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UV Exposure Box & Timer

posted Jan 9, 2012, 3:28 AM by Andrew Jessop   [ updated Jan 10, 2012, 2:59 AM ]
April 2006

I was getting into microcontrollers such as the AVRs and I needed a quicker, easier and more flexible way of building circuits. I have since seen some insane circuits built with veroboard and enamel copper wire, but I am too impatient to build circuits this way and I also like the neatness associated with PCBs.

I therefore set out to build a UV Exposure box to etch my own boards. I bought 4x18W fluorescent battens from Bunnings for $20.00 each and designed a box to fit them all in. I drew up the design in Autocad, which is basically a box with a small compartment on the side for the wiring and a timer to switch the tubes down the track. The drawing isn't dimensioned and some parts of the design changed while building, but the basics are the same. The tubes are mounted 75mm apart on their axis, and are 60mm below the glass plate. I purchased the sheet of glass for ~$20 to fit in on the top.

Here is a basic parts list of my box, and a picture of the box nearing completion.

2 x base/ lid 800 long x 350 wide
2 x front/back 165 high x 800 long
3 x sides 325 wide x 165 high
1 x plate of glass 650mm x 325mm x 4mm
2 x hinges



UV Exposure Box Timer

After building the exposure box, it was decided that a timer would speed up the PCB making process and help to control some of the variables when still learning. A suitable pre-made timing module was found at Jaycar Electronics (XC-0124) for reasonably cheap (around $10 if I remember correctly).

The circuit schematic is fairly simple and is based on standard parts. A 12v relay is connected to H2 and is switched after the time has elapsed. After looking at the simple data sheet provided, the timer required a 1.5v supply and would go high while the timer was counting down. When the counter had finished the output would go low again. To power the timer a small 12V AC transformer was mounted inside the wooden box. The circuit would then rectify and regulate this power to DC to run the timer, a relay to switch the UV lights and some leds to indicate power and when the UV lights were on or not.


A simple PCB of the circuit was made which can be used to create your own. A capture of the design is shown below.


A wiring diagram of the control and power of the box shows how the internals are connected.

Ċ
Andrew Jessop,
Jan 9, 2012, 3:28 AM
Ċ
Andrew Jessop,
Jan 9, 2012, 3:28 AM
Ċ
Andrew Jessop,
Jan 9, 2012, 3:28 AM
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