Hi friends

I have one stepper driver with IC A3977
When i rotate Stepper motor or vary the speed of Stepper motor, it produce Audible noise of current in winding.

so guys do you have any suggestion to reduce this noise.
Any one have any idea or link,
Please tell me, Suggestion is highly appreciated
Thanks in advance

 

Hello,

Can you post the current schematic?
With that at hand we can have a look if this needs some adjustment.

Greetings,
Bertus

 

Noise is normal in PWM motor drives. The usual way to make it inaudible is to increase the frequency above 20KHz.

 

Markd77 suggestion is the solution. The windings of the motor and/or losse metallic parts vibrate due to the change in the magnetic field. If the magnetic filed changes with a frequency of less than 20kHz then the windings vibrate at this frequency (or close to it). This is in the audible range and causes this annoying noise.

 

I read this to be a stepper motor - it won't drive with PWM.

 

It is all in the datasheet as usual.....

The A3977 is a complete microstepping motor driver, with builtin
translator. It is designed to operate bipolar stepper motors in
full-, half-, quarter-, and eighth-step modes, with output drive
capability of 35 V and ±2.5 A. The A3977 includes a fixed
off-time current regulator that has the ability to operate in
slow-, fast-, or mixed-decay modes. This current-decay control
scheme results in reduced audible motor noise, increased step
accuracy, and reduced power dissipation.

So try a different decay mode.....

A stepper motor system will have reduced audible
noise if the microstepping driver can switch between
slow-decay and mixed-decay mode PWM operation. The
A3977 includes circuitry that automatically sets the
current decay mode either slow or mixed decay, which
eliminates the need for the user to provide additional
control lines.

Slow decay has the advantage of minimum
current ripple. However, when microstepping at higher
step rates, slow-decay chopping may fail to properly
regulate current on the falling slope of the sine wave when
current is decreasing. This is a result of motor BEMF
overriding the voltage applied to the motor, forcing the
current to increase during the decay period. motor current
pushes the limitations of slow-decay chopping.
This distortion in the current will
cause increased audible noise in the motor.

 

I read this to be a stepper motor - it won't drive with PWM.

the A3977 implements a PWM to drive the stepper ...

The A3977 is a complete microstepping
motor driver with built in translator for easy operation
with minimal control lines. It is designed to operate bipolar
stepper motors in full-, half-, quarter- and eighth-step
modes. The current in each of the two output full-bridges,
all N-channel DMOS, is regulated with fixed off-time
pulse-width modulated (PWM) control circuitry.

 

PWM is needed to achieve microstepping.

See http://forum.allaboutcircuits.com/showthread.php?t=19061

Alberto

A3977 has built in PWM :

The current in each of the two output full-bridges,
all N-channel DMOS, is regulated with fixed off-time
pulse-width modulated (PWM) control circuitry.

external PWM not necessary, only have to provide step and direction logic controls for this IC.....

 

The built in PWM (in A3977) is used to achieve microstepping!

Alberto

We have already cover this topic, but yes, PWM is necessary for microstepping, and it is built into the A3977..... so NO EXTRENAL PWM CIRCUIT IS NEEDED FOR USING THE A3977 AS A MICROSTEPPING STEPPER CONTROLLER.

The OP's problem with audible noise is not due to the PWM or the microstepping, it has to do with the current decay scheme he selected to used, if he uses the mixed-decay mode, this might reduce the audible "noise"...

Slow decay has the advantage of minimum
current ripple. However, when microstepping at higher
step rates, slow-decay chopping may fail to properly
regulate current on the falling slope of the sine wave when
current is decreasing. This is a result of motor BEMF
overriding the voltage applied to the motor, forcing the
current to increase during the decay period. motor current
pushes the limitations of slow-decay chopping.
This distortion in the current will
cause increased audible noise in the motor.