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GSM SIM900A V4.0 Wireless Extension Module with Antenna

$54.52 USD

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GSM SIM900A V4.0 Wireless Extension Module with Antenna

A quad-band GSM/GPRS wireless communication module based on the SIMCom SIM900A chipset, providing SMS, voice call, and GPRS data connectivity for Arduino, STM32, and Raspberry Pi projects. The V4.0 board includes an onboard SIM card slot, antenna connector, UART interface, and power regulation, making it a complete GSM solution for IoT remote monitoring, GPS tracking, home security, and industrial telemetry applications.

Technical Specifications

Parameter	Value
Chipset	SIMCom SIM900A
Frequency Bands	850 / 900 / 1800 / 1900 MHz (quad-band GSM)
GPRS Class	Class 10 (max 85.6 kbps downlink)
SMS	MT, MO, CB, text and PDU mode
Voice	Full duplex voice call (AT command controlled)
Interface	UART (AT commands, 9600 baud default)
SIM Card	Standard SIM (2FF) slot onboard
Antenna	External SMA antenna included
Supply Voltage	5V DC (onboard regulator)
Operating Temperature	−40°C to +85°C
Certification	CE, RoHS

AT Command Reference (Key Commands)

Command	Function
AT	Test communication (returns OK)
AT+CMGF=1	Set SMS text mode
AT+CMGS="+1234567890"	Send SMS to number
ATD+1234567890;	Dial voice call
AT+SAPBR	Configure GPRS bearer for HTTP/FTP
AT+HTTPINIT	Initialise HTTP session

Typical Applications

Remote SMS Alerts: Send SMS notifications from Arduino when sensor thresholds are exceeded — temperature alarms, door open alerts, power failure notifications
GPS Vehicle Tracker: Combine with a GPS module (NEO-6M) to build an SMS-based vehicle tracker that reports location on demand
Home Security System: GSM alarm dialler that sends SMS and makes voice calls when a PIR motion sensor or door contact is triggered
Industrial Remote Monitoring: GPRS data uplink for remote sensor stations, water level monitors, and weather stations without WiFi coverage
Smart Agriculture: Soil moisture and irrigation control with SMS command interface for remote farm management
Vending Machine Telemetry: GPRS-connected vending machine status reporting and remote inventory monitoring

Arduino Wiring

VCC → Arduino 5V | GND → GND
TX (module) → Arduino D10 (SoftwareSerial RX)
RX (module) → Arduino D11 (SoftwareSerial TX) via 1kΩ voltage divider
Use SoftwareSerial sim900(10, 11); and sim900.begin(9600);
Insert a 2G-compatible SIM card (nano SIM adapter required for some carriers)

FAQ

Q: Does the SIM900A support 3G or 4G?
A: No. The SIM900A is a 2G (GSM/GPRS) module only. It does not support 3G (UMTS/HSPA) or 4G (LTE). Verify that your local carrier still supports 2G networks before purchasing.

Q: What SIM card size does this module use?
A: Standard SIM (2FF, 25×15mm). Use a SIM adapter if you only have a micro or nano SIM card.