How to Use Triple Axis Accelerometer (ADXL335): Examples, Pinouts, and Specs

The ADXL335 is a small, thin, low-power triple-axis accelerometer with signal-conditioned voltage outputs. It measures acceleration with a minimum full-scale range of ±3 g. It can measure the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion, shock, or vibration. Common applications include gaming devices, mobile devices, sports and health devices, and system orientation detection.

• Power Supply: 1.8V to 3.6V DC
• Sensitivity: Typically 300 mV/g at 3V (X, Y, Z)
• Measurement Range: ±3 g
• Bandwidth: Selectable between 0.5 Hz and 1600 Hz
• Temperature Range: -40°C to +85°C
• Zero-g Bias Level: 1.5V (typical at V_S = 3V)

To use the ADXL335 with a microcontroller like the Arduino UNO, follow these steps:

1. Connect VCC to the 3.3V output on the Arduino.
2. Connect GND to one of the GND pins on the Arduino.
3. Connect X-OUT, Y-OUT, and Z-OUT to three analog input pins on the Arduino (e.g., A0, A1, A2).
4. If using the self-test feature, connect ST to a digital output pin; otherwise, leave it unconnected.

Before using the accelerometer, it is important to calibrate it to ensure accurate readings. This involves reading the outputs at a known orientation (e.g., lying flat) and adjusting the readings to account for zero-g bias and sensitivity.

• Use capacitors for noise reduction if the application is sensitive to noise.
• Avoid physical shock and vibration that exceed the specified limits.
• Ensure that the power supply is stable and within the specified voltage range.

// Define the analog pins connected to the accelerometer
const int xPin = A0;
const int yPin = A1;
const int zPin = A2;

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

void loop() {
  // Read the analog values from the accelerometer
  int xVal = analogRead(xPin);
  int yVal = analogRead(yPin);
  int zVal = analogRead(zPin);

  // Convert the analog values to 'g' values
  float xG = ((float)xVal - 341.5) / 68.5; // 341.5 and 68.5 are calibration values
  float yG = ((float)yVal - 341.5) / 68.5; // Replace with your calibrated values
  float zG = ((float)zVal - 341.5) / 68.5;

  // Print the results
  Serial.print("X: ");
  Serial.print(xG);
  Serial.print("g, Y: ");
  Serial.print(yG);
  Serial.print("g, Z: ");
  Serial.print(zG);
  Serial.println("g");

  // Delay before the next reading
  delay(100);
}

• Inaccurate Readings: Ensure that the accelerometer is properly calibrated. Check for any mechanical stress or thermal variation that may affect the sensor.
• Noisy Signal: Use capacitors to filter the noise, and keep the power supply stable. Avoid long wires to reduce electromagnetic interference.
• Unresponsive Sensor: Check the connections and ensure that the power supply is within the specified range.

Q: Can the ADXL335 measure rotation? A: No, the ADXL335 measures linear acceleration. For rotation, you would need a gyroscope.

Q: What is the purpose of the self-test pin? A: The self-test pin is used to verify the functionality of the accelerometer. When activated, it applies a known force to the sensor for testing purposes.

Q: How do I convert the analog readings to 'g' values? A: The analog readings can be converted to 'g' values by first subtracting the zero-g bias level and then dividing by the sensitivity. Calibration is necessary to determine the exact values for these calculations.

Q: Can I use the ADXL335 with a 5V microcontroller? A: Yes, but ensure that the VCC is connected to a 3.3V supply, and use voltage dividers or level shifters for the analog outputs if the microcontroller's analog inputs are not 3.3V tolerant.