LMD18200 for stepper motor drive

KARTHIK R36

Other Parts Discussed in Thread: LMD18200, DRV8829EVM, DRV8829

Hi,

I m using LMD18200 for stepper motor chopper mode drive. I m using PWM control with fixed off time control.

My input voltage to chip is set at 12V, my motor R-4ohm, L-8mH. Motor coil current is 1.25A.
I m facing some issues during driving.

1) I tried to give the direction pulse at 500Hz.

2) I m seeing that the time taken for the coil current to rise is about 3msec.

3) The motor rotation is not continous.

I had implemented the ckt in general purpose PCB. Is ground noise during H bridge working an issue? My PWM off time is given as 100usec. If you require I m ready to send the oscilloscope plots also.

Let me know anyone using this chip for stepper motor drive.

Please help to correct the same.

Regards

Karthik.R

over 8 years ago

0 Wilson Zuo over 8 years ago

TI__Mastermind 26065 points

Hi Karthik.R

We will check this and get back to you later.

Best regards,

0 Rick Duncan over 8 years ago in reply to Wilson Zuo

TI__Guru** 114905 points

Hi Karthik,

What is the BRAKE setting? Depending on the setting, your average current may be much less than desired. Most stepper motor drivers use an off time of 30us or less. Reducing the off time may help.

Please provide scope plots of the current in the windings if possible.

If you are new to steppers, the DRV8829EVM provides a platform to evaluate stepper operation. The DRV8829 has similar current specs, but lower voltage ratings.

There are other DRV8xxx devices that require a simple step and direction input. These devices reduce the load on the mcu. If interested, please click ( LINK )

0 KARTHIK R36 over 8 years ago in reply to Rick Duncan

Prodigy 40 points

The brake pin is grounded. I hope the off time you asked is the off time given for freewheeling ( when pwm signal I low). I had given 10us as off time for freewheeling. I can't use any other chip. I want to use only this chip.
I will send you the current plot and also the ckt which I wired and tested.
Thanks for your reply.

Regards,
Karthik

0 Rick Duncan over 8 years ago in reply to KARTHIK R36

TI__Guru** 114905 points

Hi Karthik,

Our expert on this device has been notified and should reply soon. Please send the current plot and ckt.

0 KARTHIK R36 over 8 years ago in reply to Rick Duncan

Prodigy 40 points

CURRENT PLOT AND CIRCUIT IS ATTACHED,PLS GO THROUGH IT AND GIVE ME A FEEDBACK

0 KARTHIK R36 over 8 years ago in reply to Rick Duncan

Prodigy 40 points

Dear Rick, hope u had seen the current plots and ckt. Hope u r working on that to give a solution to my problem.

0 Mathew Jacob1 over 8 years ago in reply to KARTHIK R36

TI__Expert 5900 points

Karthik,
The LMD18200 is designed for DC brushed servo and it looks like your application is a DC stepper motor. Does not mean its a problem but you need to verify if the response time meets your need. Please check pin 1 to make sure the bootstrap voltage is not dropping. If you have a current probe it would be ideal to check the current in the phase to see if it is rising faster than the 3ms.
Regards,Mathew

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LMD18200 for stepper motor drive