Sensors are sophisticated devices that are frequently used to detect and respond to electrical or optical signals. A Sensor converts the physical parameter (for example: temperature, blood pressure, humidity, speed, etc.) into a signal which can be measured electrically. Let’s explain the example of temperature. The mercury in the glass thermometer expands and contracts the liquid to convert the measured temperature which can be read by a viewer on the calibrated glass tube.
Criteria to choose a Sensor
There are certain features which have to be considered when we choose a sensor. They are as given below:
- Environmental condition – usually has limits for temperature/ humidity
- Range – Measurement limit of sensor
- Calibration – Essential for most of the measuring devices as the readings changes with time
- Resolution – Smallest increment detected by the sensor
- Repeatability – The reading that varies is repeatedly measured under the same environment
Sensors can be classified based on power or energy supply requirement of the sensors:
- Active Sensor – Sensors that require power supply are called as Active Sensors. Example: LiDAR (Light detection and ranging), photoconductive cell.
- Passive Sensor – Sensors that do not require power supply are called as Passive Sensors. Example: Radiometers, film photography.
Different Types Of Sensors With Their Applications
Smart Home Lighting Control Systems
User will be able to control the light by LDR sensor automatically. In automatic light control system, Light Dependent Resistor (LDR) sensor is used to detect bright/medium/dim/dark conditions. The number of LED lit is controlled by themaster controller and depends on the lighting condition of the room and is inversely proportional with the brightness of the room. This application is important for saving the energy.
Humidity Sensing System
The humidity of the room is measured by using a sensor. The sensor can be a basic, ultra-low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin. The data is received by master controller and the temperature and humidity is viewed on the computer screen.
LPG/Smoke Detecting System
The smoke sensor is not only sensitive to smoke, but also to flammable gas. The smoke sensor reports smoke by the voltage level as output. The more smoke is there, the greater the voltage output. By adjusting the potentiometer, one can change how sensitive it is to smoke, so there is a form of calibrating it to adjust how much voltage it will give in relation to the smoke it is exposed to.
Smart Home Security Systems
A security system consists of a portable panel consisting of pushbuttons, a LCD screen and a camera. On start up the system requires a 4 digit password which was previously set up by the user. If the entered password matches the previously set up password then sends an affirmative message to the master controller via USB cable so the door opens and the entire smart home system turns ON. If the password does not match, then the camera captures an image of the intruder and saves the image in the system and also e-mails the image to the user and the door remains locked.
A special features for our smart home system which will be highly beneficial for elderly or differently disabled person. The user will be able to turn on and control the brightness of lights (led) by giving voice commands. A program is written in visual basic to accomplish this action. Using this program, the system recognizes the voice command and sends a predefined message according to the command, to the master controller. The master controller turns ON/OFF the lights or control the brightness according to the message received.
A device which gives temperature measurement as an electrical signal is called as Temperature sensor. This electrical signal will be in the form of electrical voltage and is proportional to the temperature measurement. There are different types of sensors used for measuring temperature, such as Contact type temperature sensors, Non-contact type temperature sensors. Design of Industrial Temperature Controller for controlling temperature of devices used in industrial applications is one of the frequently used practical applications of the temperature sensor.