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Old 08-23-2005, 04:36 PM
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Join Date: Jul 2004
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I have been trying to follow what you have been doing, and I don't see where you connected the two grounds. Did you do that? If so, you should next see if the circuit has enough range to get to the right speed.

When you block the fork, it should appear to the PLL that the disk is too slow, hence the circuit should run up to maximum speed. On the other hand, if the gate of the MOSFET is grounded temporarily, the motor should slow way down or stop.

I also think the connections of pins 3 and 14 are correct in the schematic - if the disk is slow (test by blocking the fork), the output on pin 13 should go high, turn on the MOSFET, and make the motor run fast.

It does not matter if the input pulses are wide or narrow, since this phase detector detects pulse edges. So, you should be able to use either polarity of fork signal, as long as it swings from zero to twelve volts. However, the edges should be fairly clean and quick rise/fall time.
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