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UV Exposure Box By pawon |
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The circuit diagram is quite simple. There is one AVR microcontroller, which
is the heart of the circuit. Besides that we have the LCD and some push-button
as human interface devices, we have the relay to power our fluorecent lights,
and some other minor stuff.
Because the PCB had to fit in the scanner housing, I desided to make it as small
as possible. The circuit and PCB layout are drawn with Eagle.
I printed the layout on transparant paper from 3M. I used an old laser printer
to print the layout on it, and used extra ink (let dry and whipe off with wet
cloth) to darken the tracks some more..
 After the UV-light has done it's work, but before etching..
 The final result, with the sheets used on the background..
Now it was time to drill the holes and solder everything together..
After testing, I made a few changes to the design: is supplied the relay with
12V, beacause I only had a 12 volt version laying around and I added a 100 uF
capacitor on the power supply, to 'survive' the switching of the relay. Because
of the limited space, the small transformer I used just didn't have enough power
to cope with the current-peak when powering the relay. With the extra capactitor,
this problem was solved.
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