HELP: Cutting VIN from VUSB killed brand new Teensy 4.0

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nickreulbach

Member
As stated from the title, I cut the VIN from the VUSB and now the Teensy is completely dead. Before the cut, I tested the USB and was able to upload and execute code. Now the light does not turn on. I have tried supplying both the 3.3V and 5V to no success. I even verified the voltages with my multmeter. Nothing. What do I do? This was a brand new Teensy 4.0.
 
I soldered the VIN back to the VUSB and it works again. Can someone help me uderstand how to upload code while powering the teensy externally??
 
How forcefully deep was the cut between the pads made?
Noted in a thread some time back there was one PCB lay that had some other trace down a layer IIRC.
 
Not very deep, I used a small razor blade. Additionally I can not seem to power a teensy externally with 5V whatsoever. Maybe I am misunderstanding something here but why can I not? Verified again with multimeter. I have read everywhere I can about this but something just is not working
 
I was able to power the Teensy off of my 100A Hobbywing ESC 5V controls that is connected to a 22.2V battery but a 3.3V, 5V, and 6V(with a resistor voltage divider) all do not work independently. Is there a reason to explain this?


Additionally, extra help on how to best cut the VIN and VUSB would be greatly appreciated. Thank you!
 
nickreulbach said:
Verified again with multimeter
Click to expand...

Please remember we can't see how you're connecting your multimeter or even the voltage is showed. We can better help if you show us and let us actually see what you're testing, rather than simply telling us you did the test and your conclusion was it looked ok to you. We can't see anything that way.

For a specific test, with 5V power supplied to the VIN pin and GND pin, please measure the voltage between 3.3V and GND. The idea is to check whether the 3.3V regulator is turning on and working properly to create the 3.3V power from your 5V input.

For more background info about how the power works, check the T4 bootloader page and scroll down to Power Up Sequence. Together with the map of test points on the Teensy 4.0 page, maybe this can give you ideas of other places to measure.

Again, if you want better help here, please try to show us what you actually measured. Over and over on this forum we've had problems that turned out to be just a misunderstanding... and if you just give us your opinion without letting us see what really happened there no way we can help if the problem is related to how you're connecting the wires or doing the measurements.
 
nickreulbach said:
The pin after the 5V and GND?
Click to expand...

PaulStoffregen said:
Please remember we can't see how you're connecting your multimeter or even the voltage is showed. We can better help if you show us and let us actually see what you're testing, rather than simply telling us you did the test and your conclusion was it looked ok to you. We can't see anything that way.

For a specific test, with 5V power supplied to the VIN pin and GND pin, please measure the voltage between 3.3V and GND. The idea is to check whether the 3.3V regulator is turning on and working properly to create the 3.3V power from your 5V input.

For more background info about how the power works, check the T4 bootloader page and scroll down to Power Up Sequence. Together with the map of test points on the Teensy 4.0 page, maybe this can give you ideas of other places to measure.

Again, if you want better help here, please try to show us what you actually measured. Over and over on this forum we've had problems that turned out to be just a misunderstanding... and if you just give us your opinion without letting us see what really happened there no way we can help if the problem is related to how you're connecting the wires or doing the measurements.
Click to expand...
Thank you for the thorough response! I will try and get some photos after my classes. I’m a senior in MechE and electrical has always been a weaker subject of mine so I appreciate all the help I can get!

In the meantime, I would like to ask a question about how to best power the teensy externally for my application. I am building an RC plane and using the teensy as a flight controller. It will be attached to an ESC (controlling the main motor), multiple servos for the flight control surfaces, radio receiver, and sensors to calibrate the teensy as a flight controller.

The ESC/main motor is powered by a 22.2V battery while the control surfaces are powered by a separate 6V battery. The ESC releases 5V on its control pin and can power the Teensy but I was hoping to power it via the 6V battery in the hopes to maintain radio/flight control incase of power loss to the main motor.

Would you recommend the 6V power system or to stay with the 5V ESC control pins.

I additionally attached two photos (captured from video sorry for any quality issue) of previous servo motor control tests with the 6V battery and the teensy being powered by the usb and only sending signals to the motors. Is that circuit possible with just the 6V and no usb?
 

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Those photos don't really help much. Can you just wire it up powered by external 5V as described as not working in the first post and take a picture?

It sounds like the easiest way to power it would be taking the 6V from the battery through a basic power diode (e.g. 1N4004) to drop the voltage to around 5.3V, which would then be safe to feed to the Teensy's 5V VIN.
 
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Besides the possible wiring issue, also keep in mind that the maximum voltage on the VIN pin is 5.5V. You cannot directly connect 6V. If you want to use the 6V battery, connect a silicon diode in series between the 6V battery and the VIN pin to drop it down to a safe level.
 
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