This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.
This list includes a generic resistor set
as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.
This system integrates an Arduino Uno microcontroller with a SIM800L GSM/GPRS module to facilitate cellular communication, including sending and receiving SMS messages and voice calls. The SIM800L module operates on a 2G network using a Micro SIM card and requires a stable, high-current power source—typically provided by a dedicated 1200mAh LiPo battery or an LM2596 DC-DC buck converter—because cellular transmission draws current spikes that standard Arduino 5V pins cannot supply. Communication between the Arduino Uno and the SIM800L module is established via serial communication using the SoftwareSerial library, allowing the digital pins on the Uno to emulate serial ports. Because the SIM800L uses 3.3V logic levels, a resistor voltage divider constructed from 10K Ohm and 20K Ohm resistors is placed on the Arduino TX to SIM800L RX line to step down the 5V signal from the Arduino, protecting the module from overvoltage damage. A helical or 3dBi GSM antenna is attached to the module to ensure reliable signal reception from cellular towers. Programmed via the Arduino IDE, the microcontroller sends AT commands over the serial interface to control the SIM800L module, enabling automated text messaging, call handling, and remote device interaction.
Why Build This
Develop remote home automation and security alert systems capable of notifying users via SMS during trigger events.
Implement low-cost remote telemetry devices and garden sprinkler controls that respond to missed calls or remote commands over cellular networks.
Real-World Application
Remote home automation, security alert systems, garden sprinkler control via missed calls, and remote telemetry devices.
Skills You'll Learn
Serial communication configuration
AT command protocol utilization
voltage level shifting
power management for high-current peripherals
microcontroller peripheral integration
Safety Precautions
Always connect GND before VCC when powering the SIM800L module, and disconnect VCC before GND to prevent damage. Use a voltage divider on the Arduino TX to SIM800L RX line to protect the 3.3V logic of the module.
Technology Tags
SIM800L
GSM
GPRS
UART
SOFTWARESERIAL
AT COMMANDS
LIPO BATTERY
BUCK CONVERTER
Frequently Asked Questions
The SIM800L module draws high current spikes (up to 2A) during cellular network transmission and registration. The onboard regulators on an Arduino Uno cannot supply this amount of current, which causes the module to reset or brown out. A dedicated power supply like a 1200mAh LiPo battery or an LM2596 buck converter is necessary.
Yes. The Arduino Uno operates on 5V logic, while the SIM800L RX pin is strictly 3.3V tolerant. Sending a direct 5V signal from the Arduino TX pin to the SIM800L RX pin can permanently damage the module over time, making the voltage divider essential.
First, verify that you are using a functional 2G Micro SIM card, as many modern carriers have phased out 2G networks. Additionally, ensure your antenna is securely attached and that your power supply is capable of delivering enough current during network searches.
Gallery
This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.
Kitkraft Project Hub — curated from the maker community, credited at the source.
Arduino UNO R3 Board (Compatible) – ATmega328P Microcontroller with USB Cable
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10pcs - 220 ohm 1/4 W Resistor Set
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400 Points Mini Solderless Prototype PCB Breadboard High Quality
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MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi
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