Overhead Projector: 3M, Elmo, WolfVision, Liesegang?
Powerful basis: Liesegang 400 W OHP 2510
Since projectors were introduced to the market, the familiar overhead type has become completely outdated. This fact means that you don't have to part with much cash at all for a model with high luminosity. If your main concern is functionality, you could go for an older device with an old-fashioned housing, and save even more. Used projectors can be picked up for around $50.
A prime consideration when buying a projector is the brightness, which mainly depends on the lamp used. We used a simple data projector from Liesegang (OHP 2510), equipped with a 400 W halogen lamp , which, according to the datasheet, produces 3,500 ANSI lumens. The top-of-the-line models feature HQI lamps of 600 W and even more.
As most of the energy is given off as heat loss, operating a projector means the surroundings become heated. Most importantly, the LCD panel must be sufficiently cooled to prevent any damage. We have included a special section on this.
Simple construction: the opened overhead projector with bulb holder, transformer and fan
A major advantage of a projector with a normal halogen lamp is its price: replacement lamps are available for less than $30, where HQI lamps are much pricier. Here, too, it's worth comparing with the projector we settled for. Its lamps costs upwards of $200 each - the manufacturers take this into account in the overall price calculation.
If they break, these halogen lamps cost $30 dollars at most - but a lamp for a new device is at least $200!
Our recommendation when all's said and done: for good illumination and adequate brightness, your projector should have at least a 350 W lamp. At low brightness, the room has to be effectively darkened to achieve a good picture on the screen's large dimensions.
Lamp socket: in our case, it is designed for a maximum of 400 W. Metal halide lamps are also available for 600 W and more.