TT Motor Controller

hagtech · « **Reply #60 on:** 29 Aug 2009, 10:50 pm »

I just need chassis designs that are easier to work with. Perhaps then I can make them available for DIY.

Meanwhile, thinking I might just eliminate the output transformer altogether...

jh

tubesforever · « **Reply #61 on:** 30 Aug 2009, 06:54 am »

Jim the Lansing case work is gorgeous.

All you need to do is find a local machine shop with a cnc and you are in business. They can cut out all the holes in minute accuracy.

When I do them on my drill press, its easy to get off a 1/16 of an inch. That is visible to the eye.

I bet there are shops salivating to do some extra work for profit.

Hey if anyone wants to contribute some extra dollars my way I will invest in the CNC and do the case work for everyone. Its only 25-60k dollars to do CNC.

Penny change!

Jim, I want to super charge my new SL1200 Technics project table. Its a 30 v affair. HELP me! BTW there are approximately 3 million SL1200 turntables sold around the world. This would be a good market for a DD motor control.

Cheers!

Galibier_Numero_Un · « **Reply #62 on:** 30 Aug 2009, 04:05 pm »

Jim's problem is twofold:

Manufacturing in Hawaii (all but impossible) - means that he needs a good source on the mainland which adds to cost and the difficulty of policing quality.
Producing a minimum quantity to make the project worthwhile.

Regarding the second point, my guess (based on his earlier experiences) is that this puts him in a bit of a pickle. There are quite a few "me too" / "I need one now" folks - people swept up in their enthusiasm until the time comes to write a check. Ask me how I know:o It's difficult to get a read on the real demand for any product, and further complicated by the current climate of economic uncertainty.

Maybe when the design begins to take form, he can model the first run after what Doc B. did with the first Foreplay line stage - do some kind of subscription deal. The bookkeeping could be onerous however.

Cheers,
Thom

Tone Deaf · « **Reply #63 on:** 30 Sep 2009, 06:55 pm »

Just thought I'd pob by and say hello, and stop this thread from disappearing off the bottom of page 1 !!

Still hoping the idea gets off the ground. Is it still in your mind Jim? I appreciate the difficulty in finding a novel approach and your reluctance to just put out a "me too" product. Be great if you manage it though!

TD

hagtech · « **Reply #64 on:** 30 Sep 2009, 11:52 pm »

I put a lot of thought and drawings into what it should be and do. Suprisingly, it turned out to be a lot like the VPI box. I guess that's where many of the suggestions came from?

Looking at ways to get the price down. Clever, simple circuit tricks. Trying to squeeze into a small box. Worked out an elegant way to synthesize the waveforms without resorting to PLL or other jittery type circuits. The sinewaves are created using simple counters and a 1236 sequence. I have crystal locked (direct) frequency control to better than 0.01Hz increments. Think I will split system into two boards: one controller and one power supply / amplifier. That way, one controller can drive three amplifier cards for a 3-phase solution. The regular product will just be 1-phase. I have it doing 33.3 and 45 rpm at flick of switch, variable frequency and output amplitude. Display is 2 x 16 character LCD. Everything microprocessor controlled. Output amplifier probably a class-D synchronous amplifier, no tranny.

I measured my REGA P3. Only 1.5W to drive motor. Starts up even at 95Vac and if spinning, will continue to run down to less than 50Vac.

Haven't decided how to do the power supply yet. Should it be a PFC type? That would save on size and cost. I also need a low voltage supply for processor and opamps. Two tranformers? Actually, a tube tranny would work, using B+ for output and heater windings for the digital stuff. It comes down to cost and size. This can't be no ordinary inverter, either. The output has to be a very clean low distortion sinewave. Still some inventing to do before I start drawing the schematic.

Display might look something like this:

MODE SPEED POWER
33 33.34 089

jh

tubesforever · « **Reply #65 on:** 1 Oct 2009, 07:54 am »

Jim,

Its very heartening to hear your beginning to flesh out a product. Please don't be too perfectionistic here. Get out a workable solution and use the profit to enhance it and perfect it.

This is definitely a product where even basic improvements to the power supply will yield easy to hear improvements.

Get it perfected over time and we will all be in your debt.

I don't know if folks out there realize how much of the wow and flutter is due to the motor power control or lack there of.....

BobM · « **Reply #66 on:** 1 Oct 2009, 12:47 pm »

How about driving it with a 12 watt lead acid battery and take it completely off the grid? That's what Mark Kelly did with his controller. As an option you could also throw in a simple voltage regulator and a jack and have it driven from a 12V DC laptop power supply (that's how I implemented Mark's design).

hagtech · « **Reply #67 on:** 1 Oct 2009, 09:32 pm »

Having a battery leads to more issues. Recharging, more cost, size, etc. It's like an unnecessary bandaid - to correct something that wasn't designed right in the first place. I don't see using rotten ac power is a real problem. The whole idea is to clean it up.

jh

PET-240 · « **Reply #68 on:** 6 Feb 2013, 11:15 am »

Hey Jim,

Just wondering where this got too?

Thanks, hope all is well.

Drew.

Berndt · « **Reply #69 on:** 6 Feb 2013, 02:53 pm »

Ditto Jim !
Still using these papst motors. I'd be stoked to have a speed controller. I don't need a case..

hagtech · « **Reply #70 on:** 6 Feb 2013, 08:07 pm »

Haven't put much thought into it. Although I have done some very relevant work with microcontrollers lately...

jh

Berndt · « **Reply #71 on:** 6 Feb 2013, 08:10 pm »

I'd be happy to spring for two to start.
I can do the casework and final assembly.
Thanks for still considering this project..

PET-240 · « **Reply #72 on:** 7 Feb 2013, 12:48 pm »

Hey Jim,

I would also look seriously at it, looking at an ft that is set up for 60hz and Aussie don't have that!

Thanks,

Drew

PET-240 · « **Reply #73 on:** 8 Feb 2013, 01:30 pm »

Hey Jim,

To be clear, require 3 phase for papst motor as per Mark Kelly's efforts.

Many Thanks,

Way beyond my skills!

hagtech · « **Reply #74 on:** 8 Feb 2013, 06:24 pm »

I had been thinking of a modular design with a common controller that would generate the three phases. Then a separate output driver. If you needed three phase, then you make two extra output drivers. Or something like that - it complicates a little when thinking of power supplies...

jh

roscoeiii · « **Reply #75 on:** 8 Feb 2013, 06:35 pm »

This may be OT, but what are the advantages of upgrading a motor controller vs upgrading a motor?

PET-240 · « **Reply #76 on:** 8 Feb 2013, 09:32 pm »

That'd be sensational, do believe you have two crash test dummies in Berndt and I. I do machine control for a living, whilst I could use a3 phase vsd, I worry about the carrier freq noise etc. Currently using 24vdc and a 110v 60hz puresine inverter. Still dunno how good that is.
Appreciate your efforts Jim!

hagtech · « **Reply #77 on:** 8 Feb 2013, 11:34 pm »

Two reasons to upgrade. One is the obvious noise on your existing AC line. Look at it on a scope. If you have a big SS amplifier on the same branch then the top and bottom of sinewave is likely lopped off. There will also be other kinks and distortions, perhaps a lot of hash. Things like laser printers, refrigerators, fluorescent lights all contribute different types of noise back onto the power line. And that is the same AC you are sending to your TT motor.

Fortunately, this is pretty easy to clean up with low pass filtering from a good AC line filter. That one trick alone will help to stabilize the motor so it is not trying to respond to any other signals other than the main 60Hz component.

The other reason is speed stability and variation. Ok, all the power plants are driven from master clocks, so long term drift is not an issue. Your clock on the wall will keep perfect time. However, there may be subsonic variations, although I can't imagine they are very big. But when it comes to constant pitch playback, every bit helps. We want the motor driven at a very steady pace. It is also desirable to change that pitch! Not every TT is machined perfectly or perhaps the belt drive is worn. A motor controller with frequency adjustability can fix this.

Oh yeah, and for 3-phase motors, again, they are not machined or wound perfectly. The magnetic fields may not be perfectly 120 degrees apart! Minimal vibration or cogging of the motor may require slight phase tuning of the three drive signals.

jh

roscoeiii · « **Reply #78 on:** 9 Feb 2013, 12:03 am »

Thank you for taking the time to give that excellent answer.

And in what cases would it be a good idea to upgrade a motor itself? Barring motor malfuctions, of course...

PET-240 · « **Reply #79 on:** 9 Feb 2013, 12:11 pm »

One other I can think of is that single phase motors have two windings, the current in one of the winding is out of phase with the voltage by 90', this generates the rotating magnetic field in the windings that the stator follows. Dependant on the number of poles in the motor, the slip %, which is the amount the stator is trailing the rmf in rpm etc. For example, a 4 pole motor at 50hz has a synchronous speed of 1500rpm, however the stator can only output from around 1350-1450rpm. The loss is the slip, the slip is not always constant dependant on load, so a transient groove in the lp may cause the speed to fluctuate slightly and change the way it was intended to sound, PRAT is probably the audiophile term I would put forward. Rega tables apparently have a rep for great PRAT, I haven't heard one to say.
Does that make sense?
Cheers,

Drew.