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jackrabb1t

Hello folks,

I am a newbie here, with a suggestion.

I spoke to some people who work in early literacy in villages, and the most expensive thing for them is a projector.

They use it to show videos regarding hygiene, etc.

This is a community of great thinkers and builders, and I searched if you have designed a projector, but could not find anything.

So, here is my initial requirements ( I have absolutely no idea if this will work ):

* The projector does not have to be compact, but it needs to have wheels or some mechanism to move it from place to place ( or be able to broken down after the show )

They are generally tied to the bicycles behind the driver seat; so it cannot be extremely large as well.

* The projection light source should be easily available and cheap and should not take up much battery.

* It should work on rechargeable batteries that allow it to play video upto 1 hour, or solar ( battery needed, because this is played at night ) -- electricity will not be available; car battery too expensive option in asian villages; or it can run off a small inverter.

* The screen will be a white cotton cloth that is held scaffolded; cannot assume the existence of white walls; this design can also be planned; at the end of the show, the cloth can be folded and put away. Similarly with the scaffolding sticks

* If the projector can be built as parts that can be quickly assembled on the scene and later broken down for storage/carrying, it would be great. Allows carrying this from different places.

* The projector lens should be cheap, and if possible, reused from some other product.

* The sound output should be available to some cheap outside amplifiers that can be connected; this could reuse existing amplifier/speakers

* The video quality does not need to be great, but good enough to hold attention.

* The intended initial usage of this will be in Asian villages, though it can be used in any other setting; therefore parts need to be available in that market. ( screws/bolts/ etc ); also electrical is 220v ( if using locally available invertors )

4ndy

"The projection light source should be easily available and cheap and should not take up much battery."
Easily available and cheap: incandescent bulbs, some HID lamps and CFL's.
Not take up much battery: LED's
As far as I am aware, you can't have both at present. LED's work well off of a battery source though without involving the inefficiency of an inverter, and should be easily available in urban Asia.

Re-purposing a fresnel lens from an old projector can work for a one-off project such as this hack, but for a generic design, moulding or milling a lens to design parameters would be preferrable. This is understandably difficult with glass, so we could look at moulding and polishing other materials with similar refraction characteristics, such as PET, however this increases the importance of cooling in order to prevent a plastic lens from warping.

Provided an LCD re-purposed from an old computer monitor, the rest should be relatively trivial compared to sorting out appropriate lighting.

I think this project is a great idea since it could be an area of significant money-saving, compared to commercial options for a video projector, which usually tie customers in with an expensive consumables model as printer manufacturers do, with proprietary lightbulb fittings.

Beluga

About LEDs, I quote from AVS Forum:
one big problem with high power LEDs in projectors is thermal
management. The hotter they run, the shorter the life. That is one of
the reasons that Samsung dumped LED rear projection sets. It wasn't
helped any by the fact that they also had to run the red LED close to
its limits to get sufficient output.

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