How to Use SIM800L to Send SMS and Control Relay by SMS

Introduction: How to Use SIM800L to Send SMS and Control Relay by SMS


This tutorial is showing how to use SIM800L to send sms and receive sms to control relay. SIM800L module is small in size and can be used to interface with Arduino to send sms, receive sms, call, receive call and else. In this tutorial, we only focus on send sms and control relay by receiving sms.


  • GPRS multi-slot class12 connectivity: max. 85.6kbps(down-load/up-load)
  • GPRS mobile station class B
  • Controlled by AT Command (3GPP TS 27.007, 27.005 and SIMCOM enhanced AT Commands)
  • Supports Real Time Clock
  • Supply voltage range 3.4V ~ 4.4V
  • Supports A-GPSSupports 3.0V to 5.0V logic level
  • Low power consumption, 1mA in sleep mode
  • Compact size 23mm x 35mm x 5.6mm

Step 1: Material Preparation

Step 2: Follow the Video

Step 3: Source Code

Download source and click library SIM800L link:

  1. Library SIM800L: Adafruit FONA

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    11 months ago

    Hi, i have a problem wit my module, my module always blink for every second, can't get the signal. Have you an idea?

    Johnny sandkly
    Johnny sandkly

    Reply 10 months ago

    i had this issue also
    i have fixed it by using external 4v 5A PSU


    1 year ago

    this code have a problem. if sim800l be reset (with each reason for example power or network or handly reset) , arduino can not auto reconnect , just with reset. have you an idea?