How to Use Encoder: Examples, Pinouts, and Specs

The HEDM-5500#B13 is an optical incremental encoder manufactured by Broadcom. Encoders are devices that convert information from one format or code to another, and this specific model is designed to transform mechanical motion into digital signals. It is widely used in applications requiring precise motion control, such as robotics, CNC machines, printers, and industrial automation systems.

This encoder is particularly valued for its compact design, high resolution, and reliable performance in converting rotational motion into digital pulses, making it ideal for use in digital circuits and motion feedback systems.

The HEDM-5500#B13 encoder is designed for high accuracy and reliability. Below are its key technical details:

The HEDM-5500#B13 encoder typically has a 5-pin interface. Below is the pinout and description:

1. Power Supply: Connect the VCC pin to a regulated 5 V DC power source and the GND pin to the ground of your circuit.
2. Signal Outputs: Connect the A and B output pins to the digital input pins of your microcontroller or motion control system. These pins provide quadrature signals for determining direction and speed.
3. Index Pulse (Optional): If your application requires an index pulse for absolute positioning, connect the Index pin to a digital input pin.
4. Pull-Up Resistors: Use pull-up resistors (typically 10 kΩ) on the output pins if the encoder outputs are open-collector.
5. Mechanical Mounting: Secure the encoder to the shaft of the rotating object using the appropriate mounting hardware. Ensure proper alignment to avoid mechanical stress.

• Debouncing: Use software or hardware debouncing to filter out noise from the encoder signals.
• Signal Conditioning: If the encoder is used in a noisy environment, consider using shielded cables and signal conditioning circuits.
• Resolution: The resolution of 500 CPR means the encoder generates 500 pulses per revolution per channel. With quadrature decoding, this translates to 2000 counts per revolution.
• Direction Detection: Use the phase relationship between channels A and B to determine the direction of rotation.

Below is an example of how to connect and read the HEDM-5500#B13 encoder using an Arduino UNO:

• Connect the VCC pin to the Arduino's 5V pin.
• Connect the GND pin to the Arduino's GND pin.
• Connect the A and B pins to digital pins 2 and 3 on the Arduino.

// HEDM-5500#B13 Encoder Example with Arduino UNO
// Connect Channel A to pin 2 and Channel B to pin 3

volatile int encoderPosition = 0; // Variable to store encoder position
int lastEncoded = 0;             // Stores the last encoder state

void setup() {
  pinMode(2, INPUT_PULLUP); // Channel A
  pinMode(3, INPUT_PULLUP); // Channel B

  // Attach interrupts to handle encoder signals
  attachInterrupt(digitalPinToInterrupt(2), updateEncoder, CHANGE);
  attachInterrupt(digitalPinToInterrupt(3), updateEncoder, CHANGE);

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

void loop() {
  // Print the encoder position to the Serial Monitor
  Serial.print("Encoder Position: ");
  Serial.println(encoderPosition);
  delay(100); // Small delay for readability
}

void updateEncoder() {
  // Read the current state of Channel A and Channel B
  int MSB = digitalRead(2); // Most Significant Bit
  int LSB = digitalRead(3); // Least Significant Bit

  int encoded = (MSB << 1) | LSB; // Combine the two bits
  int sum = (lastEncoded << 2) | encoded; // Track state changes

  // Update position based on state transitions
  if (sum == 0b1101 || sum == 0b0100 || sum == 0b0010 || sum == 0b1011) {
    encoderPosition++;
  } else if (sum == 0b1110 || sum == 0b0111 || sum == 0b0001 || sum == 0b1000) {
    encoderPosition--;
  }

  lastEncoded = encoded; // Update the last state
}

1. No Output Signals:

   • Ensure the encoder is properly powered (5 V DC).
   • Verify all connections, especially the ground and signal pins.
   • Check for loose or misaligned mechanical mounting.

2. Incorrect Position Readings:

   • Verify the phase relationship between channels A and B.
   • Ensure the encoder resolution matches the software configuration.
   • Use pull-up resistors if the outputs are open-collector.

3. Noise in Signals:

   • Use shielded cables to reduce electromagnetic interference.
   • Add capacitors (e.g., 0.1 µF) across the signal lines for filtering.

4. Index Pulse Not Detected:

   • Confirm that the Index pin is connected to a digital input.
   • Check if the encoder is completing a full revolution.

Q: Can the HEDM-5500#B13 be used with a 3.3 V system?
A: No, the encoder requires a 5 V DC power supply. Use a level shifter if interfacing with a 3.3 V system.

Q: How do I calculate speed using the encoder?
A: Measure the time interval between pulses on Channel A or B, and use the formula:
Speed (RPM) = (Pulse Frequency × 60) / (Resolution × 4).

Q: What is the purpose of the Index pulse?
A: The Index pulse provides a single pulse per revolution, useful for absolute positioning or homing.

This concludes the documentation for the HEDM-5500#B13 encoder.