i built a project to monitor and control temp in my mini server room using a DHT22, Arduino UNO and a relay. The sketch is supposed to check temp, if it goes above 78F turn on fan (activate relay) for 10 min, check temp and deactivate relay if temp is below 78F.
I believe the crash results from memory shortage. I've read the guidance on use of millis(), and tried just about everything i can think of to fix the crashing/hanging. After an hour or so the sketch "hangs" and i have to reset the Arduino.
Sketch uses 29686 bytes (92%) of program storage space. Maximum is 32256 bytes.
Global variables use 1515 bytes (73%) of dynamic memory, leaving 533 bytes for local variables. Maximum is 2048 bytes.
Can someone take a look at my code? I would really appreciate any suggestions.
#define BLYNK_PRINT Serial
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 4); // set the LCD address to 0x27
#include <SPI.h>
#include <Ethernet.h>
#include <BlynkSimpleEthernet.h>
#include <DHT.h>
char auth[] = "XXXXXXXXXXXXXXXXXXXXXXXX"; // Auth Token Blynk
#define DHTTYPE DHT22
unsigned long startMillis;
unsigned long currentMillis;
const int DHTPIN = 2; // digital DHT sensor pin
const int RelayPin = 4; // digital relay pin
const unsigned int MaxTemp = 78; // defined temperature threshold
const unsigned long FanRunTime = 10 * 60 * 1000UL; // fan run time
// unsigned long interval;
DHT dht(DHTPIN, DHTTYPE); // initialize DHT sensor
BlynkTimer timer;
void setup() {
pinMode(RelayPin, OUTPUT); // pin for relay module set as output
digitalWrite(RelayPin, HIGH); // set default relay pin state, inactive = high
Serial.begin(9600);
Serial.println("DHT22"); // serial print sensor type
Blynk.begin(auth);
dht.begin();
lcd.begin(); // initialize the LCD
lcd.setCursor(3, 0);
lcd.print("XXXX");
}
void loop() {
Blynk.run();
delay(2000); // Wait a few seconds between measurements
float h = dht.readHumidity(); // read humidity as percentages
float t = dht.readTemperature(); // read temperature as Celsius (the default)
float f = dht.readTemperature(true); // read temperature as Fahrenheit (isFahrenheit = true)
if (isnan(h) || isnan(t) || isnan(f)) { // check if any reads failed and exit early (to try again)
Serial.println("Failed to read from DHT sensor");
return;
}
Blynk.virtualWrite(V5, h); // display state on Blynk
Blynk.virtualWrite(V6, f); // display state on Blynk
Blynk.virtualWrite(V7, dht.computeHeatIndex(f, h)); // display state on Blynk
float hif = dht.computeHeatIndex(f, h); // Compute heat index in Fahrenheit (the default)
float hic = dht.computeHeatIndex(t, h, false); // Compute heat index in Celsius (isFahreheit = false)
Serial.print("RS: "); // serial print relay state, 0 = on, 1 = off
Serial.print(digitalRead(RelayPin));
Serial.print("\t");
Serial.print("Humidity: "); // serial print temperature (C & F)
Serial.print(h);
Serial.print(" %\t");
lcd.setCursor(0, 2); // display humidity on LCD
lcd.print("Humidity: ");
lcd.print(dht.readHumidity());
lcd.print("%");
Serial.print("Temperature: "); // serial print temperature (C & F)
Serial.print(t);
Serial.print(" *C ");
Serial.print(f);
Serial.print(" *F\t");
lcd.setCursor(0, 1); // display temperature (F) on LCD
lcd.print("Temperature: ");
lcd.print(dht.readTemperature(true));
lcd.print("F");
Serial.print("Heat index: "); // serial print heatindex
Serial.print(hic);
Serial.print(" *C ");
Serial.print(hif);
Serial.println(" *F");
int relayState = digitalRead(RelayPin); // read relay state
if (relayState == LOW) { // if relay active
lcd.setCursor(0, 3), // display value on LCD
lcd.print("Fan Status: ON"), // display fan status
Blynk.virtualWrite(V8, "ON"); // display state on Blynk
}
else { // relay inactive
lcd.setCursor(0, 3), // display value on LCD
lcd.print("Fan Status: OFF"), // display fan status
Blynk.virtualWrite(V8, "OFF"); // display state on Blynk
}
if (f > MaxTemp ) { // check temperature and compare to threshold
currentMillis = millis(); // get the current time
digitalWrite(RelayPin, LOW); // activate relay if above threshold
}
if (currentMillis - startMillis >= FanRunTime) { // check clock for time elapsed on interval
startMillis = currentMillis; // save the start time
digitalWrite(RelayPin, HIGH); // deactivate relay if interval complete
}
}
