trying their luck. to me, this forum seems like a closed circle that has no beginning, and seemingly no end as well.

A agree with you. Im kind of tired of seeing everyone use an OHP and an lcd pannel. In my opinion, that is no way to go if you want to make an lcd projector. There are so many other ways to go, and people still flock to the ohp setup. Why? I guess it is easy, but what is the fun in that? Mabey we should start a thread, "new ideas and concepts."

[verbose mustafa]

Originally posted by rbraithwaite
Does anyone know if it's safe to put a dimmer switch between the mains cable and the ballast of a 400w MH lamp. Just wondered if I did this that I might affect the volts, amps, etc. going to the lamp?

Thanks in advance, Richard

No offence, but you really need to look up the meanings of volts, amps etc. The whole idea of a dimmer switch is to limit or in your words "affect" the voltage to the light. So (unless your light will; not work on lower voltage which it probably will) there is nothing wrong with a dimmer switch.

[eebasist]

Not going to work.......a dimmer doesnt affect voltage, and you'll most likely do one of two things....nothing at all, or fry your ballast

[verbose mustafa]

http://www.howstuffworks.com/dimmer-switch.htm

[Redevil]

Does anyone know if it's safe to put a dimmer switch between the mains cable and the ballast of a 400w MH lamp. Just wondered if I did this that I might affect the volts, amps, etc. going to the lamp?

Thanks in advance, Richard

A dimmer would not be effective at all.
Metal halides operate with constant voltage between an arc gap
filled with gas.
Going below the rated voltage will end up turning the bulb off.
All other lamps that produce light using filaments will be able to use a dimmer eg. Incandescent and halogens.
L8r

[remp]

From Redevil

A dimmer would not be effective at all.
Metal halides operate with constant voltage between an arc gap
filled with gas.
Going below the rated voltage will end up turning the bulb off.


Redevil is correct.

The ballast lamp fault condition sensor will turn the power off. It is possible to use a dimmer with a Metal Halide arc lamp and is done by people with aquariums to simulate various daylight conditions as in nature, but it is not a simple matter.
Search for aquarium lighting.

[slize]

Originally posted by prjctr_builder
the previous post sounded to me like it was written about 2 years ago, when we knew nothing about projection....

my point is... though we did have some progress with learning a thing or two about projection, and some people even had pretty good results, most of us never applied new concepts to their projects. Many people told us which way not to go, but still everyone keeps trying their luck. to me, this forum seems like a closed circle that has no beginning, and seemingly no end as well.

If you think this is old, i didn't manage to explain exactly what i meant.
I am NOT using a regular tft panel for ohps which you can buy at ebay. It is a TFT MONITOR for PCs, that's the difference (better picture, response time <30ms and you can buy it everywhere). The fact is, if there aren't panels in a 2" format with 1024x768(or at least 800x600) pixels payable for us (about 3000$ plus controllers all in all over 4000$) we need a fresnel lense (the best and cheapest are from damaged ohps), otherwise you are not able to spread the light through such a big screen (over 10"). And in my opinion a MH bulb is not needed because the installation costs and the price for one bulb(40$) are too high. My bulb only costs 4.99$... The NEW thing on it is the cooling of the lamp. Because i can use a 500W bulb without a fan which makes noise like an airplane and the panel is not damaged because there comes absolutely no heat to the panel... The second thing is; it is really hard to build an optic for the projection. and all the guys in here telling they are using a fresnel lens for the projected image itself are lying, because it is not possible. Physic tells you will never have a sharp picture with only one lense, you need at least 2; and real good pictures are only available with three lens optics. ()-)(-!) <---- image of a 3lens optic like in ohps [convex-concave-plan convex] and why not using the one of your damaged ohp.....

So i think my way is a new concept because no one ever showed a finished result of his projector with a PC TFT Monitor and a REALLY cheap bulb, and i will in about one week...

By the way prjetr_builder do you have a new concept??? or are you still using your ohp setup??

[remp]

Slize

Please refrain from using the word lying. You can still make your point by better choice of words not so abrasive.

For example you could say "People using a single lens may experience slight bluring of the colours which can be improved by using two or more lens.

I have a 3M 1705 OHP which uses a single lens and I have examined the image carefully and can find no objectionable colour blurring at all. And every part is well focussed.

Technically you are correct. Practically is a different matter.

[slize]

yap you're right. i apologize if it sounds agressive but my english is very bad. I did not mean lying, i just meant they do not say the truth ;-)
The first point is: I said single lens, but what i meant was fresnel lens. It is not possible to have a 99% sharp picture with a single lens (except those from ohps). Your single lens is also possible because it is from a ohp just like mine... and pictr_builder says ohp is no good idea.
The second point is: it is important to have a perfect combination of the focuses of the fresenel lens and the optic for the image projection. In your case it fits, because you use an ohp. But others who try to combine two different types of lenses won't get a good result; at least i didn't see any in this forum yet. And two fresnel lenses (one for light spreading one for projection) won't work at all... that's a fact

[Mystique]

I am new to posting to this forum but am not new to reading the forum. I've been around for a about 6months reading everyones post. Only reason I have not put my 2cents in is because I did not have a complete working lcd projector and didnt think it would be wise to post ideas on somthing i dont even have.

I will agree that using a 500watt halogen bulb might not be up to par......but whats wrong with using a 15inch lcd panel for a computer. The only bad thing I can see about going this route is the project case will be much bigger and you will also have to have a computer to use the monitor. It seems to me that most people on this forum are talking about SIZE....everyones talking about making thier projector smaller...using smaller lcd's. I dont have a problem with smaller size either.....i think a small lcd projector would be very practical. Slize on the other hand is going for quality, minus the 500watt halogen, and you guys are knockin him for it, saying that his post seems 2years old.....I've looked all over the post and have yet to find someone acctually saying they used a 15inch lcd monitor. Just post from people saying they know a guy/heard of a guy that used a ViewSonic VG 150. I think Slize idea is a great one if you want a big picture with nice quality....lets face it once you go past 40inches on the 5inch lcd the image gets pretty crapy. From what im reading unless you have $4000 to buy a 1inch super lcd on crack there is no way you are going to go bigger then 40inches with a 5inch lcd with nice quality. Saying that I hope that some of people that have been here in this forum from the begining of time will comment on why they think using a 15inch lcd is bad/good



I've also found a solution for converting the Kelvin of your lightsource to 5500k. Its a gel thats used in filming studios to put over halogen lights....but works the same on metal halides. It can be found here for 6.95 for a 20"x 24" its called Roscolux Tungsten Conversion Filters get the Full Blue. http://64.213.162.194/catalog/ws2001...s-theater.html
I use mine on a 400watt metalhalide with 4100k Why convert a 400watt metalhalide you ask. The main reason being that 5500k-6000k is ideal for projecting. The other is because as many of you know the metal halide is greatly known for for its fluctuation of Kelvin threw hours of use, by using this filter you have a constant output of 5500k. AND YES some lumens are lost in the process of going threw the filter. I asked that guy at Full compass how much light is lost on average threw the filter and he says no more the 5-10% but if you look at the data for a while i think you'll find just as I have that the pro's outway the con's. I hope my first 2cents has helped the DIYLCD comunity look forward to replies....both good and bad.