Stepper motor testing

[Tasos]

Dear fellow Nottinghackers, 

I am a reprapper who recently joined Nottinghack. Just returned from China where among other things I visited stepper motor factories and came back with motor samples. Can anyone help me to learn how to test and benchmark them with the hackspace's oscilloscope?  

Will reward in beer and motor!

Best, 

Tasos

[Pat McDonald]

Best way to test them is with a driver circuit and see if they step. You can use a silly scope to test the circuit is firing pulses properly and then try connecting a motor to the circuit.

Just scoping a motor does not tell you about a physical problem like a seized bearing, bent shaft etc.

If you got an Arduino Mega, RAmP shield and a Pololu driver that should let you test 12 V stepper motors.

Stepper motors built for other voltages would mean modding the RAMP shield at least, so first check what voltage the motors expect.

Stepper motors with 4 or 6 connections are much easier to test rig than ones with 8 pins on such a setup.

[Tasos]

Dear Pat (and all), 

I have Arduinos, RAMPS, drivers and printers to check the motors are working. 

But I wanted to run technical tests with the oscilloscope like here:

http://hydraraptor.blogspot.co.uk/2009/12/motoring-on-with-a3977.html

(e.g. noise levels at different currents, frequency, etc) 

I have chosen all samples to have the right specs for repraps. 

All bipolar (4 wires), 5-12V, 0.5-2A, with torques 36-60 mN.m. 

With a 12V power supply, I think it is the high voltage (~12V) ones 

that will perform more poorly, but I wanted to quantify this too. 

Anyone willing to help?  Should be great fun!

Tasos   

[Chris ((drazziweht)) Cain]

Interesting, question, at first it would seem that an oscilloscope would not be a good way to test a stepper motor...

But.

If you connect a scope across a stepper winding then set it to single shot capture with trigger.

Then give the motor a quick twist.

You will get on the scope an output sine wave (stepper as perm magnet generator)

The amplitude will give a good idea of the nominal voltage to operate the stepper (steppers are often operated a lot over nominal with current limiting to give better speed

Turning the motor through a fixed angle (say 90 deg) and counting the output cycles will give you the steps per rev

so you can find out quite a lot from a scope on a stepper :-)

Best way though is probably to put the model number into google and find a data sheet.....

Chris

[Pat McDonald]

Good news that you plan to test motors within the given limits.

Not so good news that you want to hack like Nophead. Guy is somewhat cutting edge at hacking repraps...

... Suggest you have a good fiddle with the scope first. It takes getting used to.

If you want some guidance around the atea, ok can do that. But if you eant to just turn up and experiment on your own, that's fine too.

I'm not actually qualified on anything electrical, just hands on experience. :)

[paul meynell]

Here's a great video tutorial, for the scope in the space.

Hope it helps

http://youtu.be/rZqRN5BpcDA

[Tasos]

Dear Pat (and all), 

Good point, but I don't dream to hack like Nophead in that I am not planning to develop any clever method from scratch. I just wanted to repeat what he has done on that post. In fact I was hoping to see him at the TCT show and ask him for instructions, but he told me he was not going to the show this year (and indeed he was not there on Wed). However, I talked to RichRap at the show and he liked it: he told me he would think about the best way of doing this and I'll talk to him again next week. I'm sure Nophead would give his input if we have any specific questions, as he has advised me on other things in the past.  So if you are happy to play around with the motors with me following Chris' and Richard's advice, it would be fantastic and great fun!  

In the meantime, I'll watch the video Paul sent. Thanks Paul!

Best, 

Tasos