The sys admin's daily grind: Charly's doorbell Pi
Ring, Ring
When Charly puts on his headphones at home, he often fails to hear the doorbell. So, he dreamed up a solution with a Raspberry Pi Zero, a noise detector, and a power outlet with a LAN connection.
Sometimes I sit in my home office using a headset, listening to some good old electric guitar music or taking part in a teleconference – which is naturally slightly less invigorating. As a consequence of my acoustic escapism, I tend not to hear anyone who rings the doorbell.
To restore my social presence, I opted for the smallest version of the Raspberry Pi, the Zero. The Pi needs to detect the bell circuit closing and output a visual alert. In Germany, doorbells use 8 to 12V alternating current. You could convert this to DC and tune it down to a Pi-compatible voltage, but this would involve a mess of wire in the doorbell housing.
So, I went for a noise sensor. These things are very simply made, need a supply voltage of 5V, and send a signal via the output pin when they pick up a noise [1]. A blue rotary potentiometer lets me set the noise level. The sensor and the Raspberry Pi both fit into the doorbell housing (Figure 1).
Figure 1: Noise sensor (right) and Raspberry Pi (left) have plenty of space in the doorbell housing.
Because of its proximity to the acoustic event, I can set the sensor's switching threshold to a fairly high level – it will not be tripped by the kids shouting or the dog going mad in the hallway.
Lights and Tweets
The small Python program from Listing 1 evaluates the signal in an infinite loop. The GPIO Zero library [2], which I used here, might not support noise sensors, but its Button() function is all I need to evaluate the sensor's short voltage pulse. Luckily, it includes a debounce feature: bounce_time=2 summarizes all the signals the Raspberry detects within two seconds.
Listing 1
Doorbell Script
01 #!/usr/bin/env python3
02 from gpiozero import Button
03 from signal import pause
04 import os
05
06 def bell_rang ():
07 os.system("/usr/local/shellscripts/bell.sh")
08
09 button = Button(21, bounce_time=2)
10 button.when_pressed = bell_rang
11 pause()
When the delivery man rings the bell now, the script bell.sh launches, which actuates a power outlet connected to my LAN, which switches on a lamp in my office. At the same time, the script sends a tweet on Twitter. I know you can buy wireless doorbells down at the hardware store, but the doorbell Pi is more my style.
Charly Kühnast
Charly Kühnast is a Unix operating system administrator at the Data Center in Moers, Germany. His tasks include firewall and DMZ security and availability. He divides his leisure time into hot, wet, and eastern sectors, where he enjoys cooking, freshwater aquariums, and learning Japanese, respectively.
Infos
- Source for noise sensor: http://www.amazon.de/gp/product/B00N1TSM7K
- GPIO Zero: http://gpiozero.readthedocs.org
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Direct Download
Read full article as PDF:
Price $2.95
News
-
KaOS 2022.06 Now Available With KDE Plasma 5.25
The newest iteration of KaOS Linux not only adds the latest KDE Plasma desktop but sets LibreOffice as the default.
-
Manjaro 21.3.0 Is Now Available
Manjaro “Ruah” has been released and includes the latest Calamares installer, GNOME 42, and much more.
-
SpiralLinux is a New Linux Distribution Focused on Simplicity
A new Linux distribution, from the creator of GeckoLinux, is a Debian-based operating system with a focus on simplicity and ease of use.
-
HP Dev One Linux Laptop is Now Available for Pre-Order
The System76/HP collaboration Dev One laptop, geared toward developers, is now available for pre-order.
-
NixOS 22.5 Is Now Available
The latest release of NixOS with a much-improved package manager and a user-friendly graphical installer.
-
System76 Teams up with HP to Create the Dev One Laptop
HP and System76 have come together to develop a new laptop, powered by Pop!_OS and aimed toward developers.
-
Titan Linux is a New KDE Linux Based on Debian Stable
Titan Linux is a new Debian-based Linux distribution that features the KDE Plasma desktop with a focus on usability and performance.
-
Danielle Foré Has an Update for elementary OS 7
Now that Ubuntu 22.04 has been released, the team behind elementary OS is preparing for the upcoming 7.0 release.
-
Linux New Media Launches Open Source JobHub
New job website focuses on connecting technical and non-technical professionals with organizations in open source.
-
Ubuntu Cinnamon 22.04 Now Available
Ubuntu Cinnamon 22.04 has been released with all the additions from upstream as well as other features and improvements.