DRV11873EVM External PWM interface

Mike,

Yes, you can send an external PWM signal to the DRV11873EVM PWM input to set the motor speed. Please note sections 2.2 and 2.4 of the EVM document. These sections describe how to disconnect the on board PWM circuit and connect an external PWM. The recommended maximum voltage for the PWM input in the datasheet is 5.5V. Please do not exceed this.

Controlling the DRV8313EVM with an external PWM signal is more difficult. To do so requires a combination of an external PWM input and firmware to determine the duty cycle of the PWM input added to the existing code on the EVM.

I take it that on the DRV8313EVM the external PWM signal is then going through the onboard processor which then coverts this to its output PWM signal to the motor controller?

Has this been already done, is there example code available with the process to update the code on the evm?

You are correct. The external PWM signal will be converted to a duty cycle measured by the onboard processor. Once the PWM input duty cycle is calculated, then the processor will drive the DRV8313 inputs using this value.

This has not been done before, and there is no example code.  A quick check of the MSP430 forum for duty cycle yielded the following post:

http://e2e.ti.com/support/microcontrollers/msp430/f/166/t/193425.aspx

I got a 11873 EVM and out of the box tried to drive a Robbe ROXXY BL-Outrunner 2827-35 BLDC motor, http://www.robbe.de/roxxy-bl-outrunner-2827-26.html#, and it doesn't drive the motor at all. It spins a bit on power up and then periodically every so often (even with speed control all the way counterclockwise, which is odd). Speed control has no effect on motor or spinning the shaft at different speeds, it doesn't matter if I have it all clockwise or counter clockwise, doesn't spin except every so often it perks up and spins about twice.

I have 12VDC going to board with current clamped at 3A. Power LED is lit green and voltage on power supply isn't being pulled down, i.e. not seeing any current limiting.

MOTA signal going to blue wire of motor

MOTB signal going to grey wire of motor

MOTC signal going to black wire of motor

COM signal is floating, i.e. motor only has three wires coming from it

I have another type of motor control board, the one I want to replace with TI part, and have it wired the same way and it drives the motor

Am I overlooking something here?  Am I using wrong type of motor with board?

Mke,

COM input needs to be created for motor with delta winding or star configuration without neutral. Refer to attached pdf document. Besides this, please make sure all jumper connections as per DRV11873 EVM userguide available at Ti website.

4174.Creating_COM_DRV11873.pdf

Best Regards

Milan

Ok, that helped, noticed a few things the manual says that the to lower motor speed to turn potentiometer counterclockwise, but if I'm looking at the board with the silkscreen text oriented in a normal reading orientation, have to turn the dial clockwise to lower and counterclockwise to speed up. Also at the lowest dial position the motor still spins.

With that being said, I mistakenly got the wrong driver for the motor, the driver is rated at 2A and the motor is rated at 10A. Do you have a motor driver that has an EVM that I can use to test out design?

Also I ordered multiple EVMs, but have no need for them now, how can I return them.

Mike,

You can choose either DRV8301 (http://www.ti.com/tool/drv8301-hc-c2-kit) or DRV8302 (http://www.ti.com/tool/drv8302-hc-c2-kit) based EVM, both of them will meet 10A reqruirements.

Regarding returing of EVMs, I would need to check with respective business unit.

Best Regards

Milan

Mike,

You can contact the support center at the numbers listed in the email below for returns.

http://www.ti.com/general/docs/contact.tsp