DRV8307: Motor runs faster in one direction than the other

Larry Knight

Part Number: DRV8307
Other Parts Discussed in Thread: DRV8308EVM

I've seen this problem previously but there wasn't an exact cause or solution given.

What could cause this? Could the motor's hall sensors be misaligned from the factory?

Thanx!

over 2 years ago

0 Aaron Barrera over 2 years ago

TI__Mastermind 26046 points

Hi Larry,

This is possible. If the voltage and duty cycle is consistent in both directions, then it either could be hall sensor misalignment or poor Hall sensor feedback as shown in this post: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/590702/drv8307-drv8307-to-change-direction-the-motor-speed-is-different

Suggestions:

1) Can you analyze the Hall signals to see if they're 60 degrees apart for each state, clean, and has defined rising/falling edges?

2) Can you try with a different motor to see if the issue still occurs? If it goes away, then I believe it is Hall sensor misalignment.

Thanks,
Aaron

0 Larry Knight over 2 years ago

Prodigy 10 points

Here are some wavefroms. CH1 - U, CH2 - V, CH3 - W. The scope probes were set at x10.

This is where the motor runs normally. DIR = 1, CW.
normal

This is where the motor runs slower. DIR = 0, CCW.

Here is the PWM during all tests.

And these are the hall sensor waveforms.

Looks like I'm getting some noise on the hall sensor pins, I'll clean that up and see if it helps.

hall noise.mp4

0 Aaron Barrera over 2 years ago in reply to Larry Knight

TI__Mastermind 26046 points

Hi Larry,

Looks the Hall inputs are not symmetrical, so there could be Hall sensor misalignment causing the slower motor performance in one direction.

Thanks,
Aaron

0 Larry Knight over 2 years ago in reply to Aaron Barrera

Prodigy 10 points

That's very interesting. The motor is a good brand motor made by Trinamic. I opened the motor and there is no real adjustment. I will send an email to the company and see what they say. I'll eventually need more motors so I'll order another and see what happens. I'll keep you posted.

Thanx!

+1 Aaron Barrera over 2 years ago in reply to Larry Knight

TI__Mastermind 26046 points

Hi Larry,

Sure thing. If you have any other BLDC motors with integrated Hall sensors, please try these as well. The DRV8308EVM includes a Telco 24-V BLDC motor we use commonly in the lab, these EVM kits should be in stock in a few weeks with motors.

Thanks,
Aaron

0 Larry Knight over 2 years ago in reply to Aaron Barrera

Prodigy 10 points

OK! I haven't heard in from Trinamic yet but I got in a different motor today. It's a BEI 12V motor and it runs fine in both directions. The HALLOUT is about 114 Hz in both directions. So that pretty much wraps it up. If there is any new info I'll post it here.

Thanx!

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DRV8307: Motor runs faster in one direction than the other