I’ve been using the DVR8835 motor driver in IN/IN mode to drive two 6V micro metal DC motors and stopped getting a useful output at output pins yesterday. The connections are:
GND->GND
VCC->5V
VIN->6V
AIN1->PWM1 Signal (Pico GPIO0, 90% duty cycle, 3 V measured at AIN1 pin)
AIN2->PWM2 Signal (Pico GPIO1, 0% duty cycle, ~0 V measured at AIN2 pin)
BIN1->PWM3 Signal (Pico GPIO2, 90% duty cycle, 3 V measured at BIN1 pin)
BIN2->PWM4 Signal (Pico GPIO3, 0% duty cycle, ~0 V measured at BIN2 pin)
AOUT1/2->Motor 1
BOUT1/2->Motor 2
Mode->GND
VMM->Disconnected
The voltage measured at the output pins oscillates from 1.2 V to 100 mV with 0 V voltage difference measured across BOUT1/2 and AOUT1/2. The voltage measured at the VMM pin is 6 V as expected. The GNDs of the pico, battery pack, and driver are connected. Is there anything I’m missing with my setup or did I fry the board?
Your connections sound okay. It sounds like you are using a Raspberry Pi Pico to control your board with 3.3V logic, so it might be better practice to power VCC with 3.3V instead of 5V, but I still expect it to work the way you have it.
How long had the driver been working for before you ran into the current issue, and what was it doing when the issue appeared? Can you post some pictures that show all of your connections along more details about the setup including what specific batteries and motors you are using?
I first set up the board on Thursday October 24th and was successfully driving two micro metal motors until that Sunday when I moved the circuit around to integrate it into the body of the RC car I’m building. It’s definitely possible I miswired something during that time. I have tried powering VCC with the 3.3 V output of the pico without any luck.
The batteries are 4 rechargeable NIMH AA batteries wired in series with an output voltage of approximately 5 V as shown below. The protoboard is from another project and is used as a simple way to connect the battery pack to the breadboard. The voltage shown on the multimeter is measured across the battery pack input and ground (red and blue wires which are connected to breadboard).
The breadboard circuit is shown below. For testing purposes, I only have one motor connected, which is connected to AOUT1 and AOUT2. VMM and MODE have been left disconnected. The 6V input voltage to motor driver pin VIN is provided from Step-Up/Step-Down Voltage Regulator S7V8A. The voltages were rechecked right before posting and are correct to the schematic below.
The motor was also checked by connecting one wire to the 6 V output of the regulator and the other to GND, it ran as expected. The voltages measured at the pins of the motor driver are:
The voltage at the output pins did fluctuate so while there is a difference between the values shown above, when measuring across the two pins of the motor, there is no voltage across.
Just a couple more things to check. Which specific Micro Metal Gearmotors are you using, and have you tried checking the voltage across the output pins if the motors are disconnected? Also, if you have not done so already, could you try moving your DRV8835 to a different location in your breadboard in case one of the rails it’s currently placed in is damaged?
Thanks for checking that. Unfortunately, it does seem like the driver has been damaged somehow. If you email us with your order information, we can help you out with a replacement.
