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Originally Posted by mbates14
I thought i would try something new, so I made a scanning disk TV ... I got everything working, but I have one problem. No Sync. ... But for some reason, my motor is running full tilt boogie. and its not slowing down to the incoming sync.
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That's exactly the same result which I got when I have built the motor drive circuit according to Peter Smith's schematics:
http://www.nbtv.wyenet.co.uk/speedctrlckt.gif
First check the pulse from the opto fork. I had to vary the distance of the light emitting diode to find the point were I get the best pulse. When I have found it, the adjustment of the 47K poti was not critical.
If you compare Peter Smith's schematics with mine you will see that I had done some changes. These were necessary for getting a line sync. The frame sync is not working well now. The 4046 needs a clear-cut digital input signal. In the next step I will insert a Schmitt-trigger between the opto fork and the 4046.
Another problem is the IRF520. The original IRF510 (which I couldn't get here) needs a lower gain for regulating the motor speed. The IRF520 will be overdrived by the 4046, so I lowered the input voltage.