Stepper Motors - Quick Question

[Greg Zapf]

When some old dirty stepper motors are powered, but not being told to step, should they be silent, or is a hum expected?  Thanks, --Greg

[Keith]

They will pull current when stopped. The hum could be due to a chopper-based current limiting controller that rapidly cuts the current on and off to limit the current to a set value.

 

Keith

[Greg Zapf]

Cool, I believe the Hobby CNC controller that I have is indeed a chopper type, and I didn't know what that meant.  Thanks!  --Greg

[MemphisArtGuy]

I know its silly, but I'll ask anyway, what kind of stepper? bipolar and unipolar?

[Danny Chamberlin]

So why does "bipolar stepper" sound like a description of my Irish step dancing cousin?

Danny

[Greg Zapf]

I'm actually not sure. They are 6 wire, and all 6 get connected to the included older generation Hobby CNC controller/driver board.  I think that all points to them being Unipolar... but I'm new to this.  Does unipolar vs. bipolar make a difference in terms of them having a standby whine/hum?  --Greg

On Fri, Oct 26, 2012 at 8:14 AM, MemphisArtGuy <memphi...@gmail.com> wrote:

[Keith]

The unipolar 6 wire steppers require only 4 transistors and consist of 2 centertapped coils with the centertaps going to the positive side of the power supply and the remaining 4 wires connected to the 4 transistors to ground. They are called unipolar because the current only flows one direction through the coils.

 

The bipolar steppers are 4 wires with 2 coils but require 8 transistors in 2 "H" bridge configuations so that current flows in two directions through the coils.

 

Stepper motors can be used as 3 phase permanent magnet alternators or as encoders as well.

 

Take Care,

 

Keith

----- Original Message -----

From: Greg Zapf

To: midsout...@googlegroups.com

[MemphisArtGuy]

Yes,  say you have these steps

1234

oo--

1234

o-o-

1234

 -o-o

1234

--oo

but your wire for

1234

--oo

1234

oo--

1234

 -oo-

1234

o--o

What you end up with a a failuter to make a step, and it would make a hum. Yours could be more complicated cause you coulds have patterns from 123456. What the model and make, I was able to find info on my 1984 steppers so thier data sheets thend to have a long life spand depending on manufacture. 

Idealy a good connection should act like a break which could be used to check the coils or a voltage meter with a continuity check. Unipolar you'll find a common wire or set of wires, Bipolar you'll find the coils are seprated.

As you can imagine mis-wiring a unipolar is very easy, while I have had bipolar steppers sing to me at the space using the easy stepper controller v4.1 simular to the ones used in Sonny's egg bot.

If you want to bring it to the space I be happy to look at what you've got. 

-Dru

[Dan Hess]

If I had to make a guess it's exactly what Keith mentioned.  Mine when they are idle, if the current is up to high will make a whining noise.  Typically they'll pulse too, with the lower you turn the current the further between the pulsing.

Thanks,

Daniel H.

Google Voice:  (901) 214-5326

- Copying one is plagiarism, copying many is research.

[Greg Zapf]

Thanks for all the info everyone!  I confirmed that the noises I'm hearing are expected for my combination of motors and driver (old school chopper 4AUPC).  I'm extremely impressed with EMC2, by the way... running the LiveCD from linuxcnc.org, I had my motors operating very very soon after confirming that I had my wiring right.  Once I get couplers in, I'll get further into this... might get to the point to do a demo after a while.

--Greg

On Mon, Oct 29, 2012 at 11:04 AM, MemphisArtGuy <memphi...@gmail.com> wrote:

[Sonny Mounicou]

And don't forget that many current drivers implement microstepping, which causes there to be intermediate steps between the poles by sending less current to the varying poles.  This lowers your torque, but makes motion smoother.  Some stepper drivers dynamically change the level of stepping on the fly so that it moves quicky, but has great torque when needed.

--Sonny

On Mon, Oct 29, 2012 at 11:04 AM, MemphisArtGuy <memphi...@gmail.com> wrote: