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Lighting with LED

A project log for Kodak Slide Projector Scanner

Use a Kodak projector and DSLR camera to automate digitizing slide photography

Bryan HowardBryan Howard 06/17/2018 at 06:080 Comments

I used the power connection and switch from a dead computer power supply to convert the projectors black plastic vent/remote plug area to the power input area.

Behind that, I connected up a laptop power charger that outputs 19v DC 3amp and connects from AC plug. This laptop charger will be my source for clean DC power that will drive the LED driver and later drive the Arduino microcontroller after being stepped down to 5v.

The LED needs some form of active cooling to keep it from burning up. I’m using a copper heatsink from a an old computer GPU and a 24v fan. The LED has thermal paste where it contacts the copper heatsink and is held in place with some bits of clear plastic screwed into place. The fan is a bit overkill in size but because I’m powering it from the same 14v-15v LED driver it’ll spin slow and not add to the vibrations. I have the fan in the pull config that way it'll  not blow dust out of the scanner. 

The LED driver is an adjustable CC CV step down buck converter. On it’s input is around 19v and I’ll be bringing it down to between 14v-15v to drive the LED.

I’ve decided to disassemble the light assembly from the projector and keep only the glass lens.  

Doing some initial tests you can see that the LED produces a very uniform beam.  You can see how the light beam shape changes as the distance from the LED to the lens changes.

I have some plastic diffuser sheets out of a dead computer LCD screen I might do some tests with to get an even more consistent back lighting, but It might not be necessary and could possibly reduce the light quality if it absorbs specific wavelengths of light. More testing will be necessary.

Next thing on my list of things to do will be trying to isolate the AC motor vibrations and making some kind of housing to hold the LED module and glass lens in place.

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