Obstacle-avoiding robot car

Parts in this circuit

Wiring, pin by pin

Red = 5 V, orange = 3.3 V, black = GND, other colours = signals. “Pin” is the position on the 40-pin header; the GPIO number is what the code uses. Power the Pi from a 5.1 V supply and wire with the power off.

Python code (gpiozero)

from gpiozero import Motor, DistanceSensor
from time import sleep

motor = Motor(forward=5, backward=6, enable=12)
sensor = DistanceSensor(echo=24, trigger=23, max_distance=2)

while True:
    cm = sensor.distance * 100
    if cm > 40:
        motor.forward(0.9)                 # clear: full speed
        print("Clear,", round(cm), "cm: driving fast")
    elif cm > 15:
        motor.forward(0.4)                 # something ahead: slow down
        print("Object at", round(cm), "cm: slowing down")
    else:
        motor.stop()
        print("TOO CLOSE:", round(cm), "cm. Backing away")
        motor.backward(0.5)
        sleep(1)
        motor.stop()
    sleep(0.2)

How the code works

• sensor.distance gives metres. Multiplying by 100 gives centimetres.
• motor.forward(0.9) runs at 90 % speed. The enable pin carries the PWM signal.
• The if, elif and else give three zones, so the car slows down before it has to stop.
• The sleep(0.2) makes the car check five times a second.

Parts to buy

The links open a search on each store, so you see what is in stock today. Check the model, voltage and price before you order.