Stepper Motor Power Help

Hello,

I am new and stuck with best way forward to power my robot.

I have Arduino micro UNO, Giro MPU6050, two DRV8825 controllers, and two JK42HS40-1684 stepper motors.

I think the steppers are 12v 1.6A. Should I get a 4S LIPO with 12v and 5v voltage regulators?

David.

Batteries are a poor choice for stepper motors (or vice versa) because stepper motors are very inefficient. Your two motors could be consuming almost 1.6 * 4 = 6.4 amps continuously (1.6 amps per coil) even when the motors are not moving. You will need a battery with a large capacity to keep that going for more than a few minutes.

Also, if you need high speed and high torque from a stepper motor you will probably need a higher voltage.

Post a link to the datasheet for your stepper motors so we can be sure we have the correct data.

What sort of robot are you making? What will the stepper motors be doing?

...R
Stepper Motor Basics
Simple Stepper Code

Hello

Stepper Motors are:

I am wanting to make something similar to this URL:

but want to get just have the stepper motor and balance first with a giro.

David.

According to your link your motors need 1.68 amps so my concerns about battery capacity remain. However if it was my robot I think I would be content with 5 or 10 minutes of run time (I have a short attention span).

I have these Sparkfun stepper motors that only consume 0.33 amps and I wonder if they would be adequate for your project.

In the video at the bottom of this link @zhomeslice made something like you want with simple DC motors.

...R

Hello,

Just noticed the stepper motors I have are 12 volt and the guy I am following is using 2.8 volt both the same current rating.

So maybe I should go out and by new stepper motors bugger... what do you think.

David.

The voltage rating for a stepper motor is not all that relevant. What matters is the current. Of course with a high resistance coil you have no option but to use a higher voltage to get the required current.

Another important factor is that if your motor takes 1.68 amps at 12v it will consume about 12 * 1.68 * 2 = 40 watts. Whereas a motor that takes 1.68 amps at 2.8v will only consume about 2.8 * 1.68 * 2 = 9 watts - only 25% of the power of the 12v motor.

The correct way to select a stepper motor is to identify the required torque first. In this case, maybe take the value from the motors the guy in the project is using. How does the motor you have compare with his where torque is concerned? Have you link to the datasheet for the guy's motors?

It may indeed be the case that the motors you have selected are not ideal.

...R

Robin2:
According to your link your motors need 1.68 amps so my concerns about battery capacity remain. However if it was my robot I think I would be content with 5 or 10 minutes of run time (I have a short attention span).

I have these Sparkfun stepper motors that only consume 0.33 amps and I wonder if they would be adequate for your project.

In the video at the bottom of this link @zhomeslice made something like you want with simple DC motors.

...R

You are confusing current with power.

Steppers of the same size have the same winding power ratings, typically, since thermal heating is the
limiting factor for continuous use (especially now in the era of rare-earth permanent magnets).

If you want high performance from steppers use low impedance steppers and a chopper driver like DRV8825.

That way you get speed from them and automatically buck-convert from the supply in the process, so the
fact the windings get 1.6A does not imply the supply sees anything like 1.6A.

In fact that motor is likely to be about 1.7ohm, so its dissipation (stationary) is about 4 to 5W. This is
pretty much the same for all NEMA17 motors.

MarkT:
You are confusing current with power.

I wasn't. I was merely speculating if a different motor might be adequate. At that point there was no indication of what power was required. And we may still not know.

...R

Ok so the stepper motor is 1.68A and 1.65ohm so does that mean it is 2.8v?

I am not worried about the amps because the 8825 can be adjusted but still need to understand what volts to supply.

I have also read that the supply is volts * 4 so the supply is 2.8 * 4 = 11.2. This would work with a lipo 3s.

1.68 * 1.65 = 2.772 (or 2.8v). That is the only significance of the 2.8v figure. It does NOT mean that you should, or must run the motor with 2.8v. In general stepper motors work better the higher the voltage. But your stepper driver MUST ensure that the current does not exceed 1.68amps or the smoke will probably escape eventually.

You really need to do some experiments to see what voltage is needed for the performance you require. This is probably not easy to do with a balancing 'bot because it may just fall on its face and provide no useful feedback.

The 4s LiPo you mentioned in your Original Post should be worth trying. But get one with the largest capacity you have space for.

When you think of the problem of getting a 'bot to balance it seems to me that dc motors would be more suitable because they can have variable torque and smooth motion whereas a stepper motor has essentially fixed torque and rough motion.

...R