Printed circuit board fabrication brought real pain back in college, I used a lamp and two pieces of glass to sandwich the artwork in acetate and the negative acting photosensitive board – and the pain I’m talking about? It takes me three to four tries to get a board right since either I over exposed the board or I under expose it, and on one occasion I actually forgot that I was processing a board – bomber huh?
Vassilis Papanikolaou came up with just the thing that could have saved me a lot of boards, a dark room timer that would ensure that just the right exposure is experienced by the board. Lights are turned on when the timer starts and after the time ticks to zero the lights are turned off. It is packed with a lot of indicators, including an LCD option and a seven segment option, a status indicator is also installed using a bicolor LED. A PIC16F84AP microcontroller is used to keep the time and drive the display, it also takes care of triggering the opto-isolator that separates the PIC16F84AP from the relay driving transistor. Simply yet elegant way – and why didn’t I think of this before?