Why does my raspberry pi zero w crashes when controlling a DC motor with an L9232D and a 9g Servo motor?

Question

I use this simple circuit to control a DC motor with an L293D, and a 9g servo motor with a Raspberry PI Zero W:

I use the simple following code to test the circuit:

from time import sleep
import RPi.GPIO as GPIO   

ServoPin = 32

MotorPin1 = 3
MotorPin2 = 5
MotorEnable = 33

GPIO.setmode(GPIO.BOARD)

GPIO.setup(ServoPin, GPIO.OUT)

GPIO.setup(MotorPin1, GPIO.OUT)
GPIO.setup(MotorPin2, GPIO.OUT)
GPIO.setup(MotorEnable, GPIO.OUT)

servoPWM = GPIO.PWM(servoPIN, 50)   # 50 Hz
servoPWM.start(2.5)                 # Duty cycle (0.0 <= dc <= 100.0)

motorPWM = GPIO.PWM(MotorEnable, 100)
motorPWM.start(0)

GPIO.output(MotorPin1, GPIO.LOW)
GPIO.output(MotorPin2, GPIO.HIGH)

sleep(0.5)

servoPWM.ChangeDutyCycle(5)
motorPWM.ChangeDutyCycle(25)

sleep(0.5)

servoPWM.ChangeDutyCycle(10)
motorPWM.ChangeDutyCycle(50)

sleep(0.5)

GPIO.output(MotorPin1, GPIO.HIGH)
GPIO.output(MotorPin2, GPIO.LOW)

servoPWM.ChangeDutyCycle(2.5)
motorPWM.ChangeDutyCycle(80)

sleep(0.5)

The raspberry crashes (reboot) often, mostly when controlling both the motor and the servo at the same time. Any idea why?

I followed those instructions for the DC motor wiring.

Answer 1

the spike caused by motors, drops the controller voltage.

in this case (the pi), it will drop to 4.6 v for example, which is enough to cause to to reboot.

either use an adapter for rpi, or give it another clean power source.

plus, for the same reason DIY quadcopters have separate batteries dedicated for the controller.

Answer 2

"The only thing is that I connected the 3.3V of the L293D on a 5V pin, but I assumed it is not a big deal..."

Translation AKA edited as is common on this forum **I am using common power source for all devices **

IT IS A HUGE DEAL ! Electromechanical devices are 1. power hungry 2. when initialized /started they are EXTREMELY power hungry - tech term is "power surge" 3. require "HARD" power source - tech term "power source producing SAME power (level) during initial power-up."

Your RPi power goes bellow nominal 3.3V during your devices start causing it to reset.

The solution Provide SEPARATE power for your motors. Make sure RPi outputs are ISOLATED from your devices - optocouplers works fine. Make sure your motors have BEMF "back electromotive force" protection - your hardware diver should do fine.

PS Next post do not spent time making fancy circuits layouts pictures - they do not grantee it is actually wired as shown and invite unnecessary criticism of your post. Your verbal post was all what was needed and you did good job.