I need a good replacement motor

[herring_fish]

http://asaherring.com/Reef/Tower/RobotAssembly.jpg
This is a rendering of my 2 axis plankton feeder.

I have a stepper motor that was given to me but I don't think that it is working at its best. When I turn it manually, the resistance is not constant as it makes a full rotation.

The motor was being tested without having to move the carriage. It just has to drive wire around the two wheels that are 8 feet apart. There isvery little drag on the system. That being said, when I run the assembly, it is not running well. It is slow and chatters. Given the same amount of power from the driver, should I go bigger or smaller?

I motor that I now have is a 57BYG084/1.8 Step Angle/12V/4 phase/0.6A per/100ohm(500VDC)/20ohm per/Class B/25mH Inductance per/Rotor inertia 38g.cm2/holding torque 6Kg.cm

It is powered by an Arduino Mega 2560 with a Rugged Stepper Motor Driver.
Rugged Motor Driver

I am wondering if I should by the same motor or go with a different size, either bigger or smaller?

[Al_The_Man]

I have a stepper motor that was given to me but I don't think that it is working at its best. When I turn it manually, the resistance is not constant as it makes a full rotation.

If you are measuring resistance using a standard ohmmeter then you may be seeing the generation effect causing the meter reading to change because of this voltage appearing on the leads when spinning the shaft?.
Al.

[bonmotwang]

The 1.8 degree per step is at the tolerance of +-5%. So I don't think the resistance tolerance is an issue. And part of the angle tolerance is caused by this resistance tolerance.
But 5% is the whole story.


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[herring_fish]

I'm sorry. I used the wrong term. I meant that when I turn it manually, I feel a difference in how hard it is to turn. Perhaps I should have said drag? I don't know.

But if I use:
int maxRPM = 150; // Top running speed of main stepper
instead of 300

and it still chatters and can barely turns the cable, (besides the potentially ailing motor) do you think that a bigger or smaller motor would perform better, powered by the Rugged Stepper Motor Driver.

The spec.(s) on the driver say that it has a Peak DC current per phase of 2.8A

I am running it at 30V from a printer adapter. It supplies .83A which could be part of the problem as well. ?

[James Newton]

See this web page techref.massmind.org/techref/io/steppers.htm#Estimating

The trick is to measure the actual torque required to move what you are moving, then do the calculation to find the wattage required at the speed you want it to move. Then break that down into a reasonable combination of amps and volts. Then buy a motor / driver system than can manage that combination.

[H500]

Are you aware that it is normal for a stepper motor to move in a jerky motion at low speed? If that is not OK, get a microstepping driver.

If the rotor feel like it is binding at certain positions, then it is probably defective.

[bonmotwang]

Make sure the 4 wires are connected in the right way. I had once make the connection wrong, It was doing the similar thing.
Easy way to verify is: tape something on the shaft so that you can see one step(1.8). Then power on the coil phase by phase using half of the rated voltage (not your driver's voltage!). You should see the shaft turning one direction step by step.


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