Reaction time game

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 LED, Button
from time import sleep, time
from random import uniform

led = LED(17)
button = Button(27)

print("Reaction game: press the button as soon as the LED lights.")

while True:
    led.off()
    print("Get ready...")
    sleep(uniform(2, 5))              # random wait of 2 to 5 seconds
    led.on()
    start = time()                    # note the time
    button.wait_for_press()
    reaction = (time() - start) * 1000
    led.off()
    print("Your reaction time:", round(reaction), "ms")
    button.wait_for_release()
    sleep(1.5)

How the code works

• uniform(2, 5) picks a random wait so you cannot guess when the LED will light.
• time() gives the clock in seconds. The difference between two times is the reaction time.
• Multiplying by 1000 turns seconds into milliseconds.

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.