car_charge_switch_led_v1.ino

/*         This is my second Arduino sketch, I wanted to monitor the output generated from my solar panels and switch power onto our Nissan Leaf BEV
 *      when sufficient solar power is available to minimise power useage from the grid.
 *
 *          My first sketch, still currently in use, used a clip on current transformer, bridge rectifyer, load resistor and capacitor smoothing.
 *      I used, and will continue to use, a Sonoff TH which turns on a remote Sonoff POW just inside the garage door. This enables me to see how much power
 *      I have put into the car. I took the TH part to pieces expecting to find a thermistor only to find a I2C I/F. However I found a lead to switch high and low,
 *      giving a "temmperature" of -19 to +3 degrees. Also found 3.3v to power the Arduino all input via 3.5mm jack and socket.
 *      Problems are A, getting the clip on ampmeter into the solar box was difficult. B, smoothing was inadequate causing calculated
 *      watts to vary. C, I needed to guess what the wattage was using other measurements and found that output was not consistant and varied across the range,
 *      possibly caused by cable loops inside the box. D. To change the turn on threshold according to the season, I need to change the sketch and upload it.
 *
 *         This system works very well on the Leaf, but I cannot confirm any other models. I have heard that the Renault Zoe can get grumpy if power is turned off and on,
 *      it is from the same stable as the Leaf, so possibly someone was switching too quickly.
 *
 *        To test the second sketch, I used a cyle led light that had a flashing option. I simply blanked off various number of flashes and checked that output was consistent
 *      for the same number of blanked flashes. Variation was very small, mostly exactly the same.
 *
 *        This second sketch utilises the flashing LED on the generation meter and grid meter to give a very accurate watt reading and eliminate intrusion into power boxes.
 *      I have tested it on the grid meter and the readings are a very close match to a "proper" mains monitor.
 *
 *        My eventual aim. sketch 3, is to also monitor the grid LED and output both readings to a Nextion and have a button on the screen to
 *      adjust the turn on threshold remotely. I suspect I will have to learn about interrupts to do this.
 *
 *      I apologise if my novice sketch causes some raised eyebrows among the experienced Arduino programmers.
 *
 *      Terry Rowland, retired computer hardware engineer.
 */


unsigned long blinkfirst;                        // note time of flash
unsigned long blinkInterval;                     // calculated time measured between flashes
          int blinkmeter;                        // Flash from generation meter,0 = off, 1 = on, 1000/hr = 1Kwh;
unsigned long blinksecond;                       // note time of next flash

       String chargeState="Reset";               //simply not on, off or blank
unsigned long currentTime;

          int inPin = 7;                         // output from digital light sensor connected to digital pin 7

unsigned long setWaitTime=120000;                // used to set time between car charge on/off frequency, 2 minutes.
          int switchOff;                         // stop charge threshold, set in setup to switchOn - 200, simply a "reasonable" range
 volatile int switchOn=1900;                     // start charge watts threshold, plan to use nextion buttons to change this with the seasons

unsigned long time;

unsigned long waitTimeStart;                     // note time charge on/off check interval start
unsigned long wattConversion = 3600000;          // 1000 flashes/hr = 1 Kwh, taken from meter info on generation meter;
                                                 // 1000 flashes/3600 secs = 1 Kw;
                                                 // 1 flash/3.6 secs = 1 Kw;
                                                 // 1 flash/3600 msecs = 1 kw;
                                                 // 1 flash/3,600,000 msecs = 1 watt;
                                                 // 3,600,000 divided by blinkInterval = watts
          int watts;



void setup()                                     // the setup routine runs once when you press reset or power on;
{
  switchOff=(switchOn-200);                      // arbitory range, this way means Nextion button need change volatile switch On only.
  Serial.begin(9600);
  pinMode(9,OUTPUT);
  pinMode(inPin, INPUT);
  pinMode(13,OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);                // only used during debug/testing
  watts=0;
  digitalWrite(9, LOW);                          // to ensure sonoffTH is off to start with, it is on otherwise
  watts = constrain(watts, 0, 4000);             // stops spurious values observed during debug/testing, probably cured by trim pot on photo sensor board
  time=millis();
  waitTimeStart=time;
}


void loop()
{


                  /* Serial.print(waitTimeStart);
                     Serial.print(" Start Time ");     Used for debug/testing
                     Serial.print(latestTime);
                     Serial.print(" latest time ");
                     Serial.println((latestTime-waitTimeStart));
                  */
      while(digitalRead(inPin)==HIGH)           //high = LED off so wait for led to flash on
            {
             time=millis();
             currentTime=time;
             if ((currentTime-waitTimeStart)>setWaitTime) CheckChargeState();
                   /*  Serial.print(waitTimeStart);
                       Serial.print(" Start Time 1, ");        Used for debug/testing
                       Serial.print(latestTime);
                       Serial.print(" latest time 1,");
                       Serial.println((latestTime-waitTimeStart));
                   */
            }

     time=millis();
     blinkfirst=time;                          // time when led turns on
     blinkInterval=(blinkfirst-blinksecond);
     watts=(wattConversion/blinkInterval);
     if(blinkInterval<850)watts =0;            // meter led on constantly when no generation gives blinkInterval of 800ms delay
     // Serial.println(blinkInterval);         // used for debug/testing
     Serial.print(watts);                      // will o/p to Nextion next version meanwhile enables check of solar output, not convenient but useful.
     Serial.println(" Watts a");               // will o/p to Nextion next version
     delay(800);                               // kills possible de-bounce/flicker, 800ms is outside max generation of my solar panels

      while(digitalRead(inPin)==HIGH)          //LED off, digital light sensor inverts light input
            {
              time=millis();
              currentTime=time;
              if ((currentTime-waitTimeStart)>setWaitTime) CheckChargeState();
            /*  Serial.print(waitTimeStart);
                Serial.print(" Start Time 2 ");
                Serial.print(latestTime);              used for debug/testing
                Serial.print(" latest time 2 ");
                Serial.println((currentTime-waitTimeStart));
             */
            }

        time=millis();
        blinksecond=time;                         // note when led turns on again

        blinkInterval=(blinksecond-blinkfirst);   // calculate time beteen meter LED blinks.
        watts=(wattConversion/blinkInterval);
        if(blinkInterval<850)watts =0;
        Serial.print(watts);                      // will o/p to Nextion next version meanwhile enables check of solar output, not convenient but useful.
        Serial.println(" Watts b");
                                                  /* meter led on constantly when no generation
                                                     gives blinkInterval of 800 from de-bounce delay.
                                                     Ensures car turns off if blinks stop unexpectedly and leave a value in watts.
                                                     Under normal operation watts gradually decrease to turn car off.
                                                  */

               /*Serial.println(blinkInterval);   // used for debug or testing.
                 Serial.print(watts);
                 Serial.println(" Watts b");
               */
        delay(800);                               // de-bounce/flicker kill

}                                                 // end of void loop
   void CheckChargeState()
   {
    if (watts > switchOn)
       {
        digitalWrite(9, HIGH);                   // change to LED_BUILTIN, LOW for testing
        chargeState="Car charging.";
       }
    if (watts < switchOff)
       {
        digitalWrite(9, LOW);                    // change to LED_BUILTIN, LOW for testing
        chargeState="Car not charging.";
       }
    Serial.println(chargeState);                 // will not need when Nextion working
    time=millis();
    waitTimeStart=time;                          //delay between charge stop/start
           /* Serial.print(waitTimeStart);       //used for debug/testing
            Serial.println(" Start Time 3 ");
           */
    time=millis();
       currentTime=time;
            /*Serial.print(latestTime);
              Serial.print(" latest time 3 ");   // used for debug/testing
            */
   }