UV Exposure Box Controller

[IonizedGears]

I designed UV exposure box controller using a PIC and I just wanted to share but I'll take any advice or criticism you can offer.

If you notice that the finished boards are missing the programming header, it's because I realized I forgot it and only realized after the fab house began production. I had to solder some temporary wires to the chip to program the PICs. The board files have since been updated with some slight changes and fixes.

I have no clue how Chinese FAB houses are able to get their prices down to the $11 shipped for ten boards (I got 11 of these boards in the mail) but nothing beats the speed of milling or etching at home for prototyping.

The Controller

The way the controller works is pretty simple. The controller goes up to 999 seconds which works out to 16 minutes 39 seconds which is more than enough for photoresist exposure.

"Start/Stop" starts and stops the UV exposure.
"Increment" increases the set time based on the placement of the cursor.
"Decrement" decreases the set time by based on the placement of the cursor.
"Shift" moves the cursor to the left per button press, resetting the position back to the beginning after the leftmost position.

The user enters a set time with these inputs and can start the timer with the start/stop button.
The set time is saved to the internal EEPROM whenever the timer is started so the user really only needs to set the timer value once.
When the timer runs out, the SSR is turned off and a buzzer sounds for two seconds.

The Exposure Box

I haven't made a proper wooden enclosure for the box yet since this cardboard prototype works fine but I might do it if the box breaks or I get bored.
Inside there are four 10W 365nm T8 fluorescent tubes powered by two ballasts which are controlled by a SSR. The UV lamps are above the exposure area since I like to sandwich the PCBs between two transparencies and glass panes for alignment purposes and this allows easy placement for that.


So, I'm wondering if there's a market for this where I could sell either the standalone PCBs or full kits. The latter would require larger demand since I would probably get the MCUs pre-programmed by Digikey; I would prefer not to be selling pre-assembled boards since I'm still in school and I'd rather not dedicate my time to soldering these things... All that being said, I would also be totally fine with releasing all of the files as open source. I did this as a personal project and I could care less if I make money off of it or not. I do want the extra boards I have to go to a good home, however, so maybe I can give them out to people who want them at my university.

Personally, I think there really isn't a market for this to sell. I'm just checking because it would be cool to release a product of my own.

[Berni]

This breaks the good ol tradition of UV exposing a PCB for a exposure timer using a stopwatch and pulling the plug. It also makes you appreciate your new timer circuit that much more when you know how annoying it is sitting there, waiting to turn it off at the right moment.

I have stopped using mine as id imagine a lot of other people have too. The PCBs from china have been getting so cheap that its not worth the effort anymore. Especially if you ever tried making a double sided board at home.

[IonizedGears]

That's how I did it in the beginning but I had poor UV LEDs where my exposure time was about 10 minutes so that was pretty bad. Yeah, the fab houses have made it stupid cheap to get high quality boards but it still takes two weeks to get the boards where chemical etch and milling can give you a board in an hour. The only difficult part about two sided boards for me with chemical etch is via size. If you look at the eagle picture, you'll see that the vias are massive so that I could use wire.

The way I view it, chemical etch and milling are for prototyping and the fab houses are for final products if they get to that stage (honestly, these finished boards are beautiful).