DRV8711: Stepper motor make noise and excessive heat.

Hi Haroon,

The schematic of the DRV8711 looks good.

What are your register settings?
Have you monitored the current through the stepper motor?
What is the sense resistor value used (are all 5 sense resistors populated)?

Well, I have used recommended settings mentioned in "DRV8711 Quick Spin and Tuning".

If I use above configuration, motor doesn't rotate. Please help me with correct configuration for my design. 

My stepping motor specifications are : 

TYPE: 57BYGH56-410A 

1.8 Degrees , 3.0 A, 1.2N.m 

FH  No : 20170409 

I am running out of time , please help me to sort out as soon as possible. thanks. please mention register configurations i use for this stepping motor. 

Hi Haroon,

Please answer my prior questions.

1) What are your register settings? --> (Specifically what is the torque setting)
2) Have you monitored the current through the stepper motor? --> (Please provide a scope capture of the current through one phase of the stepper and the STEP pulse, or the voltage across the sense resistors and the STEP pulse. Zoom out until one full electrical cycle is shown.)
3) What is the sense resistor value used (are all 5 sense resistors populated)?

Questions 1 and 3 help determine if you have the proper current setting for the motor.

If you have the DRV8711EVM, please use it to determine if the operation is the same on both your custom board and the DRV8711EVM. If the operation is different, you can perform A/B comparisons to find the difference.

Thanks for your reply.

I have received EVM today. Now I wanna configure my stepper motor using DRV8711 EVM .  My stepping motor is:

Series Model : 57HS11242A4

Step Angle: 1.8 Degrees

Rated Current :  4.2 A

Phase Resistance : 1.4 ohms

Phase Inductance :  3.8  mH 

I have burnt 3 custom boards already , i fear , i would burn EVM ...as well .
what register configuration would be optimal , please share. 

moreover, i noticed the voltage waveform across A+ and A- . It's not pure sine wave. why is this so.?

Hi Haroon,

I received your reply to my questions, but the reply did not appear on the forum.

Thanks for your reply.

Ans1: I have used Rsense= 5mohm as you can see schematics attached with the post.

Ans: My register configuration is:

//0xaddress,0xdata

SPI_DRV8711_Write(0x06,0x0F2); //DRIVE

SPI_DRV8711_Write(0x05,0x0020); //STALL

SPI_DRV8711_Write(0x04,0x0305); //DECAY

SPI_DRV8711_Write(0x03,0x09a); //BLANK

SPI_DRV8711_Write(0x02,0x005); //OFF

SPI_DRV8711_Write(0x01,0x003); //TORQUE 0x017f

SPI_DRV8711_Write(0x07,0x0000); //CTRL

SPI_DRV8711_Write(0x07,0x0000);

motor still makes noise and vibration. although no excessive heat.

 

The schematics show 10mOhm (5, 50mOhms resistors in parallel). Is this correct?

For the EVM, please start with the recommendations in the users guide. The recommendations are for Ichop = 1A.

If you have no load this should be no problem. You can raise the torque as required using equation (1) in the datasheet.

Now to your settings.

If the original torque setting was 0x7f, this called for 27A when microstepping and 19A when operating at full step through the motor. The motor would limit the current to ~17A, due to the resistance. 

It is recommended to increase the gain to 40 and keep the torque setting at 0x25 to begin. This will set the current to ~1A. The max torque setting for the motor should be  0x9c (156 decimal) if the sense resistor is 10mOhm assuming the gain is 40.

Lower the blank time to 0x32. As long as you do not have a fault the device will continue to drive current to reach the desired level.

Increase your TOFF time to 0x3C for a 30us off time. Your blank time is longer than your off time, which can lead to undesired operation.

The DRV8711 and similar devices control the current through the stepper motor. The voltage waveform is not intended to be a pure sine wave. The current through the winding is intended to closely match a sine wave.

1768.Step_Motor_Controller.pdf

Hi Rick !

Thanks for your reply.

The stepper motor works fine with EVM. But when i use same configuration with my custom board, the motor doesn't rotates normally and makes noise. I suspect the hardware configuration of my custom board. Although, i made my custom board pretty similar to EVM. I have attached PCB schematics of my custom board. please help me to figure the problem asap.

Hi Haroon,

It does appear your custom board is causing the problem. The best approach to determining the problem is to begin with the no load and compare the inputs and outputs of the your board with the EVM.

While you are doing the comparison, please send the layout with more detail. It is difficult to determine the locations of the FETs, resistors, and traces on the back side of the board.

Thanks for your reply. 

PCB layout has been attached as requested. 

please suggest solution to fix the issue (hardware Bug). 

Hi Haroon,

I will evaluate the board, but in my opinion you will find any issues sooner than me. You have the ability to perform a comparison between the boards by monitoring the behavior.

Please compare the operation of the boards also.

Hi Haroon,

I did not see anything that would cause a problem on your board. Have you found anything by comparing the operation of the boards?