Introduction: Android and Arduino SMS Based Home Automation
! ! ! N O T I C E ! ! !
Due to the local cellphone tower being upgraded in my area, I am no longer able to use this GSM module. The newer tower no longer supports 2G devices. Therefore, I can no longer give any support for this project.
Recently, I received a relatively cheap Quad Band GSM/GPRS module to play with. It is a SIM800L module, and communicates with any micro via a serial port. It came complete with a panel mount antenna.
I decided to build a simple SMS Controller system which uses short message service (SMS) commands to control devices and indicate alarms.
Step 1: SMS Commands
AS with any communication system, specific commands need to be send to a remote device to tell it what to do. Likewise, the remote device needs to reply or react on these commands. This project consists of two parts, the SMS Controller, and an standard cellular phone.
The idea was to create a simple SMS Controller with four digital outputs. Depending on the received SMS, the unit must be able to control the individual outputs.
I also decided to include four digital inputs. This can be used to indicate alarms or other information.
Before starting the build, I decided to create specific commands for specific functions. This 'commands' will be sent using an SMS from a cellular phone.
SMS Controller Receive Commands:
o1:1 - turn output 1 On
o1:0 - turn output 1 Off
o1:p - pulse output 1 On, then turn Off
o2:1 - turn output 2 On
o2:0 - turn output 2 Off
o2:p - pulse output 2 On, then turn Off
o3:1 - turn output 3 On
o3:0 - turn output 3 Off
o3:p - pulse output 3 On, then turn Off
o4:1 - turn output 4 On
o4:0 - turn output 4 Off
o4:p - pulse output 4 On, then turn Off
???? - Request status of Inputs and Outputs
#### - Reset system
For feedback, the SMS Controller should respond to the received commands, and reply with an SMS. I decided that this reply SMS should include the status of all I/O pins.
SMS Controller Response Commands:
i1:x i2:x i3:x i4:x o1:x o2:x o3:x o4:x
where x is the I/O status, 1 for On, 0 for Off.
Step 2: Building the SMS Controller
Equipment required:
Any Arduino, or stand-alone ATMEGA328p on a breadboard
SIM800L GSM/GPRS Module with a sim card capable of sending and receiving SMS's
Step down DC/DC converter
NOTE !!!
The DC/DC converter is required to power the SIM800L module. This module operates between 3.7V and 5V, depending on the version you have. This module also requires a power supply that can deliver up to 2A when the module transmit data. It can not be powered directly from the Arduino Uno !!!
The circuit is quite simple. I have assembled and tested it on breadboard.
The power to the circuit is via the DC/DC converter, with the output voltage set to 4.5V. There are four LEDs to simulate the digital outputs, and four buttons for the digital inputs. The SIM800L is connected to the Rx/Tx pins of the ATMEGA328p.
A 5th LED is used to indicate when the system in busy sending an SMS.
Step 3: Programming the ATMEGA328p
Before programming, open the INO file, and edit the phone number. Replace xxxxxxxxxx with your own cellular phone number in line 46. Recompile, and upload the file.
Also, read the instructions on how to configure the Software Serial port in the INO file.
//=============================================================================
//
// ! ! ! NOTE ! ! !
// ================
//
// BUFFER IN SOFTWARE SERIAL LIBRARY TO BE CHANGED TO 200
//
// To use Software Serial, the user should also change the Software Serial BUFFER to 200.
// This must be edited in the following file:
//
// C:/Program Files/Arduino x.x.x/Hardware/Arduino/AVR/Libraries/SoftwareSerial/src/SoftWareSerial.h
//
// Change buffer as below:
//
// #ifndef _SS_MAX_RX_BUFF
// #define _SS_MAX_RX_BUFF 200
// RX buffer size
// #endif
//
//=============================================================================
Refer to this instructable to program the ATMEGA328p on the breadboard using an Arduino UNO.
Attachments
Step 4: Using the SMS Controller
Using the SMS Controller
The SMS Controller will automatically send an SMS to your phone if any of the four inputs are triggered. The details of the trigger will be contained in the SMS text.
The SMS messages and commands can be edited to your needs in the INO file.
Testing the SMS Controller Outputs
From your cellular phone, send the following commands to your SIM800L simcard number:
o1:1, this will turn on output 1.
On your phone, you will receive the following SMS:
i1:0 i2:0 i3:0 i4:0 o1:1 o2:0 03:0 o4:0
01:0, this will turn off output 1.
On your phone, you will receive the following SMS:
i1:0 i2:0 i3:0 i4:0 o1:0 o2:0 03:0 o4:0
01:p, this will turn on output 1 for 1 second, then turn output 1 off again (pulsed).
On your phone, you will receive the following SMS:
i1:0 i2:0 i3:0 i4:0 o1:0 o2:0 03:0 o4:0
Testing the SMS Controller Inputs
On the SMS Controller, press button 1 briefly
On your phone, you will automatically receive the following SMS:
i1:1 i2:0 i3:0 i4:0 o1:0 o2:0 03:0 o4:0
On the SMS Controller, press button 2 briefly
On your phone, you will automatically receive the following SMS:
i1:1 i2:1 i3:0 i4:0 o1:0 o2:0 03:0 o4:0
On the SMS Controller, press button 3 briefly
On your phone, you will automatically receive the following SMS:
i1:1 i2:1i3:1 i4:0 o1:0 o2:0 03:0 o4:0
As can be seen on the received SMS, the outputs changes according to the commands received. However, the inputs does not change back from a 1 to a 0 after the buttons were pressed. Because I wanted to be able to see any changes on the inputs, I decided to seal in the input status until a reset command is send to the SMS Controller.
Reset Alarms
To reset the input status, send the following command:
####, this will reset the input status.
On your phone, you will receive the following SMS:
i1:0 i2:0 i3:0 i4:0 o1:0 o2:0 03:0 o4:0
Status Updates
You can also request the status at any time by sending the following command:
????, this will request a status update of the I/Os.
On your phone, you will receive the following SMS:
i1:x i2:x i3:x i4:x o1:x o2:x 03:x o4:x
where x indicates the status, 1 for on, 0 for off.
Step 5: Android Application
Using MIT App Inventor 2 (http://ai2.appinventor.mit.edu/), I created a simple user interface for my Android cellular phone. This app allows you to customise the description of each I/O. It also allows for entry of the telephone number.
The four buttons are used to control the Outputs, while the check boxes indicate the input status.
To edit the app, create a MIT App Inventor 2 account, and import the AIA file.
To install the app on your phone, copy the APK file to your phone, and install it. You will have to enable the installation of apps from "Unknown Sources" under your phone's security settings.
Participated in the
Automation Contest 2016
