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Topic: A4988 Undervoltage (Read 157 times) previous topic - next topic

Master_Aar

Hello,

I have been looking around for stepper motor drivers, and have several choices: the a4988, drv8825, or tb6612 (technically just a DC motor controller but works for steppers). The tb6612 can power motors with voltages as low as 4.5V, however the other two drivers need at least 8V. I need to drive a stepper motor at 5-6 volts, and I want to be able to adjust the current being supplied to it (which the tb6612 cannot do).

My question is, can I run stepper motor drivers at 3 volts under their minimum motor voltage? If not, are there any stepper motor drivers that you know of that can accept 5-6 volts and have adjustable current?

Here are my sources:
https://www.pololu.com/product/1182
https://www.pololu.com/product/2132
https://www.pololu.com/product/713

PaulS

Quote
can I run stepper motor drivers at 3 volts under their minimum motor voltage?
Can you clarify what you mean by "run stepper motor drivers..."? The voltage that needs to be supplied to the driver, and make the hardware work has nothing to do with the voltage that needs to be supplied to the motors that the driver makes step.
The art of getting good answers lies in asking good questions.

Master_Aar

I mean the voltage going to the motor, not the 3-5v signal from an arduino. The website says that the voltage going to the motor needs to be greater than 8v. I don't see why there would be any minimum since this is just the power for the stepper motor. The a4988 chip itself will have a signal voltage of 3.3v (from an arduino).

If the voltage that needs to be supplied to the motors has nothing to do with the signal voltage, I don't see why there would be any minimum, which is what I'm asking here.

jremington

#3
Jun 22, 2017, 04:46 pm Last Edit: Jun 22, 2017, 04:49 pm by jremington
The A4988 driver itself requires 8V minimum for proper operation.

The voltage rating of a stepper motor is not important, but you may not exceed the motor current rating. Less current is fine, you will just have less torque.

Post a link to the motor specs.

Master_Aar

Wait...so I can overpower the stepper motor with a 9V supply and be fine, as long as I limit the current?

jremington

#5
Jun 22, 2017, 11:27 pm Last Edit: Jun 22, 2017, 11:28 pm by jremington
You MUST limit the current to be within the motor ratings.

The higher the motor power supply voltage, the faster the motor will run.  40-80 V is common, but obey the motor driver limitations.

MarkT

Wait...so I can overpower the stepper motor with a 9V supply and be fine, as long as I limit the current?
The entire point of the A4988 is that it limits the current...  Steppers are current driven, the voltage
of the supply affects the maximum speed achievable, nothing else.

What motors are we talking about and how fast are you wanting them to turn?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Master_Aar

I am using a salvaged stepper motor from an old printer. It has no writing on it at all so I really don't know anything about it...

As far as speed is concerned, this thing is meant to go in a motorized camera slider that I'm making to take timelapses, so it doesn't need to go fast at all.

jremington

You are much better off with an identifiable motor that meets your requirements. Otherwise you just have to experiment. Good luck with the project.

Master_Aar

Ok, I'm going to purchase a stepper motor and an a4988 driver. Thanks!

MarkT

I am using a salvaged stepper motor from an old printer. It has no writing on it at all so I really don't know anything about it...
You can measure the winding resistance, and you know how big it is, which sets the max heat dissipation,
so you can roughly figure out the current setting from I-squared-R and heat dissipation limits for
similarly sized stepper motors....
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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