Hi all 

My primary school strangely enough in the age of powerpoint and computerised overhead projectors, had for the school hall, a overhead projector that you put on the table and basically it had a fresnel lens surface and then a mirror on a top that looks into a second lens. On the fresnel surface you'd place your info (in our case hymns for singing sessions in assembly) on transparent A4 film paper and under the fresnel lens would be the halogen lamp inside the 'box' of the overhead projector. Whenever it was in use, there would be the whirring noise of the fan because I've heard that these halogen powered overhead projectors need a fan to keep the concealed halogen lamp cool or otherwise it would melt/rupture

Anyone encountered these such things?

Flurofan96 

I use one daily in my classroom. Very efficient, no computer needed, just transparencies and power. They also work very fast as you don't have to wait for a computer to load pages, etc. They can be slow if you misplace your transparencies, though.

You can also write on the transparency while it is being projected. If you buy special transparency film, you can run the sheets in a photocopier or laser printer. Don't try this with standard film as it will melt in the fuser. The heat safe kind is clearly marked for photocopiers.

I believe they can still be bought new, although I don't know which manufacturers do. Mine's a 3M.

Mind you I also have an LCD projector and a MimioTeach device which I use as well.

Hi Sol

Great that you're still using one of these classic overhead projectors now then is there any possibility to open the door that allows you to access the light bulb? I'm extremely interested in seeing what type of halogen bulb, its shape, size, wattage, make etc    if you do get the chance to do so, then it would be great to either see pictures of your overhead projector on LG 

I don't have pictures, but it uses ENX lamps rated at 82V and 360W. Here's one on eBay that's identical to mine.

Ah yes, the ancient overhead projector.  We used these all the time while I was in school.  Different types of bulbs, wattages, and what not there was no uniform standard. 

I used to see overhead projectors during my studies at the elementary school and I think also at Leo-Beack junior high school. I've seen a media projector at the junior high school at one of the computer rooms (Long before they became popular at homes and everywhere). The projector was of the expensive type that being used for eductional and academic purposes, and used short-arc MH lamp.

I have a couple of overhead projectors I bought from yard sales.Remember them from school.One of mine has the roll transparency devices on it.You could put a roll of the material on it and draw on-write on it then crank out a fresh area.Don't have the roll,though.At one time there was a computer monitor that you could put on the stage of an overhead projector.Some folks have converted old laptops to use in this way.

Also, some people in the art community used them to enlarge drawings. You would trace a drawing onto a transparency with a fine marker (usually Staedtler Lumocolour) and project onto a writable surface and trace the enlarged image. It was a common practice when I was in school, and nowadays I don't have use for this purpose but occasionally a teacher's aide will borrow mine for that reason.

Yes, those lamps aren't standard. My particular model uses ENX, but the one (older) that I had before used EYB. There were (are) many more different lamps.

I too grew tothe light of those in the primary school. Most of ours were with the lamp in the base i.e. the transparencies are placed on top of a backlit Fresnel lens, not on top of a mirror. The fans in them were audible but fairly quiet

Aha thanks for the input of the various types of high wattage halogen lamps used for these overhead projectors.

BTW what does the blue top halogen bulb does, is it a way to control the beam or to increase colour temperature since its blue colour? The halogen bulbs posted here are the low voltage but very high wattage type that run very hot and are known to rupture, hence thats why the overhead projectors needed the fan to cool the bulb down so it doesn't melt inside the enclosed case with only a small vent. The fan used in the overhead projector in my school was audible that it could be heard throughout the entire hall but not too loudly, only when we pupils had to be silent whilst the teacher/host of assembly was speaking.

I know a friend who is really into art big time as she does oil painting, bit of drawing and even sculpting!! Think I'll introduce her to the overhead projector if he wanna enlarge her sketches on a big piece of paper or canvas