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).

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
Direct Download
Read full article as PDF:
Price $2.95
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Find SysAdmin Jobs
News
-
OpenMandriva Lx 23.03 Rolling Release is Now Available
OpenMandriva "ROME" is the latest point update for the rolling release Linux distribution and offers the latest updates for a number of important applications and tools.
-
CarbonOS: A New Linux Distro with a Focus on User Experience
CarbonOS is a brand new, built-from-scratch Linux distribution that uses the Gnome desktop and has a special feature that makes it appealing to all types of users.
-
Kubuntu Focus Announces XE Gen 2 Linux Laptop
Another Kubuntu-based laptop has arrived to be your next ultra-portable powerhouse with a Linux heart.
-
MNT Seeks Financial Backing for New Seven-Inch Linux Laptop
MNT Pocket Reform is a tiny laptop that is modular, upgradable, recyclable, reusable, and ships with Debian Linux.
-
Ubuntu Flatpak Remix Adds Flatpak Support Preinstalled
If you're looking for a version of Ubuntu that includes Flatpak support out of the box, there's one clear option.
-
Gnome 44 Release Candidate Now Available
The Gnome 44 release candidate has officially arrived and adds a few changes into the mix.
-
Flathub Vying to Become the Standard Linux App Store
If the Flathub team has any say in the matter, their product will become the default tool for installing Linux apps in 2023.
-
Debian 12 to Ship with KDE Plasma 5.27
The Debian development team has shifted to the latest version of KDE for their testing branch.
-
Planet Computers Launches ARM-based Linux Desktop PCs
The firm that originally released a line of mobile keyboards has taken a different direction and has developed a new line of out-of-the-box mini Linux desktop computers.
-
Ubuntu No Longer Shipping with Flatpak
In a move that probably won’t come as a shock to many, Ubuntu and all of its official spins will no longer ship with Flatpak installed.