How do you power 12 28byj48 stepper motor?

One of my project requires powering 12 28byj48 stepper motors at the same time. The movements are in sync so I will use a single Arduino to signal the 12 drivers, but I wonder what power source should I use that can deliver enough current to the steppers?

I want it to be portable, if possible.

Thanks

If your motors are 5V (they also come in a 12V version) it will draw about 110 mA in full step mode and twice that (220 mA) in half step mode, 12 times 0.22 = 2.64 Amps, I would go with a 4 Amp power supply.

Can I use a battery pack or battery bank?

I don't want to have to plug it in in order to use it.

Thanks

Can I use a battery pack or battery bank?

Of course you can. Don't forget to connect all the grounds.

The intent is to use the motors to power a gripper. I need to grip multiple identical items at the same time. I believe it was mentioned that the 28byj48 can be stalled with no issues, which is what happens when the gripper grips something. But I wonder if it can cause the motor to overheat if stalled for too long. Are there better options? Maybe those hobby servos?

thanks

It's a stepper. It won't use any more power when running freely or when stalled - always maximum current is flowing through its coils.
Very different from brushed DC motors which WILL use much more current (and may burn) when stalled.
Servos and steppers have rather different use cases. For a gripper a servo is indeed often the better option, as you probably want to know the position of the gripper itself. Servos may also heat up when stalled (i.e. pushed away from where they are told to go).

12 28byj48 would draw quite a bit of power, especially if they are going to be used a lot. I don't think a battery pack would last long. If I use a power supply, that's going to limit mobility and makes it quiet unwieldy. Are there more power efficient solutions that can enable the use of a battery pack and still last hours?

Thanks

I have used a 150 Ohm resistor in series with the power supply to reduce current to about 30% when the stepper is at standstill and bypass the resistor with a p-channel MOSFET when stepping. May not work in your application because gripping torque would be reduced by 2/3 and the gripper might relax enough to drop the object.
vp2206-1.png

paulwece:
12 28byj48 would draw quite a bit of power, especially if they are going to be used a lot. I don't think a battery pack would last long. If I use a power supply, that's going to limit mobility and makes it quiet unwieldy. Are there more power efficient solutions that can enable the use of a battery pack and still last hours?

Thanks

If you need to run 2.6A for 1 hour, you need a 2.6Ah battery. This may be written as 2600mAh. That is not a large battery. Some AA batteries hold that much. Unfortunately though you won't get that energy out of them at that rate: internal losses mean that using them fast will reduce the total mAh output.

Stretching it out to 4 hours requires 10.4Ah. This is getting close to the capacity of a D cell. But it would be better to buy a battery pack, maybe something based on Lithium, which is usually pretty good at delivering high currents like this.

Are all your grippers gripping for 4 hours straight? If you can shut down some or all of them for some time then you will increase your run time.

A typical mobile phone power bank can supply 2-3A. Two such power banks, 7,200 mAh each, will run this thing for 4-6 hours. Make sure to connect the grounds, NOT the 5V lines, and spread out the steppers over the two batteries. One of them would also power the Arduino so make sure you have good decoupling (a Pi filter - two large caps plus inductor - may be in order).

paulwece:
The intent is to use the motors to power a gripper. I need to grip multiple identical items at the same time. I believe it was mentioned that the 28byj48 can be stalled with no issues, which is what happens when the gripper grips something. But I wonder if it can cause the motor to overheat if stalled for too long. Are there better options? Maybe those hobby servos?

thanks

Be aware that if you continue to step the motor after it reaches the “stalled” position, it will step backwards 1 step then forward again whenever the coils are powered for the step immediately prior to the stalled position.

I think it might be easier to just use a bunch of springs instead, and have a mechanism that retract all springs to loosen the grippers and a way to release all springs. lol