I didn't know, so I asked someone that did - manually moving the X-carve

Asked TI ( maker of the DRV8818 used on the gShield ) -

“Can you damaged the driver chip if you manually turn the stepper motor without power applied to the driver chip?”

TI response:

Rick Duncan replied to DRV8818: Back EMF when driver is not powered.

Hi Larry,

The answer depends on how the device is connected when spinning the motor, how fast the motor spins, and how long the motor spins.

Assuming the exposure of the device is constrained within the absolute maximum ratings, the device should not be damaged.

The overall concern is spinning the motor for long periods could overheat the device, or generate voltages outside the absolute maximum ratings.
As the motor spins any current through the body diodes can heat the device. With no power to the device, the protection circuitry is not active. The device could fail due to overtemperature conditions.

Rick Duncan
Motor Applications Team


Actually, this is the real problem.

Voltage would be more of a concern than current.

I read it this way, It’s like statistics, it only matters to you if you are the one when the odds are one in a million.

In the simple case yes. But there is more to consider than just the winding induced voltage. If you had other voltages present, oh like static electricity, it could push the voltage beyond the limit, where neither voltage alone was enough and without power the driver chip has no defenses.

It’s very similar to laser damage to eyes. you only have to exceed the limit for less than a nanosecond to fry the eye, or in this case the driver chip.

Having said all this (in this thread) I still think the odds of damage are low.

Let’s just say I don’t move my X-carve around without power applied to the chips.

1 Like


I’m reading it same as you. Point by point:

  • “device is constrained within absolute maximum ratings”. Little chance of going outside the maximum ratings by hand.
  • “spinning the motor for long periods of time could overheat”. Again, little chance of generating too much heat by hand.
  • “generate voltages outside the absolute maximum ratings”. Same as above. By hand, very little chance off exceeding maximum ratings.

All of my “by hand” comments are constrainted to moving the x,y,z axis gently and slowly with the power turned off to the machine.


Soooo…who will be the first to hook up a stepper to a A4988/DRV8825 and spin it with a drill…

How would you know? The chip manufacturers do not state a maximum for back EMF on the motor pins with or without power applied.

Rick also said it depends on how the motor is connected. Since he didn’t say specifics, it might depend on what protective circuitry is added by the board maker (none for the gShield or the X_controller with the TB6600 look alike).

It is a very complex issue.

The only way to know for sure would be to put a meter or scope on it and to measure what happens. I don’t think it would do any damage if it was moved a few inches, but common sense dictates that it wasn’t designed for manual movement so why chance it? Also, different sized steppers will generate different results. I’ll be using 269oz steppers and don’t plan to move them manually. Having said that I couldn’t see a 269 oz stepper causing damage IF it was moved SLOWLY for a inch or two. Bottom line there are way too many variables to know for sure, so why take chances? The only guarantee is that when they are used as designed they should work fine, any other use and you’ll be rolling the dice…

1 Like

Some people are rich, have money to waste, and like to gamble :grin:

Let us know what you upgrade to when you burn it out.

Haaa… I kid, hope you are lucky and nothing happens :wink:

Once again I will ask - Has anyone first hand experience at causing this damage by moving by hand? I am sure many of us do yet don’t seem to have a problem. If it was a major concern wouldn’t SOMEONE have had it happen? And if no one has had it happen is it a real world problem or just a problem on paper?

The same reason most all of us take chances everyday - convenience! Probably the single thing with the highest chance of killing you is riding in a car, yet we do it everyday. Why take the chance.

1 Like

Simple math. On a normal Xcarve with 8X microstepping:

200 steps/rev * 8 = 1600 steps/rev
40 steps/mm = 1015.228 steps/in
Revs/in = 0.635
Revs per min at 100 ipm = 63.5 rpm

Many times it’s smaller steppers and different electronics. It’s simple physics just like a loudspeaker can be used as a microphone and vice versa.

Since you are in an experimenting mood, try connecting the coil windings of your stepper to a (un-needed) speaker (no need for any power connection) and then quickly turn the stepper by hand, you’ll get some interesting “sound effects” :grin:

That’s where the variables come into play.

What size stepper?

How quickly was it turned?

For what duration was it turned?

Did the circuit board have any reverse protection?

Was the stepper back-driven while the driver is still powered on? (for most people this will be yes, which is much more dangerous).


Wire is bi-directional. You’ve already mentioned the stepper would act as a generator. See where this is going? :grin:

I would add Schottky diodes if I was planning on turning the steppers manually.

Well said :+1:

BTW, In the CompTIA A+ complete study guide under stepper motors (page 144) it specifically says not to move them by hand. Also, many printer companies will void the warranty if the print head is manually moved. Printers use small stepper motors.

1 Like

Turn the current pot way down and I bet you can.

But you said it best, do what you want to do on your machine because it’s your machine.

I move mine around. I know the harms. I know the risks. Am I slinging it around and junk? No. But I move it so I can square it up.

1 Like

Only because it was mentioned - here goes ----

I have read two cases on the forum where the poster swears that when they moved their gantry by hand it destroyed the gShield. A replacement gShield fixed their problem, both cases.

Now there’s no way to verify that moving the gantry caused the failure, but it was reported that way.

Even if their stories are true, that’s a pretty low failure rate.

Was just reading some data on a stepper motor manufactures website, where they say not to turn the stepper any faster than 1 rev/second.

Yeah, we were supposed to get a trace of snow today. We’re at 9 inches and it’s still snowing.

1 Like

Ours turned to ice. Kept me home from work. Literally couldn’t make it outta my neighborhood.