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Software (arduino code)

A project log for Classic car intermittent wiper motor controller

Reversible, no extra switch, multiple frequencies delay module for classic British cars.

Frederic LFrederic L 10/31/2020 at 11:340 Comments

Programmed using the Arduino framework.

I commented the code as much as I could, and it's fairly straight forward. Original 60 years old switch is debounced in software, and millis() function is used instead of delay() to avoid loop interruptions (we need to be able to read the switch state changes at all times).

The loop() function reads and interprets the switch state.

The wipe() function sends a wipe pulse when necessary.

#include <Arduino.h>

/* I/O PARAMETERS */
#define PIN_WIPER_OUTPUT 3 // PIN to wiper relay
#define PIN_INPUT_SWITCH 4 // Pin reading wiper dashboard switch position
#define SWITCH_DEBOUNCE_DELAY_MS 50 // Switch debounce delay in ms
#define TOGGLE_LIMIT_DELAY 2000 // Time to consider an ON-OFF-ON as a toggle

/* INTERMITTENT CONTROL PARAMETERS */
#define INTERMITTENT_1_MS 10000 // Intermittent delay 1 in ms
#define INTERMITTENT_2_MS 7500 // Intermittent delay 2 in ms
#define INTERMITTENT_3_MS 5000 // Intermittent delay 3 in ms
#define INTERMITTENT_4_MS 2500 // Intermittent delay 4 in ms

/* WIPER MOTOR RELATED PARAMETERS */
#define RELAY_TIME_MS 500 // Duration (ms) the relay stays closed to initiate the wiper swipe

uint8_t toggles = 0; // Track the ON->OFF->ON toggles
uint8_t switchState = LOW; // Keep track of previous switch status
uint8_t lastSwitchState = LOW;   // the previous reading from the switch
uint8_t forceWipe = false;  // Force a wipe now
unsigned long lastWipeTime = 0;
unsigned long lastOffTime = 0;  // Last time the switch was in the OFF position
unsigned long lastDebounceTime = 0;  // the last time the switch was toggled
unsigned long debounceDelay = 50;    // the debounce time in ms

void setup() {
  // Initialize PIN modes
  pinMode(PIN_WIPER_OUTPUT, OUTPUT);
  pinMode(PIN_INPUT_SWITCH, INPUT);

  // If wiper switch ON at power up, activates wipers
  if(digitalRead(PIN_INPUT_SWITCH)){
    switchState = HIGH;
    lastSwitchState = HIGH;
  }
}

void wipe() {
  // Wipe outputs based on switch position and toggle numbers
  if(switchState == HIGH) {
    int intermittentDelay = 0;
    // Wipers are on
    switch (toggles) {
      case 0:
        intermittentDelay = INTERMITTENT_1_MS;
        break;
      case 1:
        intermittentDelay = INTERMITTENT_2_MS;
        break;
      case 2:
        intermittentDelay = INTERMITTENT_3_MS;
        break;
      case 3:
        intermittentDelay = INTERMITTENT_4_MS;
        break;
      default:
        // Continuous wipers
        intermittentDelay = 0;
        break;
    }

    if(millis()-lastWipeTime > intermittentDelay || forceWipe) {
      //Send a wipe pulse
      digitalWrite(PIN_WIPER_OUTPUT, HIGH);
      lastWipeTime = millis();
      forceWipe = false;
    }

    if(millis()-lastWipeTime > RELAY_TIME_MS) {
      // End the pulse after the required delay
      digitalWrite(PIN_WIPER_OUTPUT, LOW);
    }

  } else {
    // digitalWrite(PIN_WIPER_OUTPUT, LOW);
  }
}

void loop() {

  // read the state of the switch into a local variable:
  int reading = digitalRead(PIN_INPUT_SWITCH);

  // check to see if you just switched the button
  // and you've waited long enough
  // since the last change to ignore any noise:

  // If the switch changed, due to noise or pressing:
  if (reading != lastSwitchState) {
    // reset the debouncing timer
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {
    // whatever the reading is at, it's been there for longer than the debounce
    // delay, so take it as the actual current state:

    // if the button state has changed:
    if (reading != switchState) {
      switchState = reading;

      // If ON to OFF detected
      if(switchState == LOW){
        lastOffTime = millis();
        digitalWrite(PIN_WIPER_OUTPUT, LOW); // Switch OFF the wipers (in case it's not a toggle, just an OFF action)
      }

      // If OFF to ON detected
      if(switchState == HIGH) {
        // Force a wipe as we either just switched on the wipers or are increasing the frequency
        forceWipe = true;
        if(millis()-lastOffTime < TOGGLE_LIMIT_DELAY) {
          // Toggle detected
          toggles++;
        } else {
          // Switching to ON only (not a toggle)
          toggles = 0;
        }
      }
    }
  }
lastSwitchState = reading;

// Finally...
wipe();
delay(10);
}

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