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DC & Stepper Motor HAT has been burned
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DC & Stepper Motor HAT has been burned

by n_akikan55 on Tue Jan 14, 2020 1:33 pm

Hi,
I purchased the product of "Adafruit DC & Stepper Motor HAT for Raspberry
Pi-Mini Kit", but the motor driver was burned out.

So I have a few questions.

There is " Can run motors on 4.5VDC to 13.5VDC " on the homepage.
Is it possible to operate a 3V DC motor?
If so, are there any precautions?
(I used a 12V5A power supply for a 3V DC motor, which led to this failure.
When "motorkit_dc_test.py" was executed, the power light blinked and the motor driver burned out.
https://github.com/adafruit/Adafruit_Ci ... r/examples
)

Is it possible to use a 12V DC motor and a 3V DC motor together?

Thank you for your response.
Attachments
burned.png
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n_akikan55
 
Posts: 3
Joined: Tue Jan 14, 2020 6:32 am

Re: DC & Stepper Motor HAT has been burned

by adafruit_support_bill on Tue Jan 14, 2020 1:42 pm

Is it possible to operate a 3V DC motor?

The TB6612 drivers on the board have a low-voltage cutoff of 4.5v. So it is not possible to power a 3v motor at its rated voltage.
I used a 12V5A power supply for a 3V DC motor, which led to this failure.

If you power a motor with 4 times the rated voltage, it will draw about 4 times it's rated current. If that exceeds the current rating of the HAT (1.2A), it can burn out the chips. If the chips survive, you would likely burn out the motor fairly quickly.

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Re: DC & Stepper Motor HAT has been burned

by n_akikan55 on Tue Jan 14, 2020 2:05 pm

Thank you.
If you use a 3V DC motor, use a different driver.

I have one more question.
When using a 6V DC motor and a 12V DC motor, is it safe to use a 12V power supply?

n_akikan55
 
Posts: 3
Joined: Tue Jan 14, 2020 6:32 am

Re: DC & Stepper Motor HAT has been burned

by adafruit_support_bill on Tue Jan 14, 2020 5:12 pm

Most DC motors can tolerate some overvoltage. But it does cause them to draw more current and run hotter. This will shorten the usable life of the motor. At 2x the rated voltage, the motor will draw 2x the current and get quite hot. However, you can control the average voltage via the HAT. Running a 6v motor with a 12v supply should be OK if you keep the throttle setting for the motor below 50%.

The other thing to consider consider is the motor current rating:

Most motors will have a "No-Load Current" rating - which is mostly meaningless - since there is no point to having a motor if it is not going to do any work.

The motor should also have a "Stall Current" rating. This is the maximum current the motor will draw at the rated voltage (at higher voltages it will be proportionally higher). This represents the worst case where the motor is too overloaded to move.

The maximum efficiency point of the motor will typically be somewhere around 50%-75% of the stall current.

For use with the HAT, try to choose a motor with a stall current of 1.2A or less. If you expect frequent stall conditions, you may want to consider a more advanced driver with current limiting - such as the DRV8871. https://www.adafruit.com/product/3190

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Re: DC & Stepper Motor HAT has been burned

by n_akikan55 on Wed Jan 15, 2020 1:23 am

It was very helpful.
Thank you!

n_akikan55
 
Posts: 3
Joined: Tue Jan 14, 2020 6:32 am

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