The Teensy main control was burned out after the circuit board was connected to a 22V power supply (a 6S lithium - ion battery).

Question

After I connected a 6S RC aircraft battery power supply (with a voltage of approximately 23V) to the circuit board, the Teensy 4.1 control board suddenly burned out, but the Arduino Nano remained undamaged.

Before installing the Teensy 4.1 and Nano on the expansion circuit board, I connected the same 6S battery to the expansion board and tested the voltages of the pins where the Teensy and Nano would be mounted. Among these pins, the voltages of the 5V power supply pins of both the Teensy and Nano relative to ground were normal, while the other pins had no voltage relative to ground—either zero or a very small voltage relative to ground. As far as I can remember, this should be normal.

Furthermore, after installing the Teensy and Nano on the expansion board for the first time, I also tested with the same battery and uploaded a simple verification program, and everything worked normally at that time.

However, during the most recent power-on (using the same 6S battery, with a voltage of approximately 23V), the Teensy was directly burned out. The symptom was that a resistor on the Teensy heated up abnormally, and the output voltage of the 3.3V pin was less than 1V. Strangely, the Arduino Nano still worked even when the Teensy was burned out. I think the 5V pins of the Nano and the Teensy are connected in series, right?

I really can't figure out what's going on—could it be that the voltage fluctuation when plugging or unplugging the power supply burned out the Teensy? I hope you can provide some suggestions. Additionally, if I buy another Teensy to install on the expansion board, what methods can be used to prevent similar incidents from happening again?

 · Answer

One of our current hypotheses is that the Teensy is too fragile, so voltage fluctuations easily burn out the 5V-to-3.3V voltage regulator module inside the Teensy board.

This incident has caused us significant losses. A solution we have now thought of is to use a low-voltage battery to power the PCB board, and a separate higher-voltage battery to power the motor.

I would like to know if this solution is feasible.

Besides this solution, could you please provide me with some more suggestions in this regard?

 · Answer

After consideration, we tend to believe that the Teensy is too fragile, so it may not be able to withstand the voltage fluctuations caused by plugging and unplugging the power supply.

Because when I used the same 6S battery (approximately 23V) to power another identical expansion board (without Nano and Teensy installed), the measured voltage of the 5V pins that supply power to Nano and Teensy remained stable at 5.1V (all other pins had no voltage). This phenomenon should be normal.

In addition, I want to know that under the scheme of using a low-voltage battery to power the PCB board and a higher-voltage battery to power the motor separately, will the voltage of the 5V pins on the expansion board that supply power to Teensy and Nano also fluctuate due to the start and stop of the motor, thereby damaging these two microcontrollers?

We do not have the conditions to measure such voltage fluctuations here. It would be great if you could help verify these ideas!

We sincerely look forward to your reply!

Shanpu Fang · Answer

@wuyang

Thanks for reaching out. According to the datasheet that comes with Teensy, the Vin pin on the Teensy can take up to 5.5 V. First, could you verify that the Teensy is plugged into the PCB in the designed orientation? We’ve seen both Teensy and Nano overheat when inserted incorrectly. I’d also check for any potential short circuits on the PCB caused by manufacturing or assembly issues, especially around the Teensy/Nano pin sockets.

Could you verify those two items and share an update?

Regarding powering the PCB with two separate power supplies, this should work as long as you remove the DC-DC converter and connect the GND and VIN pins to the low-voltage supply. Capacitor C16 and the Teensy’s onboard capacitor should provide sufficient filtering for power supply fluctuations.