AC Motor Power Supply Project - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 3rd June 2002, 07:02 PM   #1
diyAudio Member
 
Join Date: Jan 2002
Location: France
Default AC Motor Power Supply Project

I am designing an AC power supply for my turntable (VPI HW-19), something along the lines of the VPI 'electronic flywheel'. The goal is an accurate, 60/81.8 Hz (33/45 RPM) 120 VAC sine wave generator, approx .5 amp capacity.

What I have in mind is: accurate low level adjustable oscillator, into a class B amp module, output of which would go to a step up transformer.

I realize that this may not be the most refined approach, but I am not an electronics desigh specialist, I am more of a systems person.

I would appreciate any comments from the group.

Refer to the attached file for a block diagram.
Attached Images
File Type: jpg ac-ps-block.jpg (16.4 KB, 1777 views)
  Reply With Quote
Old 3rd June 2002, 08:35 PM   #2
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Default That'll work.

I built one similar about 10 years ago, and it worked fine. Here's one I have on file, but I don't remember where I got it from, so I can't credit it. It's also about 250k, so I can't directly post it here. It's for a Garrard 401.

The one I linked uses an oscillator based around the 741 opamp, whereas mine used the xr8038 oscillator chip as I had some lying around. I think it might also be more temp and voltage stable. Mine drove a 24V Papst motor, so I used an ILP 20W integrated amp module, and as it was single speed, I used extra opamps to lower the xr3038 distortion further.

My Rock TT has a power supply that's also similar, so it's a doable idea.


<a href="http://members.optusnet.com.au/~xx308/401psu.jpg">TT psu</a>
<a href="http://www.amnesiak.com/ee478/xr8038a.pdf">XR8038 datasheet in pdf</a>

There's no reason why you couldn't also do it with an eprom blown with a wavetable clocked out through a dac. It would be a bit more complicated, and requires access to an eprom programmer.
  Reply With Quote
Old 3rd June 2002, 08:54 PM   #3
diyAudio Member
 
Join Date: May 2002
Location: Northville, MI
Did you know that there was an article by Gary Galo that appeared in Audio Amateur around 1988 dealing with a power supply/speed control for AC motors?

I built it about eight years ago, and it made a world of difference in my vinyl playback. I suggest you check it out before re-inventing the wheel.
  Reply With Quote
Old 4th June 2002, 01:43 AM   #4
diyAudio Member
 
Join Date: Oct 2001
Location: .
The Gary Galo article was issue 1/1986. The issue 4/1988 article was by Robert Bodmer.

ray.
  Reply With Quote
Old 4th June 2002, 08:10 AM   #5
AuroraB is offline AuroraB  Norway
diyAudio Member
 
AuroraB's Avatar
 
Join Date: May 2001
Location: Norway, -north of the moral circle..
If you want to roll your own, this should be ideal for a class D amp, with the transformer as part of an LP or BP filter....
  Reply With Quote
Old 22nd June 2002, 07:15 PM   #6
diyAudio Member
 
Join Date: Apr 2002
Look at
http://www.velleman.be/Product.asp?lan=1&id=9075

There you will see an AC speed controller.
  Reply With Quote
Old 24th June 2002, 04:12 PM   #7
diyAudio Member
 
Join Date: Oct 2001
Location: Munich, Germany
Quote:
Originally posted by Electro
Look at
http://www.velleman.be/Product.asp?lan=1&id=9075

There you will see an AC speed controller.
Hi,

these are not for AC motors (magic words: motor with brushes), it is a phase cutting device giving only a fraction of full phase of the AC power to the motor.
What you need is a real "motor controller" for 3 phase motors.

regards,
Hartmut
  Reply With Quote
Old 25th June 2002, 12:51 AM   #8
diyAudio Member
 
Join Date: Apr 2002
That kit is a start.

With all AC motors you can't get very accurate. For an accurate of 33 RPM or 45 RPM. gilid, could use a stepper motor. They are much more accurate and he or she can use it on any outlet or car. Though if gilid will be doing some effects with the turntable. He or she can not do it with stepper motors because of they have a built in breaking system.
  Reply With Quote
Old 25th June 2002, 01:01 AM   #9
diyAudio Member
 
Join Date: Jan 2002
Location: France
Quote:
Originally posted by Electro
That kit is a start.

With all AC motors you can't get very accurate. For an accurate of 33 RPM or 45 RPM. gilid, could use a stepper motor. They are much more accurate and he or she can use it on any outlet or car. Though if gilid will be doing some effects with the turntable. He or she can not do it with stepper motors because of they have a built in breaking system.
I fail to see why AC motors are inherently inaccurate. A synchronous motor (like the one in my TT) will lock on (ie, synchonize; hence the name) to the AC power waveform, as long the frequency is within its design limits. The only downside I see is a relatively large moment of interia, compared to a DC motor of equivalent output.

I would not use a stepper motor because of the inherent cogging effect. Yes, that can be minimized by proper waveform shaping, but that requires a very complex controller.

I think I will stick to my original concept, as layed out in my starting post. Which brings to mind another question - is this concept scaleable? Could it be taken from a low powered unit (25 W or so) to a high power (>500W), suitable for providing AC power to a preamp or amplifier, a la Power Station?
  Reply With Quote
Old 25th June 2002, 01:48 AM   #10
PassFan is offline PassFan  United States
diyAudio Member
 
Join Date: Aug 2001
Location: Central FL
Everything I could find on synchronous motors indicate that dc is used to excite the rotor into movement. When the rotor reaches speed it switches over to ac and then as you said maintains its speed. There are actually two things that determine a motors synchronous speed:

1) the number of poles
2) the frequency of the applied voltage

Be careful how many poles the motor has that you buy. I would take a look at the circuit that drives the motor in your turntable and see how they did it first. Good luck
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LP12 Motor and Power Supply suggestions dsavitsk Analogue Source 7 30th September 2011 01:10 AM
Variable DC power supply to drive TT motor IZHAKKATZ Analogue Source 9 9th April 2009 08:33 PM
Seperate/Dedicate 12V Power Supply for TT's Motor mike_junior Power Supplies 0 26th January 2009 02:31 PM
Frequency pitch power supply for motor Stefanoo Power Supplies 25 19th October 2008 11:22 PM
AC motor power supply calucci Analogue Source 21 3rd September 2007 05:36 PM


New To Site? Need Help?

All times are GMT. The time now is 04:11 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2