How to Use MMA7361: Examples, Pinouts, and Specs

The MMA7361 is a low power, low profile capacitive micro-machined accelerometer. It features signal conditioning, a 1-pole low pass filter, temperature compensation, self-test, and g-Select which allows for the selection between two sensitivities. This versatile component is widely used in various applications such as motion sensing, tilt detection, and vibration monitoring.

• Mobile devices for screen orientation
• Gaming controllers for motion detection
• Robotics for balance and movement control
• Automotive systems for crash detection and airbag deployment
• Industrial equipment for vibration monitoring

1. Power Supply: Connect the Vdd pin to a 3.3V power supply and the GND pin to the ground.
2. Analog Outputs: Connect the Xout, Yout, and Zout pins to the analog input pins of a microcontroller (e.g., Arduino).
3. Sensitivity Selection: Use the G-Select pin to choose the sensitivity. Connect it to GND for ±1.5g or to Vdd for ±6g.
4. Self-Test: To perform a self-test, set the ST pin high. This will apply a known force to the sensor to verify its operation.
5. Sleep Mode: To reduce power consumption, set the Sleep pin high to put the device into sleep mode.

• Decoupling Capacitor: Place a 0.1 µF capacitor close to the Vdd pin to filter out noise.
• Mounting: Ensure the accelerometer is mounted securely to avoid false readings due to vibrations.
• Calibration: Calibrate the sensor in a known orientation to ensure accurate readings.
• Temperature Effects: Be aware of temperature variations and their potential impact on sensor readings.

// MMA7361 Accelerometer with Arduino UNO
// Connections:
// MMA7361 Vdd -> 3.3V
// MMA7361 GND -> GND
// MMA7361 Xout -> A0
// MMA7361 Yout -> A1
// MMA7361 Zout -> A2
// MMA7361 G-Select -> GND (for ±1.5g sensitivity)

const int xPin = A0; // X-axis output
const int yPin = A1; // Y-axis output
const int zPin = A2; // Z-axis output

void setup() {
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  int xValue = analogRead(xPin); // Read X-axis value
  int yValue = analogRead(yPin); // Read Y-axis value
  int zValue = analogRead(zPin); // Read Z-axis value

  // Convert analog values to g-force
  float xG = (xValue - 512) * (3.3 / 1024) / 0.8;
  float yG = (yValue - 512) * (3.3 / 1024) / 0.8;
  float zG = (zValue - 512) * (3.3 / 1024) / 0.8;

  // Print values to serial monitor
  Serial.print("X: ");
  Serial.print(xG);
  Serial.print(" g, Y: ");
  Serial.print(yG);
  Serial.print(" g, Z: ");
  Serial.print(zG);
  Serial.println(" g");

  delay(500); // Wait for 500 milliseconds
}

1. No Output Signal

   • Solution: Check the power supply connections. Ensure Vdd is connected to 3.3V and GND to ground.

2. Inaccurate Readings

   • Solution: Calibrate the sensor. Ensure the sensor is mounted securely and not subject to external vibrations.

3. High Power Consumption

   • Solution: Use the Sleep mode by setting the Sleep pin high when the sensor is not in use.

4. Self-Test Fails

   • Solution: Verify the ST pin connection. Ensure it is set high during the self-test procedure.

Q1: Can I use the MMA7361 with a 5V microcontroller?

• A1: Yes, but you need to use a voltage regulator to step down the 5V to 3.3V for the MMA7361.

Q2: How do I change the sensitivity of the MMA7361?

• A2: Use the G-Select pin. Connect it to GND for ±1.5g sensitivity or to Vdd for ±6g sensitivity.

Q3: What is the purpose of the self-test feature?

• A3: The self-test feature applies a known force to the sensor to verify its operation and ensure it is functioning correctly.

Q4: How do I reduce noise in the sensor readings?

• A4: Use a decoupling capacitor (0.1 µF) close to the Vdd pin and ensure proper grounding. Additionally, you can implement software filtering techniques.

This documentation provides a comprehensive guide to using the MMA7361 accelerometer. Whether you are a beginner or an experienced user, following these instructions and best practices will help you effectively integrate this component into your projects.