gary wrote:As long as both pulse trains are identical in frequency there is no *technical* reason you shouldn't be able to achieve speed lock. If you had a half size picture it implies one or other of the pulse trains was twice the speed of the other (it is always possible to lock at harmonic intervals).
I have to have a look if i made a wave file of the test i recall the picture looked a little washed out and half picture size i was thinking it might be because i couldn't adjust the pulse width of the crystal clock ...i suppose the disk speed is still the problem sync might be cleaner but the nikpow speed was still varying .If you have a different number of pulses between the two pulse trains then lock is unlikely to be achieved.
mmmm still have a mechanical clock if i tried to cheat using the crystalsIf you had a free running clock at EXACTLY 400 Hz, and your disc was running at EXACTLY 750 RPM and you used a single frame pulse from the disc to reset the free running clock then yes, the free running clock pulses would be the same as that created from an encoder on the disc.
However the two *EXACTLY*'s are somewhat difficult to achieve methinks.
Yes still have the motor speed problem which all comes down to again the motor and disk motor control electronics how well you made it all LUCKIf on the other hand you generated a single pulse, 1 out of 32, from the free running clock and used THAT to phase lock with the disc frame pulse (which is what a single pulse from the 32nd line of the disc is) then you might be in business - I am just not sure that one pulse per revolution is enough to overcome windage, temp changes etc. But from a purely theoretical point of view it could.
Thats good to know what you think i wonder if a PLL locking on 12.5 hz
on one mechanical pulse is easier better? than a 32 mechanical pulses
......is slow easier or harder for a PLL for a bistable it wouldn't matter a pulse is a pulse so long as its there .
How about that one mechanical 12.5hz pulse triggering a bistable having a free running 400hz clock on the other then you would have 32 pulses which should match what would of been there if you had used a 32 line encoder ...i am again only thinking of cleaner electronic sync pulse .