When you turn on the 3V3 power cable from the JetBot driver motor, the display turns off - why?

Hi all,
I assembled my own set of a jet bot, everything was done according to the instructions posted on the website www.jetbot.org.
But I have a problem that I cannot solve for over a month. What can I do with a council for help?
When I plug in the 3V3 power cable from the JetBot driver motor, the display goes blank - why?
Can’t figure out if the motor driver is connected correctly. I am using two types of USB cable for testing, but the display goes blank anyway. I bought a second display, but the problem persists. When I turn on everything in order, everything works, but as soon as I turn on the red wire from the motor driver, the display goes out.
Tell me what to do
Below I list all the technical characteristics:

  1. Power bank
  2. MD adafruit
  3. Сonnection
  4. Video of connecting the red cable 3V3 - before that everything was checked twice, everything is connected correctly.

Hi @sashabilokon82 ,

I just thought the power part about your subject. You energize the motor driver from 3.3V which is coming from Jetson module. The little voltage fluctation might be cause to get blank your display. Do you have a chance to use 3.3v voltage regulator for your display? You may get 5V input from Jetson module as input for voltage regulator and the output of 3.3V should be used for your display.

You can use regulator module like below.

I dont know if it works but I hope you solve this problem.


Thank you very much for your advice, I will definitely try it after buying a stabilizer. I would like to correct the original wiring diagram. And in the original circuit there is no voltage stabilizer. Also on the forum I saw an advice that you need to replace the USB cable with a more expensive and better quality one, since in a cheap cable the resistance of the conductor leads to a decrease in the voltage in the circuit and the display goes out.
I also discovered one more feature if the motor driver is not connected to the power bank and I connect the wires from the Jetson nano to the motor driver, then the system turns off after connecting the ground.

Hi sashabilokon82,

Would you tell me what would happen if you connect everything before powering it on?
Generally, we want to avoid live connecting circuits.

Also, do you think you can make sure the motor driver’s VM pin (the terminal block pin marked with + sign) is getting 5V from the USB power bank?

I have the following connection algorithm:

  1. I am connecting ground (GND) and power (3V3) wires (Jetson with motor drive).
  2. Connect data wires (SDA & SCL) to Jetson and engine driver.
  3. I am connecting power from the motor driver to
    power bank, and the diode on the driver motor lights up

    And my last step, I connect the power from the power bank to the Jetson and the diode on the Jetson lights up


As for whether it gets 5 volts from the powerbank to the driver’s motor board, I’m not sure. I thought about it that I need to check it and I can do it in a few days.

I just checked the voltage output from the power bank and my tester showed 2.4V
And also if I do it through an adapter (DC 5V = 3A) from a 220 V network. then my tester shows 5V output voltage.
But my bank, according to its characteristics, should also give out this voltage, I don’t understand why?

Thank you, you prompted me and inspired me to carefully check the output voltage from the power bank and it turned out to be 2.4V. (I don’t know why this happens if the manufacturer declares the output voltage higher.)
After that I checked the whole circuit, but applied 5V and it worked.
But after that I tried to run the basic motion program and got the error on the second line

Do you know why this is happening?

Now the issue you are currently facing looks like the issue related to the I2C communication.
I’d suggest checking the I2C pin wire connections (orange and yellow in your case).
Is the OLED display working?

As to the powerbank issue where you measured 2.4V;
I think this is one unfavorable spec of certain powerbank, that is some powerbank shuts down when not much current is being pulled by a device.
This comes to be a problem when the device only consumes very little current when stand-by.
Some powerbank implements an additional mode called “wireless headphone charging mode” that is to disable the auto-shutdown feature.
You may want to check if your powerbank has such feature.

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