3 Phase Class D amp for DIY BLDC motor Drive

Brush less DC drives are common in inverter refrigerators now.
You could adapt one to use for yourself.
Look in scrap and repair shops, or shops selling Refrigerator/Air conditioner parts. A/c drives will have higher ratings.

Now the latest energy saving ceiling fans have those too, BLDC motors, the fans are in the 30 watt range, more or less useful...fridges will be 70 watts to maybe 400 watts.
That will save you some work.
 
I ordered a bunch of these in case anyone needs one (for free)

Hi, just wondering if these 4mm to 3/16 adapters ended up working for you and if so did you use them with a VPI pulley? I am thinking of trying this but can't seem to find anyone that has the adapters in stock.

Do you still have any and if so would you be willing to sell me a couple? I will pm you.

Thanks,
Sean
 
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I'm having a strange problem with an SG4/MA3D controller. I've built a 3 of these without any problem. This one is driving a BLWR motor. It works fine for about 45-60 seconds. Then it stops. I'm still getting a sine wave of correct voltage on all three phases. I haven't yet checked to see if there was a phase slippage/change. Any suggestions of what else to check would be appreciated. Thanks.
 
You didn't say whether the 3 sine waves were present on the input or the output. If they are present on the former but not the latter, the chip amps are shutting down. Depending on the amplitude setting on the inputs, the DC input offset could be lower than the bias level on the chip inputs, in which case, reverse the polarity on the input caps C5, C6 & C11.

The DC output offset should be Vcc/2 on all 3 channels. If this gets out of balance, the chip amps will shut down.
 
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Thanks, Bill. This is helpful information. I'll do some digging when I get back in town on Friday. At one point I was getting sine wave at both input and output but motor still wouldn't turn. Now I'm getting sine wave at all 3 inputs but only getting output on 240 degree (U2).
 
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Anaheim Automation seems to be out of stock on the BLWS231S-24-2000 motor (NEMA square) and I can't backorder one, so I suspect it may be out of production. Has anyone found another source for these motors? I've used this motor and the BLWR motor (round) and prefer the square one. It seems to be ever so slightly quieter than the round version.

I thought this question had been answered earlier in this thread but I can't find it, so I apologize if this is a duplicate question.

Cheers.
 
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Can it work with a Lenco idler drive

I have found the Lenco motor to be noisy in a full range system.

I noticed on 45 rpm records this noise was greatly diminished so I was hoping I could use the small end of the spindle to get the rpm up. Well, there is obviously a frequency limit with EAGLE, So I had to use the 45 rpm setting and on the cusp between the tapered section and the flat section (16 rpm) of the spindle. Not ideal but it does show there is something that needs fixing!

I was able to get a fairly steady 33.3 - of course the tach and the controller can no longer work together.

But it did make a tremendous difference in the low frequency noise. Of course, groove noise is still there but on quiet pressings it is an amazing difference. Getting rid of this noise made everything sound much better, Much, much better.

I figure there is no way to trick EAGLE into doing what I want to do and then I revisited this thread.

Do you think this motor would be able to work in the Lenco? If anything the 4mm spindle is larger than the Lenco's spindle for 16 rpm. I am not sure if it is the idler itself spinning quicker or the motor being that much smoother at the higher speed.

I have my motor detached from the plinth so implementing this would be pretty easy if you think the motor has the torque to do this. Of course, if it is the motor making the most difference I could use a larger pulley on the motor.

I would like to have the ability to play 33.3 and 45 rpm disks so I wonder about the frequency generator being able to do that in this case.

I would appreciate your counsel, Mr. Carlin. Maybe there are others who are wondering this same thing?

Thanks and take care,
 
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I figure there is no way to trick EAGLE into doing what I want to do and then I revisited this thread.

Actually, you can. If leave the feedback connected and SLOWLY move the idler to the smaller diameter, the Eagle will continue to increase the speed of the motor in an attempt to keep the speed at 33.333 RPM. If the actual speed drops below 30.000 RPM, it will no longer apply correction so you must keep the speed between 30 and 33.333 and you slide the idler down. The tach has a lower limit of 27.5 RPM.

Per our private discussion, as the motor speeds up, it looses torque, so you want to keep the output voltage at maximum (no reduced voltage). If it works now at 45 RPM it should work when you fool it into increasing at 33 RPM, but at some point, this will no longer work. As the frequency goes too high, the motor speed will actually start to drop and the only way to recover is do a factory default reset and start over.


Do you think this motor would be able to work in the Lenco? If anything the 4mm spindle is larger than the Lenco's spindle for 16 rpm. I am not sure if it is the idler itself spinning quicker or the motor being that much smoother at the higher speed.

I don't think this is a good idea. The Lenco motor is running at ~1700 RPM; if the tapered spindle is larger than the ¼" motor shaft, the BLDC motor will have to run fast and it is rated for 2000 RPM max. The frequency would be 66.66Hz so the SG4 is capable, but the voltage would have to be 24VPP.

A better alternative would be this:

https://www.lencoheaven.net/forum/index.php?topic=31895.0
 
Thanks for considering my question.

The step in the LENCO spindle is rather drastic and ruins any chance of a smooth transition. Once you go "over the cliff" the platter will continue to spin but at a speed much slower than 33.33.

In case I misunderstood what you wrote - if i tried your motor system there would not be a need for a LENCO style spindle would there? I would either install a pulley or hope the 3/16 inch sleeve you speak about would suffice.

I had noticed even with 46 rpm there is a lack of torque - which is interesting since when the idler was placed further up the spindle (larger radius) I do not remember there being such a wimpy response to record dusting.

I am assuming the idler sitting on the edge of the cliff is not a very efficient transfer of energy so it does not take much to slow it down.

I know that electric motors produce maximum torque at 0 rpm and it does down from there.

Out of curiosity what frequency would the LENCO motor require to spin twice as fast as 33.3 - and would this destroy the motor?

Could one connect a frequency generator to the EAGLE amplifier to see what happens?

I remember that post on LENCO HEAVEN - I need to look it over again and will RIGHT NOW!

Thanks very much, Mr. Carlin.
 
I took a longer look at the Italian offering.

He is incorporating the motor into the LENCO frame so he can continue with the motor mounted to the top plate/plinth.

My motor is connected to neither - so all of the LENCO framework just takes up space.

EDIT: most importantly it looks like this is really not going to be available.

Please clarify for me if you are more concerned the motor cannot turn the platter with an idler. I would not have any trouble getting the motor situated to work if it CAN work.

If the speed of the motor is the concern I would use a pulley size you recommend.

I wish I could understand these motor speed/platter speed relationships better. I figure with this motor my concerns about vibration are not the same as they would be with the LENCO motor.

Of course all of this is my surmising!

Thanks, again,
 
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I'm unsure what you are doing with your motor. Is there an idler wheel between the motor shaft and the platter or is there an idler wheel directly connected to the motor?

This thread is about a 600 RPM belt drive system using the SG4, a BLDC motor and 3 channel amplifier. I stated in the OP that I would not get involved in bespoke designs using different components, but I don't discourage people who understand the technology from trying different things. I don't think I would try to run an idler between the short shaft of the motor and the platter, nor would I attempt to bolt an idler directly to the motor to turn the platter. If you have machining skills (or access to a machine shop), you might try to duplicate the DC Lenco motor design that I linked to, using the BLDC motor. The native Lenco motor runs at 1700 RPM for 33 RPM with a specific shaft diameter at a specific location on the platter. You may be able to make this work with the BLDC version and eliminate the 27Hz rumble, or you may have to increase the motor speed to accomplish this. AA make motors that run faster than 2000 RPM, but you are on your own for adapting the MA3 to drive them. The equations for frequency vs speed are straight forward and I can provide them, but your biggest problem is getting the output drive level to match the motors requirements which has to be done empirically and may require voltages in excess of the MA3 design.
 
I know I am overstepping what you said about going afield.

Enthusiasm does that to me!

I would use the motor just like the LENCO motor - the motor shaft drives the Lenco idler arm and idler and would be in the same position as regards the platter as the stock motor. As I am using it now the motor is on a sub-plinth with the platter and tonearm plinth above this on springs so I retain the isolation from the motor.

When I asked the question I thought it would be easy and nothing is ever as easy as we would like!

Thanks for your patience.

Take care,
 
I will bother you one more time! (mea culpa)

I want to use the motor as you have designed it. I am sorry I started conflating two dissimilar ideas in an attempt at brevity. I do not expect you to change anything.

Thinking about this - I was not taking into consideration that this motor intrinsically will have less vibration than the LENCO motor so my desire to run it at high speed is not needed.

If I size the pulley to work at 600 RPM it would seem I could make it work. A larger pulley is not a problem since I can position the motor anywhere I want beneath the plinth.

I have no intention of using the LENCO motor spindle.

The big consideration is can I simply have a pulley that works with the existing LENCO idler and arm with the motor "as is" or does the motor need a second bearing - like the LENCO motors having the shaft supported at both ends? Would the pressure exerted by the idler against the motor shaft without another support ruin the motor? I see a collar not much longer than the shaft since the idler will be in a fixed position since that is how I use it now. The motor would be laying on its side, of course, to do this. Positioning is not a big deal. I have learned with my motor being mounted away from the plinth how to get the two pieces to work together. I use minimal pressure against the the motor shaft. I use Nantais's weight and string method and use the smallest amount of weight i can - which is 20 grams/.

I am not asking you to assure me it will work - I would just like to know if there is a chance. It seems like an interesting project for me - not for you! I know you have plenty of your own!

I hope I have not totally made you mad since that is the last thing I want to do.

This motor project sounds so interesting i cannot help myself.

Thanks again for your patience and kindness.