Photo Exposure Box
Another project I’m helping with is Cory’s photo box. I said I had a few project ideas that would be useful to have around a couple weeks back, and he stepped up to work on this. It ended up being a pretty sweet little timed UV light box with auto shut off.
The first step he did was finding a small ballast and and bulbs, which ended up being a lot easier said than done. He ordered them through a local electrician supply store, and it took them quite a few weeks to actually get the parts. The tubes themselves are the variety that go in insect killers, and they’re powered by a 150 watt ballast. The tube end-caps are mounted to a sheet metal backpane to reflect the light up evenly across the entire board. When he finally got the parts, he just wired it up to a working state with control being provided by plugging and unplugging it.
To make it a little bit more useful, he and I wired up up a relay (really big one that’s overkill) and ATtiny13 to control the function of the box. Usage is really simple. You hold down the front button for 1 second, and it puts 30 seconds on the timer. Keep holding it, and every second the indicator LED will flash, and 30 seconds will be added. If you go over what you wanted to expose for, keep holding it for 15 flashes (7.5 minutes worth of time) and you can safely release it. If the time on the clock is 7 minutes or less, then when you release the button, the IR tubes will switch on. During the final 30 second slot, the indicator will flash rapidly to alert you that it’s almost done exposing. Time can be added during operation, and the 7.5 minute max can be used to shut off the device early. (Or you can unplug the controller.) Code is located here.
There are still 3 I/O pins available on the AVR, so some additional features could be added. (Another button, or a switch sensor that only allows the light to turn on when the case is closed.)