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3 Phase Class D amp for DIY BLDC motor Drive
3 Phase Class D amp for DIY BLDC motor Drive
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Old 26th October 2017, 12:07 PM   #251
Pyramid is offline Pyramid  United States
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It is a 2.1mm x 5.5mm cable that I had lying around. Mouser sells them (cables) but they are more expensive than the wall adapter it came from. They sell the individual plugs for <$2. You can also find both connectors and cables on e-Bay.

Enter: 2.1mm DC cable or 2.1mm DC connector in either search case.
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Old 6th November 2017, 10:30 PM   #252
mattzan is offline mattzan  Brazil
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Ok. Having some trouble with the alignment. Using my AC voltmeter I can't adjust rv1, rv2, rv3 to the proper VRms, I only get 3,5VRms aprox on each phase. I checked everything on the board and found nothing wrong. Can anyone help me?
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Old 7th November 2017, 11:28 AM   #253
Pyramid is offline Pyramid  United States
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Is the SG4 set to maximum (128) in the reduced voltage mode?

Are you supplying 15VDC to the MA-3D?
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Old 7th November 2017, 05:53 PM   #254
mattzan is offline mattzan  Brazil
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Quote:
Originally Posted by Pyramid View Post
Is the SG4 set to maximum (128) in the reduced voltage mode?

Are you supplying 15VDC to the MA-3D?
Yes 128.
Yes, 15.64V.
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Old 8th November 2017, 01:14 AM   #255
Pyramid is offline Pyramid  United States
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The caps on the SG4 LPFs appear to be different. Can you confirm the values?

The output of the SG4 at maximum should be ~1.75VRMS (5VPP). Can you confirm?

The MA-3D gain is fixed at 20dB (10x) so with the pots at maximum, the output should be pushed to the 15VDC rails. Does the output change with the adjustment of the pots at all? You should be able to reduce the output to zero and 15VPP (5.3VRMS). Are you measuring the output voltage at motor output pins?
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Old 8th November 2017, 12:55 PM   #256
mattzan is offline mattzan  Brazil
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Quote:
Originally Posted by Pyramid View Post
The caps on the SG4 LPFs appear to be different. Can you confirm the values?

The output of the SG4 at maximum should be ~1.75VRMS (5VPP). Can you confirm?

The MA-3D gain is fixed at 20dB (10x) so with the pots at maximum, the output should be pushed to the 15VDC rails. Does the output change with the adjustment of the pots at all? You should be able to reduce the output to zero and 15VPP (5.3VRMS). Are you measuring the output voltage at motor output pins?
Thank you Pyramid for your attention. So, I got confused and I was measuring the input instead of the output. Never the less I could only get the 0 phase right (4.2VRMS), 120 and 240 keeps variating the voltage which makes impossible to be precise.
Here's a video: Dropbox - Video 08-11-2017 11 13 47.mov

TP1 I'm having 0.41Vrms. The output of the SG-4 is 1.75Vrms. The caps on the SG4 are all right (473, 104, 223, 10), I just used one different 223 film cap (yellow one). I used different 1uf elet caps on MA-3d that I had left here from different projects but I don't that's the problem.
As I was moving forward with the alignment I got confused on how to adjust the correct reduced voltage setting for 4.1VRms (BLWR) - where do I measure to get this right? The outputs of the SG4 on each phase I get max 1.75Vrms like I said before.

Thanks again for your help.
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Old 8th November 2017, 05:08 PM   #257
Pyramid is offline Pyramid  United States
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Originally Posted by mattzan View Post
Thank you Pyramid for your attention. So, I got confused and I was measuring the input instead of the output. Never the less I could only get the 0 phase right (4.2VRMS), 120 and 240 keeps variating the voltage which makes impossible to be precise.
Here's a video: Dropbox - Video 08-11-2017 11 13 47.mov
The variation isn't too bad; without a scope it is difficult to tell what might be happening. It may just be the connection at the PCB with either the positive or negative probe. Try to use alligator clips or some other method of sure contact. Also, check that the input to each phase is steady.

Quote:
Originally Posted by mattzan View Post
TP1 I'm having 0.41Vrms. The output of the SG-4 is 1.75Vrms. The caps on the SG4 are all right (473, 104, 223, 10), I just used one different 223 film cap (yellow one). I used different 1uf elet caps on MA-3d that I had left here from different projects but I don't that's the problem.
As I was moving forward with the alignment I got confused on how to adjust the correct reduced voltage setting for 4.1VRms (BLWR) - where do I measure to get this right? The outputs of the SG4 on each phase I get max 1.75Vrms like I said before.
TP1 will probably never get to zero, but you should be able to get it down to 20 or 30 mV. If the output levels are not the same, then TP1 will be higher; if the levels are exactly the same and there is no distortion, the TP1 will be very close to zero.

Adjust the reduced voltage setting for 4.1VRMS at the outputs.
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Old 9th November 2017, 10:52 PM   #258
mattzan is offline mattzan  Brazil
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Yes the input is steady, so I can rule out the sg-4 right? I managed to get 0.37 tp1 and decided to go foward with the alignment. Installed the motor but it didnt function smoothly, lots of vibration, kind of chocking sometimes very weird.
I think Im gonna start fresh, dont know what happened.

Thanks again Bill.
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Old 22nd November 2017, 08:56 AM   #259
coolmaster is offline coolmaster
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Originally Posted by Pyramid View Post
BLWR series: Machine a 4mm center bore pulley or use a 4mm-3/16" sleeve and use an existing pulley.

------snipped----------

If there is anyone with some machining capabilities, the attached file has CAD drawings for 600 RPM pulleys for both 4mm and 1/4" center bores.
Hi Bill,
Very recently I had a custom metal pulley machined out locally following your basic design but with alterations to diameter, height and more grooves to what I thought that suit my VPI Classic 1 Hurst motor at 500rpm/50hz. For main purpose and intent, I think I've achieved a good deal save for its a tad slower at 33.0rpm as opposed to original pulley at 33.33 - + 0.1rpm on the 2nd step. I followed the same pitch and groove angle as your design. I followed the same exact diameter as the previous pulley. My ears could discern music at 0.33rpm slower, but no matter if I ignore it all. My measurements are without the use of any speed controller and plugged into the wall socket which is quite consistent at 50hz most of the time.

I suspect its the groove angle of 120deg that could be the issue, perhaps a lesser degree say 60deg groove angle achieve making up for the discrepancy? I'm not sure. I've no way of telling whats the 3 angles of the original stepped pulley which does make a speed variation difference. I'm aware that there could be other calculations or fabrication limitations that obstruct ideal results. Can I kindly request your views on what I could do next to try achieve exactly as the original pulley?

Lee

Last edited by coolmaster; 22nd November 2017 at 09:17 AM.
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Old 22nd November 2017, 12:10 PM   #260
Pyramid is offline Pyramid  United States
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The angle of the grooves shouldn't make any difference in speed, except for how they affect the depth.

The approximate formula for pulley diameter is:

(Pulley Dia + belt thickness)/(Platter Dia + belt thickness) = Platter Speed/Motor Speed.

If you can't change the motor speed (and you don't want to change the platter diameter), the only other variables are the Pulley diameter (including groove depth) and the belt thickness.

Unfortunately, your platter speed is slow, so the belt needs to be thicker or the pulley diameter needs to be larger. If the platter was fast, you could just machine the pulley slightly smaller.

You said you followed the same diameter as the previous (VPI factory) pulley? Did the pulley have both 33 and 45 RPM spindles, or was it only 33? If it was 33/45, the spindles are tapered for coarse speed adjustment so the diameter at the top will be undersized and the diameter at the bottom of the 33 spindle will be oversized. If you measured at the top, that would account for your slower speed.

Last edited by Pyramid; 22nd November 2017 at 12:13 PM.
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