1.8 Service Bell

Today, we will use Micro Switch, speakers, audio amplifier module, Raspberry Pi and scratch to make a service bell.

Tap the Micro Switch to make the service bell sound.


Build the Circuit


Load the Code and See What Happens

Load the code file (1.8_service_bell.sb3) to Scratch 3.

Press the micro switch and the service bell will ring once.


If your Raspberry Pi is connected to a screen with speakers, it may cause no sound from this external speaker, please refer to Change Audio Output for the solution.

Also, if you want to adjust the volume level, please refer to Adjust Volume.

Tips on Sprite

Select Sprite1 and click Costumes in the top left corner; upload bell1.png and bell2.png from the home/pi/raphael-kit/scratch/picture path via the Upload Costume button; delete the default 2 costumes, and rename the sprite to bell.


In the Sounds option, upload the bell.wav from the home/pi/raphael-kit/scratch/sound path to Scratch 3.


Tips on Codes


When pin17 is high (the Micro switch is not pressed), switch the costume of the bell sprite to bell1 (released state).


Press the micro switch, gpio17 is low level. At this time, switch the costume of the bell sprite to bell2 (press state), and play a sound effect through the speaker.