stepper: manually rotation and current protection

Hello,

When a stepper motor is manually rotated it produced current that goes back to the driver possibly damaging it.

I have a few questions:

  1. is this always true? on the stepper drivers (like A4988, TMC21xx, DRV88xx, ecc) there is an enable pin. I am using this pin to disable the motor so I can rotate it without effort. If I disable it would the current cause anyway an harm to the driver?
    From the A4988 datasheet:

This input turns on or off all of the FET outputs

Shouldn't this be enough?

  1. in case that is not enough can you recommend a circuit to prevent any damage to the stepper?
    All I found is this: Stepper motor rotating by hand: Arduino protect - Motors, Mechanics, Power and CNC - Arduino Forum

I did what you are suggesting on a coil winder I built. I disabled the controller so the operator could rotate the coil while soldering the wire to the terminals on the coil form. Works fine.

Paul

Which controller driver are you using? the protection may vary from different drivers

Also, someone knows how the current consumption changes when moving a stepper and when it is stationary?

aster94:
Which controller driver are you using? the protection may vary from different drivers

Also, someone knows how the current consumption changes when moving a stepper and when it is stationary?

The winder was sold as part of my company closing auction, so I don't have any information on the controller.

And current consumption is easily measured using your DVM, digital volt meter, in the current measuring position.

Paul

With modern steppers the driver supply voltage is a lot higher than the EMF the motor will produce if turned normally, so no current would flow with the drive not enabled.

When the drive is enabled it controls the current completely.

The most likely scenario for damage is rotating the motor with the driver powered off - this will force current
into the supply rails through the free-wheel diodes, perhaps enough to bring a 5V rail into operation and then
phantom powering the control logic.

MarkT:
The most likely scenario for damage is rotating the motor with the driver powered off

This is something I haven't thought about, do you have any idea on how to prevent the phantom power? Except for manually disconnecting the motor!

Add series resistors in the step and direction lines?

I just checked some schematics of a 3d printers (example: https://reprap.org/mediawiki/images/7/75/Rambo1-1-schematic.png and other) and these don't use series resistors between the MCU and the STEP/DIR driver's pin. Especially during calibration the axis are moved so maybe I am overthinking for a not-existing problem and the driver already provide some kind of protection

I doubt they provide any protection. Its still worth having that protection if anything in the system is
higher than 5V, as 12V getting into an Arduino will trash it totally in a fraction of a microsecond - a few
resistors are a wise investment to protect the much more expensive microcontroller.

Today I took a little bit of time and I tested on a breadboard if while powering the motor at 12V with enable high (disabled) and rotating the motor would change the voltage on step and dir pin

https://streamable.com/1net19

It seems that nothing change but anyway You are right, two resistor doesn't cost anything, would 1k works ok in your opinion?

NOTE: I checked only the voltage not the current itself