Build a DIY Beamer (Videoprojecteur) Friday, June 17, 2005, 09:53 At the end of May 2005, while I was buying some electronic parts at Selectronic, I ask the cashier about little TFT screens with VGA input. At that point we needed a tiny monitor to be used with a MacMini that drive the 171 acoustic panel in the Ircam Concert Hall. The cashier told me about ALLinBox, a french website dedicated about build your own beamer. After a week, spending evenings to read the posts and the different topics, I decided to start my own project, theErv Box.Other websites about this subject exist, in particular the German DIY Community .While the basic knowledge is accessible on the website, it is a bit difficult to obtain clearanswers about how things works if you don't read the whole forum (takes days'n da ys). Here is a small summary of some important topics you should b e aware of if you plan to start a DIY Beamer Project : - A beamer requires a light source which is suppo sed to be ponctual. - You cannot use halogene (like garden projector) because a "pencil-like" bulb is not ponctual AND because the temperature of color is too "yellow" (around 4300 �K) while a good beamer need a really white light (around 5500-6000 �K). This explains why a spare light bulb for a real beamer is so expensive. - The almost only solution to have a ponctual light source with proper light is HQI, which is used for aquarium. This very special bulb comes with a (heavy) transformer, a capacitance and a starter which provide the high voltage needed to start the lighting process through high voltage discharge in the bulb - HQI has a much better efficiency compa red to halogene lights (more light, less heat) - A condenser lens is sometime used to grab more peripheral light rays and thus gain a bit of lumens. - The use of a sphericalreflector (also cold cold mirror) is the only way to properly grab the light emitted from the back of the HQI bulb. The spherical shape guaranties to send the rays at the right place (ie with the right incidence angle on the fresnel lens). - The Fresnel Lens is used to shape the light rays so that the y pass perpendiculary thru the illuminated object (the TFT screen). The fresnel is split in two to insert the TFT in the middle of the sandwich so that ra y a really perpendicular to the TFT. Fresnel lenses and TFT can be mounted with long screws on the original TFT metallic frame - The fresnel lens must be placed at its focal d istance from the light source : this is the way that incident ray are all parallel between each other. If this condition is not respected, the light won't be uniform all over the TFT panel. - The parts are quite easy to buy now. Two online website distribute most of the hardware you'll need to buy your beamerIzzotekExclusive OnlineA nice program (freeware) to simulate optics :OptoGeoMy Beamerat AllInBox.com
At the end of May 2005, while I was buying some electronic parts at Selectronic, I ask the
cashier about little TFT screens with VGA input. At that point we needed a tiny monitor to be used with a MacMini that drive the 171 acoustic panel in the Ircam Concert Hall. The
cashier told me about ALLinBox, a french website dedicated about build your own beamer.After a week, spending evenings to read the posts and the different topics, I decided to startmy own project, the Erv Box.
Other websites about this subject exist, in particular the German DIY Community.
While the basic knowledge is accessible on the website, it is a bit difficult to obtain clear answers about how things works if you don't read the whole forum (takes days'n days).
Here is a small summary of some important topics you should be aware of if you plan to
start a DIY Beamer Project :
- A beamer requires a light source which is supposed to be ponctual.- You cannot use halogene (like garden projector) because a "pencil-like" bulb is not
ponctual AND because the temperature of color is too "yellow" (around 4300�K) while agood beamer need a really white light (around 5500-6000�K). This explains why a spare
light bulb for a real beamer is so expensive.- The almost only solution to have a ponctual light source with proper light is HQI, which
is used for aquarium. This very special bulb comes with a (heavy) transformer, a
capacitance and a starter which provide the high voltage needed to start the lighting processthrough high voltage discharge in the bulb
- HQI has a much better efficiency compared to halogene lights (more light, less heat)
- A condenser lens is sometime used to grab more peripheral light rays and thus gain a bit
of lumens.- The use of a sphericalreflector (also cold cold mirror) is the only way to properly grab the
light emitted from the back of the HQI bulb. The spherical shape guaranties to send the raysat the right place (ie with the right incidence angle on the fresnel lens).- The Fresnel Lens is used to shape the light rays so that they pass perpendiculary thru the
illuminated object (the TFT screen). The fresnel is split in two to insert the TFT in themiddle of the sandwich so that ray a really perpendicular to the TFT. Fresnel lenses and
TFT can be mounted with long screws on the original TFT metallic frame- The fresnel lens must be placed at its focal distance from the light source : this is the way
that incident ray are all parallel between each other. If this condition is not respected, the
light won't be uniform all over the TFT panel.- The parts are quite easy to buy now. Two online website distribute most of the hardware
you'll need to buy your beamer
Izzotek
Exclusive Online
A nice program (freeware) to simulate optics : OptoGeo
The nice 7" TFT from Exclusiv-Online.Exclusiv Online advertising is true : this TFT is really easy to unmount and unpackage (5
minutes). Be sure to have really tiny cross screwdrivers to unmount the last little panel
(double-sided taped to the TFT backlight). Be extremelly careful with this small panel andto the 2 ribbon cables which do not accept any flexion or torsion.
After a cut (with the Dremel drilling machine and a mini circular saw) in the corner, I useda cutter to separate the two fresnel lenses (made of acrylic resin, really hard, but however
The Fresnels lenses split in two. To cut them at the right dimension, use the same method
as cutting glass or ground tiles. Hard pass the cutter on both sides the lens, and then bend it
on the edge of a hard material until it snaps. Be sure to ALWAYS PROTECT both sides of the lens with some CLEAN and fluff-free fabric or disposable tissue
