BuddyC
Published © GPL3+

AV Cabinet Fan Controller

Arduino powered thermostat and fan controller with overheating alarm.

EasyFull instructions provided8,033
AV Cabinet Fan Controller

Things used in this project

Hardware components

Arduino Nano R3
Arduino Nano R3
×1
DHT11 Temperature & Humidity Sensor
DHT11 Temperature & Humidity Sensor
×1
5v DC Relay Module
×1

Story

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Schematics

Temp Controlled Fan

Tempcontrolledfan schem

Code

FanTempController

C/C++
Arduino sketch that uses the average temp reading from a DHT11 sensor to turn on a fan via a relay.
// Temperature controller for A/V Cabinet
// Fan is controlled by 10A relay connected to a 12v (computer) or 5v (USB) Fan
// Piezo alarm for alternate overheating alert


int FANTEMP = 95;      // High temp at which the fan turns on (90*F)
int ALARMTEMP = 120;   // Overheating temp (120*F)
int FANLED = 2;        // Pin for fan "on" LED
int TEMPOK = 3;        // LED for when temp is under FANTEMP
int ALARMLED = 4;      // Alarm LED 
int ALARMPIN = 7;      // Audible alarm for overheating
// DHTPIN = 8;        (defined below)
int FANPIN = 9;        // Relay for fan switch

#include "DHT.h"        // Written by ladyada, public domain
#define DHTPIN 8        // DHT Sensor

// Uncomment whatever type you're using!
#define DHTTYPE DHT11   // DHT 11 
//#define DHTTYPE DHT22   // DHT 22  (AM2302)
//#define DHTTYPE DHT21   // DHT 21 (AM2301)

// Initialize DHT sensor for normal 16mhz Arduino
DHT dht(DHTPIN, DHTTYPE);
// NOTE: For working with a faster chip, like an Arduino Due or Teensy, you
// might need to increase the threshold for cycle counts considered a 1 or 0.
// You can do this by passing a 3rd parameter for this threshold.  It's a bit
// of fiddling to find the right value, but in general the faster the CPU the
// higher the value.  The default for a 16mhz AVR is a value of 6.  For an
// Arduino Due that runs at 84mhz a value of 30 works.
// Example to initialize DHT sensor for Arduino Due:
//DHT dht(DHTPIN, DHTTYPE, 30);

// Readings used for average
const int numReadings = 10;

// Set variables to zero
float avetemp = 0;                
float temp = 0;
float checkdelay = 0;           

void setup() {
  Serial.begin(9600); 
  Serial.println("Temp Monitor Started");
  
  dht.begin();
  pinMode(FANPIN,OUTPUT);
  pinMode(ALARMPIN,OUTPUT);
  pinMode(ALARMLED,OUTPUT);
  pinMode(FANLED,OUTPUT);
  pinMode(TEMPOK,OUTPUT);
  
  digitalWrite(FANPIN, HIGH);
  digitalWrite(FANLED, HIGH);
  digitalWrite(ALARMLED, HIGH);
  digitalWrite(TEMPOK, HIGH);
    for(int x = 0; x < 5; x++){                // Test Alarm 
        tone(ALARMPIN, 220 * x, 75);
        delay(100);                  
       }
   Serial.print("Fan Test Started (5 Seconds) "); 
    for(int x = 0; x < 5; x++){
     Serial.print(".");
     delay(1000); 
    }
    Serial.println("Done");
  digitalWrite(FANPIN, LOW);
  digitalWrite(FANLED, LOW);
  digitalWrite(ALARMLED, LOW);
  digitalWrite(TEMPOK, LOW);
  noTone(ALARMPIN);
 }

void loop() {
  // Wait a few seconds between measurements.
  delay(2000);
  temp = 0;

    Serial.print("Realtime Temp: \t");

  for (int x = 0; x < numReadings; x++){
    float f = dht.readTemperature(true);            // Read temperature as Fahrenheit
    Serial.print(f);
    Serial.print("\t");
    temp = f + temp;
    delay(3000);                                    // delay in between reads for stability  
  }    
  Serial.println();
  
  avetemp = temp / numReadings;                    // calculate the average
  Serial.print("Average Temp is ");
  Serial.println(avetemp);                         // send it to the computer as ASCII digits

     // Check if any reads failed and exit early (to try again).
  if (isnan(temp)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Set off alarm if overheating  
    if (avetemp>ALARMTEMP) {
      digitalWrite(ALARMLED, HIGH);
      Serial.print("Temperature is over ");
      Serial.print(ALARMTEMP);
      Serial.println(", Alarm is on");
       for(int x = 0; x < 3; x++){                  // Sound the alarm for 5 seconds 
        tone(ALARMPIN, 660, 1000);                  // Fan should already be running from last loop, if not, it will start right after alarm sounds
        delay(500);
        tone(ALARMPIN, 440, 1000);
        delay(500);
        }
     noTone(ALARMPIN);
     checkdelay = 30000;                            // Switch the normal 5 min delay to 30 seconds before going through the loop again 
   } else {
    digitalWrite(ALARMLED,LOW);
    Serial.print("Temperature is under ");
    Serial.print(ALARMTEMP);
    Serial.println(", Alarm is off");
    checkdelay = 300000;                            // Unless temp is over 120*F the fan runs for 5 minutes before temp is checked again
  }

// Turn on fan if cabinet is warm
  if (avetemp>FANTEMP) {
    digitalWrite(FANPIN, HIGH);
    digitalWrite(FANLED, HIGH);
    digitalWrite(TEMPOK, LOW);
    Serial.print("Temperature is over ");
    Serial.print(FANTEMP);
    Serial.print(", Fan is on (for ");
    Serial.print(checkdelay / 1000 / 60);
    Serial.println(" minutes)");
    delay(checkdelay);                               // turn on minimum of 5 min (unless alarm is going off, then it loops after 30 seconds)
   } else {
    digitalWrite(FANPIN,LOW);
    digitalWrite(FANLED,LOW);
    digitalWrite(TEMPOK,HIGH);
    Serial.print("Temperature is under ");
    Serial.print(FANTEMP);
    Serial.println(", Fan is off");                   // When fan is off, Temp is read every 30 seconds
  }
    
  Serial.println();
  Serial.println();
  
}

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BuddyC

BuddyC

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