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VIDEO_OPERATED_CONTROLLER

2016-09-11 06:36  
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VIDEO_OPERATED_CONTROLLER
If you need a timer that is programmable, precise, and will provide long delays, almost any VCR can be used without any internal modification. All that is required is a circuit that will detect the presence of the video output signal when the recorder turns on. The first diode (D1) clamps the negative video to ground. The rest of the circuit responds to the frame markers to charge up the capacitor and turn on the relay. A tape isn't even required (in most cases) if the recorder is tuned to an active channel because the video-out signal appears as soon as the recorder is turned on. Therefore, the circuit's ON time is not limited by tape length.