lamaPLC project: Digitales Potentiometer Board Moduls

A digital potentiometer (or “digipot”), such as the Renesas X9C series, is a semiconductor device that replicates the function of a mechanical potentiometer—varying resistance—but replaces the manual knob with digital control signals.

The X9C102, X9C103, X9C104, and X9C503 are digitally controlled (XDCP) potentiometers. The device consists of a resistor array, wiper switches, a control section, and nonvolatile memory. The wiper position is controlled by a three-wire interface.

The potentiometer is implemented using a resistor array composed of 99 resistive elements and a wiper-switching network. Between each element and at either end are tap points accessible to the wiper terminal. The position of the wiper element is controlled by the CS, U/D, and INC inputs. The wiper position can be stored in non-volatile memory and recalled upon subsequent power-up.

The device can be used as a three-terminal potentiometer or a two-terminal variable resistor in a wide variety of applications, from control to signal processing to parameter adjustment.

• Resolution: 100 Wiper Tap Points (0–99).
• Interface: 3-wire serial (CS, U/D, INC).
• Memory: Non-volatile EEPROM (retains position for 100 years).
• Supply Voltage (Vcc): 5V
• Resistance Tolerance: ±20% end-to-end.
• Typical Wiper Resistance: 40 Ω at 1 mA

Full datasheet: https://www.renesas.com/en/document/dst/x9c102-x9c103-x9c104-x9c503-datasheet

The Renesas X9C series module board, commonly known as the X9C103S module, organizes the chip's pins into two separate header rows, making it more convenient to connect with breadboards and microcontrollers such as Arduino. Usually, it includes a 5-pin control header on one side and a 3-pin potentiometer header on the opposite side.

Quick Wiring Guide

• For 0-5V Voltage Divider: Connect VH to 5V, VL to GND, and read the output from VW.
• Control Interface: Connect CS, INC, and U/D to any three digital GPIO pins on your microcontroller.
• Saving Settings: To save the current resistance so it persists after power-off, you must pull CS HIGH while INC is already HIGH.

To operate a Renesas X9C series digital potentiometer (such as the X9C103S) with an Arduino, you can either utilise a dedicated library like DigiPotX9Cxxx or manually control the pins. Here is a straightforward example that gradually varies the resistance from minimum to maximum without requiring any external library.

Wiring Diagram

// Pin Definitions
const int CS_PIN = 10;
const int INC_PIN = 9;
const int UD_PIN = 8;
 
void setup() {
  Serial.begin(9600);
 
  // Set control pins as outputs
  pinMode(CS_PIN, OUTPUT);
  pinMode(INC_PIN, OUTPUT);
  pinMode(UD_PIN, OUTPUT);
 
  // Initial state: deselect chip and set high idle
  digitalWrite(CS_PIN, HIGH);
  digitalWrite(INC_PIN, HIGH);
 
  Serial.println("Starting X9C Sweep...");
}
 
// Function to move the wiper 1 step
void moveWiper(bool up) {
  digitalWrite(UD_PIN, up ? HIGH : LOW); // Set direction
  digitalWrite(CS_PIN, LOW);             // Select chip
  delayMicroseconds(1);
 
  digitalWrite(INC_PIN, LOW);            // Falling edge moves wiper
  delayMicroseconds(1);
  digitalWrite(INC_PIN, HIGH);           // Return to high
 
  digitalWrite(CS_PIN, HIGH);            // Deselect to end movement
}
 
// Function to reset the wiper to 0 (by moving down 100 times)
void resetToZero() {
  for (int i = 0; i < 100; i++) {
    moveWiper(false);
  }
}
 
void loop() {
  resetToZero(); // Start from a known position (0)
  Serial.println("At 0% resistance");
  delay(2000);
 
  // Gradually increase resistance
  for (int i = 0; i < 100; i++) {
    moveWiper(true);
    int value = analogRead(A0); // Read voltage at wiper
    Serial.print("Step: "); Serial.print(i);
    Serial.print(" | Analog Value: "); Serial.println(value);
    delay(50);
  }
 
  Serial.println("At 100% resistance");
  delay(2000);
}

Key Logic Steps

• Selection: The chip is only active when CS is pulled LOW.
• Direction: The U/D pin indicates whether the resistance increases or decreases.
• The “Pulse”: The INC pin is negative-edge triggered. A transition from HIGH to LOW triggers the movement.
• No Feedback: These chips cannot tell the Arduino their current position. The resetToZero() function ensures you start at a known point by forcing the wiper down 100 times.

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