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UV LED exposure unit from an old HP scanner...

Picture of UV LED exposure unit from an old HP scanner...
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Found an old HP scanner and decided to make a UV exposure unit out of it. Purchased 200 straw hat uv leds on ebay even though I only used 145 of them. I may even be able to use the scanners power supply board as it has 12 and 5 volts. Hopefully I can use the 12 to power the leds and the 5 to power an avr or pic timer circuit. 

The only thing I haven't figured out is how to make some sort of diffuser. 

Update: Upon further inspection it looks like the power supply wont work as the leds draw more current than the power supply puts out. At least from the 12 volt side.  

Last couple of pictures are of the plexi I bought and sanded on both sides. It was then tapped to the underside of the scanners glass. I guess I'll find out how good it works when I finally use it. 
Plexi & Lexax block UV. You need to use a non UV Glass to work as an exposure unit.

Foxtrot701 year ago
Similar to craftydan's suggestion - try a sheet of frosted or translucient ( they are two different types ) plexi or lexan. This would give the diffusing characteristic along with physical ridgidity for mounting..
purpulhaze (author)  Foxtrot701 year ago
Definitely will look into that. Just hoping plexi or lexan doesn't block any of the uv light.
I don't think that it would block UV. Easy enough to determine as demonstrated in your pics. Go to a hardware store shine a UV LED thru a sheet of plexi and view with your camera or camera on your cellphone. It looks like an exciting project. Hats off to you.
purpulhaze (author)  Foxtrot701 year ago
Thanks for the advice. Headed to Home Depot today to check out the plexi and or lexan. The only reason I was concerned is that I heard that some plexi or lexan are UV resistant . I have a small uv flash light and camera on my phone to check. I guess if it dims quite a bit that means it maybe uv resistant.
You got it. This is a quick way to verify the material without spending a bunch of bucks and then have a piece of scrap plexi on your hands. Now if this fails you might try a few of the UV LEDs and lightly buff them with 800 or 1000 grit sand paper. This would give you a defused light right from the source.
craftydan1 year ago
Try a sheet of vellum. I've had great success with that and they should come in large sheets at any better office supply or scrapbooking store.

To mount it, I'd recommend laying it on top of the glass surface and adhear a second sheet of glass above it. The paper needs to be pressed flat and have some distance from diffuser to work surface to work well.

Word of caution: try to hold it up to the light and see how uniform the material is -- not all vellum is as clean as others, but it shouldn't be too hard to find a good sheet.
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