Intercooler water spray for ESP-32

iw_water_spray.ino

/*
  Intercooler Water Spray Controller  /  ZC33S
  ------------------------------------------------------------
  MCU      : ESP32 (Arduino core "ESP32 Dev Module")
  Boost in : AutoGauge 548 boost sensor WHITE wire (signal, ~1V @0bar)
             tapped via 1k series -> ADS1115 A0.  Sensor BLACK -> common GND.
             RED is left alone (the gauge powers the sensor). READ-ONLY: never
             drive voltage onto WHITE.
  Pump out : logic-level MOSFET low-side. Gate needs an external 10k pulldown
             to GND so the pump stays OFF whenever the MCU is unpowered.
             Flyback diode across the pump. Fuse (5-7.5A) on the pump 12V.
  LEDs     : RED  = hardware only, 5V rail -> 330ohm -> LED -> GND (power on/off)
             GREEN= GPIO -> 220ohm -> LED -> GND (lit while spraying; case A:
                    mirrors the pump, so it pulses with interval bursts)
  Master   : a toggle on the 12V(ACC) feed to the buck cuts MCU power = OFF.
             No software involvement; gate pulldown guarantees no spray.
  Config   : phone -> WiFi AP "ICWS-ZC33S" -> http://192.168.4.1
             Thresholds / interval / calibration are editable and persisted
             to NVS (survive power cycles). No logging.
  Libraries: Adafruit ADS1X15 (+ Adafruit BusIO). WiFi/WebServer/Preferences
             are part of the ESP32 core.
  ------------------------------------------------------------
  CALIBRATION (boost_bar = (mV - v0mV) / slopeMvBar):
    1) Key ON, engine OFF (manifold = atmosphere = 0 bar). Open the page,
       tap "Capture 0 bar" -> sets v0mV.
    2) Do a pull to a boost the AutoGauge gauge clearly shows (use its
       peak-recall). The page holds Peak mV. Then set slope by hand:
       slopeMvBar = (peakMv - v0mV) / peakBoost, type it into "slope",
       or while sitting at a known steady boost use "Capture slope point".
*/

#include <Wire.h>
#include <Adafruit_ADS1X15.h>
#include <WiFi.h>
#include <WebServer.h>
#include <Preferences.h>

// ---------- Pin map (ESP32) ----------
const int PIN_MOSFET    = 25;   // -> gate (EXTERNAL 10k pulldown to GND required)
const int PIN_LED_GREEN = 26;   // -> 220ohm -> green LED -> GND (spray active)
const int PIN_BTN       = 27;   // momentary push to GND (INPUT_PULLUP)
// I2C: SDA=21, SCL=22 -> ADS1115 (addr 0x48)

// ---------- WiFi AP ----------
const char* AP_SSID = "ICWS-ZC33S";
const char* AP_PASS = "spray12345";   // must be >= 8 chars

Adafruit_ADS1115 ads;
WebServer server(80);
Preferences prefs;

// ---------- Config (persisted in NVS) ----------
struct Config {
  float    boostOn;     // bar, arm threshold
  float    boostOff;    // bar, disarm threshold (hysteresis)
  uint32_t onMs;        // interval spray ON  (set offMs=0 for continuous)
  uint32_t offMs;       // interval spray OFF
  float    v0mV;        // white-wire mV at 0 bar (gauge)
  float    slopeMvBar;  // mV per bar
} cfg;

void loadCfg() {
  prefs.begin("icws", false);
  cfg.boostOn    = prefs.getFloat("boostOn", 0.40f);
  cfg.boostOff   = prefs.getFloat("boostOff", 0.20f);
  cfg.onMs       = prefs.getUInt ("onMs",    3000);
  cfg.offMs      = prefs.getUInt ("offMs",   1000);
  cfg.v0mV       = prefs.getFloat("v0mV",    456.2f);  // from screenshot; recalibrate with real sensor in car
  cfg.slopeMvBar = prefs.getFloat("slope",   456.2f);  // from screenshot; recalibrate with real sensor in car
  prefs.end();
}
void saveCfg() {
  prefs.begin("icws", false);
  prefs.putFloat("boostOn", cfg.boostOn);
  prefs.putFloat("boostOff", cfg.boostOff);
  prefs.putUInt ("onMs",    cfg.onMs);
  prefs.putUInt ("offMs",   cfg.offMs);
  prefs.putFloat("v0mV",    cfg.v0mV);
  prefs.putFloat("slope",   cfg.slopeMvBar);
  prefs.end();
}

// ---------- Runtime state ----------
bool  adsOk = false;
float lastMv = 0, lastBoost = 0, peakMv = 0;
bool  armed = false, sprayPhaseOn = true, spraying = false;
uint32_t lastPhase = 0, lastSample = 0;

float readMv() {
  if (!adsOk) return 0;
  int16_t raw = ads.readADC_SingleEnded(0);
  return ads.computeVolts(raw) * 1000.0f;
}
float toBoost(float mv) {
  if (cfg.slopeMvBar < 1.0f) return 0;
  return (mv - cfg.v0mV) / cfg.slopeMvBar;
}

// ---------- Web ----------
String page() {
  String s = F("<!doctype html><html><head><meta name=viewport "
               "content='width=device-width,initial-scale=1'><title>ICWS</title>"
               "<style>body{font-family:sans-serif;margin:16px;max-width:480px}"
               "input{width:90px}fieldset{margin-bottom:12px}"
               ".b{font-size:20px;font-weight:bold}</style></head><body>");
  s += F("<h2>IC Water Spray</h2><div>Live: <span class=b id=live>--</span></div>");
  s += F("<div>Peak: <span id=peak>--</span> mV "
         "<form style='display:inline' method=POST action=/resetpk>"
         "<button>reset peak</button></form></div>");
  s += F("<form method=POST action=/set><fieldset><legend>Thresholds</legend>");
  s += "ON (bar) <input name=boostOn value=" + String(cfg.boostOn,2) + "><br>";
  s += "OFF (bar) <input name=boostOff value=" + String(cfg.boostOff,2) + "><br>";
  s += "Spray ON (ms) <input name=onMs value=" + String(cfg.onMs) + "><br>";
  s += "Spray OFF (ms) <input name=offMs value=" + String(cfg.offMs) + "></fieldset>";
  s += F("<fieldset><legend>Calibration</legend>");
  s += "v0 (mV @0bar) <input name=v0mV value=" + String(cfg.v0mV,1) + "><br>";
  s += "slope (mV/bar) <input name=slope value=" + String(cfg.slopeMvBar,1) + "></fieldset>";
  s += F("<button type=submit>Save</button></form>");
  s += F("<form method=POST action=/zero><button>Capture 0 bar (v0 = now)</button></form>");
  s += F("<form method=POST action=/cal>known boost (bar) "
         "<input name=kb value=1.0><button>Capture slope point</button></form>");
  s += F("<script>setInterval(function(){fetch('/live').then(r=>r.json()).then(j=>{"
         "document.getElementById('live').textContent="
         "j.boost.toFixed(2)+' bar  ('+j.mv.toFixed(0)+' mV)  '+"
         "(j.spray?'SPRAY':(j.armed?'armed':'idle'));"
         "document.getElementById('peak').textContent=j.peak.toFixed(0);});},500);"
         "</script></body></html>");
  return s;
}

void handleRoot() { server.send(200, "text/html", page()); }
void handleLive() {
  String j = "{\"mv\":" + String(lastMv,1) + ",\"boost\":" + String(lastBoost,3)
           + ",\"peak\":" + String(peakMv,1)
           + ",\"armed\":" + (armed ? "true" : "false")
           + ",\"spray\":" + (spraying ? "true" : "false") + "}";
  server.send(200, "application/json", j);
}
float argF(const char* n, float d) { return server.hasArg(n) ? server.arg(n).toFloat() : d; }

void handleSet() {
  cfg.boostOn    = argF("boostOn", cfg.boostOn);
  cfg.boostOff   = argF("boostOff", cfg.boostOff);
  cfg.onMs       = (uint32_t)argF("onMs", cfg.onMs);
  cfg.offMs      = (uint32_t)argF("offMs", cfg.offMs);
  cfg.v0mV       = argF("v0mV", cfg.v0mV);
  cfg.slopeMvBar = argF("slope", cfg.slopeMvBar);
  if (cfg.boostOff > cfg.boostOn) cfg.boostOff = cfg.boostOn;  // keep hysteresis sane
  saveCfg();
  server.sendHeader("Location", "/"); server.send(303, "text/plain", "");
}
void handleZero() {
  cfg.v0mV = readMv(); saveCfg();
  server.sendHeader("Location", "/"); server.send(303, "text/plain", "");
}
void handleCal() {
  float kb = argF("kb", 0);
  if (kb > 0.05f) {
    float sl = (readMv() - cfg.v0mV) / kb;
    if (sl > 100.0f) { cfg.slopeMvBar = sl; saveCfg(); }
  }
  server.sendHeader("Location", "/"); server.send(303, "text/plain", "");
}
void handleResetPk() {
  peakMv = lastMv;
  server.sendHeader("Location", "/"); server.send(303, "text/plain", "");
}

void setup() {
  Serial.begin(115200);
  pinMode(PIN_MOSFET, OUTPUT);    digitalWrite(PIN_MOSFET, LOW);
  pinMode(PIN_LED_GREEN, OUTPUT); digitalWrite(PIN_LED_GREEN, LOW);
  pinMode(PIN_BTN, INPUT_PULLUP);

  loadCfg();

  Wire.begin(21, 22);
  adsOk = ads.begin();                       // ADS1115 @ 0x48
  if (adsOk) ads.setGain(GAIN_TWOTHIRDS);    // +-6.144V (headroom; add divider if signal nears 5V)
  else       Serial.println("ADS1115 not found");

  WiFi.mode(WIFI_AP);
  WiFi.softAP(AP_SSID, AP_PASS);
  server.on("/",        handleRoot);
  server.on("/live",    handleLive);
  server.on("/set",     HTTP_POST, handleSet);
  server.on("/zero",    HTTP_POST, handleZero);
  server.on("/cal",     HTTP_POST, handleCal);
  server.on("/resetpk", HTTP_POST, handleResetPk);
  server.begin();
}

void loop() {
  server.handleClient();
  uint32_t now = millis();

  if (now - lastSample >= 20) {            // sample ~50 Hz
    lastSample = now;
    lastMv    = readMv();
    lastBoost = toBoost(lastMv);
    if (lastMv > peakMv) peakMv = lastMv;

    if      (lastBoost >= cfg.boostOn)  armed = true;    // hysteresis
    else if (lastBoost <= cfg.boostOff) armed = false;
  }

  if (armed) {                             // interval duty machine
    if ( sprayPhaseOn && (now - lastPhase >= cfg.onMs))  { sprayPhaseOn = false; lastPhase = now; }
    if (!sprayPhaseOn && (now - lastPhase >= cfg.offMs)) { sprayPhaseOn = true;  lastPhase = now; }
  } else {
    sprayPhaseOn = true; lastPhase = now;  // next arm starts on a spray burst
  }

  bool autoSpray = armed && sprayPhaseOn;
  bool manual    = (digitalRead(PIN_BTN) == LOW);   // held = force spray, ignores boost
  spraying = autoSpray || manual;

  digitalWrite(PIN_MOSFET,    spraying ? HIGH : LOW);
  digitalWrite(PIN_LED_GREEN, spraying ? HIGH : LOW);   // case A: green mirrors the pump
}