The DHT sensor line (DHT11/22) is one of the most commonly used in many electronic projects, ranging from home weather stations to plant automation systems, due to its simplicity and compactness as a temperature/humidity sensor. Although the more accurate and expensive DHT22 may be substituted (with some changes in the code), the DHT11 sensor module will be used in this project. With a basic 3-pin interface, the DHT11 sensor that will be used in this project is not the standalone 4-pin sensor version but rather, a 3-pin module that has a built-in capacitor & pull-up resistor, hence eliminating the need for additional components when building this circuit. Therefore, when interfaced with an Arduino board, the DHT11 sensor module can directly be connected to a digital pin which processes and feeds the serial data from the sensor to the microcontroller, for us to read.
In this DIY PCBA project, the temperature and humidity data from the DHT11 sensor will be displayed on a 0.96″ 128×64 OLED (organic light-emitting diode) display for us to visibly read. An advantage of using an i2c OLED display compared to other display types is that it only requires a 4-wire connection to the Arduino board and with a wide variety of libraries, it can be programmed with ease. A noticeable feature of an OLED display is its clarity, sharpness and visual quality of texts, figures & images that it can display.
Altogether, this is a fairly simple circuit project that is suitable for absolute beginners as it only requires a few components and some basic coding skills. However, for those who are more advanced, this project can definitely be improved upon and upgraded to add more features such as wireless communication (RF, LoRa, Bluetooth PCB, Wi-Fi, etc), RTC (real-time clock) data, additional sensor data (altitude, atmospheric pressure, gas concentrations, etc) and many other features. In order to realize this project, you will need to purchase components:
If you are using a different development board, it may require a different type of breadboard. For this project, FS Technology is utilizing an Arduino Nano, which necessitates the use of a breadboard. However, if an Arduino Uno is being used instead, the jumper wires can be directly plugged into the board pins, eliminating the need for the breadboard. Despite the change in board, the wiring for the DHT11 sensor module and OLED display to the Arduino board remains consistent. Furthermore, the wiring diagram for the DHT11 temperature and humidity sensor circuit is provided below.
#include
#include
#include
#define screen_width 128
#define screen_height 64
#define OLED_RESET 4
Adafruit_SSD1306 display(screen_width, screen_height);
#include “DHT.h”
#define DHTPIN 2
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);
void setup() {
dht.begin();
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
display.clearDisplay();
}
void loop() {
display.clearDisplay();
display.setTextSize(1);
display.setTextColor(SSD1306_WHITE);
display.setCursor(0, 15);
display.print(“Temperature:”);
display.setCursor(80, 15);
display.print(dht.readTemperature());
display.setCursor(110, 15);
display.print(” C”);
display.setCursor(0, 35);
display.print(“Humidity:”);
display.setCursor(80, 35);
display.print(dht.readHumidity());
display.setCursor(110, 35);
display.print(“%”);
display.display();
delay(2000);
With a fundamental understanding of this project and the basic principles that are involved in interfacing a sensor to an OLED display, there are certainly a multitude of ways which this project can be upgraded and improved upon. Most commonly, a setup like this can be integrated into a much larger weather station project by possibly adding on more sensors, a larger display, wireless capabilities, a case, etc. As demonstrated by this project, just by familiarizing yourself with some of the Arduino libraries that are available to use, it then becomes relatively effortless to code your very own weather station. A future project may involve the wireless transmission of such weather data from one microcontroller board to another in order to monitor a remote environment or centrally control an autonomous system. Nevertheless, projects like this are excellent to introduce hobby electronics to an absolute beginner and can very well also be targeted toward a more experienced PCBA manufacturer who may want to explore other aspects of electronics.
