Distance meter with an LED bar

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 DistanceSensor, LEDBarGraph
from time import sleep

sensor = DistanceSensor(echo=24, trigger=23, max_distance=2)
bar = LEDBarGraph(5, 6, 13, 19, 26)

while True:
    cm = sensor.distance * 100            # metres to centimetres
    bar.value = 1 - sensor.value          # closer object = more LEDs
    print("Distance:", round(cm), "cm")
    sleep(0.5)

How the code works

• The sensor sends a burst of sound from the trigger pin and times the echo. The Pi turns the time into a distance.
• sensor.distance is in metres, so multiply by 100 for centimetres.
• sensor.value runs from 0 (touching) to 1 (max distance). 1 minus that value gives more LEDs when closer.

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.