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### Author Topic: Power Supply Unit  (Read 56327 times)

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#### kolias

• 1,011
##### Power Supply Unit
« on: January 08, 2011, 04:34:51 PM »
Power Supply Unit

Not very good with the electrical staff so I hope someone can help.

I have 4 Keling motors (the spec sheet is attached for more info) which I will connect as Unipolar and as per spec sheet that gives me 3.0A per motor or 12.0A total.

Besides the motors I will have 4 drivers and one BOB from Probotix. Each driver is 3A, 42V output rating whatever this means and they also say that the voltage should be limited to about 42V DC. So I guess I figured that I need another 12.0A for the drivers.

The BOB is listed as 12 to 40V capables of at least 100mA, so I figured 1.0A here. I will also have 8 LED lights and a small fan so lets say another 2.0A

Total Amps I need = 27A. So I bought a power supply 12V DC / 29A / 350 Watts.

Do you see any problem with the power unit I purchased? Any suggestions?
Nicolas

#### HimyKabibble

• 1,687
##### Re: Power Supply Unit
« Reply #1 on: January 08, 2011, 05:36:08 PM »
"Do you see any problem with the power unit I purchased?" - Yes.  What you really want is about a 37V/10A supply.  12V is nowhere near enough to get decent performance from those motors.  The ideal voltage for the motors is given by 32 times the square root of the motor inductance (in mH), which gives about 47.5V.  This is assuming bipolar parallel mode, which is what you want to use.  But your drivers are rated for 42V maximum, so you want to stay a bit below that maximum rating, so knock it down to 37V.  The current rating of the supply should be about 70% of the sum of all the motor currents, or about 8.5A.  Round that up to 10A.  You won't get best performance out of this setup, as the drivers are not well matched to the motors.  You will be losing about 25% of the potential torque, since your drivers won't allow you to run full rated current on the motors (4.2A for the motors, vs 3A for the drivers).

Regards,
Ray L.
« Last Edit: January 08, 2011, 05:39:00 PM by HimyKabibble »
Regards,
Ray L.

#### ger21

• 6,292
##### Re: Power Supply Unit
« Reply #2 on: January 08, 2011, 05:38:06 PM »
You don't need 3 amps for the motors and drives. Just 3 per set.The drives don't draw any current, they just pass it to the motors.
A 15 amp supply is probably plenty.
Gerry

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http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
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#### ger21

• 6,292
##### Re: Power Supply Unit
« Reply #3 on: January 08, 2011, 05:39:50 PM »
Yes, as Ray said, 12V is too low. Speed is proportional to voltage, so a 36V power supply would give you 3 times more speed.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

#### kolias

• 1,011
##### Re: Power Supply Unit
« Reply #4 on: January 08, 2011, 06:17:04 PM »
Glad I asked, so I will get another power supply around 36V DC / 10 - 15A

Thank you
Nicolas

#### kolias

• 1,011
##### Re: Power Supply Unit
« Reply #5 on: January 08, 2011, 06:29:33 PM »
The only place I know to buy power supply is
http://cgi.ebay.com/12V-DC-29A-350W-Regulated-Switching-Power-Supply-/370412404026?pt=LH_DefaultDomain_0&hash=item563e4cbd3a

The best I can see are: 22-26VDC / 14.6A, 26-30V / 13A, 36V / 9.7A. Don't know why but seems as the voltage increases the Amps decreases

Any suggestions?
Nicolas

#### RICH

• 7,422
##### Re: Power Supply Unit
« Reply #6 on: January 08, 2011, 06:47:05 PM »
Try    Camtronics        as they sell power supply kits.

RICH

#### kolias

• 1,011
##### Re: Power Supply Unit
« Reply #7 on: January 08, 2011, 07:03:45 PM »
Try    Camtronics        as they sell power supply kits.

RICH

Thanks RICH but did not see any power supply at Camtronics-CNC. I have purchased everything and all I need now is the Power Supply
Nicolas

#### Hood

• 25,835
• Carnoustie, Scotland
##### Re: Power Supply Unit
« Reply #8 on: January 08, 2011, 07:14:48 PM »
You can easily make your own power supply, Bob Campbell has a good pdf describing how to do it, heres the link.
http://campbelldesigns.net/files/power-supply-part-1.pdf

Hood

#### RICH

• 7,422
##### Re: Power Supply Unit
« Reply #9 on: January 08, 2011, 07:23:12 PM »
Don't know where you looked but:

power supply 36V 25A \$125 ( email me at dmauch@seanet.com I do not want to sell power supply kits to unqualified people.

Power Supply ( email me at dmauch@seanet.com I do not want to sell power supply kits to unqualified people.
110 primary 33VDC at 20A ideal for the 600 oz in Ametch motors and others.

RICH