Thread: Identifying centre tap on coil

1. Identifying centre tap on coil

Hi guys and gals, this is my first post here. Hope you are all well.

In a nutshell, I have an unidentified stepper motor. Well it's Astrosyn Minebea 23nema, but it looks like it's proprietary as I can find no data sheet on it anywhere. Believe me I've looked. I've had it turning hooked up to an arduino and an L298 driver, but I'm sure it could be better. It makes a horrible grinding noise when turning. It also can easily be opposed by touching the drive shaft. So I'm assuming is lacking current.

First off, is there an easy way of identifying the centre tap of the coils? So I can make sure I'm driving it correctly It's six wires so uni polar I'm assuming. Using a meter I can prove which wires are connected to which coils and have three on each. phew!

Secondly is there an easy way of finding out current rating and required supply voltage to drive it at it's most efficient?

Thanks guys. This is my first attempt at anything like this, and hopefully I can get this working to drive my x-axis. Y and z to follow? Hopefully!

Regards.

Hoppo

2. Hi Hoppo ,

once you have found the three wires to a coil

the resistance from the centre tap to each end will be half the total
measured from end to end

eg
and you marked the wires
A , B and C for coil 1
D , E and F for coil 2

the results could be

A to B = 5 ohms , A to C = 2.5 ohms , B to C = 2.5 ohms
D to E = 2.5 ohms , E to F = 2.5 ohms , D to F = 5 ohms

for coil 1 the centre tap would be terminal C
for coil 2 the centre tap would be terminal E

for a given motor size the wattage dissipated by each winding
will be more or less constant

once you measure the resistance of the windings
you could get an idea of the current required from other manufactures data for 23nema size motors

the exact current being limited by the temperature of the motor

John

3. Hi Hoppo

The maximum current rating of the winding relates to the power dissipation and hence to the physical dimensions of the motor. Frame size shape and body length. Yours is frame size NEMA 23. Take a look at this link NEMA 23 > Hybrid Stepper Motors > Product Range > Home > Astrosyn International Technology Ltd

Presumably your motor has no type marking other than the makers name and as such might well be a special. IMHO start with a conservative phase current and monitor the case temperature. These motors run hot and are normally rated for a case temperature of 50 to 60 degrees Celsius - that is unpleasant to touch but not enough to burn on light contact. John has given a good way of sorting out the windings. You will also find that the colours used are given in the various Astrosyn data sheets and this should also help sort out the connections.

Regards - Pat

4. Thanks John,

I measured with a meter when I got home, and have identified the centre taps. It doesn't make much difference to the operation, it still sounds rough when turning. The coils measure 1.8ohms each 0.9ohms to centre tap. I'll have a look at other data sheets and look for similar ratings.

WildwestPat, I'm driving it with an L298n driver chip. The chip gets hot, but motor gets nowhere near, not even warm. I've also since discovered that the model number is 23KM-K033-03, but cannot find any data sheets for that specific model.

Will experiment over the weekend and see if I can figure out optimal Voltage and Current settings.

Cheers