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I am working on two stepper motors and trying to control them using RPi3(Ubuntu mate) with A4988 motor drivers. I successfully managed to drive the motors with external 12V battery source. After sometime, I tried to test the circuit again but now the RPi is heating up and not booting. I don't know what happened. Please help

The red LED is glowing but its not booting. Also I am only connecting the stepping mode pins and STEP, DIR pins of the A4988 to the RPi. There are two motors whose Vdd and Vmot pins are connected together. An LM2596 is used to step down (12v to 5v) the voltage used for Vdd

Update: I checked each of the A4988 drivers,they are in working conditions. Only the Rpi got fried. I hope somebody could explain ,why only the Rpi got fried? and What are the precautions to be taken to ensure this does not happen again?

Update2: I used another Rpi to test the same circuit and its working fine. I think the reason for the RPi getting fried is that there was an open 12V wire coming from the source which might have accidentally touched the RPi.

I tried booting the fried Rpi and I found that it's actually booting up, but the processor is heating up. I don't know the reason for this behaviour. I read something about the polyfuse which takes time to reset. Maybe the polyfuse might have blown and now resetting.

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  • Do either of the red/green LEDs light up or blink? Also, can you share some more details (schematic or picture) on how you wired up your motors, drivers and battery to the Pi?
    – Roger Jones
    Dec 17, 2018 at 9:57
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    If the Pi gets very hot very quickly it is dead. Especially so when it doesn't even boot so isn't running any software. Somehow you have fed more than 3V3 into a Pi GPIO or have connected more than 6V to a 5V pin or more than 3V3 to a 3V3 pin.
    – joan
    Dec 17, 2018 at 11:52
  • but all of the pins where output pins. There were no inputs to the rpi.Does that mean the drivers also got fried. As I am a beginner ,Can you point me towards safety measures to be taken while working with circuit. Thank you for the reply
    – AK46
    Dec 17, 2018 at 12:06
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    Making a pin an output does not protect it from being damaged by excessive input voltage, I'm afraid.
    – Roger Jones
    Dec 17, 2018 at 12:28
  • How to stop excessive input voltage?
    – AK46
    Dec 17, 2018 at 12:37

2 Answers 2

Reset to default
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It is highly likely that a voltage >3.3v went into the Raspberry Pi and it was damaged becuase of that. Unfortunately you will need to buy a new Pi.

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  • I know that my Rpi is damaged but I cannot figure out how a voltage >3.3V went into the Rpi. Aren't motordrivers supposed to keep the voltages in check?
    – AK46
    Dec 21, 2018 at 5:16
  • They will if they are not damaged and the grounds are not opened.
    – Gil
    Nov 24, 2022 at 2:18
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Consider you take a piece of thread about 100 meters and then use it to repel down a steep cliff, the results would be bad and you would be "broken" when you landed. If an ant did that it would arrive safely at the bottom. Electronics is like that, it has all type of limits and when exceeded it gets broken, sometimes in nanoseconds and no smoke. Did the drivers get fried, no clue you need to check them. I don't know your resources but you need at least an inexpensive multimeter to check voltages, resistance, etc. Since the drivers are not that expensive rather than risk another Pi replace them. It is also advisable to use LEDs with a resistor to check your outputs first. Then use your multimeter to check all the connections that go to the Pi and be sure they are not greater then 3V3 (3.3 volts).

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