Production counter with batch alarm

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 Button, LEDBarGraph, Buzzer
from signal import pause

beam = Button(17)                       # beam broken = "pressed"
reset = Button(27)
bar = LEDBarGraph(5, 6, 13, 19, 26)     # shows the progress in the batch
horn = Buzzer(18)

BATCH = 5
total = 0

def part_passed():
    global total
    total += 1
    in_batch = total % BATCH
    print("Part", total, "- batch progress:", in_batch or BATCH, "of", BATCH)
    if in_batch == 0:
        bar.value = 1                    # all five LEDs on
        horn.beep(0.15, 0.1, n=3)
        print("BATCH COMPLETE:", total // BATCH, "batch(es) done")
    else:
        bar.value = in_batch / BATCH

def reset_count():
    global total
    total = 0
    bar.value = 0
    print("Counter reset")

beam.when_pressed = part_passed
reset.when_pressed = reset_count
print("Click the beam sensor to drop a part")
pause()

How the code works

• An infrared emitter and receiver face each other. A part passing through breaks the beam, and the signal changes. gpiozero sees this as a button press.
• Every press calls part_passed(). It adds one to total and uses total % BATCH to know how far the batch has gone.
• When the remainder is 0 the batch is complete: the bar is full and the horn beeps 3 times.
• The Reset button brings the counter back to zero, like a counter reset on a real machine.

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.