What's the difference between Stepper Motors ?

how to measure the torque in stepper motor

I got a lot of stepper motor but cant seem to find the modal for it. Most of it have 4 line and some got 5 and 6. Whats the difference between them?....
I got an UC3637N or UC3717AN driver to drive it. Using 8051 to drive the stepper

Re: Stepper Motor

try this:
**broken link removed**

Re: Stepper Motor

Stepper motors can be classified into unipolar and bipolar.

Bipolar ones have simple windings, just 2 wires per winding. Thus they make better use of the available winding area and produce more power. However, to drive them you need to be able to reverse the voltage across the windings, which means more complicated drivers. The chips you mention are designed for such motors.

Unipolar ones have center-tapped windings, that is they use 3 wires per phase (winding). The center tap is connected to a voltage source and the ends of the winding are driven by transistors. Thus, no voltage reversal is needed. But the available power is lower and the stress on the transistors is twice the supply voltage.

The 4-wire motors you have are most likely bipolar ones, having two windings (phases). The 5 and 6-wire ones could be unipolar. Thus, you can have a common center tap and 4 wires (2 windings) or you could have 2 ceneter-tapped windings, each with its common plus 2 wires (although the 6-wire ones ccould be different).

The only way to know for sure is to measure with an ohmmeter and tell which wires are connected to the same winding and by measuring the resistances actually tell which are the center-taps, if any.

Stepper Motor

so by measuring the things i can find out which winding is connected. Btw how to tell the max torque of each motor.. or do all the motor have the same max torque. I got most of my stepper out of old printers.

Stepper Motor

Stepper motors have a maximum holding torque. This torque is partly a function of the motor and partly how you drive it. Whether unipolar or bipolar, you can energize two windings at one time for more torque OR you can energize one winding at a time for less torque but less power consumption. If you're half stepping (for more precise movement), you will be energizing one winding half the time and two windings half the time.

Now, once you know how you plan to drive it, you can energize the windings. If you take a pair of plyers you should be able to apply enough torque to get the motor to turn (it will resist you). The minimum torque where you get it to turn is the maximum holding torque of the motor. You might could measure it with a torque wrench.

OR if you don't have a torque wrench you can attach a pulley to the rotor and a rope on one end of the pulley. Add weight to the rope until it causes the motor to slip. Then calculate the torque with the known pulley radius and known weight.

Re: Stepper Motor

The method descried by jonw0224 works and I used it. The only problem is that it will only give you the holding torque, you cannot get any info about the pull-in or pull-out torque for a certain step frequency.
The best way is to try and get the datasheet, if you can.