What type of motor is this?


I purchased an XY table from eBay that was parted from a spectrophotometer. There are two unmarked/unbranded motors attached which I assumed were stepper motors, but tonight as I test it I think they may be something else.

Here is what I was able to determine: 6 wires with three pairs. 2 wires (one of the pairs) appear to be ground in that the insulation is clear showing the copper When I connect the other two pair (red-yellow or blue-green) to the multimeter and spin the motor, it produces AC voltage of around 5V, but the faster I move the table, the higher the voltage. Testing the "ground pair" in the same manner produces no voltage, but one "ground lead" to one lead from the other wires produces about half as much voltage.

I'm assuming I'll need to get a motor controller, and then send the pulse signals from the Arduino, but I don't know what type of controller... two phase, three phase... and then how do I hook the motor to the controller? It seems like the controllers I've seen only have three connections for the wires from the motor.

Am I on the right track?

Thanks for your help! -Mark

It is very likely to be a 2- or 4-phase stepper motor (two independent windings with a center tap on each winding).

Measure the resistances between all the leads and tell us what they are. If the above is correct, there will be only two resistance values, with one being twice the other.

I forgot to mention that I tried testing the resistance first... and the values are all over the place fluctuating from 2 to 500 ohms. It's a digital meter... maybe the battery is bad? I don't understand why the resistance would fluctuate like that.

OK I replaced the battery in my multimeter and that fixed the fluctuating. Here's what I got Red-Yellow: 2.7 Ohms Blue-Green 2.7 Ohms Copper-Copper 3.3 Ohms

It looks like it's three separate coils. No other connections produced a result. And to double check I used a continuity check.

Photo of the motor, wires and any nameplace please.... This may be something more exotic.

I hope I still have some people reading this thread. As was asked, attached are some pictures, in addition I hooked the motor up to a scope and rotated the shaft manually. Here is what I found:

No significant markings other than a serial number

Copper-Copper: 5.2 Ohms
Blue-Yellow: 2.5 Ohms
Red-Green: 2.5 Ohms
All other connections registered as open on the multimeter

Input1: Blue-Yellow
Input2: Red-Green
Input3: Blue-Copper

Now I’m really confused. Input1 and Input2 are out of phase by 90 degrees just like you’d expect. But Input3 is generating voltage in phase with Input 1 (to a much lesser extent) even though that connection read as open on the multimeter.

Am I over thinking this? Is it just a simple 6 wire unipolar stepper? I’d really like to hear your opinion.


Link to photos:


Nice platform - are those ballscrews even? Probably $1000 or more in value if so.

The motors look like standard steppers, 2 phase, plus a thermocouple perhaps? I think its kaptan insulation for the other wire pair - a give away they are probably a temperature sensor.

Anyway I'd suggest driving the two match pairs as if a bipolar stepper and see what the motor does - start at 0.5A or something like that, it's probably rated for 1 to 1.5A really (given the winding resistance and motor size), but don't risk over heating the thing.

You probably should figure out the limit switches and ensure the thing can't damage itself mechanically too.