ESP32 - Cooling System using DS18B20 Temperature Sensor

This tutorial instructs you how to make a cooling system using ESP32, DS18B20 temperature sensor and fan. In detail:

If the temperature read from DS18B20 sensor is above a threshold, ESP32 automatically turns the cooling fan on.
If the temperature read from DS18B20 sensor is below another threshold, ESP32 automatically turns the cooling fan off.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	Micro USB Cable
1	×	Temperature Sensor DS18B20
1	×	4.7 kΩ resistor
1	×	Relay
1	×	12V Cooling Fan
1	×	12V Power Adapter
1	×	Jumper Wires
1	×	(Optional) 5V Power Adapter
1	×	(Optional) DC Power Jack
1	×	(Optional) ESP32 Screw Terminal Adapter

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Introduction to Cooling Fan and DS18B20 Temperature Sensor

We have specific tutorials about DS18B20 temperature sensor and fan. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

How System Works

The ESP32 reads the temperature from the DS18B20 temperature sensor
If the temperature is above an upper threshold, ESP32 automatically turns the fan on
If the temperature is below a lower threshold, ESP32 automatically turns the fan off

ESP32 keeps checking the temperature infinitely.

The lower threshold and upper threshold can be the same value.

ESP32 Code

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-cooling-system-using-ds18b20-temperature-sensor */ #include <OneWire.h> #include <DallasTemperature.h> #define TEMP_UPPER_THRESHOLD 30 // upper temperature threshold #define TEMP_LOWER_THRESHOLD 15 // lower temperature threshold #define SENSOR_PIN 2 // ESP32 pin connected to DS18B20 sensor's DQ pin #define RELAY_FAN_PIN A5 // ESP32 pin connected to relay OneWire oneWire(SENSOR_PIN); DallasTemperature DS18B20(&oneWire); void setup() { Serial.begin(9600); // initialize serial DS18B20.begin(); // initialize the DS18B20 sensor } void loop() { DS18B20.requestTemperatures(); // send the command to get temperatures float temperature = DS18B20.getTempCByIndex(0); // read temperature in Celsius if (temperature > TEMP_UPPER_THRESHOLD) { Serial.println("Turn the fan on"); digitalWrite(RELAY_FAN_PIN, HIGH); // turn on } else if (temperature < TEMP_LOWER_THRESHOLD) { Serial.println("Turn the fan off"); digitalWrite(RELAY_FAN_PIN, LOW); // turn off } delay(500); }

The above ESP32 code automatically turns the fan on if the temperature is above 30°C, and keeps the fan on until the temperature is below 15°C

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
On Arduino IDE, Navigate to Sketch Include Library Manage Libraries

Type “OneWire” on the search box, then look for the OneWire library by Paul Stoffregen
Click Install button to install OneWire library.

Type “Dallas” on the search box, then look for the DallasTemperature library by Miles Burton.
Click Install button to install DallasTemperature library.

Copy the above code and paste it to Arduino IDE.
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
Make the sensor colder or hotter. For example, putting the sensor near a hot cup of coffee
Check the fan's state

Advanced Knowledge

The algorithm used on above tutorial to control the tmperature is called the on-off controller (also known as the "bang-bang" controller, or the signaller). This algorithm is simple to implement and works well in temperature control.
An alternative for the above algorithm is the PID controller. The PID controller makes the desired temperature more stable. However, it is very difficult to understand and implement. Therefore, the PID controller is not widely used in temperature control.

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