PLL motor control

HFGuy · 12th July 2005, 09:03 PM

Ive seen many ppl using PLL for DC motor control but why not use a PLL for an ac syncro motor ? Throw a crystal on the input. Use filters to clean up the VCO's output, followed by a nice large BJT output stage to drive the motor. Including the filter and output filter in the PLL's feedback loop wil miminize distortion and phase shifts. You can also throw in a multiplier and programmable divider and you could have very fine adjustments of the oscillator frequency. Just some random ideas of mine. Seems simple enough to me, any reason why this wouldnt work ?

peranders · 13th July 2005, 05:09 AM

Have you checked White Noise Audio and their crystal controlled 50 Hz TT drive?

The idea is good, a heavy overkill, but will work. I have thought the same thing.

rayfutrell · 13th July 2005, 02:13 PM

The Thorens TD125 used a power wein bridge oscillator to drive a synchronous motor. There was a pot on the top of the turntable chassis for fine frequency adjustment of the oscillator. A neon bulb illuminated a strobe ring on the platter so you could adjust the oscillator frequency correctly. There were two strobe rings, one for 50 Hz and the other for 60 Hz. Very ingenious.
Regards,
Ray

HFGuy · 13th July 2005, 10:14 PM

I just finished my undergrad EE thesis on PLLs. SO i have have PLL's on the brain. Doesnt seem like overkill at all to me, and since when is overkill in audio a bad thing

. On further thought if we use a high Q/low phase noise PLL we shouldnt even need any filtering of the output.

GUILHERME · 14th July 2005, 03:12 PM

Hi.

Why would you use a pll if the crystal alone can be very stable on its own ? If its because of freq. adj., there are other ways to go about that.

Anyway, on such a device, if you want to control 110/220v type motors, the place to burn a few braincells is not in the generation of a stable low-distortion sinewave, but raising it to 220Vrms and still get stability and low distortion.

Of course, and this goes without saying, if you think you have a good idea, go for it ! - If you take it further, I for one would like to know about your progress.

Best Regards,

J.Guilherme

12th July 2005, 09:03 PM	#1
HFGuy diyAudio Member Join Date: Sep 2004 Location: Toronto, Ontario	PLL motor control Ive seen many ppl using PLL for DC motor control but why not use a PLL for an ac syncro motor ? Throw a crystal on the input. Use filters to clean up the VCO's output, followed by a nice large BJT output stage to drive the motor. Including the filter and output filter in the PLL's feedback loop wil miminize distortion and phase shifts. You can also throw in a multiplier and programmable divider and you could have very fine adjustments of the oscillator frequency. Just some random ideas of mine. Seems simple enough to me, any reason why this wouldnt work ?

13th July 2005, 05:09 AM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Have you checked White Noise Audio and their crystal controlled 50 Hz TT drive? The idea is good, a heavy overkill, but will work. I have thought the same thing. __________________ /Per-Anders (my first name) or P-A as my friends call me

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13th July 2005, 02:13 PM	#3
rayfutrell diyAudio Member Join Date: Sep 2004 Location: virginia	The Thorens TD125 used a power wein bridge oscillator to drive a synchronous motor. There was a pot on the top of the turntable chassis for fine frequency adjustment of the oscillator. A neon bulb illuminated a strobe ring on the platter so you could adjust the oscillator frequency correctly. There were two strobe rings, one for 50 Hz and the other for 60 Hz. Very ingenious. Regards, Ray

13th July 2005, 10:14 PM	#4
HFGuy diyAudio Member Join Date: Sep 2004 Location: Toronto, Ontario	I just finished my undergrad EE thesis on PLLs. SO i have have PLL's on the brain. Doesnt seem like overkill at all to me, and since when is overkill in audio a bad thing . On further thought if we use a high Q/low phase noise PLL we shouldnt even need any filtering of the output.

14th July 2005, 03:12 PM	#5
GUILHERME diyAudio Member Join Date: Oct 2002 Location: PORTUGAL	Hi. Why would you use a pll if the crystal alone can be very stable on its own ? If its because of freq. adj., there are other ways to go about that. Anyway, on such a device, if you want to control 110/220v type motors, the place to burn a few braincells is not in the generation of a stable low-distortion sinewave, but raising it to 220Vrms and still get stability and low distortion. Of course, and this goes without saying, if you think you have a good idea, go for it ! - If you take it further, I for one would like to know about your progress. Best Regards, J.Guilherme

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