Re: [CAD_CAM_EDM_DRO] 5 Wire steppers

>How can I tell the center tapped wire on this type of motor as all the
>wires have the same ohm reading. I think you can use it on a bipolar
>stepper drive if you can find the centre wire.

Actually, I believe that it is designed for UNIPOLAR, not a BIPOLAR drive.

Take any two wires, measure the resistance. As long as it is not
zero, you should be okay.

Take any two other wires, if it is the same, you have found the
centertap (it's the one you didn't try yet.)

Since you have two wires you know are not zero ohms and you know the
voltage/current needed by this motor, put 1/4 of that voltage across
the two wires (it's not critical, but smaller is better
here.) Measure the voltage from one of them to one of the other
wires. If it is the same, that is the centertap, if it is 1/2 the
voltage, you have two ends of one winding (or two ends of two
windings.) Use a different pair and repeat, this time either the
centertap will be obvious or I am confused! The other two wires you
just tested should either read 1/2 (the centertap is the remaining
wire), full (the centertap is the wire with full voltage in) or zero
(the centertap is the one with no voltage in.)

While it sounds complex, it is easy. Label the wires 1 through
5. Put a smaller voltage than the motor wants across 1 and 2,
measure 3. Is 3 the same as 1? 1 is the centertap. Is 3 the same
as 2? 2 is the centertap. Only if 3 is about 1/2 of the voltage
from 1 to 2 do you need to go on.

Put a smaller voltage than the motor wants across 4 and 5, measure
3. Is 3 the same as 4? 4 is the centertap. Is 3 the same as 5? 5
is the centertap. If 3 is 1/2 the voltage from 4 to 5 and 1 to 2 (in
the previous test), it is the centertap!

You can do this with 4 1K resistors (or whatever you have) and a
single "D" cell (which is very safe.)

Remember steppers are inductive, when you remove power, you will
generate a big voltage and can get zapped!

David G. LeVine
Nashua, NH 03060