New DC motor controller design.

Vinyl Asylum

Welcome Licorice Pizza (LP) lovers! Setup guides and Vinyl FAQ.

I'm happy to say that after several months I seem to have reached my desired goal of being able to lock the speed of an external DC motor to a stable frequency reference.
You will forgive me for not revealing all the details on how it works, I don't wish to compromise my IP in this. Basically I used some techniques borrowed from analogue computers to derive a frequency from the motor voltage and current. I then wrapped this into a frequency locked loop with a reference frequency provided by an oven stabilised crystal oscillator. The loop locks the motor speed to the oscillator frequency.
I need to do more testing (and listening) but it actually seems quieter than the motor with my standard DC controller was. Not sure what the speed stability is yet, it's beyond my measurement range. I suspect it's about 1 part per million which is about 100 times better than a standard quartz PLL and about 1000 times better than a mains synchronous motor.

First application will be as a replacement motor and drive for the Garrard 301, so I now have to make it work on three speeds. Since everything is slaved from the oscillator this shouldn't be hard, i'll keep you posted on progress.
Mark Kelly

This post is made possible by the generous support of people like you and our sponsors:

Signature Sound

[ Signature Sound Lounge ]

Topic - New DC motor controller design. - Mark Kelly 03:07:03 09/15/06 (11)

three speeds - OMalley 17:18:20 09/15/06 (1)

Probably not. - Mark Kelly 19:14:46 09/15/06 (0)

Re: New DC motor controller design. - dean man jim 07:28:39 09/15/06 (0)

Yes, but shouldn't the speed be locked .... - Garth 03:18:30 09/15/06 (7)

Common but wrong - Mark Kelly 04:45:32 09/15/06 (6)

Re: loose coupling - user510 13:28:49 09/15/06 (1)

Someone else - Mark Kelly 16:30:28 09/15/06 (0)

Oh, you didn't mention your drive type. - Garth 06:11:59 09/15/06 (3)

Re: Oh, you didn't mention your drive type. - Aleksunder 06:24:25 09/15/06 (2)

I use a tape drive and/or rubber belt. No wow with either. (nt) - Garth 07:23:55 09/15/06 (1)

Re: I wouldn't expect wow to be a problem with either ... - Aleksunder 08:10:07 09/15/06 (0)

You can not post to an archived thread.