Category: Solar

#include <WiFi.h>
#include <HTTPClient.h>

/* Server and WiFi configurations are fake */

#define SERVER_IP "192.168.1.5"

#ifndef STASSID
#define STASSID "##############-iot"
#define STAPSK  "##################"
#endif

#define uS_TO_S_FACTOR 1000000

#define BATT_VOLTAGE_GPIO 36
#define GRID_PULSE_GPIO 25
#define SOLAR_PULSE_GPIO 26

float volt = -1.0;
RTC_DATA_ATTR int currentState = -1;

void setup() {

    pinMode(BATT_VOLTAGE_GPIO, INPUT);
    pinMode(GRID_PULSE_GPIO, OUTPUT);
    pinMode(SOLAR_PULSE_GPIO, OUTPUT);

    digitalWrite(GRID_PULSE_GPIO, LOW);
    digitalWrite(SOLAR_PULSE_GPIO, LOW);

    Serial.begin(115200);

    Serial.printf("Connecting to %s..\n", STASSID);

    WiFi.begin(STASSID, STAPSK);
    while (WiFi.status() != WL_CONNECTED) {
        delay(250);
        Serial.print(".");
    }

    Serial.print("\nConnected with IP: ");
    Serial.println(WiFi.localIP());
}

void pulse(int pin) {
    digitalWrite(pin, HIGH);
    delay(200);
    digitalWrite(pin, LOW);
}

// the loop function runs over and over again forever
void loop() {

    WiFiClient client;
    HTTPClient http;

    digitalWrite(LED_BUILTIN, HIGH);

    float v = 0;
    for (int i = 0; i < 200; i++) {
        v += analogRead(BATT_VOLTAGE_GPIO);
        delay(2);
    }
    volt = v / 200.0;

    Serial.print("Voltage Read: ");
    Serial.println(volt);

    http.begin(client, "http://" SERVER_IP "/autoTransferSwitch.php"); //HTTP
    http.addHeader("Content-Type", "application/x-www-form-urlencoded");

    // start connection and send HTTP header and body
    String postStr = "id=sunroom";
    postStr += "&volt=" + String(volt);
    postStr += "&state=" + String(currentState);

    int httpResponseCode = http.POST(postStr);
    digitalWrite(LED_BUILTIN, LOW);

    Serial.printf("Response code: %d\nResult: ", httpResponseCode);

    String instructions = http.getString();
    Serial.println(instructions);

    String result = "nothing";
    long sleepTime = 5L;

    char buffer[100];
    strncpy(buffer, instructions.c_str(), 100);

    const char d[2] = ",";
    int field = 0;
    char* token = strtok(buffer, d);
    while ( token != NULL ) {
        if (field == 0) {
            result = String(token);
        }

        if (field == 1) {
            sleepTime = atol(token);
        }
        token = strtok(NULL, d);
        field++;
    }

    if (result.equals("solar")) {
        pulse(SOLAR_PULSE_GPIO);
        currentState = 1;
    } else if (result.equals("grid")) {
        pulse(GRID_PULSE_GPIO);
        currentState = 0;
    } else {
        digitalWrite(GRID_PULSE_GPIO, LOW);
        digitalWrite(SOLAR_PULSE_GPIO, LOW);
    }

    http.end();

    Serial.print("Sleeping for seconds: ");
    Serial.println(sleepTime);

    esp_sleep_enable_timer_wakeup(uS_TO_S_FACTOR * sleepTime);
    esp_deep_sleep_start();
}

<?php

date_default_timezone_set('America/Toronto');

// I've changed the location to protect my own privacy

$lat    = 42.9293;
$log    = -102.9478;
$zenith = 90;

$nextWait = 900;

// The voltage levels are ADC readings from ESP32 (divided by 10) and not actual volts

// voltage level when battery is fully charged and can either be used or be charged with solar
$solarChargeLevel = 280;

// voltage level when battery is okay to be used with or without solar (come off of grid)
$okChargeLevel    = 260;

// voltage level when battery must be charged (get on grid)
$mustChargeLevel  = 252;

$now = time();

$sr = date_sunrise($now, SUNFUNCS_RET_TIMESTAMP, $lat, $log, $zenith);
$ss = date_sunset($now, SUNFUNCS_RET_TIMESTAMP, $lat, $log, $zenith);

$srStr = date("D M d Y - h:i:s", $sr);
$ssStr = date("D M d Y - h:i:s", $ss);

$logFile = "/home/kang/log/autoTransferSwitch.log";
$dateStr = date("Y-m-d H:i:s");

header("Content-Type: text/plain");

$id      = isset($_POST["id"]) ? $_POST["id"] : null;
$batVolt = isset($_POST["volt"]) ? $_POST["volt"] : null;

// -1 = initial, 0 = grid state, 1 = solar state
$currentState = isset($_POST["state"]) ? intval($_POST["state"]) : -1;

file_put_contents($logFile, "$dateStr, " . 
    "device reported: battery voltage: $batVolt and current state: $currentState\n",
    FILE_APPEND);

if (!is_null($id)) {

    if ($id === "sunroom") {
        $action = "nothing";
        $b      = intval($batVolt) / 10.0;

        // During day is defined by one hour after sunrise and one hour after sunset
        $duringDay   = (($sr + 3600) <= $now && $now <= ($ss - 3600));
        $duringNight = (!$duringDay);

        if ($currentState == -1) {
            if ($b <= $mustChargeLevel) {
                $action       = "grid";
                $currentState = 0;
            } else {
                $action       = "solar";
                $currentState = 1;
            }
        } else if ($currentState == 0) {

            // We are charging from the grid

            if ($duringDay && $b >= $okChargeLevel) {

                // During the day we want to use solar or the battery as much as possible;
                // This is a trickle charge so that we can take advantage of the sun.

                $action       = "solar";
                $currentState = 1;

            } else {

                // Otherwise charge until battery is full

                if ($b >= $solarChargeLevel) {
                    $action       = "solar";
                    $currentState = 1;
                }

            }

            if ($b >= 0.985 * $solarChargeLevel) {
                // We are getting closer to fully charge so
                // reduce communication interval from 15 min to 5 min
                $nextWait = 300;
            }

        } else if ($currentState == 1) {

            // We are either using the battery or the solar panels

            if ($b <= $mustChargeLevel || $now > $ss + 3600) {

                // Charge the batteries if we must or one hour past sunset

                $action       = "grid";
                $currentState = 0;
            }

            if ($b <= 1.025 * $mustChargeLevel) {
                // We are getting closer to require charging so reduce
                // communication interval from 15 min to 5 min
                $nextWait = 300;
            }

        }

        // for testing purpose
        // $nextWait = 15;
        echo ($action . "," . $nextWait);

        file_put_contents($logFile, "$dateStr, $batVolt, $action, " .
            "sun: [$srStr - $ssStr], new state: $currentState, wait: $nextWait\n",
            FILE_APPEND);
    }

}