In our projects, we use sensors to convert physical magnitudes such as light, temperature, distance into electrical signals and establish decision-making mechanisms to process this information. You can also take your projects one level further with the sensor guide we have prepared.
How Does the Sensor Work? What is the Principle of Operation?
Before we go into the detail of the sensor types, we need to know that these sensors basically exist in two types: analogue and digital. Analog sensorsoutput a current or voltage that varies proportionally to the physical size they perceive. Analog-digital converters (ADC) are used to connect this type of sensor to our digital working control cards. Analog-digital converters will also be included in microcontrollers (e.g. Arduino analog input pins) can also be connected externally if the number or sensitivity is not enough. Unfortunately, the Raspberry Pi, a popular single-card computer, does not have an analog-digital converter built in. Therefore, when we need analog input, we will have to use an external integrated. Digital sensors, on the other hand, usually talk to the computer (microprocessor) through a communication protocol such as I2C, SPI, OneWire etc. In addition, most analog sensors can be used in consitions to output a logic 1 (usually 5V or 3.3V) above a certain level. Thus, analogue output sensors can be used with controllers that do not have ADC, such as the Raspberry Pi.
In addition, the sensors are divided into active sensors and passive sensors. After generating their own signals, active sensors perform the detection process by controlling the change of this signal in the environment. Ultrasonic and infrared sensors are included in this group. Passive sensors perform the detection process by controlling the signals they receive from the environment. Examples include LDR (light-sensitive resistance), NTC/PTC (heat-sensitive resistors), phototransistors (light-sensitive transistors).
Areas of Use of Sensor Types
Gas sensor: A gas sensor or detector detects gas leakage in a specific environment. We can use it anywhere there's a chance of a kitchen and gas leak. Color sensor: It has the ability to distinguish different colors between one another. You can use quality control systems in packaging systems. Image sensor: It is capable of taking an optical image and then converting it into an electrical signal.You will find them on many devices today, but the digital cameras that you will be most familiar with. Infrared Sensing Sensor (IR Sensor): They are light-based sensors used in various applications such as object and proximity detection.It is used in color estimation, object detection, distance measurement and robotic applications. Pressure sensor: It is a device that converts to analogue electrical signals that vary depending on the pressure change. It is used in factories for load measurement in gas and liquid banishment, biomedical devices, mobile phones and electronic scales. Photoelectric sensor: It is the electronic circuit element that detects the light and receiver using the light emitting source and emitting this light. The sensor outputs as soon as the light between the light source and the receiver is blocked. Automatic door is used in automotive industry, machinery industry, storage and conveyor systems and packaging applications. Humidity sensor: Another name for such sensors is hygrometers. It is a tool that measures net humidity and humidity in a particular area and air. They can sense and measure relative humidity.You can determine moisture in HVAC (air conditioning) systems, greenhouses and environments where there is a herd of animals, which are usually found at home. Vibration sensor: Light strokes and vibration detection in a specific area are also used. We can most commonly see it in vehicle alarm and safety systems. Motion sensor: there are two types of motion sensors, active sensors and passive sensor, with detection features. Active motion sensors send ultrasonic sound waves, while passive sensors detect infrared energy.
- Passive harem sensors: Passive motion detection sensors emit infra-red rays into the environment where dual passive infrared dedector (infra-red detector) rays are located, detecting the body temperature radiation around the infra-red detector (PIR) thanks to the Fresnel Lens on which it is located, detecting movement and outputting to operate the lamp connected to the sensor.
- Active motion sensors: It is also called radar-based motion detectors in the market and sends ultrasonic sound waves to actively scan the desired area, either absorbing it or creating an echo. The waves that reach the object are precisely calculated for subsequent comparisons. When the moving object or person notices the area in its area, the frequency of the waves is reflected to the sensor and the sensor outputs to detect the movement of the object in the area.
I'd like to talk a little bit about these sensors, which are most commonly used in robotic systems.
What is Ultrasonic Sensor?
The ultrasonic sensor takes its name from the combination of the words "ultra" and "sonic". It means "louder sound". These sensors are used for distance measurement purposes. The operating principles are as follows: Ultrasonic sensors send a sound wave signal out. They wait for the sound wave they send to reach an object and return to it. The distance of the sensor to the object is calculated based on the time it take for the signal to be sent and returned. (x = v * t / path = Speed * Time)
What is a Passive Infra-Red (PIR) Sensor?
PIR sensors are sensors that detect movement according to temperature and infrared wave changes in the environment. These sensors are most commonly used in alarm systems and automatic lighting. The working principles are as follows: All objects emit temperature and infrared waves into their environment. Pir sensors also have a fresnel lens in their structure. Thanks to this lens, the rays in the environment fall right on top of the sensor and focus. The sensor detects and notifies the system when constant temperature and infrared waves change. For example, the PIR sensor mounted in a room checks the constant wave values emitted by the walls and objects in the room. When a person enters the room, these values will change, so the sensor detects and informs the system to which it is connected.
What is a Hall Effect Sensor?
Hall effect sensors are sensors that detect magnetic fields and provide signal output. These sensors are used for distance, speed, current detection and positioning.