|
Are all the pulses full amplitude and clipping at the max voltage now? That is the first important thing.
The 4046 contains more than one phase detector, connected to different output pins. The one used in all the club schematics is edge-triggered (I think positive-going edges, but I forget), so it doesn't care about the pulse width. However, it may not like pulses that rise too slowly, so plenty of signal amplitude and clipping or else a Schmidt trigger to make sure it rises quickly is the second important thing. The other nice thing about this phase detector is that it is also a frequency detector, so if the disk speed is too high or low, it will be forced back toward the correct value.
The other more common types of phase detector (including the unused ones in the 4046) are sensitive to pulse width and might like to have a 50% duty cycle on both input pulses, depending on the design. They also have only a weak frequency-offset response, so the speed has to be within a certain "pull-in" range to start with.
Can you post a picture of the oscilloscope trace of your optical pulses?
|