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I'm working on a device that controls three stepper motor actuators, one servo motor and a DC motor/encoder. The stepper motors and DC motor are run at 6V and are controlled by an Arduino Nano's GPIO pins, connected to four L293D half-bridge motor drivers.

Arduino and L293D U3

L293D U4 and U5

L293D U6, L4940V5, OKR-t/3-W12-C

In the above schematic, U6 is connected to the DC motor. U5 and U4 both control stepper motors and share GPIO connects as they are expected to operate in sync on an axis. U3 also controls a stepper motor, but on another axis.

I've been running into a problem where one particular L293D (U3) overheats and burns out, forcing me to replace it. The other L293Ds do feel warm when I'm testing (possibly uncomfortably so, I haven't burned myself yet), but it doesn't feel like they're getting nearly as hot as U3 does.

I'm considering replacing the L293D with a different motor driver, but I don't want to make such a big change without determining as best I can why U3 in particular keeps overheating like this. I'm still gathering information, but if anyone sees something already, I'd be glad to hear it.

Update: Okay, I've been able to do some more testing, and it seems that U4 &5 are also getting hotter than I expected. I'm still pretty sure that U3 is getting hotter at a more rapid pace than U4 & U5, but its still all uncomfortable temperatures that could burn if left alone. I still don't know why U3 is the one that keeps actually breaking, but I think it's fair to say that all three L293Ds connected to the steppers are at least in danger of burning out. That said, this doesn't seem to be common to all the boards I'm working with. I'm working on getting some proper current measurements to go with this.

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    \$\begingroup\$ @Andyaka Are these ones more to your liking? \$\endgroup\$
    – E.HP.S
    Jun 26, 2023 at 15:54
  • \$\begingroup\$ Problems with L293, L298 and SN754410 H-bridge drivers on a low voltage supply \$\endgroup\$
    – Andy aka
    Jun 26, 2023 at 16:05
  • \$\begingroup\$ Is the motor attached to U3 the same as the others? Disconnect them and measure the winding resistance to verify. \$\endgroup\$
    – rdtsc
    Jun 26, 2023 at 16:26
  • \$\begingroup\$ Is U3 physically located between some other devices which are heating it? \$\endgroup\$ Jun 26, 2023 at 16:29
  • \$\begingroup\$ @rdtsc Yeah, I checked the winding resistance against the other two. It matches. I'm wondering if it's a PCB problem. \$\endgroup\$
    – E.HP.S
    Jun 26, 2023 at 16:32

1 Answer 1

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  1. you may use glued heat sinkers (ex 7x7x6 mm on ali: https://www.aliexpress.com/item/1005004214087361.html?spm=a2g0o.order_list.order_list_main.21.21ef1802Qh3lMA)
  2. the heating could be caused by improper timings/operation by the MCU, for example currents may still flow via motor windings even then motor is not rotating in this time.
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  • \$\begingroup\$ Neither of your two points address the asked question why the chip overheats. \$\endgroup\$
    – Justme
    Jun 26, 2023 at 15:49
  • \$\begingroup\$ If a timing problem was the case, couldn't I expect to also see the other two stepper motors burning up? At the moment, it's just U3 getting to the point of not working. The other two get warm, but not painful (so far as I've encountered) \$\endgroup\$
    – E.HP.S
    Jun 26, 2023 at 16:40
  • \$\begingroup\$ @E.HP.S, the signals could differ (all depends of the firmware in MCU), also you may check if the motor itself is heating higher then others two \$\endgroup\$
    – Pinus
    Jun 26, 2023 at 16:54

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