Teensy 4.1 not recognized after connecting IR sensor and relay

Dante Jared

New member
Hi everyone,

I'm a university student from Mexico working on a sumo robot project using a Teensy 4.1. It was working perfectly, until I connected a Sharp IR sensor (GP2Y0A21YK0F) and a 5V relay (JQC-3FF-S-Z) to the Teensy’s 5V and GND. The yellow signal wire from the IR sensor was connected to pin 14.

After powering everything up, the red LED on the Teensy started blinking a few times and then turned off. Since then:

- The Teensy is no longer recognized as a USB device by my computer (Windows 11).
- The red LED sometimes turns on briefly when I connect it, but the Arduino IDE never detects it.
- I used a multimeter to test F1 and L2 — both show continuity (~0 ohms).
- I tried Zadig and Teensy Loader. The Loader detects `VID:2808 PID:0106`, so I believe the bootloader is still working.
- I tried pressing and holding the button on the Teensy before connecting it to USB (for forced bootloader mode).
- The Teensy Loader opens and loads the .hex file, but the "Program" button never becomes active.
- No COM port appears in Device Manager, and I can't upload new sketches from Arduino.

I suspect the USB peripheral of the MCU may have been damaged, possibly due to inductive kickback from the relay (I didn’t use a protection diode, sadly).

Is there any way I can recover it? Or could I get a replacement or repair option?

Thank you so much in advance.

— Dante Cruz
 
I believe anything over 4V can immediately destroy it. Think of it as a 1.8V processor with 3.3V tolerant inputs...
 
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