greenhouse_monitor.ino in Arduino

The whole greenhouse: two hysteresis loops and a CSV report line.

// The whole greenhouse: soil pump, heat lamp, and a serial report.

const int SOIL_PIN = A0;
const int TEMP_PIN = A2;
const int PUMP_PIN = 7;
const int HEAT_PIN = 4;

const int SOIL_DRY = 700;
const int SOIL_WET = 500;
const float TEMP_LOW_C = 16.0;
const float TEMP_HIGH_C = 20.0;

bool pumping = false;
bool heating = false;
unsigned long lastReport = 0;

float readCelsius() {
  float volts = analogRead(TEMP_PIN) * (5.0 / 1023.0);
  return (volts - 0.5) * 100.0;
}

void setup() {
  pinMode(PUMP_PIN, OUTPUT);
  pinMode(HEAT_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("time_s,soil,temp_c,pump,heat");
}

void loop() {
  int soil = analogRead(SOIL_PIN);
  float tempC = readCelsius();

  // Hysteresis on both actuators keeps the relays calm.
  if (!pumping && soil > SOIL_DRY) pumping = true;
  if (pumping && soil < SOIL_WET) pumping = false;
  if (!heating && tempC < TEMP_LOW_C) heating = true;
  if (heating && tempC > TEMP_HIGH_C) heating = false;

  digitalWrite(PUMP_PIN, pumping ? HIGH : LOW);
  digitalWrite(HEAT_PIN, heating ? HIGH : LOW);

  if (millis() - lastReport >= 5000) {
    lastReport = millis();
    Serial.print(millis() / 1000); Serial.print(',');
    Serial.print(soil); Serial.print(',');
    Serial.print(tempC); Serial.print(',');
    Serial.print(pumping); Serial.print(',');
    Serial.println(heating);
  }
}

How it works

1. Soil and temperature each get a two-threshold band.
2. readCelsius converts the TMP36 the standard way.
3. Every five seconds one CSV row logs state for the plotter.

Keywords and builtins used here

• HIGH
• LOW
• OUTPUT
• Serial
• analogRead
• begin
• bool
• const
• digitalWrite
• false
• float
• if
• int
• long
• loop
• millis
• pinMode
• print
• println
• readCelsius
• return
• setup
• true
• unsigned
• void

The run, in numbers

Lines

50

Characters to type

1295

Tokens

322

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 322 seconds.

Type this snippet

Step 2 of 3 in Encore, step 26 of 27 in Language basics.

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