need some advice
24 Aug 2016 23:55 - 24 Aug 2016 23:56 #79388
by strobes
Replied by strobes on topic need some advice
[/quote] B.TH.W i would not go over 50V on cheap 80V drives, they tend to blow when hitting E-stop while moving heavy loads due to back EMF[/quote]
Well this goes to original concern about inexpensive components made oversea......
I think I go with www.ebay.com/itm/141870897819. at this price if BOB goes, I'll get a better one.
For drivers - if I use 48V power supply, They may last longer. What do you think?
Regarding steppers. This one rated 5A. But recommended voltage is from 24 to 60V So at what volts it is 5A?
www.ebay.com/itm/US-Ship-Dual-Shaft-8-5N...f:g:XY4AAOSwd0BV5U1s
Well this goes to original concern about inexpensive components made oversea......
I think I go with www.ebay.com/itm/141870897819. at this price if BOB goes, I'll get a better one.
For drivers - if I use 48V power supply, They may last longer. What do you think?
Regarding steppers. This one rated 5A. But recommended voltage is from 24 to 60V So at what volts it is 5A?
www.ebay.com/itm/US-Ship-Dual-Shaft-8-5N...f:g:XY4AAOSwd0BV5U1s
Last edit: 24 Aug 2016 23:56 by strobes.
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- tommylight
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25 Aug 2016 00:25 #79389
by tommylight
Replied by tommylight on topic need some advice
Both of your choices are OK, and the 48V is much more reasonable if you do not intend to push the motors to fast.
That combination can move some serious hardware.
The thing with PWM is ( i did a search for it and all are way to complicated ) it takes the power from the power supply and sends it to motors in short bursts, so even though the motors get more amps, the power supply does not see it, due to capacitors in the drive that provide the extra power for those short periods.
From experience, i use most of the time power bricks from old laptops ( regulated with current limiting and isolated from mains and very good quality ) that deliver 19V @3 to 7A to drive my machines, they have proven sufficient to drive even big machines with gantry weighting over 200 Kg, but at lower speeds.
That combination can move some serious hardware.
The thing with PWM is ( i did a search for it and all are way to complicated ) it takes the power from the power supply and sends it to motors in short bursts, so even though the motors get more amps, the power supply does not see it, due to capacitors in the drive that provide the extra power for those short periods.
From experience, i use most of the time power bricks from old laptops ( regulated with current limiting and isolated from mains and very good quality ) that deliver 19V @3 to 7A to drive my machines, they have proven sufficient to drive even big machines with gantry weighting over 200 Kg, but at lower speeds.
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25 Aug 2016 02:57 - 25 Aug 2016 02:59 #79392
by strobes
Replied by strobes on topic need some advice
Ok, this very good reference point. I'll read some more and may reply with my final selection for final scrubs before sinking dough in it. Also sound like better to use separate PS for each axes if it has smaller rating.
Thank you.
Thank you.
Last edit: 25 Aug 2016 02:59 by strobes.
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25 Aug 2016 10:43 #79406
by rodw
On the other hand, I think Gecko says somewhere doubling voltage increases torque about 4x. I built an Arduino based rotary table controller to drive a 6" 90:1 rotary table with small NEMA 23 stepper. Initially, I started with a 19v laptop power supply and found I was missing steps. Upgrading to 48 volts solved all issues without upgrading the stepper motor. The gearing of the RT means a fair bit of torque is required to turn it as the stepper maxes out at about 4 rpm at the table. Implementing accellaration and decellaration algorithms helped by lowering speed on start to maximise torque to get overcome static inertia while the thing got moving. If you can find a torque curve for your stepper it will become apparent why.
Replied by rodw on topic need some advice
From experience, i use most of the time power bricks from old laptops ( regulated with current limiting and isolated from mains and very good quality ) that deliver 19V @3 to 7A to drive my machines, they have proven sufficient to drive even big machines with gantry weighting over 200 Kg, but at lower speeds.
On the other hand, I think Gecko says somewhere doubling voltage increases torque about 4x. I built an Arduino based rotary table controller to drive a 6" 90:1 rotary table with small NEMA 23 stepper. Initially, I started with a 19v laptop power supply and found I was missing steps. Upgrading to 48 volts solved all issues without upgrading the stepper motor. The gearing of the RT means a fair bit of torque is required to turn it as the stepper maxes out at about 4 rpm at the table. Implementing accellaration and decellaration algorithms helped by lowering speed on start to maximise torque to get overcome static inertia while the thing got moving. If you can find a torque curve for your stepper it will become apparent why.
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25 Aug 2016 13:12 - 25 Aug 2016 13:14 #79416
by strobes
Replied by strobes on topic need some advice
Yes, with constant coil resistance, the current is proportional to applied voltage. And torque is proportional to current. Still I need to figure out how manufactures rate max current in published specifications.
Last edit: 25 Aug 2016 13:14 by strobes.
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25 Aug 2016 15:17 #79431
by andypugh
There isn't constant coil resistance, the effective resitance is a strong function of motor speed (back-EMF) and furthermore the stepper drive acts as a constant-current source.
For the same drive current the stall torque will be identical independent of the supply voltage. However as the speed increases the torque will ramp out more slowly with a higher supply voltage.
There will be a point where the torque is 4x as high with double the voltage. There will be a different speed where it is 10x more.
Replied by andypugh on topic need some advice
Yes, with constant coil resistance, the current is proportional to applied voltage
There isn't constant coil resistance, the effective resitance is a strong function of motor speed (back-EMF) and furthermore the stepper drive acts as a constant-current source.
For the same drive current the stall torque will be identical independent of the supply voltage. However as the speed increases the torque will ramp out more slowly with a higher supply voltage.
There will be a point where the torque is 4x as high with double the voltage. There will be a different speed where it is 10x more.
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25 Aug 2016 20:44 #79446
by rodw
The most comprehensive discussion on stepper motor sizing and the math involved I have found is this one.
www.mycncuk.com/threads/1524-What-size-stepper-motor-do-I-need
It may help. The author has built a spreadsheet that puts it all together that is posted on this thread. Download it and see if it helps. Sorry but my eyes glaze over 30 years after ever applying any engineering....
Replied by rodw on topic need some advice
Yes, with constant coil resistance, the current is proportional to applied voltage. And torque is proportional to current. Still I need to figure out how manufactures rate max current in published specifications.
The most comprehensive discussion on stepper motor sizing and the math involved I have found is this one.
www.mycncuk.com/threads/1524-What-size-stepper-motor-do-I-need
It may help. The author has built a spreadsheet that puts it all together that is posted on this thread. Download it and see if it helps. Sorry but my eyes glaze over 30 years after ever applying any engineering....
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26 Aug 2016 02:12 - 26 Aug 2016 02:15 #79454
by strobes
Replied by strobes on topic need some advice
I was looking ones more at selected components:
drivers www.ebay.com/itm/141870897819
stepper www.ebay.com/itm/US-Ship-Nema-24-Stepper...3:g:0~QAAOSwu4BVmzzG
Looks like driver designed for 4 wire motor, so I can not configure my stepper for Uni-Polar? Only Bi-Polar Series or Parallel, right?
drivers www.ebay.com/itm/141870897819
stepper www.ebay.com/itm/US-Ship-Nema-24-Stepper...3:g:0~QAAOSwu4BVmzzG
Looks like driver designed for 4 wire motor, so I can not configure my stepper for Uni-Polar? Only Bi-Polar Series or Parallel, right?
Last edit: 26 Aug 2016 02:15 by strobes.
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- Todd Zuercher
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26 Aug 2016 03:05 #79455
by Todd Zuercher
Replied by Todd Zuercher on topic need some advice
The difference between bi-polar and unipolar, only really has to with the driver and how it needs to be wired. A unipolar drive is old tech, and is a work arround to the fact that the circuits in these drives can not revers polarity of the motors windings, positive is always positive and negative is always neg. So for the drive to be able to spin the motor in both directions the motor must have two separate sets of windings, turned in opposite directions, or in the case of the 6 lead step motor one set with center taps. Any motor that can be used with a unipolar drive can be used equally efficiently with a bipolar drive with only using 4 of the 6 or 8 leads. In the case of the 8 lead motor it may even offer better performance by wiring the motor in a parallel configuration.
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26 Aug 2016 03:30 #79456
by strobes
Replied by strobes on topic need some advice
Reason I asked is because Uni-Polar gives me good combination of torque and current vs. parallel config need more current and I'd assume generate more heat. What is the best way to connect this motor to get about 400 oz.in? And to what current should I set the driver? I plan to use 48v.
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