Raspberry Pi Buzzer delay

Question

this is my first raspberry pi project and it’s for university. I have a led, a button a buzzer and a servo motor connected, they all work perfectly fine. The idea is, when the servo motor is moved, the LED goes on and if the LED is on for more than 5 seconds the buzzer needs to go off. For some reason, I can’t delay the sound, is there a way to delay the sound of the buzzer for 5 seconds? Any help or guidance is appreciated!

This is the code I used:

buzzer = Buzzer(18)
servo = Servo(17)
button = Button(2)
led = Led(27) 

While True:
button.wait_for_press()
led.on()
servo.max()
buzzer.on(on_time_0.5,off_time:5,n=None,background=True)
sleep(0.5)
button.wait_for_press()
buzzer.off()
led.off()
servo.min()
sleep(0.5)

Answer 1

There's a few ways you could do this. One is to use the signal module and set an alarm (see python docs). An alarm can trigger asynchronously after a set period of time, then call a function that checks if the led is still on and sound the buzzzer. eg.

import signal

# define alarm signal handler
def buzzer_active(signum, stackframe):
   if led.is_lit:
       buzzer.on()
       print('buzzing!')
   else:
       print('not buzzing')

# assign a callback for SIGALRM
signal.signal(signal.SIGALRM, buzzer_active)

# your program
while True:
    button.wait_for_press()
    led.on()
    servo.max()
    signal.alarm(5)  # led is on, trigger the alarm buzzer in 5 sec

# rest of your program - use signal.alarm(0) to cancel the alarm if it didn't
# trigger before the button was pressed again, but this may not be needed if the
# led is turned off as the callback will check the led state.