Unable to trigger 12V DC Stepper Motor without driver

Question

I am trying to test a 12V stepper motor using just a 12V DC adapter without any driver, but I am unable to get it triggered. I am using Velleman's MOTS1 motor and as per the data sheet attaching the power's negative terminal to the red wire and the positive terminal one by one to the other four wires.

1). To eliminate the possibility of a faulty motor, I even tried with two different motors of the same model. But both motors did not work.

2). I also realized that the adapter is delivering 11.8V instead of exact 12V. So, to eliminate the possibility of lower voltage, I supplied 15V using batteries, but that too did not work.

3). Also, using the same adapter and battery sets, I am able to trigger other regular 12V DC motors.

So most probably, I am doing something wrong here specific to stepper motors.

Please help! Let me know if you need more information from me.

I am an absolute newbie electronics hobbyist and have just 3 months of basic theory and practical experience. So, I guess, every suggestion is helpful :) .

Motors specifications from the Velleman's website - https://www.vellemanusa.com/products/view/?id=351245&country=us&lang=enu

• resistance: 280 ohm
• rated voltage: 12 Vdc
• current: 32 mA
• impedance: 380 ohm
• phase: 4
• step angle / step: 5.625° / 64
• reduction ratio: 1/64
• detent torque: 4.86 ozf.in
• pull-in torque: 4.17 ozf.in
• max. starting pulse rate: 550 pps
• max. slewing pulse rate: 90 pps
• temperature range: 77 °F
• noise: 40 dB
• cable: 420 mm AWG 1095#28
• terminal: JST SPH-002T-P0.5S
• insulation strength: AC 600 V - 1 sec. cut-off current: 10 mA
• colors:
  1. B1: pink
  2. A1: orange
  3. A2: yellow
  4. B2: blue
  5. GND: red
  6. GND2 (for MOTS2): brown

DC Adapter specifications:

• DC Volt Output: 12V
• DC Current: 2.5 A

Answer 1

Driving a stepper motor is a bit more complicated than driving a regular brushed DC motor. Stepper motors require a stepper controller to energize the phases in a timely sequence to make the motor turn. I strongly recommend you build yourself a driver for this motor.

All the best, keep well.

Answer 2

You can test your motor(s) by simply applying voltage (below 12V is also acceptable) and seeing a small movement only. For further spin test requires more advanced driver circuitry.

Looking at the reference page, your motor looks like a 5-wire unipolar motor.

5-Wire Motor This style is common in smaller unipolar motors. All of the common coil wires are tied together internally abd brought out as a 5th wire. This motor can only be driven as a unipolar motor.

(Refer to: https://learn.adafruit.com/all-about-stepper-motors/types-of-steppers)

Simply tie GND pin to ground and apply positive voltage to A1, A2, B1 and B2 pins one-by-one.

What a simple stepper driver does is applying sequential pulses to the windings. This application manual is very explanatory for beginners.

Answer 3

the ST28 datasheet does not indicate if the /64 and the 5.625 are a repetition of the same parameter or describing two processes in series, this has cause some confusion.

However the motor st24 is interesting it has 7.5 degree steps and a 85.56 reduction ratio... clearly the steps and the reduction ratio are two separate parameters here.

so this ST28 motor has a gear chain between the rotor and the output shaft reducing the 5.625 degree steps but a further factor of 64. it may not be possible to see the shaft stepping with only a manual drive. The shaft turns less than one tenth of a degree with each step.

You should be able to make the motor turn by pulsing the coil wires in the correct order

if you can identify coil1 and coil2 and repeatedly pulse the wires in the right order repeatedly it should rotate slowly

the order is either A1 B1 A2 B2 if A and B are coils and 1 and 2 are ends or A1 A2 B1 B2 if 1 and 2 are coils and A and B are ends.

eg: lay out some bare wires on a solderless breadboard wired and wire them to terminals in the order given above and drag the negative feed across them. if you hold the motor in the other hand you may be able to feel the rotor stepping.

11 volts should be plenty, it will be a little weaker than with 12V but should have plenty of strength to move a light pointer

Answer 4

Thank you all for helping me figure out the issue. Here is the problem.

In the Velleman specs, the red wire is designated as GND. Thats the issue. Once I used the red wire as positive, and applied negative voltage one by one to the other 4 pins, the motor turned very small steps. Less than one degree per pulse.

Now, I am trying to design a driver circuit for this motor using a 555 timer, 4017 counter and 2N222 Transistors and facing another issue. But I will post that in another thread.

Thanks again for helping me figure out the problem

• Anurag