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Fellow inmates, more than a year ago I started to develop a DIY 3 phase variable frequency motor drive (VFD) for my Papst motors, that I planned to use in a DIY TT project. I used a 3 phase signal generator, chip amps, and step up transformers available for cheap on ebay from China.My prototype had 2 problems, one, because I'm not an engineer I over built, which led to too much RFI noise, and unnecessary heat. The other problem was that the Chinese signal generator was not accurate enough, as they overstated it's accuracy, but it did work. This 1st prototype (Jethro) was posted in April 2016.
A similar project/thread (optimally driving a (VPI) synchronous turntable motor) was started on the DIY forum in August 2016 by some way smart folks on the DIY forum. They downsized the unnecessarily powerful amps, and supplies, which solved the heat and noise issues. They then started using signal generators with phase splitters to drive the the amps and transformers. That eliminated the problematic ebay 3 phase generator. There were several successful VFDs built using this approach.
In October 2016 Bill Carlin (Phoenix Engineering) stepped in and graciously offered, at cost, professionally engineered PC boards and a programmed uP for a purpose built digital signal generator that offers many features, and can regulate both the voltage and frequency very very accurately at 0, 90, 120, and 240 degrees (among other things). You should go to the thread (DIY 4 phase Generator For Turntable Motor Drive) and see all the features of the SG4. This is a real step up from the signal generator and phase splitter approach. I really can't say how much I appreciate Bill Carlin doing this for the DIY community! It's so generous of his time and resources, truly one of the good guys in the DIY community.
This generator can run motors on either single, 2, or 3 phase depending on the outputs you use and the configuration of the amps and transformers. The amps and transformers are up to the individual builder to get right and there are additional threads to help with that. You can run anything from the 7.5 watt Hurst motor up to a big honk'n 45 watt Papst capstan motor from a professional studio tape recorder, as well as BLDC motors.
Here is a thread that describes the early development with signal generators and phase splitters:
http://www.diyaudio.com/forums/analogue-source/295367-optimally-driving-vpi-synchronous-turntable-motor.html
Here is a thread about the SG4 signal generator:
http://www.diyaudio.com/forums/analogue-source/298018-diy-4-phase-sinewave-generator-turntable-motor-drive.html
Here is a thread about amps and transformers to drive the smaller single and 2 phase motors, also gets into the use of BLDC motors as well:
http://www.diyaudio.com/forums/analogue-source/300371-60-wpc-amplifier-diy-turntable-motor-drive.html
These threads are pretty long and the info somewhat fragmented, but a person with some DIY skills could make a VFD (variable frequency drive) from them.
I have promised for a long time to detail a VFD, with instructions, photos and a BOM, posted all in one post. The one I have been working on is a true 3 phase version, capable of driving a big Papst motor. I have version 2 up and running with smaller amps and supply, with the ebay/Chinese 3 phase signal generator. No longer any problems with heat and RFI, but it just isn't accurate enough with the ebay signal generator. RPM was rock solid, but the generator doesn't allow for small enough steps in adjustment (frequency). The advertised frequency steps weren't even close to the actual frequency steps. Motor runs much smoother and has way more torque, runs cooler too. All I have to do to finish is to build the SG4 board, and install on my existing project.
With all these developments, and several other very complicating factors in my life, I just haven't found the time to finish the project. In the next couple of months, barring any more complications in my life (heaven help me) I should have it finished and will post.
I am handling the US distribution of the SG4 uP, and anyone interested can purchase some through me. You will have to order the boards separately from a board fabricator, and Bill has set up a cart at Mouser for the board parts. This info is in the SG4 thread. If you are interested in getting uPs you can send an email from your private email to mine: twystd3 at yahoo dot com, and I will send a PayPal invoice to your email (payment via PayPal only please). The price is $7.15 shipping Priority Mail (almost any number of uPs), and the uPs are $7.00 each. The invoice will include PayPal fees as well. This is at a cost basis, I'm just covering my expenses, and doing it for the service of the DIY community. It is very important that you include your name and forum name, shipping address, and the number of uPs you require in this email.
The only reason you'd need a feedback loop with this drive is if you had belt slip or stretch issues, but I don't think having the motor hunt a good thing. I would think idler/rim drive wouldn't stretch or slip (assuming it is accurately adjusted), idler drive is the approach I plan to take with my TT project.
The motors will lock onto this drive, as it is immune from variations in mains/line voltage and frequency fluctuations. This drive is especially advantageous if you are running an AC synchronous hysteresis motor on 3 phase, very little if ANY cogging with these motors. The Papst "flywheel" motors, or the like, IMO are the best route possible because they have the effect of having a much heavier platter as well being more powerful, smoother, and they lock unto the frequency almost perfectly. Also of course this VFD eliminates the need for any mechanical linkage to change speeds, as well as having the ability to fine tune and maintain turntable speed to a very high degree of accuracy.
twystd
Edits: 05/13/17 05/13/17 05/13/17 05/13/17 05/14/17Follow Ups:
^^^ very sorry. I figured it out. ***I am the proud owner of a Rek-o-Kut K33H (with Papst motor) and was looking to build the SG4. Was looking for BoM from Mouser but can't find it on their site. Of course I will be looking for the board and the SG4 from you or ??
Thanks in advance.
Edits: 10/03/19
Just as an aside I'm providing the SG4 uP for the rest of the world, and in addition I also have a small stock of boards.
SG4 chip. £10.00
Circuit board £20.00
SG4 chip + board £30.00
All the above prices exclude post and packing which will be £3.00 for UK, £4.00 for Europe, and £5.00 for anywhere else in the world.
I prefer to only supply single boards, if you require more than 1 board I
would suggest you buy them direct from Oshpark as it will work out cheaper for you.
I will of course supply multiple chips as required.
I am in awe of your perseverance, even though you apologize for the time taken. I bought a PE Phoenix and RR on the day I learned PE were going out of business, so I may not "need" to build a drive system, but your information will help me to understand the principles behind it. Thanks so much for your generosity in sharing knowledge you've gained.
Especially putting all the DIY links togeather. I have some reading to do. I'm retiring in 8 weeks so I have to get cracking!
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