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help determining stepper motor pinout? Answered

im trying to build a cnc machine and i just finished the hardware portion. anyways im trying to find out what wires are what on the stepper motors i have. there are 6 pins coming out of the motor and the connections are as follows. pin 1 is not connected to anything, pin 2 has 10ohm to pin 3, pin 4 has 10 ohm to pin 5, and pin 6 is not connected to anything. what are pins 1 and 6 for, and how can i tell if this is a bi or uni polar motor. any ideas? they are made by japan servo co. number kh42jm2b079 if thats any help but i had no luck searching...



Did this info help you? I have the same motors and no luck.

When hooked up as shown

A+ = (DEAD)
Acom = ok +volts
A- = ok ccw
B+ = ok cw
Bcom = ok +volts
B- = (DEAD)

So it wiggles <> when engaged
Pins 1(1) and 6 (11) do not respond.
This is constant on all 3 of my kh42jm2b079 motors...

help? plz?

I'm a little confused with how you are hooking up the motor. How are the  output terminals of your stepper motor driver labeled and how are you attaching to those terminals? The KH42JM2 motors can be used as either unipolar or bipolar, how you wire it up would depend on what type of controller you are using.

The link above has an chart of how to pulse the motor. 

A break down of the motor number is:

KH = two phase stepping motor
42  = mounting size (42 mm)
J    =  motor length (40-42 mm)
M   = motor type (HB type)
2    = 1.8 degree step

I have not been able to determine what the b079 means, however it has to do with the winding specifications.

The following link and the links above should provide good info for you:

I procured and thank you for the PDF. I followed it exactly as shown and no luck. I am currently using Tom's driver board on three steppers (5 wire) from printers and they work great! Now that I am familiar with all the in's and out's of these beasts I wanted to upgrade my steppers... ooops. I am having no luck with these bad boys. I put the COM's together and no matter how I attempt to hook it up no luck. Even bench stepping is fruitless. I'm about to toss em :( Or bench test them with a hammer :)

I thank you for your effort and if there is a motor you recommend (about the same as these) I would love to know.

i just got back to this project and i was so frustrated i opened up the motors (carefully) to see if i could determine the pinout that way. im looking at it right now and pins 1 and 6 are not connected to anything each of the other pins have 2 wires coming off going to 2 diffrent coils.
also there are 8 coils

Final thought:

kh42jm2b079 motors will not work with Tom's awesome board.

This motor is bipolar.

Pins 1 and 6 are dead.
(Thank you rickyfelten)

I just purchased five kh42jm2b140e motors.

They have 6 pins

Wire pins 1 and 2 together (Commons - black and white)

Works great with Tom's board.

Thank you ALL for your help, input and information. I finally have my cnc in working order :)

Try this if you have many motors to test

versions for PIC and Arduino. In C, should be able to adapt to other uC's

One thing I forgot to add is that you can fire each pin and see which way the stepper motor rotates until you have it right. with only 4 pins to deal with after identifying the common wire with an ohmmeter, it is not that hard. Common will always have the lowest resistance between two wires of all the wires.

1 2 3 4 forward
1 4 3 2 reverse


I used some old 5 1/4 stepper (5 wire) motors and just hooked them to the parallel port via nte2013's. A transistor bank might work also. Wrote some simple code in freebasic and it worked great. No special chips needed. usually but not always the common is the 12v+


i havent built my stepper motor driver yet so i cant really test anything, but i can use my power supply to make it step if i do it in the right order