5 years, 3 months ago.

Nucleo board failed when hooked up to BLDC motor and ESC

May someone shed light on how this circuit that I wired up shorted the Nucleo board? No smoke, fire, or visual signs of brownout, but the board was very hot to the touch. I'm disappointed that I may have fried the MCU or I/O pin and would like to prevent the same mistake in the future.

My understanding is that the board can be externally powered by Vin with voltages between 7-12V. I used a 7.4V lipo to power the board no problem. I proceeded to hook up a BLDC motor to the board with a 12A ESC. With the 3-wire connector, I grounded the brown wire, wired signal (orange) to pin PWM/09, and left the +5V BEC (red) unconnected. Instead of a separate power supply for the ESC, I thought that I can share battery power used to power the board by connecting the ESC power (red) to the Morpho connector and ground (black) it as shown in the image /media/uploads/hh0916/esc_wiring_diagram.pdf. I understand that Vin goes through an onboard voltage regulator so I'm thinking the ESC and PWM/09 cannot be overvoltaged beyond 5V to harm the MCU. Perhaps I am mistaken here?

With the battery plugged in, the motor only beeped to indicate it was powered. No signs of distress then. After manipulation of codes to send pulses, the motor actually initialized and ran for a short 2 second or so before I unplugged the battery. Second time, the motor spun up and ran for much longer before the LED lights on the board started blinking and dimming and the motor just plain stopped. Not sure what I had done wrong. Board was hot and software will no longer talk to board anymore. From what you can see, where have my logic failed?

1 Answer

5 years, 2 months ago.

Well, your problem is that you're putting the board tracks (Vin and gnd) on the way of the motor circuit. You have to do the opposite of what you are doing right now.

What you are doing right now? Connecting the battery to the board and connecting the motor to the board

What you should do is connect the battery to the motor, and then get some additional wires (Vin and ground) from the battery to power the board, in this way you will take your board out of the motor circuit.

Another thing you have to remember with the Nucleos, is to move the JP5 pin to position 1 and 2 to be able to use Vin.

Hope that helps.

Accepted Answer

Thank you for the reply. Yes, I connected the battery to the board using Vin for it to standalone and then connected the motor to the board using the same Vin power supply. It did not occur to me that current drawn to the motor through the board could fry the trace on the board. Lesson learned. How could I wire it differently to supply power to both the board and the motor without powering the motor first? I would like to eventually power multiple motors/servos using the one battery. Someone suggested I wire the battery in parallel?

posted by Heather Holmes 18 Jun 2016

Yes, you have to connect all the components in parallel with the battery, so they won't affect each other. If you want to control the power on/off of the ESCs you can put a switch that controls that section of the parallel connections.

posted by Gabriel Rivas 19 Jun 2016