Raspberry Alarm Upgrade

About the project

In this Project, my 20 years old alarm system gets an upgrade, email and SMS warnings replace the old phone calling notification.

Project info

Difficulty: Easy

Platforms: Raspberry Pi

Estimated time: 1 hour

License: GNU General Public License, version 3 or later (GPL3+)

Items used in this project

Hardware components

PTN78020 PTN78020 Power Management ICs / Power Supply Modules x 2
Sim900 Sim900 x 1
For Raspberry Pi B 4.1x2.58x1.18" Clear For Raspberry Pi B 4.1x2.58x1.18" Clear x 1


My house is fitted with a 20 years old alarm system. Unfortunately the phone warning system isn't working with our new internet provider. I thought that it was worth upgrading instead of replacing the whole setup. For that I designed a Raspberry pi "hat" with all the interfaces and components I needed.


Project definition

Even though the alarm system is pretty old, its design is hacker friendly. The motherboard has a 12V power output that can be used for future extension cards. This is the power output I used. When something is detected, the siren is triggered by an output and the voltage drops from 12V to 0V.This is very convenient for my project !

The system must be able to notify me in any conditions, for that reason I wanted three warning types:

-Email : Even if I don't have my phone I can get notifications on my laptop

-SMS : The most convenient way to notify someone

-Call : At night my laptop and my smartphone are turned off, the only communication available is my fixed-line phone

Interfaces and Components

The first type of notification is easily doable with Python on the Raspberry pi. The two others will be handled by a GSM modem.

For the modem I used a SIM900 : a popular component with a great online community support.

I needed two power supplies, 5V for the Raspberry pi and 4V for the GSM module. I used two TI PTN78000W series because they have a high efficiency and great output current.

The last and more important interface is the siren trigger. I used optocouplers to step down the voltage to 3.3v and protect the Raspberry pi.

Project Logs

New board soldered and code available

I got some time to solder the board and push some code. I haven't fully tested the board yet. It appears that you cannot power the raspberry pi 2 from the GPIO header, thus the board might not be 100% compatible with it.

New PCBs just arrived

I received this morning the new version of the PCB from China. If this version doesn't have errors, I will release all the design files.

New version coming soon !

Just graduated !! Aside from looking for a job, I'll have some time to update this project and release hardware design files as well as software !! Stay tuned !

Brieuc :


Done :

The warning system is implemented and working

To do :

Correct software bugs

Troubleshoot the battery voltage monitoring

Upload code examples

Upload PCB schematics and layout


- add capacitors next to the Module

-change the SIM card slot location (the sma connector is blocking the slot)

-new battery watching interface

-improve component placement


Photo of Muls96




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