38 Arduino Sensors You Should Know | How They Work & Where to Use Them

If you're learning embedded systems, Arduino or IoT, you're going to meet hundreds of sensors. Temperature, motion, gas, vibration, magnetic fields, rotation, sound, and many more. If you don't really know what each sensor does, what signal it produces, or where you should use it, you

can't innovate. You can only copy. By the end of this video, you'll have a much clearer idea of which sensor or module to choose for a new project. So in this video, we're going through 38 commonly used modules one by one. But this is not going to be a boring list of names. For each component, we'll answer

four practical questions. What is it? How does it work? What type of signal does it produce? And how does it send that signal to the microcontroller? And most importantly, where would you use it in a real project? One important clarification before we start. Not

everything in these kits is technically a sensor. Some are input devices, some are outputs, some are switches, and some are communication modules, but they [snorts] are commonly included together in Arduino sensor kits. So, we'll look at them from a practical electronics and

embedded systems perspective. Let's get started. One, push button. A push button is not really a sensor. It is a basic digital input device. Pressing the button changes the electrical state of the input. The microcontroller reads

that state as high or low depending on how the circuit is configured. It sounds simple buttons are fundamental to embedded systems. They are used for start and stop controls, menu selection, mode switching, manual control. One important concept here is debouncing.

Mechanical contacts can bounce for a few milliseconds when pressed causing multiple false transitions. So software or hardware debouncing may be required. Number two, joystick module. A joystick module is a two-axis analog input device with an additional push

button. Inside the module are two potentiometers. One measures movement on the X-axis and the other measures movement on the Y-axis. When you move the joystick, the output voltage of each potentiometer changes. The X output and Y output are

analog signals, so they should be connected to ADC capable GPIOs on the ESP32. The push button is a digital signal. So its switch output can be connected to a suitable digital GPIO. This gives the

microcontroller three inputs from one small module. X position, Y position, and the push button. Joysticks are useful for robot control, RC cars, robotic arms, pan and tilt systems, and

game controllers. For example, an ESP32 can read the joystick position and use Wi-Fi to control a robot wirelessly. Number three, NTC thermostatrmister. Now let's look at temperature sensing using an analog method. An NTC thermister is a

resistor whose resistance decreases as temperature increases. NTC means negative temperature coefficient. The thermostatrmister is commonly connected as part of a voltage divider. As the temperature changes, the thermostatrmister resistance changes that changes the voltage produced by the

voltage divider. The ESP32 then measures that voltage using an ADC capable GPIO. So the complete process is simple. Temperature changes the resistance. The resistance changes the voltage. The ESP32 measures the voltage. The software

converts that measurement into temperature. This is one of the best examples for understanding how a microcontroller reads a physical quantity using an analog input. Number four, LDR. An LDR or light dependent resistor changes its resistance

according to the amount of light falling on it. More light usually means lower resistance. Less light means higher resistance. The LDR is commonly used in a voltage divider so that changes in light produce changes in voltage. That voltage can be connected to an ADC

capable GPIO of the ESP32. This allows the microcontroller to estimate the amount of light reaching the sensor. A simple application is an automatic light. During the day, the light remains off. When the environment becomes dark, the ESP32 can turn the light on. You can

also use an LDR in an IoT project and send the measured light level to a dashboard over Wi-Fi. Number five, DS18B20 digital temperature sensor. The DS18B20 is a digital temperature sensor. Unlike an NTC thermostat, the sensor processes

the temperature measurement internally and sends the result digitally to the microcontroller. It uses the one wire communication protocol. A typical sensor has three connections, VCC, G&D, and data. The data connection goes to a

suitable digital GPIO on the ESP32. A pull-up resistor is normally used between the data line and the supply. One particularly useful feature is that multiple DS18B20 sensors can share the same one wire data line. Each sensor has its own unique

address. So the ESP32 can identify individual sensors even when several sensors are connected to the same bus. That makes the DS18B20 useful for monitoring temperature at multiple locations. For example, you could monitor the temperature of several

water tanks, different points in a machine, or different areas of a building. It is also useful for room monitoring, equipment temperature monitoring, and weather projects. Number six, DHT11 temperature and humidity sensor. The DHT11 measures two

environmental parameters, temperature and relative humidity. Relative humidity tells us how much water vapor is present in the air compared with the maximum amount the air can hold at that temperature. The DHT11 communicates digitally with the

microcontroller. A typical module has VCC data and G&D. The data pin carries digital information, so it connects to a suitable digital GPIO on the ESP32. It does not require an ADC capable GPIO.

The DHT11 is popular because it is simple and beginnerfriendly. It is useful for room monitoring, basic weather stations, greenhouse projects, and simple IoT systems. However, it is not designed for applications that require high accuracy or a wide

measurement range for learning and basic environmental monitoring. It is a useful starting point. Number seven, MQ2 gas and smoke sensor. The MQ2 is a popular hobby sensor used for detecting smoke and certain combustible gases. Its

sensing element changes its electrical resistance when exposed to particular gases. Typical MQ2 modules provide an analog output. Some versions also provide a digital output using a comparator. The analog output can be connected to an ADC capable GPIO of the

ESP32. The digital output can be connected to a suitable digital GPIO. The analog reading is useful for observing changes in the sensor response. However, you should not treat the raw analog value as an exact gas concentration. Accurate gas concentration measurement requires

proper calibration and appropriate sensing equipment for learning and prototyping. The MQ2 is useful for detecting changes in smoke or gas conditions. Number eight, ultrasonic distance sensor. An ultrasonic distance

sensor measures the distance to an object without physical contact. It sends a short ultrasonic pulse and measures the time taken for the echo to return. The microcontroller uses this time to calculate the distance. A common

HC, SR04 has four pins, VCC, G&D, trig and echo. Connect VCC to 5 volts, G&D to ESP32 ground, trig to a suitable digital GPIO, and echo to another GPIO through a

voltage divider or level shifter. When using the standard 5V output version, trig starts the measurement while the echo pulse duration represents the measured distance. It uses simple digital timing signals. Ultrasonic sensors are useful for robot obstacle detection, distance measurement, parking

systems, tank level projects, and object detection. Number nine, flame sensor. A flame sensor detects infrared radiation associated with an open flame. When a flame is present within the sensor's detection range, its output changes. Many common modules provide an analog

output and a digital threshold output. The analog output can be connected to an ADC capable GPIO. The digital output can be connected to a suitable digital GPIO. Flame sensors are useful for electronics demonstrations, robotics projects, and

basic flame detection experiments. However, a small hobby flame sensor should not be treated as a certified fire protection system. Number 10, IR receiver. An infrared receiver is used to receive infrared signals. A

common example is a television remote control. When you press a button on the remote, it sends a modulated infrared signal. The receiver detects that signal and provides electrical pulses to the microcontroller. The Arduino or ESP32

can then decode the timing and communication protocol to determine which button was pressed. A typical receiver has VCC, G&D, and out connections. The out pin connects to a suitable digital GPIO. With an IR receiver and an IR transmitter together, you can build a programmable infrared

controller. Number 11, IR transmitter. An IR transmitter uses an infrared LED to send infrared signals. The important point is that it is normally not just turning the LED on and off randomly. The microcontroller generates a modulated signal according