In message <37B0C4F3.D6A2DA39@eng.monash.edu.au>, Tony Nixon writes >Hi all, > >This may be an upcoming PIC project depending on it's feasabillity. > >I was wondering if a small BW video camera could be set up to monitor >the position of a horizontally moving white vertical line against a dark >background. I was hoping it may be a simple as using a comparator on the >video signal to detect where the line is. Then I could use this signal >to detect the current line position in relation to the frame width. It should be fairly simple to do, first you need a reliable source of sync pulses, the Elantec EL5481 is an excellent, easy to use, sync separator chip. It has outputs for frame sync, and composite sync, you could use a PIC to monitor both of these, first wait for the frame sync pulse, then delay until enough time has passed to get to a suitable line part way down the screen, then monitor the composite sync, waiting for the next line sync pulse. Use a comparator to monitor the video signal, set to switch at a fairly high video level, feed this to another PIC pin. Then just measure the time it takes from the line sync pulse to the comparator output changing. You will probably need a fairly fast PIC, as one TV line only lasts 64uS (for 625 line PAL), a 10MHz 16F84 should be sufficient!. -- Nigel. /--------------------------------------------------------------\ | Nigel Goodwin | Internet : nigelg@lpilsley.demon.co.uk | | Lower Pilsley | Web Page : http://www.lpilsley.demon.co.uk | | Chesterfield | Official site for Shin Ki and New Spirit | | England | Ju Jitsu | \--------------------------------------------------------------/