Introduction: Control Relay With Arduino and Sim900A by Using Mobile Phone SMS

In this article, I show how to code by using Arduino and SIM90A to turn of or turn on relay with mobile phone SMS.

Step 1: Hardware

1 Arduino pro mini Module

1 sim900A mini module1 USB UART CP2102 module for programming to Arduino1 Relay module1 Testboard

Step 2: Library for Arduino

You can download from here

Uncompress and copy to libraries folder of Arduino IDE

Step 3: Pins of SIM900A

Power: using adapter 5v / 2A for Sim900A

I using SIM900A has 5VDC power


Sim900A RX pin connect to Arduino TX pin (pin 3). See schema below to connect.

Sim900A TX pin connect to Arduino

RX pin (Pin 2) Sim900A GND pin connect to Arduino GND pin

Connect power 5VDC to 2 module

Relay 1 connect to pin 7 of Arduino
Relay 2 connect to pin 7 of Arduino

Step 5: Connect CP2102 to Arduino

Connect pins follow in image

Step 6: Source Code

Read source code for detail.

This is new version with changes

1. I using number in simcard and read it to memory

2. To check money account, please replace this line in checkTK function

sms.SendSMS("123", "TK");

with your country info

You can edit and free share


Vietnamese in this clip and English translation