According to Texas Instruments, the L293D has the following setup

Enable 1, 2 Driver Channels (5V) [   u   ]  Chip Power (5V)
                  Driver Input 1 [       ] Driver Input 4
                 Driver Output 1 [       ] Driver Output 4
                        Ground 1 [       ] Ground 4
                        Ground 2 [       ] Ground 3
                 Driver Output 2 [       ] Driver Output 3
                  Driver Input 2 [       ] Driver Input 3
               Motor Power (12V) [       ] Enable 3, 4 Driver Channels (5V)

Where the u in the middle top represents the divet present on the top of the motor driver to tell which side is "up."

For my project specifically, I will strictly only be needing the left side motor control logic (1, 2) and since I am not running a DC stepper motor, I will only run the following two states (i.e. I want output 1 to always be the +12V and output 2 to behave as the ground, or for no current to be flowing at all):

I) [OFF] Input 1: Low | Input 2: Low
II) [ON] Input 1: High | Input 2: Low 

Therefore, here is my partially completed schematic of the system (top is now on left side; Ground is the middle two pins on the bottom side of the L293D in the schematic). Schematic

Now according to the tutorial I am following, I should just ground 1 and 2 back to the Pi. However, my concern is that that would cause a problem because the motor powering circuit is powered by a 12V supply. Hence, should I ground 1 and 2 back to the Pi (bottom)? or Back to the Ground for the 12V circuit? (at the top).

Thank you and much love!


Ground is the reference voltage for all circuitry. In effect all the grounds form a single point.

You need to connect at least one Pi ground to a L293D ground.

  • Which one goes to the Pi ground and then which one goes to the 12V ground? – Gilgamesh Skytrooper Mar 20 '17 at 23:12
  • All grounds are the same. It doesn't matter. With a breadboard you normally just connect to the ground rail from the Pi and the L293D and any power supplies. – joan Mar 21 '17 at 9:05

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