First off I'm a beginner at electronics I don't understand much so bear with me.
I've just constructed my first bipolar stepper motor circuit today on a breadboard. I've actually extracted the stepper motor from an old Epson printer. I've used an lm317t adjustable voltage regulator to power the motor driver. Input is a 9v battery and I give 5v as motor power supply to the l293d motor driver. There is a separate microcontroller and its power and ground which is 5v as well.
Now I've used a pot to adjust and multimeter to check the output motor voltage of the lm317 regulator. I have set the pot such that the output is at 5v
Now my question is when the stepper motor runs successfully, the multimeter reading drops from 5v down to 4v. Why does this happen?