[Fundacion]

Hi All,
I have a NEMA34, 878 oz-in stepper motor with features as below:

• Rate Current=2A,
• Phase resistance = 3.2Ohm,
• Inductance= 15mH,
• Holding Torque = 878 Oz-In,
• Step angle = 1.8°
• Wires = 8

I need to use this with its higher torque at the range of 30 - 120 RPM.
Today I am using

• Controller: FMD24400A Microstepper (Amazon.com : 12~50VDC 2 Phase FMD2440A Stepper Motor Driver For Engraving Machine : Everything Else)
• Powesupply: 24V, 350 W
• Arduino to controll the speed. (code attached)

Today the motor works, but with very low torque, and at half or thir than the RPM that I set in Arduino sorftware (example: Arduino Speed : 200, real speed : 60)

Also I have a 36V/350W power supply but I do not want to use after being sure that I will not burn anything

Attached is the use that I will give to the motor. It is only to wound wet glass fiber, that is very sticky so I need torque to wound it.

Please any help is welcome!

[awerby]

That motor has a lot of inductance at 15 mH. Using the formula: 32 x (square root of) inductance = optimal supply voltage; you get about 124 volts, so running it on 24v (or even 36v) is not going to make it perform too well. If you really want to use that motor and get acceptable speed and torque, you need to get a different driver and power supply. If you want to use that control system, get a different motor with less inductance.

[Fundacion]

oh my!, where should I get that kind of power supply?

[kreutz]

Your 36 volts power supply is a better choice (compared to the 24 vdc PS), make sure the micro-step mode settings on your controller is the same set in your arduino's program in order to get the right amount of pulses/min from the arduino to reach the motor RPMs you want. I am not familiar with your arduino software but somehow it must have an adjustment for the micro-step mode.

For example at 60 rpm (1 rps), 8 micro-step/step your arduino's pulse frequency should be: 1600 hz

Arduino's board pulses per second = pulses per rev (200) x microsteps (8) x rev per second (rpm/60) ) = 200 x8 x 60/60 = 1600 pulses/sec = 1.6khz

kreutz

[aarggh]

As Andrew said, you'd be far better off buying a 280-380oz/in stepper that has very low inductance. There's plenty around with around 2.2-2.8mH cheap on Ebay. This will be far more suitable, give heaps of grunt, and you can still use the existing power supply (although a little more VDC would be ideal).

cheers, Ian

[James Newton]

There is some good info on power supplies at this web page:
techref.massmind.org/techref/io/stepper/power.htm

[lucas]

The RPM's you are looking for are rather low, you only need that high voltage supply for torque at fast speeds. Your driver + supply setup should have plenty of torque at 60 RPM.

[*]Controller: FMD24400A Microstepper (Amazon.com : 12~50VDC 2 Phase FMD2440A Stepper Motor Driver For Engraving Machine : Everything Else)
!

Had a quick look at this driver, the 1/2A and 1/2B microstepping settings marked on the cover did sound the "alarm bell".
This is a TB6600 drive in disguise, the design is crap and only delivers 30% of the potential torque.
For more info see this thread:
http://www.cnczone.com/forums/steppe...rive-ebay.html

A stepper motor has high torque at low speed, the torque decreases when the speed goes up.
Almost all TB6600 drives manage to kill that low speed - high torque feature of a stepping motor. These really deserve the global award for useless design.
Use a good driver and your torque will be more than 3 times what you have now.

[James Newton]

I strongly suggest listening to Lucas. As the designer of several very good drivers, he really knows what he is talking about.