UV Light Box

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Makes it much more fun to make printed circuit boards.

When I began working with electronics again after a long break, I quickly realized that I needed a UV light box to produce my circuit boards.

Breadboards and test prints are good for prototyping, but at a certain point is it necessary to have a more robust and portable version.

When I make printed circuit boards I use positive photo printing. The layout I print on transparencies on my ink-jet printer. To get good coverage I need to print layout twice on the same sheet.

Update:

The old ink jet printer gave up and have now been replaced with a new colour laser printer. I no longer need to do double printing to get a good result. That saves oceans of time, because the old ink jet transparency needed to dry totally between prints. That could easy take a couple of hours with the ink I used, even using a heating source to speed it all up a little.
The first test prints on the new printer have been quite successful. I was a little sceptic when I saw the first transparencies though - they looked quite weak, but to my surprise the result was surprisingly good. This circuit board only took a couple of hours to get to this stage. The circuit board obviously still needs the drilling.

The UV light box is made from 9mm MDF (Medium Density Fibreboard). The light source is a 8W UV-A lamp that I have taken out of an old handheld face browner I had lying around from my more vain days. After some experimenting I found the optimal exposure time to be about 25 minutes. So of course I needed a timer circuit.


The first version was a simple timer, with the familiar 555 as the main component. It worked OK and served its purpose. But I wanted to be able to get an indication of the time left, so I decided to build a new timer using CMOS technology. This time with the proven 4000 series.

The cover is locked with a small snap lock.

The UV light and reflective parabola.

The parabolic reflector is made ​​from ordinary kitchen aluminium foil glued to thin cardboard. The UV bulb is placed in the focal point of the reflector. A piece of perspex is used as the top. On the inside of the lid, I have placed some adhesive rubber foam to keep the PCB in good contact with the layout of the film.

The initial timer was build around the well known 555 timer.

Running.

There is drilled a small hole in the lid and a piece of clear plastic is inserted in the hole. That way I can see if the lamp is lit. I suspect that it will give up one day.

UV lamp was purchased somewhere in the mid 80s. Fortunately, I almost never used it, so with some luck should be able to use it for quite a few cycles before it burns out.

The wire can be curled up for easy storage.

The finished UV light box. Now with a digital timer build with the good old 40XX series CMOS.

The new timer from can be set from 1 to 99 minutes.