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Thread: Teensy 4.0 very hot and died.

  1. #1
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    Teensy 4.0 very hot and died.

    Dear Forum,

    iīve got an hardware problem with my project. I am currently working on an automatically drum tuning device. At first i used an Arduino Mega, but because of itīs size and less storage i switched to a Teensy 4.0. It worked all quite fine, but then i noticed that the controller is very hot (55-60°C). I was wondering if this is new or if the controller has been this hot all along. I figured I probably would have noticed since it had been running for two weeks at that point. Click image for larger version. 

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ID:	28496I checked the wiring but found nothing. Now the controller seems to be burned out. However, this does not smell burnt. I have put a diagram of the wiring here in the attachment.

    Basically I have a 12 volt power supply and a step down module that feeds 5 volts to the Teensy. I also measured these values with a multimeter. I have installed a diode on this line, which has 0.5 volts power loss (4.5 volts at the Teensy). This is to prevent that the current flows from the PC to the electrical components when a connection between PC and controller via micro USB. I frequently remeasured the voltages in the circuit, because fluctuations in the voltage always occurred when I had the PC plugged in addition to the normal voltage supply. As soon as this was the case, the voltage at the controller always increased by about 0.1 - 0.3 volts. This always seemed strange to me, but I also read that the Vin Pin and Micro USB are connected and then thought nothing more of it. I just installed the diode. Can you please take a look at the schematic, and check if there is a fault in there that could have caused the damage?

    Thanks a lot!

  2. #2
    Senior Member BriComp's Avatar
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    What display are you using?
    If it's a Nextion, not all of them are compatible with the T4.0, having a 5v serial interface rather than 3.3v.
    The T4.0 is NOT 5v tolerant.

  3. #3
    Under normal circumstances, the CPU should not be getting that hot. It would normally just be warm to the touch.

    If you are plugging both USB and VIN power in at the same time, besides the diode you already installed, you should also cut the VUSB trace on the back of the Teensy and add a 2nd diode across those two pads.

    Also make sure that whatever your sensor is, it is not putting out more than 3.3V. It looks like it is being powered from 5V, so it is probably putting out a 5V signal of some type. As BriComp already mentioned, putting more than 3.3V on any pin other than VIN can damage the Teensy 4.0.

  4. #4
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    Thankyou all for your good advices.

    I use the 4.3 Inch Nextion Intelligent Series NX4827P043-011C.
    I didnīt thought that the TTL could be the problem. You are right. The Nextion TTL works at 5 Volt. I bought a "logic level converter" which is designed for TTL.
    Is it also possible to use just a resistor to decrease the current in a serial connection?

    KenHahn: How can i cut the trace? Do you have a manual? Where should I add the diode? Sorry, but i didnīt get it, but thank you very much for your help.

  5. #5
    You want to cut the small trace that is between the two large pads to isolate the USB power from the VIN power.

    Use a sharp X-acto or box knife with a new blade. Angle the blade at about a 45 degree angle and press straight into the trace on one side just inside the pad. Don’t use a sawing motion as you are just cutting through thin soft copper. Move the blade to the other side of the trace and repeat the process to remove a small wedge of the trace. A magnifier definitely makes this process easier if you have access to one.

    Then solder a diode (schottky is best, but just about any will work) between the two pads with the cathode (band) facing the VIN pin. It can be a surface mount diode or you can solder the leads of a thru-hole diode to the pads.

    Here is a picture that should help clarify.

    Click image for larger version. 

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  6. #6
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    Thankyou KenHahn for your detailed instruction. I just ordered a new one and then i will try that and tell you about it. I also will monitor the internal temperature. There a code i looked up:

    Code:
    extern float tempmonGetTemp(void);
    
    void setup() {
      while (!Serial);
    }
    
    void loop() {
      Serial.print( tempmonGetTemp() );
      Serial.println("°C");
      delay(500);
    }

  7. #7
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    I tried to do all your solutions. First of all i cutted the trace which worked quite fine. The current remains on a constant level know, doesnīt matter if the Pc is connected or not. So thatīs fine. Thankyou!

    Secondly I bought a TTL-Converter. I mounted it correctly, but it didnīt worked at all. There were no signals after it was built in. So I disassembled it and measured the TTL signal without the converter. There was a peak at 3.9 volts, which surprised me because I was expecting something nearly 5 volts. Even the current is too high, i think the 0.6 volts additional current over a short time should pass the Teensy without damaging it, right? I assume, that It will not life forever, but it should work as a middle range solution.

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