PHOTOVOLTAIC SENSOR AND TEMPERATURE GRADIENT SENSOR IS USED FOR MEASURING INPUTS FROM PHYSICAL ENVIRONMENT WHICH IS MOST POPULAR IN ITS APPLICATIONS SUCH AS LED LIGHTENING AND WHITE LED'S.
2. SENSOR
• A sensor is device that detects and responds to
some type of input from the physical
environment. The specific input could be light,
heat, motion, and pressure.
4. CONTENTS
• Introduction
• Solar cell
• Working of solar cell
• Components of PV systems
• Types of PV systems
• PV Technologies
• LED Lighting
• Advantages and Disadvantages of PV systems
• Applications
• Conclusions
6. SOLAR CELLS
• The heart of photovoltaic system is a solid-state
device called a solar cell.
• Solar cells are made of silicon.
• Treated to be positive on one side and negative on
other side.
• When light energy hits the cell, electrons loose out
from the atoms in the semiconductor material
• If electrical conductors are attached to the positive
and negative sides, forming an electrical circuit, and
the flow of released electron produces the current.
8. WORKING OF SOLAR CELL
• A typical solar cell is composed with thin wafer
consisting phosphorus-doped silicon on top of boron
doped silicon layer.
• An electrical field is created near the top of surface
of cell where these two materials are in contact,
called the P-N junction.
• When sunlight strikes the surface of PV cell, these
electric field provides momentum and direction to
light stimulated electrons, resulting in flow of
current when solar cell is connected to electrical
load.
9. • Every single photovoltaic cell has small
dimensions and generally produces a power
between 1 to 3 watts at 0 to 5 volts.
• If several cells are connected themselves, creates
bigger units called modules. The modules are
connected to form panels that produces wanted
power.
13. COMPONENTS OF PV SYSTEM
• Solar modules, battery, inverter, charge controller are the main
components of PV system.
• This four components occupies more than two-thirds of the total
cost of system.
• Batteries are used to store the electrical energy generated by
photovoltaic modules.
• Power can be drawn out from the batteries whenever required
during the day or night.
• Direct current systems which power AC load must use an Inverter.
• The use of inverter increases the cost of system.
• Charge regular limits the rate at which current is drawn or added to
batteries.
• Here we are using LED as a load.
• Inverter converts DC to AC.
14. TYPES OF PV SYSTEMS
• Mainly classified as Grid connected and stand-alone
systems.
• Grid connected PV systems are designed to operate in
parallel with the electrical utility grid.
• The main component of grid connected PV system is
inverter. The inverter converts DC power produced by
PV array into AC power as required by the utility grid.
• Stand-Alone PV systems.
• Stand- alone PV systems are generally designed to
supply DC and/ or AC electrical loads.
• The simplest example of stand-alone PV system is
directly connected DC load.
15. LED LIGHTING
• Recently solar PV are coupled with Light Emitting
Diodes to give energy efficient light.
• Recent advancements in LED technology have led to
development of white light emitting diodes [LED].
• WLEDs provide a bright white light that’s ideal for
domestic lighting.
• The advantage of using LEDs with solar PV system
is that the LED requires very much low power
wattage.
• Therefore the size and cost of solar system is much
reduced.
17. ADVANTAGES
• Fuel is free and easily available.
• Easily expandable.
• No noise pollution or other type of pollution.
• PV systems which are properly design and
properly installed required nominal
maintenance.
18. DISADVANTAGES
• High cost of PV modules and equipments is the
primary limiting factor.
• The surface area required for the PV array may
be limiting factor.
19. APPLICATIONS
• It is used in instrumentation and control
applications.
• They are used both as light detector and in
power sources.
• It is used in satellites.
• It is used water pumping and water treatment.
20. CONCLUSION
• It is light to light conversion.
• It is very simple system to implement.
• LEDs are used because they need very small
voltage to operate and more life time.
• Although cost is major factor but PV systems are
long life durable and long time service provider.
22. 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.
24. 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.
25. • 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.
27. RTD(RESISTANCE TEMPERATURE
DETECTORS)
• 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.
29. COMPONENTS
• R1,R2,R3- Fixed Resistors
• RL1, RL2-Lead wire resistance
• Resistance Thermometer
• Us-Supply voltage
• U0-Output voltage
30. RTD CIRCUITRY
• The Two wire RTD is connected to a typical
wheat stone bridge circuit. In this circuit, lead
wire resistance RL1 and RL2 are added directly
to resistance thermometer.
31. 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
• 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.
32. • The voltage difference between the two
junctions is called the”Seeback effect”as a
temperature gradient is generated along
the conducting wires producing an emf.
• Hence O/P voltage is function of
temperature.
34. CIRCUITRY EXPLANATION
• Two dissimilar metals are joined together to the
measuring junction. The voltage produced at the
reference junction depends on the temperature
at both measurement junction(hot junction) and
reference junction(cold junction).
• The reference junction temperature must be
known to get an accurate absolute temperature
reading.
35. ADVANTAGES
oIn Thermocouple, no external power required,
simple in construction and cheaper in cost.
oIn RTD, the advantages are it is more stable and
has high accuracy.
o In Bimetallic thermostat, there is no need of
power source.
36. DISADVANTAGES
• THERMOCOUPLE: Least stability, low voltage,
and least sensitivity.
• RTD: Expensive and current source is needed.
• BIMETALLIC THERMOSTAT: Not very
accurate.
37. APPLICATIONS
They are used in oil level sensors, power
electronics, computers, military and aerospace
applications.
They are used in diesel engines
They are used in homes , offices, industrial
processes and businesses.
