Unipolar stepper Q

curious1

Small, unmarked stepper.
6 wires
red, black and yellow···· ·continuity
blue, white and green········· "
How to determine which are the center taps ?
My ohm meter maybe is not sensitive enough. (analog, 1K setting only)
Center tap should read less resistance than ends ?
Roughly what value differences am I looking for ?
Getting Fluke this weekend.
Thanks
RC

Uhh.... Sorry for the intrusion. Wiki had it all along. Shoulda went there first, will next time.


(For the experimenter, one way to distinguish common wire from a coil-end wire is by measuring the resistance. Resistance between common wire and coil-end wire is always half of what it is between coil-end and coil-end wires. This is due to the fact that there is actually twice the length of coil between the ends and only half from center (common wire) to the end.)

Post Edited (curious1) : 4/26/2007 8:30:15 PM GMT

Robert Kubichek

curious1 said...
Small, unmarked stepper.
6 wires

red, black and yellow continuity

blue, white and green "

How to determine which are the center taps ?

My ohm meter maybe is not sensitive enough. (analog, 1K setting only)

Center tap should read less resistance than ends ?

Roughly what value differences am I looking for ?

Getting Fluke this weekend.

Thanks

RC

Measure the 3 different combos of wires for impeadance of each set inline with a 100K 2% resistor,
TWO of the pairs in each set will have the same resistance, the THIRD will be double,
of the TWO pairs with the same resistance, the common color is the center tap...

On an analog meter, just watch the needle.
On the two pairs it will travel to the same spot, on the THIRD it will travel much farther..

Bob

curious1

Thanks BOB,
Excellent plan.
I'm gettin a good meter anyway though.
RC

This is the best example that I've ever seen. Says it ALL.
http://nanotec.de/page_static__schrittmotor_animation__en.html

Thanks Again,
RC

Post Edited (curious1) : 4/26/2007 8:45:41 PM GMT

curious1

What Now ?
The reading is the same on every combination of the 3 wires in each group.
Any clues ?
Thanks,
RC

Robert Kubichek

No, not with that VOM, I would seriously invest in a Digital that has better accuracy...
With the vom you have you cannot do any acurate readings...
Sorry...
If you could pull the motor apart and physically check the internal connections is your only other choice,
until you get a better DMM/VOM..


Bob

curious1

OKEE DOKEE,
·I'll get a GOOD meter.
Thanks for your help Bob.

Hmmm.
·· I checked 3 other unipolar motors with the VOM and they check OK.
You can clearly·see the difference in resistance with this·meter.·

But this one motor is different. I opened it up to take a look and cannot see where the wires are going.
But.... the resistance is the same everywhere.

Any help is good help,
Thanks,
RC

Post Edited (curious1) : 4/26/2007 10:46:12 PM GMT

PJAllen

Transformer windings (motor windings, etc.) are all wire, windings of wire, wire wrapped around a core.· The·resistance of wire is very little.· So, you need to accurately measure a small resistance, you need an ohmmeter with a·low-ohms scale.

One thing to do is measure the resistance of your probes, touch them together and "zero out" your meter.· On a digital meter note that resistance to subtract that from your measurements.

Refer to my attached drawing.· Given the three terminals of a center-tapped winding, you will find that the measurement between two wires will yield a measurement twice that found between any other combination --·those wires·(terminals) are the transformer "ends" and the remaining wire is the center tap.

curious1

Excellent description and illustration as always Mr. Allen. Similar to wiki.
The only thing that threw me was that I could see about 100 ohms +/- end to end, and roughly half of that from end to C tap on 3 other similar motors. Enough of a difference to determine the tap, but this one is too close for this vom.
New meter is on the way.

Hmm, Council of Despair.....?? Is that you in the picture ? You look familiar.

Take care and ..thanks again,
RC

willy1067

Curious,

I can bet you, that the black and white are your center taps.· red and yellow together and green and blue.· just have to figure out which one is the center for the color combination.·· a simple test can help you.· get a 5 volt 2 amps transformer; plug the white into the ground and touch either the red, yellow, blue or green to the +,· keep an eye in the motor. then experiment with the rest until you get it to move 4 times in the same direction, then repeat the same color code combination to continue moving·in the same direction.·· reverse the color combination to move to the reverse direction.

The only problem could be that the step motor is now ruined because you took it apart.· some stepper manufacturers remove the warranty if you take them apart.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Fernando Gomez

revinc.us
gomez-rivera.com

Never compare yourself with anyone else, there will always be someone bigger·or·smaller·than you.

curious1

Interesting technique, I'll use a new meter first, need one anyway, have for a long time.
I'm not worried about a warranty, this is salvaged from a machine that I parted out years ago.
I dont see how dissasembly could damage it, nothing really there.
A magnet on a shaft and field windings...

Thanks for the procedure Fernando,
I copied it to my workbook.
Regards,
RC

curious1

Went digital with the meter, Sperry.
End to end, 10 ohm
End to C-Tap 5
No wonder I couldn't see it with the needle.
Mr. Gomez, you were right , black and white are the C- taps.
EVERYONE was right, now I'm right too.
Thanks,
RC