Stepper and 5v Arduino output

Hey mates!

i’m going crazy with a power problem for an electronic toy i’m building as a christmas present for my cousins…

i just made a circuit for controlling a stepper motor (taken from an old epson printer) using an L293D. I’m using the Arduino Nano 5v pin as a power source for the L293D and it works perfect when i Arduino is powered from the USB.

But when i use an external power supply the motor behaves correctly just for few seconds, and then starts moving erratically, affecting all other parts of the circuit (leds start to “strobe” synchronized with the “bad” steps of the motor).
This external power supply is 12v 2amp, as i want to power a tiny portion of a monochrome led strip by using the vin pin on the Arduino Nano… but anyway, if i just remove the led strip from the circuit, the behavior of the motor is still incorrect, so it doesn’t look like the problem is related with the leds at all…

I’ve read on the forums that maybe this is related with some thermal switching of the l293d?

any clues on this?

and merry christmas!!!

12V supply going through the Nano voltage regulator, and then powering a motor with unknown current draw? Bad idea, lots of power dumped into the regulator, its going to thermally cut-out.

Use a separate voltage regulator with a heatsink. You should find out what voltage the motor is designed for - in particular what is the winding resistance. I presume its 4-wire. If the motor can run from 12V then use the 12V directly. If not a 7805 regulator perhaps (but L293's drop a few volts anyway, a 6 or 8V regulator might be better.

Don't power any motor from any of the Arduino pins.

Unless you really know enough to understand the exceptions to that simple advice.


Thanks for your quick answer MarkT and Robin!!!!

I followed your suggestion, and powered the motor directly with 12v. It works very well, but the L293d gets very hot!

i have read about piggybacking L293D.... may this help dissipate the hit of the IC?