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I've been trying to get a new 12V stepper motor to turn using the circuit below. I connected the 12V to the IC but this led to my Arduino smoking and burning out.L293D circuit with stepper motor

I'm thinking that the 12V is being pushed into the Arduino due to the common ground or my wiring is wrong. Should this circuit work be safe or will it burn out another Arduino if I connect it up again?

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  • \$\begingroup\$ Do you have pins 5,12,13 connected to ground and a heatsink as the datasheet says?? \$\endgroup\$
    – whitegreg56
    Commented Jan 30, 2018 at 22:14
  • \$\begingroup\$ Are 4 Gnd inputs 4,5, 13,12 connected? \$\endgroup\$
    – D.A.S.
    Commented Jan 30, 2018 at 22:16
  • \$\begingroup\$ No, I've only connected pin 4 to ground as this works with other motor circuits I've tried and tested. In my past experience, not all GND pins need to be connected to ground. \$\endgroup\$
    – Fraser
    Commented Jan 30, 2018 at 22:18
  • \$\begingroup\$ Did you connect clamp diodes and motor? \$\endgroup\$
    – D.A.S.
    Commented Jan 30, 2018 at 22:20
  • \$\begingroup\$ No clamp diodes but 2 motors were connnected \$\endgroup\$
    – Fraser
    Commented Jan 30, 2018 at 22:21

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You wrote: "In my past experience, not all GND pins need to be connected to ground".

This is a very, very bad assumption. You are dealing with a switched high-current inductive load. You will get sharp voltage spikes during switching. GND is very critical. Take a look at the layout example from the TI datasheet below. See the crazy number of GND vias recommended for pins 4, 5, 12 and 13? And yet you have several not even connected.

These pins are probably GND for each push/pull output. By failing to GND these pins, you are forcing the GND current to go through a longer, higher impedance internal path and you are probably getting severe voltage spikes on the internal IC GND which can then cause the IC to latch up, and/or inject spikes into your digital 5V rail.

enter image description here

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  • \$\begingroup\$ You are controlling a lot of current....all the time! You need the heat sinking, too. Is the L293D getting hot? \$\endgroup\$
    – whitegreg56
    Commented Jan 31, 2018 at 3:13
  • \$\begingroup\$ The circuit is working now with the clamp diodes added and all pins brought to GND, thank you all. I'm not using heat sinking as the IC is not getting hot, only warm. \$\endgroup\$
    – Fraser
    Commented Jan 31, 2018 at 18:29

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