U4 Chip gets extremely hot when 4.1 is connected to power.

J

jrod305

Member
So I left the minilab past Friday in a rush for a weekend trip, left the teensy in the breadboard with a wire connected from GND to GND rail on breadboard, and a loose PWM wire on pin 8 that was connected to a motor , no power being supplied whatsoever.

I get back today and supply power, how I usually do it , USB from laptop and I notice there was no reaction and laptop does not recognize the board. I notice heat radiating from the usb port and I was able to pin it down to the U4 chip.

I initially did a really bad solder job and thought I killed it but after a clean and re-solder she was fine .

I am getting 4.82V when I touch the GND and 5V pin, I get no reading when a GND and a 3.3V are touched, I’ve never diagnosed a microcontroller so I honestly have very little idea what I am doing.

Any advice is greatly appreciated I am already ordering another one but would very much like to know if this is salvageable and what could have possible happened while I was away for the weekend that caused this. I’ve read on humidity being a factor, the space I keep it in is pretty much an unventilated storage shed with no moisture, heat creeps in through the windows that’s about it.

Please let me know if any other information is needed .
 

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Connecting a motor direct to pin 8 of the Teensy? That doesn't sound safe, back EMF, burn out the pin through overcurrent, ESD through handling the motor - several ways this could be bad news.
 
MarkT said:
Connecting a motor direct to pin 8 of the Teensy? That doesn't sound safe, back EMF, burn out the pin through overcurrent, ESD through handling the motor - several ways this could be bad news.
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Thanks for reply, I was under the assumption pins 0-12 are PWM pins able to receive PWM signals , thus I connected PWM wire of servo motor to it . I’ve always used those pins, even to operate 4 servos at a time. I left only the servo PWM pin connected to pin 8 via breadboard, ground and power from servo were not connected. Is it possible to get further clarity as to how a PWM cable from a servo motor to pin 8 and a GND going from GND pin to GND rail on breadboard was able to fry a chip? Not looking to fry another one even though I know it is inevitable I will due to my inexperience.
 
jrod305 said:
Is it possible to get further clarity as to how a PWM cable from a servo motor to pin 8 and a GND going from GND pin to GND rail on breadboard was able to fry a chip?
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Unfortunately, no. Nobody can really give a clear definitive answer about what happened, or even might have happened.

First, we just don't know enough. We can't see what type of motor you're using. Maybe it's something very small like on this Servo Library page? Or maybe it's something much larger. How that motor gets power is also unwable. Your words only describe GND and pin 8, but no motor could possibly work from only the digital signal. Some other connection for power must be in play. We can't even see how the wires were really connected.

Even if we could see everything, the answer may be elusive. Often when a Teensy gets destroyed, it's due to something unintentionally going wrong. Often when projects have 12V power, just a brief moment where any wire from Teensy accidentally brushes against live 12V power instantly kills the main chip. Obviously nothing about the intended wiring would do that. It's often an unintentionally mishap that damages hardware.

I really wish I had a better answer for you, but from only the words you've written, the true cause of the problem is unknowable.
 
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