2. WHAT IS SENSOR…??
A device that detects a physical quantity and
converts it into a signal which can be read by an
observer or by an instrument.
A sensor is a device, which responds to an input
quantity by generating a functionally related output
usually in the form of an electrical or optical signal.
A sensor's sensitivity indicates how much the
sensor's output changes when the measured
quantity changes.
4. IR SENSOR
It is an electronic instrument that is used to
sense certain characteristics of its
surroundings by either emitting and/or
detecting infrared radiation.
In the electromagnetic spectrum, infrared
radiation is the region having wavelengths
longer than visible light wavelengths, but
shorter than microwaves.
5. WORKING PRINCIPLE
• The IR led keeps transmitting IR infrared rays up to some range
infrared range, the IR waves hits the object and comes back at
some angle, The Photo diode next to IR led detects that IR
infrared rays which got reflected from the object
6. BASIC CONSTRUCTION
Circuit is divided into two sections. IR TX and
IR RX are to be soldered on small general
purpose Grid PCB.
8. SOUND SENSOR
A device that can detect sound is known as a
Sound Sensor
A sound sensor is nothing but a Microphone.
9. Based on the power amplifier LM386 and the electret
microphone, it can be used to detect the sound strength of the
environment. The value of output can be adjusted by a
potentiometer.
10. TEMPERATURE SENSORS
Temperature Sensors measure the amount
of heat energy or even coldness that is
generated by an object or system, allowing
us to “sense” or detect any physical change
to that temperature producing either an
analogue or digital output.
12. BIMETALLIC THERMOSTAT
Basically consists of two different metals
such as nickel, copper, tungsten or
aluminium etc, that are bonded together to
form a Bi-metallic strip.
Both the metals have different value of linear
expansion due to which the metals bend in
different proportions
13. •When Junction is cold – The switch is closed and the current
begins to flow
•When junction is hot - The switch is open and the current flow
is resisted
14. RTD (RESISTANCE TEMPERATURE DETEDTORS
RTD’s are precision temperature sensors
made from high-purity conducting metals
such as platinum, copper or nickel wound
into a coil and whose electrical resistance
changes as a function of temperature, similar
to that of the thermistor.
15. THERMOCOUPLE
It consists of two junctions of dissimilar
metals, such as copper and constantan that
are welded together.
Temp. of ref. junc. = constant
Temp. of measuring junc. = Variable
16. When the two junctions are at different
temperatures, a voltage is developed across
the junction which is used to measure the
temperature sensor as shown below.
17. The voltage difference between the two
junctions is called the “Seebeck effect” as a
temperature gradient is generated along the
conducting wires producing an emf.
Hence O/P voltage is function of temperature
