DRV8871 only outputting 0.24 A. Could it be defective?

[blazerman345]

Hey everyone. I am using a DRV8871 motor driver to power a motor with a Raspberry PI.

The motor is DYNS1210:
https://www.hobbytown.com/tazer-380-mot ... 10/p268235

The motor specs are not listed on the website, but I called the manufacturer and they said it requires 6V minimum.
When I connect the motor directly to my 7V power source, it pulls about 2.5 A of current.

However,when I use my raspberry PI + DRV8871 to power it, I only get 0.24 A and it doesn't run. I checked the voltage between the two motor leads and it displays 6.95V, which is more than enough for the motor.

[blazerman345]

If you would like more pictures, please let me know.

[adafruit_support_mike]

I see some exposed gold on the PCB's solder pads, and that usually means the solder joint isn't making good electrical contact.

Take a look at our soldering tutorial and redo the joints to get a nice, smooth sweep from the pad up to each pin:

https://learn.adafruit.com/adafruit-gui ... -soldering

[blazerman345]

I re-soldered the connections and made sure no gold was showing. The solder connections aren't 100% perfect, but I tested them with a multi-meter and they all work properly.

[blazerman345]

The reason I believe the part is defective is because although I'm getting a full 7V across the output terminals, the amp output is extremely low. The DRV outputted 0.24A even after I fixed the solder connections, which implies something is wrong with the internals of the chip.

[adafruit_support_mike]

The DRV2605's absolute maximum supply voltage is 5.5v. Anything higher than that will probably damage the chip.

[blazerman345]

This is for the DRV8871, not DRV2605. The datasheet says the maximum voltage is 45V and the min is 6.5V.

[adafruit_support_mike]

Sorry.. grabbed the wrong datasheet.

Just to confirm, when you connect the motor directly to the power supply, are you using the same wiring shown going into the breakout's terminal blocks above? If so, that eliminates a lot of potential unknowns.

[blazerman345]

Oh, when I said "connect the motor directly to the power supply", I meant I literally connected the positive side of the power supply to one lead on the motor, and the negative side to the other lead on the motor.

I did not use the breakout board when connecting the motor directly to power and testing current.

I am a little confused. Is it possible to connect the motor directly using the terminal blocks? Current will not flow through the circuit unless a signal is sent to in1 or in2. Right?

[blazerman345]

Ahh I just reread your comment, and I understand what you mean. I will test the current with that wiring and report back with the results.

Sorry bout that.

[blazerman345]

I tested it through a breadboard, using the same wires. The motor ran perfectly at 2-2.3A. So the wiring seems to be fine.

[adafruit_support_mike]

That's exactly what I was looking for.. thank you.

Send a note containing a link to this thread and your order number to [email protected]. The folks there will get you a replacement DRV8871 breakout.


(#3190)

[blazerman345]

I ordered a new DRV8871 and wired it up again. This time I made sure the solder connections were perfect, and I tested it on a breadboard.

With an 8V power source it pulled 0.3 A. I added two batteries in series, and with a 11V power source it pulled ~0.38A. I suspected that the motor driver simply could not output 2A current with only 8-11V. My guess is the driver is stealing some of the voltage from the power source to operate.

SO I wired two DRV's in parallel with 11V, and it outputted 0.67 A of current. I might just buy two more DRVs and hook them all up in parallel.

[adafruit_support_mike]

I'm not sure what's going wrong there.. the DRV8871 should be able to transfer 2A to a load without any problems.

What voltage do you see on the breakout's IN1 and IN2 pins when the output is 200mA to 300mA?

[blazerman345]

Sorry for the late reply.

The voltage between the pins is 5.04V. I measured the voltage between the breakout pins as well as the two pins directly on the DRV8871 (same result). Interestingly the motor driver is pulling 1.03A. This is probably because the battery is fully charged.