UV light table for PCBs

For a couple of years now I have have wanted to make my own PCBs. The reason was simple. If I had to have something finished, it should not take several weeks, including sending gerber files to a PCB factory manufacturer.\r\n\r\nAn easy way of manufacturing PCBs simple, but yet with a good result is by using the following:\r\n\r\n-PCBs with UV active film.\r\n-Transparent paper print with circuit.\r\n-UV light box\r\n-Chemicals\r\n\r\nFor details on the steps on preparation and manufacturing look here (link).\r\n\r\nSince all components was buy-able for a reasonable price except the UV box, I decided to build my own. Here is how:\r\n\r\nI had seen several projects on the internet with people rebuilding an old flatbed scanner into a UV box, and since I had an old one laying around, I thought that I might as well give it try.\r\n\r\nFirst I looked at a Danish “eBay” and found a facial sun. It was only used few times and included all components to drive 4 UV neon lamps.\r\n\r\nI didn’t want to break the scanner plastic and make the form more fragile, so I took apart the entire facial sun and made space for all components one by one.\r\n\r\nThe original facial sun.\r\n\r\nfacial_sun\r\n\r\nThe facial sun inside.\r\n\r\nfacial_sun_1\r\n\r\nThe facial sun was build on a frame, which was easy removed from the plastic case.\r\n\r\nfacial_sun_2\r\n\r\nSince my flatbed scanner is relatively tall, it was no problem to fit the starter electronics and cables inside the box.\r\nAfter only one evening I had the 4 UV lamps build inside the scanner giving a perfect light.\r\n\r\nfacial_sun_lamps_in_place\r\n\r\nI decided to remove the original analog timer with my own digital circuit using an Atmel AVR mega88 as the “brain”. The advantage was, that I could mount a display, and via a few buttons control the light time within 1 second. The software also remembers last set time, so you don’t have to remember what time gave the best result.\r\nFurthermore I made a statistics counter counting how many times the light had been turned on and for long time it has been on as well. It might not be a important feature, but maybe it will turn out useful in the future.\r\n\r\nMy own PCB was of course made in the partly finished UV box.\r\n\r\ncontroller_pcb\r\n\r\nThe user interface with LCD and menu buttons was glued in place.\r\n\r\nlcd_front\r\nLuckily for me, a power supply was build in the original scanner (Lower right corner). I measured it and found a 12V DC. This was used for the relay, and a 5V regulator was soldered in place for the uC board.\r\n\r\nall_electric\r\n\r\nAnd while everything in place it was time to put a lid on the rebuild.\r\n\r\nfacial_sun_closed\r\n\r\nAnd the first test if it would turn on and give a smooth light.\r\n\r\nfacial_sun_3\r\n\r\nThe front of the scanner with its menu buttons and LCD.\r\n\r\nfront_on\r\n\r\nI know the finish inside the box is not very fine, neither the software is optimized for nervous fingers on the buttons, but the job is done and it works for me.\r\n\r\nFor bonus info I get the best result when giving my PCBs 2 minutes and 5 seconds with UV light. Maybe this time will increase in the future. When this happens I can check my statistics counter how long time the lamps can stay effectively.\r\nSchematic and board layout made in Eagle can be downloaded here (32kB zip)\r\nSource code for ATmega88 written for GCC WinAVR compiler can be downloaded here (63kB zip)




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