Stepper motor project help

Hi all,
Could you please help me figure out the best configuration to run a standard Nema 17 Stepper motor without controller and driver?
I am working on a project that only requires a limit switch to turn the motor on, so this seems like a good way to go.
Originally I tried with a DC motor, but it didn't have the power or torque,.
Then I tried with a DC motor with gearbox, but when there is no power the shaft is locked and I need it to turn freely

I watched this youtube:

But was wondering:

How many volts / amps AC adapter should I purchase?
What type / power / uF etc.. capacitor would work well / best?

Thanks for any advice!

run a standard Nema 17 Stepper motor without controller and driver?

You will need to wire up 4 switches. To make the motor turn in either direction, you will need to turn the switches on and off in a strict pattern or sequence. One full revolution will require hundreds of switch presses. I hope you do not have a low boredom threshold.

Thanks for the reply, I was hoping to get the motor running like in the youtube (it rotates on its own).
Will this not work on the nema 17?

You can make your motor run by following the instructions in the video. But you cannot expect that it will turn any load this way, it's for demonstration purpose only. And you can expect that the tortured capacitor will explode sooner or later.

For the remaining questions: determine the required torque, get a sufficiently strong stepper motor, look up its power requirements (voltage and current) and get a suitable transformer.

For a real application you'll replace the transformer by a DC power supply and driver module, and add an Arduino to control everything.

I must admit I did not watch the video. Often videos posted on the forum are long and boring with horrible music and the information they contain could be explained in a single paragraph. But that one was ok.

In the video, a bipolar stepper motor is used, and the capacitor causes a phase difference between the current in the two coils. In effect, the stepper becomes a synchronous AC motor.

So you can use a bipolar stepper. Unfortunately, the term "nema17" only tells you about the physical size of the motor, not it's internal wiring.

The video also states that unipolar steppers cannot be used like this. I can see how that would be true for some bipolar steppers, like those with 5 wires. But for the bipolar steppers with 6 wires I think it may still be possible if wired in the right way, so that they effectively become bipolar.

As for your questions about voltages, currents and capacitor ratings, again it will depend on the motor you use, and "nema17" does not describe anything but physical sizes, not electrical characteristics. For example, all the motors in this picture are nema17 but have different voltage & current requirements:

Thanks for your help,
The motor i'm using has 4 wires and has these specs:

Step angle (º): 1.8
Temp. Rise (ºC): 80 max
Amb. Temp (ºC): (-20~ +50)
Nr. of Phase: 2
Insulation Res. (M ohm): 100 min.
Insulation Class: Class B
Max. Rad. Force (N): 28
Max. Axial Force: 10
Rated Voltage (V): 2.8
Rated Current (A): 1.68
Res. / Phase (10% Ohm): 1.65
Inductance / Phase (20% mH): 3.2
Holding Torque ( 36
Detent Torque ( 150
Rotor Torque (N.cm²): 54
Weight (kg): 0.285
Body Lenght: 39
Total Lenght: 63
Total Width: 42.3
Bolt Widht: 31 ±0,2

I identified the coils using an LED, and also tried using an Arduino with a BigeasyDriver following a tutorial, but haven't had much luck.
When I plugged in 12V 2A DC adapter to the BigeasyDriver, it lights up ok but the motor doesn't move.
Increasing the amps slightly with the adjustment on the BigeasyDriver makes the motor start clicking, but it also doesn't move. At this point the BigeasyDriver gets exteremely hot, so I unplug it directly.

edit: looking back at my code, it might be that I did something wrong there. I will check this

It’s time you read the forum guide in the “please read” sticky post. Especially point 11.

Thanks for the reply, I was hoping to get the motor running like in the youtube (it rotates on its own).
Will this not work on the nema 17?

That YouTube turns the stepper into a synchronous motor.
A stepper configured like this has very low torque and not very efficient.
If you watch the entire video, at no time do they have the motor actually drive anything.
Tom.... :slight_smile:

Thanks for the advice!
Didn't realise at first about the low torque so not a good way to go with the project.
In the mean time I retried connecting a Sparkfun BigEasyDriver and it works great now! no heat and very high torque :slight_smile: now on the the rest of the project

Any idea what you did wrong with the driver before? If might help others searching the forum with similar problems.