Unipolar stepper, bipolar driver

[Artlav]

Greetings.
I got an unidentified 6-wires stepper motor, which i suppose is unipolar.
But, the motor drivers i have is for bipolar ones.
As i understand, a bipolar driver can drive a unipolar motor, by plugging in the ends of the coils and leaving the middle wires hanging.
Is it that simple or are there some caveats?

Second problem, how can i identify which wires do what?
There are two trios of interconducting wires, in each one there is a pair that gives the most resistance on rotor when shorted, but when i plugged these two pairs, the motor does not work in a consistent way - either vibrate in place or starts moving back and forth. i tried swapping one pair and different step rates to no avail.
What can be wrong?

 

[Bob S]

Read:
http://en.wikipedia.org/wiki/Stepper_motor#Bipolar_motor
Yes, an H-bridge usually can be used to drive a unipolar motor by driving the two ends and leaving the center-tap wires hanging. Read about various types of steppers in above URL. Based on stepper motor voltage and current ratings, set up the two H-bridge drivers, with series resistors if necessary, and drive the stepper at 1 or 2 Hz with the two H-bridges in phase quadrature. My experience is that many H-bridge drivers are not full-rated below ~ 6 or 8 volts, which may be too high for some steppers.
See the schematic on page 2 of:
http://www.ozitronics.com/docs/k158.pdf
for two 5-50 volt H-bridge drivers using P-type and N-type mosfets.
Two popular integrated H-bridges are the L298N and the LMD18200.
Bob S

 

[oswaler]

Greetings,

I can provide some insights and suggestions for your questions about the unipolar stepper motor and bipolar driver.

Firstly, you are correct that a bipolar driver can drive a unipolar motor by connecting the ends of the coils and leaving the middle wires unconnected. However, there are some caveats to keep in mind. The performance of the motor may not be optimal as the driver is designed for bipolar motors, which have four wires. Additionally, the current flow in the motor may not be as efficient, leading to potential overheating and damage to the motor. It is recommended to use a driver specifically designed for unipolar motors to ensure optimal performance and longevity of the motor.

Regarding identifying the wires, it is important to understand the wiring configuration of the motor. Typically, unipolar motors have five or six wires, with two wires for each coil and one or two center tap wires. The two pairs of wires with the highest resistance when shorted are likely the ends of the two coils. The remaining wires are most likely the center tap wires. To determine the function of each wire, you can use a multimeter to check the resistance between each wire and the motor casing. The wires with the highest resistance to the casing are likely the center tap wires.

If the motor is not working consistently, it could be due to incorrect wiring or a faulty driver. Double-check the wiring and make sure it matches the wiring configuration of the motor. If the issue persists, it may be worth trying a different driver or seeking assistance from a professional.

I hope this helps with your understanding of the unipolar stepper motor and bipolar driver. Good luck with your project!