PROJECT REPORT ON
REGENERATIVE
contents
Abstract
04
Project Guidance
07
Introduction to the project
08
Working principle
10
Hardware Components
11
PIN Description
23
Battery
28
Battery Lifetime
48
IR Sensors
53
Brakes
59
Chain
65
Sprocket
71
Application
77
Future Study
77
Final Kit
78
PROJECT REPORT
ON
REGENERATIVE BRAKING SYSTEM
ABSTRACT
The system will generate electrical energy while the wheel is about is stop when applying brakes. The model comprises a moving wheel arrangement with induction braking system that create regeneration of electrical energy to charge the battery. In a regenerative braking system, the electric motor that is responsible for all or part of an electric or hybrid-electric vehicle’s propulsion & also does most of the braking. When the driver steps on the brake pedal, instead of activating a conventional friction-based braking process, it sends an electronic signal to the electric motor, directing it to run in reverse mode, which creates resistance to slow the vehicle through a process that is analogous to down-shifting a standard transmission vehicle.
Regenerative Braking System is the way of slowing vehicle by using the motors as
brakes. Instead of the surplus energy of the vehicle being wasted as unwanted heat, the motors act as generators and return some of it to the overhead wires as electricity. The vehicle is primarily powered from the electrical energy generated from the generator, which burns gasoline. This energy is stored in a large battery, and used by an electric motor that providesmotive force to the wheels. The regenerative braking taking place on the vehicle isa way to obtain more efficiency; instead of converting kinetic energy to thermal energy through frictional braking, the vehicle can convert a good fraction of its kinetic energy
back into charge in the battery, using the same principle as an alternator.
Regenerative Braking System is the way of slowing vehicle by using the motors as
brakes. Instead of the surplus energy of the vehicle being wasted as unwanted heat, the motors act as generators and return some of it to the overhead wires as electricity. The vehicle is primarily powered from the electrical energy generated from the generator, which burns gasoline. This energy is stored in a large battery, and used by an electric motor that provides motive force to the wheels. The regenerative braking taking place on the vehicle isa way to obtain more efficiency; instead of converting kinetic energy to thermal energy through frictional braking, the vehicle can convert a good fraction of its kinetic energy
back into charge in the battery, using the same principle as an alternator
Definition:
Braking method in which the mechanical energy from the load is converted into electric energy and regenerated back into the line is known as Regenerative Braking. The Motor operates as generator.
Brake:-A brake is a machine element and its principle object is to absorb energy during deceleration. In vehicle brakes are used to absorb kinetic energy whereas in hoists or elevators brakes are also used
e converts kinetic energy to heatenergy. This causes wastage of energy and also wearing of frictional lining material
Braking is not total loss:
Conventional brakes apply friction to convert a vehicle’s kineticenergy into heat. In energy terms, therefore, braking is a total loss: once heat is generated, it is very difficult to reuse. The regenerative braking system, however, slows a vehicle down in a different way.
WORKING OF REGENERATIVE BRAKING SYSTEM
Working of the regenerative braking system is completely difference from the conventional braking system. In the traditional braking systems the brake pads rub against the wheels and this rubbing generates excessive heat. The heat energy produced dissipates into the air, wasting up to 30% of the power generated by the engine. Over a period of time, friction that counteracts the forward motion and the wasted heat energy reduces the fuel efficiency of the device. Under such a situation more energy or power output is required so that the energy wasted or lost during braking can be replaced.
INTRODUCTION OF PROJECT:
The system will generate electrical energy while the wheel is about is stop when applying brakes. The model comprises a moving wheel arrangement with induction braking system that create regeneration of electrical energy to charge the battery. In a regenerative braking system, the electric motor that is responsible for all or part of an electric or hybrid-electric vehicle’s propulsion, also does most of the braking. When the driver steps on the brake pedal, instead of activating a conventional friction-based braking process, it sends an electronic signal to the electric motor, directing it to run in reverse mode, which creates resistance to slow the vehicle through a process that is analogous to down-shifting a standard transmission
vehicle.
Regenerative Braking System is the way of slowing vehicle by using the motors as
brakes. Instead of the surplus energy of the vehicle being wasted as unwanted heat, the motors act as generators and return some of it to the overhead wires as electricity. The vehicle is primarily powered from the electrical energy generated from the generator, which burns gasoline. This energy is stored in a large battery, and used by an electric motor that provides motive force to the wheels. The regenerative braking taking place on the vehicle isa way to obtain more efficiency; instead of converting kinetic energy to thermal energy through frictional braking, the vehicle can convert a good fraction of its kinetic energy
BLOCK DIAGRAM:
a
b
NOTE:
MOTOR 1:
To rotate engine wheel.MOTOR 2:
Electrical power generator.Case a: Brakes applied, IR Receiver receives low signal and drives motor2 with the help of
motor driver circuit.
BATTER
Y
MOTOR1
IR
SENSORS
MOTOR
DRIVER
MOTOR 2
BRAKES
VEHICLE
Case b: Brakes not applied, IR Receiver receives high signal and motor2 does not rotate.
WORKING PRINCIPLE:
Working of the regenerative braking system is completely difference from the
conventional braking system. In the traditional braking systems the brake pads rub against the wheels and this rubbing generates excessive heat. The heat energy produced dissipates into the air, wasting up to 30% of the power generated by the car’s engine. Over a period of time, friction that counteracts the forward motion and the wasted heat energy reduces the fuel
efficiency of the car. Under such a situation more energy or power output is required so that the energy wasted or lost during braking can be replaced.
SCOPE OF THE PAPER:
Regenerative
braking just as waste recycling conserves natural resources by reusing materials such as glass, aluminum, plastics, and newsprint, an emerging technology called regenerative braking makes it possible to harvest and reuse as much as 30% of the energy that is consumed to propel a vehicle.This emission-free stored electrical energy is then available to assist acceleration, power the air conditioner, operate power steering, or perform other functions, reducing ic engine fuel
An electric motor running backwards also acts as an electric energy generator or dynamo that can convert the kinetic energy of motion into electrical energy that can be stored for future use. As an added bonus, regenerative braking with an electric motor takes most of the load off mechanical brakes, reducing brake maintenance and replacement expense.
HARDWARE COMPONENTS
• L293D Driver IC • MOTORS • IR SENSORS • 7805 REGULATOR • RESISTORS • CAPACITORS • BATTERY • BRAKE • CHAIN • SPROCKETAPPLICATIONS:
FOUR WHEELERS INDUSTRIESDC MOTORS:
A DC motor is a mechanically commutated electric motor powered from direct current DC). The stator is stationary in space by definition and therefore so is its current. The current in the rotor is switched by the commutator to also be stationary in space. This is how the relative angle between the stator and rotor magnetic flux is maintained near 90 degrees, which generates the maximum torque.
DC motors have a rotating armature winding (winding in which a voltage is induced) but non-rotating armature magnetic field and a static field winding (winding that produce the main magnetic flux) or permanent magnet. Different connections of the field and armature winding provide different inherent speed/torque regulation characteristics. The speed of a DC motor can be controlled by changing the voltage applied to the armature or by changing the field current. The introduction of variable resistance in the armature circuit or field circuit allowed speed control. Modern DC motors are often controlled by power electronics systems called DC drives.
The introduction of DC motors to run machinery eliminated the need for local steam or internal combustion engines, and line shaft drive systems. DC motors can operate directly from
rechargeable batteries, providing the motive power for the first electric vehicles. Today DC motors are still found in applications as small as toys and disk drives, or in large sizes to operate steel rolling mills and paper machines.
Brush:
A brushed DC electric motor generating torque from DC power supply by using internal mechanical commutation, space stationary permanent magnets form the stator field. Torque is produced by the principle of Lorentz force, which states that any current-carrying conductor placed within an external magnetic field experiences a force known as Lorentz force. The actual
(Lorentz) force ( and also torque since torque is F x l where l is rotor radius) is a function for rotor angle and so the green arrow/vector actually changes length/magnitude with angle known as torque ripple) Since this is a single phase two pole motor the commutator consists of a split ring, so that the current reverses each half turn ( 180 degrees).
The brushed electric motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary magnets and rotating electrical magnets.
Like all electric motors or generators, torque is produced by the principle of Lorentz force, which states that any current-carrying conductor placed within an external magnetic field experiences a torque or force known as Lorentz force. Advantages of a brushed DC motor include low initial cost, high reliability, and simple control of motor speed. Disadvantages are high maintenance and low life-span for high intensity uses. Maintenance involves regularly replacing the brushes and springs which carry the electric current, as well as cleaning or replacing the commutator. These components are necessary for transferring electrical power from outside the motor to the spinning wire windings of the rotor inside the motor. Brushes are made of conductors.
Brushless:
Typical brushless DC motors use a rotating permanent magnet in the rotor, and stationary electrical current/coil magnets on the motor housing for the rotor, but the symmetrical opposite is also possible. A motor controller converts DC to AC .This design is simpler than that of brushed motors because it eliminates the complication of transferring power from outside the motor to the spinning rotor. Advantages of brushless motors include long life span, little or no maintenance, and high efficiency. Disadvantages include high initial cost, and more
"synchronous motors" although they have no external power supply to be synchronized with, as would be the case with normal AC synchronous motors.
Uncommutated:
Other types of DC motors require no commutation.
• HOMOPOLAR MOTOR– A homopolar motor has a magnetic field along the axis of rotation and an electric current that at some point is not parallel to the magnetic field. The name homopolar refers to the absence of polarity change.
Homopolar motors necessarily have a single-turn coil, which limits them to very low voltages. This has restricted the practical application of this type of motor.
• BALL BEARING MOTOR– A ball bearing motor is an unusual electric motor that consists of two ball bearing-type bearings, with the inner races mounted on a common conductive shaft, and the outer races connected to a high current, low voltage power supply. An alternative construction fits the outer races inside a metal tube, while the inner races are mounted on a shaft with a non-conductive section (e.g. two sleeves on an insulating rod). This method has the advantage that the tube will act as a flywheel. The direction of rotation is determined by the initial spin which is usually required to get it going.
• DC motors are configured in many types and sizes, including brush less, servo, and gear motor types. A motor consists of a rotor and a permanent magnetic field stator. The magnetic field is maintained using either permanent magnets or electromagnetic windings. DC motors are most commonly used in
• Variable speed and torque.
• Motion and controls cover a wide range of components that in some way are used to generate and/or control motion. Areas within this category include bearings and
bushings, clutches and brakes, controls and drives, drive components, encoders and resolves, Integrated motion control, limit switches, linear actuators, linear and rotary motion components, linear position sensing, motors (both AC and DC motors),
orientation position sensing, pneumatics and pneumatic components, positioning stages, slides and guides, power transmission (mechanical), seals, slip rings, solenoids, springs.
Motors are the devices that provide the actual speed and torque in a drive
system. This family includes AC motor types (single and multiphase motors, universal, servo motors, induction, synchronous, and gear motor) and DC motors (brush less, servo motor, and gear motor) as well as linear, stepper and air motors, and motor contactors and starters.
• In any electric motor, operation is based on simple electromagnetism. A
current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and to the strength of the external magnetic field. As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a
DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.
• Let's start by looking at a simple 2-pole DC electric motor (here red represents a magnet or winding with a "North" polarization, while green represents a magnet or winding with a "South" polarization).
• Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator, field magnet(s), and brushes. In most common DC motors (and all that Beamers will see), the external magnetic field is produced by high-strength permanent magnets1. The
stator is the stationary part of the motor -- this includes the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotates with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator. The above diagram shows a common motor layout -- with the rotor inside the stator (field) magnets.
• The geometry of the brushes, commutator contacts, and rotor windings are such that when power is applied, the polarities of the energized winding and the stator
magnet(s) are misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets. As the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the next winding. Given our example two-pole
motor, the rotation reverses the direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic field, and driving it to continue rotating.
• In real life, though, DC motors will always have more than two poles (three is a very common number). In particular, this avoids "dead spots" in the commutator. You can imagine how with our example two-pole motor, if the rotor is exactly at the middle of its rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with a two-pole motor, there is a moment where the commutator shorts out the power supply (i.e., both brushes touch both commutator contacts simultaneously). This would be bad for the power supply, waste energy, and damage motor components as well.
• Yet another disadvantage of such a simple motor is that it would exhibit a high amount of torque” ripple" (the amount of torque it could produce is cyclic with the position of the rotor).
• So since most small DC motors are of a three-pole design, let's tinker with the workings of one via an interactive animation (JavaScript required):
• You'll notice a few things from this -- namely, one pole is fully energized at a time (but two others are "partially" energized). As each brush transitions from one commutator contact to the next, one coil's field will rapidly collapse, as the next coil's field will rapidly charge up (this occurs within a few microsecond). We'll see more about the effects of this later, but in the meantime you can see that this is a direct result of the coil windings' series wiring:
• There's probably no better way to see how an average dc motor is put together, than by just opening one up. Unfortunately this is tedious work, as well as requiring the
destruction of a perfectly good motor.
• This is a basic 3-pole DC motor, with 2 brushes and three commutator contacts.
PWM technique:
A pulse width modulator (PWM) is a device that may be used as an efficient light
dimmer or DC motor speed controller. A PWM works by making a square wave with a variable on-to-off ratio; the average on time may be varied from 0 to 100 percent. In this manner, a variable amount of power is transferred to the load. The main advantage of a PWM circuit over a resistive power controller is the efficiency, at a 50% level, thePWM will use about 50% of full power, almost all of which is transferred to the load, a resistive controller at 50% load power would consume about 71% of full power, 50% of the power goes to the load and the other 21% is wasted heating the series resistor. Load efficiency is almost always a critical factor in solar powered and other alternative energy systems. One additional advantage of pulse width modulation is that the pulses reach the full supply voltage and will produce more torque in a motor by being able to overcome the internal motor resistances more easily. Finally, in a PWM circuits, common small potentiometers may be used to control a wide variety of loads whereas large and expensive high power variable resistors are needed for resistive controllers.
• Pulse width modulation consists of three signals, which are modulated by a square wave. The duty cycle or high time is proportional to the amplitude of the square wave. The effective average voltage over one cycle is the duty cycle times the peak-to-peak voltage. Thus, the average voltage follows a square wave. In fact, this method depends on the motor inductance to integrate out the PWM frequency.
• A very simply off line motor drive can be built using a TRIAC and a control IC. This circuit can control the speed of a universal motor. A universal motor is a series wound DC motor. The circuit uses phase angle control to vary the effective motor voltage.
• A micro controller can also be used to control a triac. A PNP of transistor may be used to drive the triac. As shown, the MCU ground is connected to the AC line. The gate trigger current is lower if instead the MCU 5V supply is connected to the AC line. The MCU must have some means of detecting zero crossing and a timer, which can control the triac firing. A general-purpose timer with one input capture and one output compare makes an ideal phase angle control.
L293D DRIVER CIRCUIT:
L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as current amplifiers since they take a low-current control signal and provide a higher-current signal. This higher current signal is used to drive the motors.L293D contains two inbuilt H-bridge driver circuits. In its common mode of operation, two DC motors can be driven simultaneously, both in forward and reverse direction. The motor operations of two motors can be controlled by input logic at pins 2 & 7 and 10 & 15. Input logic 00 or 11 will stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise and anticlockwise directions, respectively.
• Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to start operating. When an enable input is high, the associated driver gets enabled. As a result,
the outputs become active and work in phase with their inputs. Similarly, when the enable input is low, that driver is disabled, and their outputs are off and in the high-impedance state.
Pin No Function Name
1 Enable pin for Motor 1; active high Enable 1,2
2 Input 1 for Motor 1 Input 1
3 Output 1 for Motor 1 Output 1
4 Ground (0V) Ground
5 Ground (0V) Ground
6 Output 2 for Motor 1 Output 2
7 Input 2 for Motor 1 Input 2
8 Supply voltage for Motors; 9-12V (up to 36V) Vcc 2
9 Enable pin for Motor 2; active high Enable 3,4
10 Input 1 for Motor 1 Input 3
11 Output 1 for Motor 1 Output 3
12 Ground (0V) Ground
13 Ground (0V) Ground
14 Output 2 for Motor 1 Output 4
15 Input2 for Motor 1 Input 4
16 Supply voltage; 5V (up to 36V) Vcc 1
A Resistor is a heat-dissipating element and in the electronic circuits it is mostly used for either controlling the current in the circuit or developing a voltage drop across it, which could be utilized for many applications. There are various types of resistors, which can be classified according to a number of factors depending upon:
Material used for fabrication Wattage and physical size Intended application
Ambient temperature rating Cost
Basically the resistor can be split in to the following four parts from the construction view point.
(1) Base
(2) Resistance element (3) Terminals
(4) Protective means.
The following characteristics are inherent in all resistors and may be controlled by design considerations and choice of material i.e. Temperature co–efficient of resistance, Voltage co–efficient of resistance, high frequency characteristics, power rating, tolerance & voltage rating of resistors. Resistors may be classified as
(1) Fixed
(2) Semi variable (3) Variable resistor.
CAPACITORS
The fundamental relation for the capacitance between two flat plates separated by a dielectric material is given by:-
Where:
-C= capacitance in pf.
K= dielectric constant
A=Area per plate in square cm.
D=Distance between two plates in cm
Design of capacitor depends on the proper dielectric material with particular type of application. The dielectric material used for capacitors may be grouped in various classes like Mica, Glass, air, ceramic, paper, Aluminum, electrolyte etc. The value of capacitance never remains constant. It changes with temperature, frequency and aging. The capacitance value marked on the capacitor strictly applies only at specified temperature and at low frequencies.
LED (Light Emitting Diodes):
As its name implies it is a diode, which emits light when forward biased. Charge carrier recombination takes place when electrons from the N-side cross the junction and recombine with the holes on the P side. Electrons are in the higher conduction band on the N side whereas holes are in the lower valence band on the P side. During recombination, some of the energy is given up in the form of heat and light. In the case of semiconductor materials like Gallium arsenide (GaAs), Gallium phosphate (Gap) and Gallium arsenide phosphate (GaAsP) a greater percentage of energy is released during recombination and is given out in the form of light. LED emits no light when junction is reverse biased.
LM7812 AND LM7805:
• Output Current of 1.5A
• Output Voltage Tolerance of 5%
• Internal thermal overload protection
• Internal Short-Circuit Limited
• No External Component
• Output Voltage 5.0V, 6V, 8V, 9V, 10V,
12V, 15V, 18V, 24V
• Offer in plastic TO-252, TO-220 & TO-263
• Direct Replacement for LM78XX
Description:
The Bay Linear LM78XX is integrated linear positive regulator with three terminals. The LM78XX offer several fixed output voltages making them useful in wide range of applications. When used as a zener diode/resistor combination
Replacement, the LM78XX usually results in an effective output impedance improvement of two orders of magnitude, lower quiescent current.
The LM78XX is available in the TO-252, TO-220 & TO-263 Packages
Applications:
• Post regulator for switching DC/DC converter
BATTERY:
In our prototype, we use 12v battery and they have variety of uses in our daily life. From consumer electronics to robotics, from health care products to industries, almost every second device we use has one battery or the other. Batteries have become an
indispensible part of our lives. We cannot comprehend living without cell phones, torches, laptop computers, music players like the ipod, but how do we power them up? Answer lies in
the battries. Similarly cars are one of the main modern day necessties which use battries to power the head lamps and backlights. In electricity, a battery is a device consisting of one or more electromechanical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery (or "voltaic pile") in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power source for many household and industrial applications. According to a 2005 estimate, the worldwide battery industry generates US$48 billion in sales each year,[2] with 6% annual
growth.
There are two types of batteries: primary batteries (disposable batteries), which are designed to be used once and discarded, and secondary batteries (rechargeable batteries), which are designed to be recharged and used multiple times. Batteries come in many sizes, from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers.
A battery is a device that converts chemical energy directly to electrical energy It consists of a number of voltaic cells; each voltaic cell consists of two half-cells connected in series by a conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the electrode to which anions (negatively charged ions) migrate, i.e., the anode or negative
electrode; the other half-cell includes electrolyte and the electrode to which cations (positively charged ions) migrate, i.e., the cathode or positive electrode. In the redox reaction that powers the battery, cations are reduced (electrons are added) at the cathode, while anions are oxidized (electrons are removed) at the anode.[23] The electrodes do not touch each other but are
electrolytes. A separator between half-cells allows ions to flow, but prevents mixing of the electrolytes.
Each half-cell has an electromotive force (or emf), determined by its ability to drive electric current from the interior to the exterior of the cell. The net emf of the cell is the difference between the emfs of its half-cells, as first recognized by Volta.[12] Therefore, if the electrodes
have emfs and , then the net emf is ; in other words, the net emf is the difference between the reduction potentials of the half-reactions.
The electrical driving force or across the terminals of a cell is known as the terminal
voltage (difference) and is measured in volts. The terminal voltage of a cell that is neither
charging nor discharging is called the open-circuit voltage and equals the emf of the cell. Because of internal resistance, the terminal voltage of a cell that is discharging is smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell that is charging exceeds the open-circuit voltage. An ideal cell has negligible internal resistance, so it would
maintain a constant terminal voltage of until exhausted, then dropping to zero. If such a cell maintained 1.5 volts and stored a charge of one coulomb then on complete discharge it would perform 1.5 joule of work. In actual cells, the internal resistance increases under discharge, and the open circuit voltage also decreases under discharge. If the voltage and resistance are plotted against time, the resulting graphs typically are a curve; the shape of the curve varies according to the chemistry and internal arrangement employed.
As stated above, the voltage developed across a cell's terminals depends on the energy release of the chemical reactions of its electrodes and electrolyte. Alkaline and zinc–carbon cells have different chemistries but approximately the same emf of 1.5 volts; likewise NiCd and NiMH cells have different chemistries, but approximately the same emf of 1.2 volts. On the other hand the high electrochemical potential changes in the reactions of lithium compounds give lithium cells emfs of 3 volts or more.
This entire power requirement means that we need a robust, portable and an efficient source of power. There are a couple of factors one has to look out while choosing the type of 12v battery. Because a twelve volt battery can be of many types, sizes, form factors, and materials. 12 volt is just the rating of the battery and it does not specify something physical. Batteries are also available in other voltage ratings such as 24, 9 and 5 volt. Its rather a quantity. There are many types of batteries depending upon the construction.
12 volt lead acid batteries:
One of the most common type of 12V battery is the 12v lead acid battery. It is a dc battery with lead terminals and an acid, usually hydrochloric acid is used as an electrolyte in lead acid battery. It is the battery of choice for cars, trucks, tanks, uninterrupted power supplies and other vehicles. 12V lead acid battery is used in cars as there is no risk of handling in cars. 12volt lead acid battery is also used in battery banks and backup systems at power sensitive systems, such as telecom switches, like any other 12v dc battery because it’s a source of dc 12volt power.
Lead acid 12V battery is rarely used in home appliances and uses. For example, computer UPS' rarely use lead acid battery as it is not very easy to handle and can cause potential hazards, such as a fire etc. Home users generally prefer a solid state battery such as the one used in dry cells over 12v lead acid batteries or rechargeable battery which provides 12volt power . Those are found in torch lights, calculators, watches, clocks and toys.
12v Battery Construction:
In a 12 volt lead acid battery, usually hydrochloric acid is used as an electrolyte in lead
acid battery. The casing is usually made up of plastic, rubber or any other hard material in order to avoid the acid housed inside. Inside, it is made of up many small cells. Metals areused for cathodes and anodes (negative and positive terminals respectively for the 12Volt Battery.
12 volt lead acid battery is the 12 volt dc battery for cars, trucks, tanks, uninterrupted power supplies and other vehicles. This type of battery is also used in battery banks and backup systems at power sensitive systems, such as telecom switches.
It is 12v dc battery but is not a portable 12v battery or 12v rechargeable battery and 12v battery pack due to its size and handling issues. For example, computer UPS' rarely use lead acid battery as it is not very easy to handle and can cause potential hazards, such as a fire etc.
Lead acid batteries used in the RV and Marine Industries usually consist of two 6-volt batteries in series, or a single 12-volt battery. These batteries are constructed of several single cells connected in series each cell produces approximately 2.1 volts. A six-volt battery has three single cells, which when fully charged produce an output voltage of 6.3 volts. A twelve-volt battery has six single cells in series producing a fully charged output voltage of 12.6 volts.
A battery cell consists of two lead plates a positive plate covered with a paste of lead dioxide and a negative made of sponge lead, with an insulating material (separator) in between. The plates are enclosed in a plastic battery case and then submersed in an electrolyte consisting of water and sulfuric acid (see figure # 1). Each cell is capable of storing 2.1 volts.
In order for lead acid cell to produce a voltage, it must first receive a (forming) charge voltage of at least 2.1-volts/cell from a charger. Lead acid batteries do not generate voltage on their own; they only store a charge from another source. This is the reason lead acid batteries are called storage batteries, because they only store a charge. The size of the battery plates and amount of electrolyte determines the amount of charge lead acid batteries can store. The size of this storage capacity is described as the amp hour (AH) rating of a battery. A typical 12-volt battery used in a RV or marine craft has a rating 125 AH, which means it can supply 10 amps of current for 12.5 hours or 20-amps of current for a period of 6.25 hours. Lead acid batteries can be connected in parallel to increase the total AH capacity.
In figure # 2 below, six single 2.1-volt cells have been connected in series to make the typical 12-volt battery, which when fully charged will produce a total voltage of 12.6-volts.
In figure # 3, above a fully charged battery is connected to a load (light bulb) and the chemical reaction between sulfuric acid and the lead plates produces the electricity to light the bulb. This chemical reaction also begins to coat both positive and negative plates with a substance called lead sulfate also known as sulfation (shown as a yellow build-up on plates). This build-up of lead sulfate is normal during a discharge cycle. As the battery continues to discharge, lead sulfate coats more and more of the plates and battery voltage begins to decrease from fully charged state of 12.6-volts (figure # 4).
In figure # 5 the battery is now fully discharged, the plates are almost completely covered with lead sulfate (sulfation) and voltage has dropped to 10.5-volts.
Lead sulfate (sulfation) now coats most of the battery plates. Lead sulfate is a soft material, which can is reconverted back into lead and sulfuric acid, provided the discharged battery is immediately connected to a battery charger. If a lead acid battery is not immediately recharged, the lead sulfate will begin to form hard crystals, which can not be reconverted by a standard fixed voltage (13.6 volts) battery converter/charger.
NOTE: Always recharge your RV or Marine battery as soon as possible to prevent loss of battery capacity due to the build-up of hard lead sulfate crystals!
Lead Acid Battery Recharge Cycle:
The most important thing to understand about recharging lead acid batteries is that a
converter/charger with a single fixed output voltage will not properly recharge or maintain your battery. Proper recharging and maintenance requires an intelligent charging system that can vary the charging voltage based on the state of charge and use of your RV or Marine battery. Progressive Dynamics has developed intelligent charging systems that solve battery problems and reduce battery maintenance.
The discharged battery shown in figure # 6 on the next page is connected to a converter/charger with its output voltage set at 13.6-volts. In order to recharge a 12-volt lead acid battery with a fully charged terminal voltage of 12.6-volts, the charger voltage must be set at a higher voltage.
During the recharging process as electricity flows through the water portion of the electrolyte and water, (H2O) is converted into its original elements, hydrogen and oxygen. These gasses are very flammable and the reason your RV or Marine batteries must be vented outside. Gassing causes water loss and therefore lead acid batteries need to have water added
periodically. Sealed lead acid batteries contain most of these gasses allowing them to recombine into the electrolyte. If the battery is overcharged pressure from these gasses will cause relief caps to open and vent, resulting in some water loss. Most sealed batteries have extra electrolyte added during the manufacturing process to compensate for some water loss.
The battery shown in figure # 7 above has been fully recharged using a fixed charging voltage of 13.6-volts. Notice that some lead sulfate (sulfation) still remains on the plates. This build-up
will continue after each recharging cycle and gradually the battery will begin to loose capacity to store a full charge and eventually must be replaced. Lead sulfate build up is reduced if battery is given an Equalizing Charge once every 10 discharge cycles or at least once a month. An Equalizing Charge increases charging voltage to 14.4 volts or higher for a short period. This higher voltage causes gassing that equalizes (re-mixes) the electrolyte solution.
Since most RV and Marine craft owners seldom remember to perform this function, Progressive Dynamics has developed the microprocessor controlled Charge Wizard. The Charge Wizard will automatically provide an Equalizing Charge every 21 hours for a period of 15 minutes, when the battery is fully charged and not in use. Our 2000 Series of Marine Battery Chargers have the Charge Wizard feature built-in.
One disadvantage of recharging a lead acid battery at a fixed voltage of 13.6-volts is the
recharge time is very long. A typical 125-AH RV or Marine battery will take approximately 80 hours to recharge at 13.6 volts. Increasing the charge voltage to 14.4-volts will reduce battery recharge time for a 125-AH battery to 3-4 hours. Once a battery reaches 90% of full charge, the voltage must be reduced from 14.4-volts to 13.6-volts to reduce gassing and water loss. The optional Charge Wizard automatically senses when a battery has a very low state of charge and automatically selects its BOOST MODE of operation. BOOST MODE increases the voltage of a PD9100 Series converter/charger to 14.4 volts. When the battery reaches the 90% charge level, the Charge Wizard automatically reduces the charge voltage down to 13.6 volts to complete the charge. Again, this is a standard feature on our Marine Chargers.
Another disadvantage of recharging a lead acid battery at a fixed voltage of 13.6-volts is that once it is fully charged, 13.6 volts will cause considerable gassing and water loss. To prevent this from occurring the charging voltage must be reduced to 13.2-volts. The Charge Wizard will automatically select its STORAGE MODE of operation (13.2-volts) once the battery reaches full charge and remains unused for a period of 30 hours. This feature is standard on all of Progressive Dynamics Marine Battery Chargers.
At a charging voltage of 13.2 volts, the converter/charger will maintain a full charge, reduce gassing and water loss. However, this lower voltage does not provide enough gassing to prevent
a battery condition called Battery Stratification. Battery Stratification is caused by the fact that the electrolyte in the battery is a mixture of water and acid and, like all mixtures, one
component, the acid, is heavier than water. Therefore, acid will begin to settle and concentrate at the bottom of the battery (see figure #8).
Most converter/chargers on the market are set at approximately 13.6-volts. During the battery recharge cycle lead sulfate (sulfation) begins to reconvert to lead and sulfuric acid.
This higher concentration of acid at the bottom of the battery causes additional build-up of lead sulfate (sulfation), which reduces battery storage capacity and battery life. In order to prevent Battery Stratification, an Equalization Charge (increasing charging voltage to 14.4-volts) must be applied periodically. The Charge Wizard automatically selects its EQUALIZATION MODE (14.4 volts) every 21 hours for a period of 15 minutes. This Equalizing Charge feature is
standard on our Marine chargers.
As you have learned, in order to properly charge and maintain a lead acid battery you must use an intelligent charging system. Progressive Dynamics, Inteli-Power 9100 Series RV converters with a Charge Wizard installed, or one of our Inteli-Power Marine Battery Chargers will provide the intelligent charging system your battery needs for a long life, with low maintenance.
From top to bottom: a large 4.5-volt (3R12) battery, a D Cell, a C cell, an AA cell, an AAA cell, an AAAA cell, an A23 battery, a 9-volt PP3 battery, and a pair of button cells (CR2032 and LR44).
Batteries are classified into two broad categories, each type with advantages and disadvantages.
• Primary batteries irreversibly (within limits of practicality) transform chemical energy
to electrical energy. When the initial supply of reactants is exhausted, energy cannot be readily restored to the battery by electrical means.
• Secondary batteries can be recharged; that is, they can have their chemical reactions
reversed by supplying electrical energy to the cell, restoring their original composition.
Some types of primary batteries used, for example, for telegraph circuits, were restored to operation by replacing the components of the battery consumed by the chemical reaction. Secondary batteries are not indefinitely rechargeable due to dissipation of the active materials, loss of electrolyte and internal corrosion.
Primary batteries:
Primary cell
Primary batteries can produce current immediately on assembly. Disposable batteries are intended to be used once and discarded. These are most commonly used in portable devices that have low current drain, are used only intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available. Disposable primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible and active materials may not return to their original forms. Battery manufacturers recommend against attempting to recharge primary cells
Common types of disposable batteries include zinc–carbon batteries and alkaline batteries. In general, these have higher energy densities than rechargeable batteries, but disposable batteries do not fare well under high-drain applications with loads under 75 ohms (75 Ω).
Secondary batteries:
Rechargeable batterySecondary batteries must be charged before use; they are usually assembled with active
materials in the discharged state. Rechargeable batteries or secondary cells can be recharged by applying electric current, which reverses the chemical reactions that occur during its use. Devices to supply the appropriate current are called chargers or rechargers.
The oldest form of rechargeable battery is the lead–acid battery. This battery is notable in that it contains a liquid in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas produced by these batteries during overcharging. The lead–acid battery is also very heavy for the amount of electrical energy it can supply. Despite this, its low manufacturing cost and its high surge current levels make its use common where a large capacity (over approximately 10 Ah) is required or where the weight and ease of handling are not concerns.
A common form of the lead–acid battery is the modern car battery, which can, in general, deliver a peak current of 450 amperes. An improved type of liquid electrolyte battery is the sealed valve regulated lead–acid battery (VRLA battery), popular in the automotive industry as a replacement for the lead–acid wet cell. The VRLA battery uses an immobilized sulfuric acid electrolyte, reducing the chance of leakage and extending shelf life. VRLA batteries have the electrolyte immobilized, usually by one of two means:
• Gel batteries (or "gel cell") contain a semi-solid electrolyte to prevent spillage.
• Absorbed Glass Mat (AGM) batteries absorb the electrolyte in a special fiberglass
Other portable rechargeable batteries include several "dry cell" types, which are sealed units and are, therefore, useful in appliances such as mobile phones and laptop computers. Cells of this type (in order of increasing power density and cost) include nickel–cadmium (NiCd), nickel–zinc (NiZn), nickel metal hydride (NiMH), and lithium-ion (Li-ion) cells By far, Li-ion has the highest share of the dry cell rechargeable market. Meanwhile, NiMH has replaced NiCd in most applications due to its higher capacity, but NiCd remains in use in power tools, two-way radios, and medical equipment. NiZn is a new technology that is not yet well established commercially.
Recent developments include batteries with embedded electronics such as USBCELL, which allows charging an AA cell through a USB connector, and smart battery packs with state-of-charge monitors and battery protection circuits to prevent damage on over-disstate-of-charge. low self-discharge (LSD) allows secondary cells to be precharged prior to shipping.
Battery cell types:
There are many general types of electrochemical cells, according to chemical processes applied and design chosen. The variation includes galvanic cells, electrolytic cells, fuel cells, flow cells and voltaic piles.
Wet cell:
A wet cell battery has a liquid electrolyte. Other names are flooded cell, since the liquid covers all internal parts, or vented cell, since gases produced during operation can escape to the air. Wet cells were a precursor to dry cells and are commonly used as a learning tool for
electrochemistry. It is often built with common laboratory supplies, such as beakers, for demonstrations of how electrochemical cells work. A particular type of wet cell known as a concentration cell is important in understanding corrosion. Wet cells may be primary cells
(non-rechargeable) or secondary cells ((non-rechargeable). Originally, all practical primary batteries such as the Daniell cell were built as open-topped glass jar wet cells. Other primary wet cells are the Leclanche cell, Grove cell, Bunsen cell, Chromic acid cell, Clark cell, and Weston cell. The Leclanche cell chemistry was adapted to the first dry cells. Wet cells are still used in
automobile batteries and in industry for standby power for switchgear, telecommunication or large uninterruptible power supplies, but in many places batteries with gel cells have been used instead. These applications commonly use lead–acid or nickel–cadmium cells.
Dry cell:
Line art drawing of a dry cell:
1. brass cap, 2. plastic seal, 3. expansion space, 4. porous cardboard, 5. zinc can, 6. carbon rod, 7. chemical mixture.
A dry cell has the electrolyte immobilized as a paste, with only enough moisture in it to allow current to flow. Unlike a wet cell, a dry cell can operate in any orientation without spilling as it contains no free liquid, making it suitable for portable equipment. By comparison, the first wet cells were typically fragile glass containers with lead rods hanging from the open top, and needed careful handling to avoid spillage. Lead–acid batteries did not achieve the safety and portability of the dry cell until the development of the gel battery.
A common dry cell battery is the zinc–carbon battery, using a cell sometimes called the dry Leclanché cell, with a nominal voltage of 1.5 volts, the same as the alkaline battery (since both use the same zinc–manganese dioxide combination).
A standard dry cell comprises a zinc anode (negative pole), usually in the form of a cylindrical pot, with a carbon cathode (positive pole) in the form of a central rod. The electrolyte is
ammonium chloride in the form of a paste next to the zinc anode. The remaining space between the electrolyte and carbon cathode is taken up by a second paste consisting of ammonium chloride and manganese dioxide, the latter acting as a depolariser. In some more modern types of so-called 'high-power' batteries (with much lower capacity than standard alkaline batteries), the ammonium chloride is replaced by zinc chloride.
Molten salt:
Molten salt batteries are primary or secondary batteries that use a molten salt as electrolyte. Their energy density and power density give them potential for use in electric vehicles, but they operate at high temperatures and must be well insulated to retain heat.
Reserve:
A reserve battery is stored in unassembled form and is activated, ready-charged, when its internal parts are assembled, e.g. by adding electrolyte; it can be stored inactivated for a long period of time. For example, a battery for an electronic fuse might be activated by the impact of firing a gun, breaking a capsule of electrolyte to activate the battery and power the fuse’s
circuits. Reserve batteries are usually designed for a short service life (seconds or minutes) after long storage (years). A water-activated battery for oceanographic instruments or military
applications becomes activated on immersion in water.
Battery cell performance:
A battery's characteristics may vary over load cycle, over charge cycle, and over lifetime due to many factors including internal chemistry, current drain, and temperature.
A device to check battery voltage
A battery's capacity is the amount of electric charge it can store. The more electrolyte and electrode material there is in the cell the greater the capacity of the cell. A small cell has less capacity than a larger cell with the same chemistry, and they develop the same open-circuit voltage.
Because of the chemical reactions within the cells, the capacity of a battery depends on the discharge conditions such as the magnitude of the current (which may vary with time), the allowable terminal voltage of the battery, temperature, and other factors. The available capacity of a battery depends upon the rate at which it is discharged. If a battery is discharged at a relatively high rate, the available capacity will be lower than expected.
The capacity printed on a battery is usually the product of 20 hours multiplied by the constant current that a new battery can supply for 20 hours at 68 F° (20 C°), down to a specified terminal voltage per cell. A battery rated at 100 A·h will deliver 5 A over a 20-hour period at room temperature. However, if discharged at 50 A, it will have a lower capacity.
The relationship between current, discharge time, and capacity for a lead acid battery is approximated (over a certain range of current values) by Peukert's law:
Where
is the capacity when discharged at a rate of 1 amp.
is the current drawn from battery (A).
is the amount of time (in hours) that a battery can sustain.
is a constant around 1.3.
Internal energy losses and limited rate of diffusion of ions through the electrolyte cause the efficiency of a real battery to vary at different discharge rates. When discharging at low rate, the battery's energy is delivered more efficiently than at higher discharge rates, but if the rate is very low, it will partly self-discharge during the long time of operation, again lowering its efficiency.
Installing batteries with different A·h ratings will not affect the operation of a device (except for the time it will work for) rated for a specific voltage unless the load limits of the battery are exceeded. High-drain loads such as digital cameras can result in delivery of less total energy, as happens with alkaline batteries. For example, a battery rated at 2000 mAh for a 10- or 20-hour discharge would not sustain a current of 1 A for a full two hours as its stated capacity implies.
Crates:
The C-rate signifies a discharge rate relative to the capacity of a battery in one hour. A rate of 1C would mean an entire 1.6Ah battery would be discharged in 1 hour at a discharge current of 1.6A. A 2C rate would mean a discharge current of 3.2A
Fastest charging, largest, and lightest batteries:
As of 2012 Lithium iron phosphate (LiFePO4) batteries were the fastest-charging and
discharging batteries (super capacitors, in some ways comparable to batteries, charge faster). The world's largest battery, composed of Ni–Cd cells, was in Fairbanks, Alaska. Sodium–sulfur batteries were being used to store wind power, Lithium–sulfur batteries have been used on the longest and highest solar-powered flight. The speed of recharging of lithium-ion batteries can be increased by manufacturing changes.
Primary batteries
Disposable (or "primary") batteries typically lose 8 to 20 percent of their original charge every year at room temperature (20°–30°C This is known as the "self discharge" rate, and is due to non-current-producing "side" chemical reactions which occur within the cell even if no load is applied. The rate of the side reactions is reduced if the batteries are stored at lower temperature, although some batteries can be damaged by freezing. High or low working temperatures may reduce battery performance. This will affect the initial voltage of the battery. For an AA alkaline battery, this initial voltage is approximately normally distributed around 1.6 volts.
Discharging performance of all batteries drops at low temperature.
Secondary batteries:
Storage life of secondary batteries is limited by chemical reactions that occur between the battery parts and the electrolyte; these are called "side reactions". Internal parts may corrode and fail, or the active materials may be slowly converted to inactive forms. Since the active material on the battery plates changes chemical composition on each charge and discharge cycle, active material may be lost due to physical changes of volume; this may limit the cycle life of the battery.
RECHARGEABLE BATTERIES:
Old chemistry rechargeable batteries self-discharge more rapidly than disposable alkaline batteries, especially nickel-based batteries; a freshly charged nickel cadmium (NiCd) battery loses 10% of its charge in the first 24 hours, and thereafter discharges at a rate of about 10% a month. However, newer low self-discharge nickel metal hydride (NiMH) batteries and modern lithium designs have reduced the self-discharge rate to a relatively low level (but still poorer than for primary batteries). Most nickel-based batteries are partially discharged when
purchased, and must be charged before first use Newer NiMH batteries are ready to be used when purchased, and have only 15% discharge in a year.
Although rechargeable batteries have their energy content restored by charging, some
deterioration occurs on each charge–discharge cycle. Low-capacity NiMH batteries (1700–2000 mA·h) can be charged for about 1000 cycles, whereas high-capacity NiMH batteries (above 2500 mA·h) can be charged for about 500 cycles NiCd batteries tend to be rated for 1000 cycles before their internal resistance permanently increases beyond usable values. Under normal circumstances, a fast charge, rather than a slow overnight charge, will shorten battery lifespan. Also, if the overnight charger is not "smart" and cannot detect when the battery is fully charged, then overcharging is likely, which also damages the battery. Degradation usually occurs
because electrolyte migrates away from the electrodes or because active material falls off the electrodes. NiCd batteries suffer the drawback that they should be fully discharged before recharge. Without full discharge, crystals may build up on the electrodes, thus decreasing the active surface area and increasing internal resistance. This decreases battery capacity and causes the "memory effect". These electrode crystals can also penetrate the electrolyte separator, thereby causing shorts. NiMH, although similar in chemistry, does not suffer from memory effect to quite this extent. A battery does not suddenly stop working; its capacity gradually decreases over its lifetime, until it can no longer hold sufficient charge.
An analog camcorder battery [lithium ion].
Automotive lead–acid rechargeable batteries have a much harder life. Because of vibration, shock, heat, cold, and sulfation of their lead plates, few automotive batteries last beyond six years of regular use. Automotive starting (SLI: Starting, Lighting, Ignition) batteries have many thin plates to provide as much current as possible in a reasonably small package. In general, the thicker the plates, the longer the life of the battery. They are typically drained only a small amount before recharge. Care should be taken to avoid deep discharging a starting battery, since each charge and discharge cycle causes active material to be shed from the plates.
"Deep-cycle" lead–acid batteries such as those used in electric golf carts have much thicker plates to aid their longevity. The main benefit of the lead–acid battery is its low cost; the main drawbacks are its large size and weight for a given capacity and voltage. Lead–acid batteries should never be discharged to below 20% of their full capacity, because internal resistance will cause heat and damage when they are recharged. Deep-cycle lead–acid systems often use a
low-charge warning light or a low-low-charge power cut-off switch to prevent the type of damage that will shorten the battery's life.
Extending battery life:
Battery life can be extended by storing the batteries at a low temperature, as in a refrigerator or freezer, which slows the chemical reactions in the battery. Such storage can extend the life of alkaline batteries by about 5%; rechargeable batteries can hold their charge much longer, depending upon type. To reach their maximum voltage, batteries must be returned to room temperature; discharging an alkaline battery at 250 mA at 0°C is only half as efficient as it is at 20°C Alkaline battery manufacturers such as Duracell do not recommend refrigerating batteries.
Imagine a world where everything that used electricity had to be plugged in. Flashlights, hearing aids, cell phones and other portable devices would be tethered to electrical outlets, rendering them awkward and cumbersome. Cars couldn't be started with the simple turn of a key; a strenuous cranking would be required to get the pistons moving. Wires would be strung everywhere, creating a safety hazard and an unsightly mess. Thankfully, batteries provide us with a mobile source of power that makes many modern conveniences possible.
While there are many different types of batteries, the basic concept by which they function remains the same. When a device is connected to a battery, a reaction occurs that produces electrical energy. This is known as an electrochemical reaction. Italian physicist Count Alessandro Volta first discovered this process in 1799 when he created a simple battery from metal plates and brine-soaked cardboard or paper. Since then, scientists have greatly improved upon Volta's original design to create batteries made from a variety of materials that come in a multitude of sizes.
Today, batteries are all around us. They power our wristwatches for months at a time. They keep our alarm clocks and telephones working, even if the electricity goes out. They run our smoke detectors, electric razors, power drills, mp3 players, thermostats -- and the list goes on. If
you're reading this article on your laptop or smartphone, you may even be using batteries right now! However, because these portable power packs are so prevalent, it's very easy to take them for granted. This article will give you a greater appreciation for batteries by exploring their history, as well as the basic parts, reactions and processes that make them work. So cut that cord and click through our informative guide to charge up your knowledge of batteries.
Disadvantages of 12 volt battery:
The main disadvantage 12volt lead acid is that it has one of the lowest energy to weight ratio. This means that this type of 12v battery also has a low energy to volume ratio, which in turn means that the size of the battery has to be big in order to provide significant amount of power. Secondly its not portable.
Another major concern about lead acid 12v battery, which is a 12volt power source, is that about environment. Almost all the batteries used in vehicles are lead acid and this means that the disposal of these batteries can beome a big hurdle. Since there are alot of cars, this mean alot of old batteries need to be dumped somewhere and improper disposal means damaged environment.The automotive industry is now looking for alternatives to replace lead acid battery in automative applications towards a environmentally safe option
Note : Please do note that the current rating is VERY important. DONOT plug in a battery which has higher amperage than your modem or router can handle. Most modems and routers are usually rated at around 1 ampere. So a 12V Battery of that rating should be used.
IR LED and IR sensor:
IR LED is used as a source of infrared rays. It comes in two packages 3mm or 5mm. 3mm is better as it is requires less space. IR sensor is nothing but a diode, which is sensitive for infrared radiation.
This infrared transmitter and receiver is called as IR TX-RX pair. It can be obtained from any decent electronics component shop and costs less than 10Rs. Following snap shows 3mm and 5mm IR pairs.
Color of IR transmitter and receiver is different. However you may come across pairs which appear exactly same or even has opposite colors than shown in above pic and it is not possible to distinguish between TX and RX visually. In case you will have to take help of multimeter to distinguish between them.
IR LED emits infrared radiation. This radiation illuminates the surface in front of LED. Surface reflects the infrared light. Depending on reflectivity of the surface, amount of light reflected varies. This reflected light is made incident on reverse biased IR sensor. When photons are incident on reverse biased junction of this diode, electron-hole pairs are generated, which results in reverse leakage current. Amount of electron-hole pairs generated depends on intensity of incident IR radiation. More intense radiation results in more reverse leakage current. This current can be passed through a resistor so as to get proportional voltage. Thus as intensity of incident rays varies, voltage across resistor will vary accordingly.
This voltage can then be given to OPAMP based comparator. Output of the comparator can be read by uC. Alternatively, you can use on-chip ADC in AVR microcontroller to measure this voltage and perform comparison in software.
An infrared detector is a detector that reacts to infrared (IR) radiation. The two main types of detectors are thermal and photonic (photo detectors).
The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena. Bolometer and micro bolometer are based on changes in resistance.
Thermocouples and thermopiles use the thermoelectric effect. Golay cells follow thermal expansion. In IR spectrometers the pyroelectric detectors are the most widespread.
The response time and sensitivity of photonic detectors can be much higher, but usually these have to be cooled to cut thermal noise. The materials in these are semiconductors with narrow band gaps. Incident IR photons can cause electronic excitations. In photoconductive detectors, the resistivity of the detector element is monitored. Photovoltaic detectors contain a p-n junction on which photoelectric current appears upon illumination. A few detector materials:
Types:
WAVENUMBER(CM-RANGE(ΜM)
1)
Indium gallium
arsenide(InGaAs)
photodiode
0.7-2.6
14300-3800
Germanium
photodiode
0.8-1.7
12500-5900
Lead sulfide (PbS)
photoconductive 1-3.2
10000-3200
Lead selenide (PbSe) photoconductive 1.5-5.2
6700-1900
Indium antimonide
(InSb)
photoconductive 1-6.7
10000-1500
Indium arsenide
(InAs)
photovoltaic
1-3.8
10000-2600
Platinum silicide
(PtSi)
photovoltaic
1-5
10000-2000
Indium antimonide
(InSb)
photodiode
1-5.5
10000-1800
Mercury cadmium
telluride (MCT,
HgCdTe)
photoconductive 0.8-25
12500-400
Mercury zinc
telluride (MZT,
HgZnTe)
photoconductive
Lithium tantalate
(LiTaO
3)
pyroelectric
triglycine sulfate
(TGS and DTGS)
pyroelectric
The range of pyroelectric detector is determined by the window materials used in their construction.
Vanadium pentoxide is frequently used as a detector material in uncooled microbolometer
Infrared Sensors or IR Sensors:
Infrared radiation is the portion of electromagnetic spectrum having wavelengths longer than visible light wavelengths, but smaller than microwaves, i.e., the region roughly from 0.75µm to 1000 µm is the infrared region.
Infrared waves are invisible to human eyes. The wavelength region of 0.75µm to 3 µm is called near infrared, the region from 3 µm to 6 µm is called mid infrared and the region higher than 6 µm is called far infrared. (The demarcations are not rigid; regions are defined differently by many).
There are different types of IR sensors working in various regions of the IR spectrum but the physics behind "IR sensors" is governed by three laws:
1. Planck’s radiation law:
Every object at a temperature T not equal to 0 K emits radiation. Infrared radiant energy is determined by the temperature and surface condition of an object. Human eyes cannot detect differences in infrared energy because they are primarily sensitive to visible light energy from 400 to 700 nm. Our eyes are not sensitive to the infrared energy.
2. Stephan Boltzmann Law
The total energy emitted at all wavelengths by a black body is related to the absolute temperature as
Wein’s Law tells that objects of different temperature emit spectra that peak at different wavelengths. It provides the wavelength for maximum spectral radiant emittance for a given temperature.
The relationship between the true temperature of the black body and its peak spectral exitance or dominant wavelength is described by this law
The world is not full of black bodies; rather it
comprises of selectively radiating bodies like rocks, water, etc. and the relationship between the two is given by emissivity (E).
Emissivity depends on object color, surface roughness, moisture content, degree of compaction, field of view, viewing angle & wavelength.
An infrared sensor is an electronic device that emits and/or detects infrared radiation in order to sense some aspect of its surroundings. Infrared sensors can measure the heat of an object, as well as detect motion. Many of these types of sensors only measure infrared radiation, rather than emitting it, and thus are known as passive infrared (PIR) sensors.
All objects emit some form of thermal radiation, usually in the infrared spectrum. This radiation is invisible to our eyes, but can be detected by an infrared sensor that accepts and interprets it. In a typical infrared sensor like a motion detector, radiation enters the front and reaches the sensor itself at the center of the device. This part may be composed of more than one individual sensor, each of them being made from pyroelectric materials, whether natural or artificial. These are materials that generate an electrical voltage when heated or cooled.
These pyroelectric materials are integrated into a small circuit board. They are wired in such a way so that when the sensor detects an increase in the heat of a small part of its field of view, it will trigger the motion detector's alarm. It is very common for an infrared sensor to be
integrated into motion detectors like those used as part of a residential or commercial security system.