How to Use EM-18 RFID Reader Module: Examples, Pinouts, and Specs

The EM-18 RFID Reader Module is a compact and efficient device designed to read RFID tags operating at a frequency of 125 kHz. It is widely used in applications such as access control systems, inventory management, attendance systems, and other automation projects. The module communicates the unique ID of an RFID tag to a microcontroller or computer via UART (serial communication) or Wiegand protocol, making it versatile and easy to integrate into various systems.

• Operating Frequency: 125 kHz
• Operating Voltage: 4.5V to 5.5V DC
• Current Consumption: 50 mA (typical)
• Communication Protocols: UART (TTL) and Wiegand
• Baud Rate: 9600 bps (default)
• Reading Distance: 5–10 cm (depending on tag type)
• Supported RFID Tags: 125 kHz passive tags (e.g., EM4100, EM4200)
• Dimensions: 32 mm x 32 mm x 8 mm

The EM-18 RFID Reader Module has a 9-pin interface. Below is the pin configuration:

To use the EM-18 RFID Reader Module with a microcontroller like the Arduino UNO, follow these steps:

1. Power the Module: Connect the VCC pin to the 5V pin of the Arduino and the GND pin to the Arduino's GND.
2. Connect the TX Pin: Connect the TX pin of the EM-18 to the RX pin of the Arduino (pin 0).
3. Optional Connections: If needed, connect the BEEP and LED pins to external indicators (e.g., a buzzer or LED) for additional feedback.

Below is an example of how to interface the EM-18 RFID Reader Module with an Arduino UNO to read RFID tag data:

// EM-18 RFID Reader Module with Arduino UNO
// Connect EM-18 TX to Arduino RX (Pin 0)
// Connect EM-18 VCC to Arduino 5V and GND to Arduino GND

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 bps
  Serial.println("EM-18 RFID Reader Ready");
}

void loop() {
  if (Serial.available() > 0) { // Check if data is available from the EM-18
    String tagData = "";        // Variable to store the RFID tag data
    while (Serial.available() > 0) {
      char c = Serial.read();   // Read each character from the EM-18
      tagData += c;             // Append the character to the tagData string
      delay(5);                 // Small delay to ensure all data is read
    }
    Serial.print("RFID Tag ID: "); // Print the tag ID to the Serial Monitor
    Serial.println(tagData);
  }
}

• Ensure the RFID tag is within the 5–10 cm range of the module for reliable reading.
• Avoid placing the module near metal objects or other RFID readers to prevent interference.
• Use a stable 5V power supply to avoid communication errors.
• If using the Wiegand protocol, additional decoding logic will be required.

1. No Data Received on Serial Monitor:

   • Ensure the TX pin of the EM-18 is connected to the RX pin of the Arduino.
   • Verify that the baud rate in the code matches the module's default baud rate (9600 bps).
   • Check the power supply voltage (should be 4.5V to 5.5V).

2. RFID Tag Not Detected:

   • Ensure the tag is within the 5–10 cm range of the module.
   • Verify that the tag operates at 125 kHz (e.g., EM4100 or EM4200).
   • Check for any nearby sources of electromagnetic interference.

3. Intermittent or Unstable Readings:

   • Use a decoupling capacitor (e.g., 10 µF) across the VCC and GND pins to stabilize the power supply.
   • Avoid moving the tag too quickly across the reader.

Q1: Can the EM-18 read multiple tags simultaneously?
No, the EM-18 can only read one tag at a time. If multiple tags are present, it may not function correctly.

Q2: Can I use the EM-18 with a 3.3V microcontroller?
The EM-18 requires a 5V power supply. If your microcontroller operates at 3.3V, use a level shifter for the TX pin to avoid damage.

Q3: How can I extend the reading range of the EM-18?
The reading range is limited by the onboard antenna and cannot be significantly extended. For longer ranges, consider using a different RFID reader with a higher power output.

Q4: What type of RFID tags are compatible with the EM-18?
The EM-18 is compatible with 125 kHz passive RFID tags, such as EM4100 and EM4200.

By following this documentation, you can effectively integrate the EM-18 RFID Reader Module into your projects and troubleshoot common issues with ease.