POWER SUPPLY DESCRIPTION:

The power supply circuit comprises of four basic parts:

The transformer steps down the 220 V a/c. into 12 V a/c. The transformer work on the

principle of magnetic induction, where two coils: primary and secondary are wound

around an iron core. The two coils are physically insulated from each other in such a way

that passing an a/c. current through the primary coil creates a changing voltage in the

primary coil and a changing magnetic field in the core. This in turn induces a varying a/c.

voltage in the secondary coil.

The a/c. voltage is then fed to the bridge rectifier. The rectifier circuit is used in most

electronic power supplies is the single-phase bridge rectifier with capacitor filtering,

usually followed by a linear voltage regulator. A rectifier circuit is necessary to convert a

signal having zero average value into a non-zero average value. A rectifier transforms

alternating current into direct current by limiting or regulating the direction of flow of

current. The output resulting from a rectifier is a pulsating D.C. voltage. This voltage is

not appropriate for the components that are going to work through it.

TRANSFORMER SHUNT CAPACITOR

BRIDGE RECTIFIER

VOLTAGE REGULATOR

1N4007

12-0-12 V

1000uF

TRANSFORMER

The ripple of the D.C. voltage is smoothened using a filter capacitor of 1000 microF 25V.

The filter capacitor stores electrical charge. If it is large enough the capacitor will store

charge as the voltage rises and give up the charge as the voltage falls. This has the effect

of smoothing out the waveform and provides steadier voltage output. A filter capacitor is

connected at the rectifier output and the d.c voltage is obtained across the capacitor.

When this capacitor is used in this project, it should be twice the supply voltage. When

the filter is used, the RC charge time of the filter capacitor must be short and the RC

discharge time must be long to eliminate ripple action. In other words the capacitor must

charge up fast, preferably with no discharge.

When the rectifier output voltage is increasing, the capacitor charges to the peak voltage

Vm. Just past the positive peak, the rectifier output voltage starts to fall but at this point

the capacitor has +Vm voltage across it. Since the source voltage becomes slightly less

than Vm, the capacitor will try to send current back through the diode of rectifier. This

reverse biases the diode. The diode disconnects or separates the source the source form

load. The capacitor starts to discharge through load. This prevents the load voltage from

falling to zero. The capacitor continues to discharge until source voltage becomes more

than capacitor voltage. The diode again starts conducting and the capacitor is again

7812

7805

charged to peak value Vm. When capacitor is charging the rectifier supplies the charging

through capacitor branch as well as load current, the capacitor sends currents through the

load. The rate at which capacitor discharge depends upon time constant RC. The longer

the time constant, the steadier is the output voltage. An increase in load current i.e.

decrease in resistance makes time constant of discharge path smaller. The ripple increase

and d.c output voltage V dc decreases. Maximum capacity cannot exceed a certain limit

because the larger the capacitance the greater is the current required to charge the

capacitor.

The voltage regulator regulates the supply if the supply if the line voltage increases or

decreases. The series 78xx regulators provide fixed regulated voltages from 5 to 24 volts.

An unregulated input voltage is applied at the IC Input pin i.e. pin 1 which is filtered by

capacitor. The out terminal of the IC i.e. pin 3 provides a regular output. The third

terminal is connected to ground. While the input voltage may vary over some permissible

voltage range, and the output voltage remains constant within specified voltage variation

limit. The 78xx IC’s are positive voltage regulators whereas 79xx IC’s are negative

voltage regulators.

These voltage regulators are integrated circuits designed as fixed voltage regulators for a

wide variety of applications. These regulators employ current limiting, thermal shutdown

and safe area compensation. With adequate heat sinking they can deliver output currents

in excess of 1 A. These regulators have internal thermal overload protection. It uses

output transistor safe area compensation and the output voltage offered is in 2% and 4%

tolerance.

Gear Motors

Gear motor is a motor that has a gear reduction system or the gearbox integrally built into

the motor. The gearbox increases the torque generating ability of the motor while

simultaneously reducing its output speed. The main advantage of a gearmotor is that the

driving shaft may be coupled directly to the driven shaft. Belts, pulleys, chains, or

additional gearing to step down motor speed are needed. Also, coupling or belting of a

motor to a separate speed-reducer unit is eliminated.

AC gearmotor consists of a series of three windings in the stator section with a simple

rotating section and an integral gearbox. DC gear motors are configured in many types

and sizes, including brushless and servo. They consist of a rotor and a permanent

magnetic field stator and an integral gearbox. They are used in variable speed and torque

applications. Direct motors are most common in industrial robots.

Important performance specifications to consider when searching for gearmotors include

shaft speed, continuos torque, continuos current, and continuous output power. The

terminal voltage is the design DC motor voltage. The continuous torque is the output

torque capability of the motor under constant running conditions. Continuous current is

the maximum rated current that can be supplied to the motor windings without

overheating. Continuous output power is the mechanical power provided by the motor

output.

Gear motors are designed and manufactured to be installed within another device. The

installation place should have ambient temperature of about 14 F ~ 104 F and ambient

humidity of maximum 85%. The motor should not be exposed to explosive, flammable

gas, to direct sunlight, dust, water, and oil. It should be placed where heat can easily

escape. Using gearmotors in location that does not satisfy the conditions can damage the

motor.

Standard

Gearmotor service factors and load classifications should confirm to AGMA

recommendations. The minimum service factor should be 1.0 for continuous operation

and the minimum gearing service factor should be 1.0 with a minimum mechanical

strength service factor of 1.3.

Applications

Gearmotors have a variety of successful applications. They are used in packaging and

labeling, case erectors, box taper, hot melt glue pumps, heat shrink tunnels, tape

dispensers and conveyor drives. They are also used in food processing industry. They are

used in ice making machines, weigh checking, baking machinery, meat slicing, cooker

drive, and breading equipment. In transport equipment they are used in wheelchairs, stair

lifts, golf carts and pipeline crawlers. In machine tools they are used in drill heads, rotary

table drives, and hardness test.

Michael Faraday invented the electric motor, which is used to convert electrical energy to

mechanical energy, in 1821. Electric current supplied from the power lines can only be

used directly in heating, lighting and other applications. To use this power to run devices

like pumps, automobiles, domestic appliances and machine tools, the electrical energy

must be converted to mechanical energy, which rotates shafts and gear trains.

Electric motors are available in three basic types of horsepower (hp) ratings: small,

medium and large. Small motors are made to produce fractional hp of 1/20 to 1 hp.

Medium motors are available in the range of 1 to 100 hp and large motors are available in

ratings of 100 to 50,000 hp. Power can also be expressed in kilowatts (1 kW = 1.33 hp; 1

hp = 746 W). Standard frequencies at which motors operate are 50 or 60 Hertz.

How Electric Motors work

The electric motor is based on the principle of electromagnetism and uses the Lorentz

law. When current flows through a wire it produces a magnetic field. The right hand rule

is used to describe the magnetic field. The right-hand rule is used to find the direction of

the force. When the thumb points in the direction of the current and the fingers point in

the direction of the external magnetic field, then the force experienced by the conductor

is in the outward direction from the palm.

An electric motor has a rotating part called the rotor and a stationary part called the

stator. Electromagnets called poles are wound on the frame called the armature. When

current is passed, the rotor rotates due to the torque generated by the wires and the

magnetic field. The rotation is transferred to a shaft which transfers its rotation energy to

any device that is attached to it.

Types of Electric Motors

Major types of electric motors are DC motors (direct current), AC motors (alternating

current) and Universal motors that can operate on either AC or DC current. Each

category is an industry by itself and has many different sub-types.

Universal Motors

These motors can use both DC and AC current and are commonly used in vacuum

cleaners, food mixers, blenders, small power tools and hair dryers and other appliances

that operate at high speed but are not used continuously. They are a variant of the wound

DC motor and special care is taken to cover the impedance and reluctance of AC motors.

Thyristors or stepped speed control circuits are used for continuous speed control.

DC Motors

DC motors provide momentary power bursts of up to five times the rated torque. The

speed can be brought down to zero smoothly and immediately raised in the opposite

direction without any power interruption.

DC motors have an electromagnet with two poles, which serve as a rotating armature. A

commutator or rotary switch is used to reverse the current direction twice in each cycle.

This causes the poles of the electromagnet to push and pull against the external

permanent magnets. When the poles of the armature pass through the poles of the

permanent magnet, the commutator reverses the polarity of the armature. The inertia

maintains the current direction at the instance when polarity is switched.

Major types of DC motors are:

Brushless DC Motors: These motors are used to drive CD-ROM spindles, fans,

office products like Xerox machines, lasers and also in expensive aircraft models.

They have a permanent external rotor magnet; three phase driving coils and Hall

Effect devices that sense rotor position. They are more efficient than AC motors,

do not produce excessive heat and last longer since there is no commutator.

Limited-Angle Torque Motors: These are special type of brushless DC motors

and the torque is produced within 180 degrees of rotation. They are used in: direct

laser mirrors, servo valves, open shutters used in heat-seeking sensors, position

missile guidance radar antennas and power systems where the degree of rotation

is small. The rotor carries field magnets and the stator carries the armature

winding.

PM DC Motors: These are small motors that produce about 50% greater torque

than other comparably sized motors. Magnets are made of Samarium-cobalt and

the torque ripple is greatly reduced.

Coreless DC Motors: In these motors, there is no iron core, thus giving a low

mass and higher acceleration and deceleration. The stator is made of a cylindrical

permanent magnet that is placed in a housing made of mild steel. Rotors are

wound in a honeycombed pattern to increase the torque. The commutator is made

of gold, platinum and other precious metals. They are used to drive Capstan in

magnetic tape drives and in high-performance servo-controlled systems.

Linear DC Motors: These are used in Maglev super fast trains and produce a

linear force and no a torque. It has a stator and a slider. The stator has a laminated

steel frame with conductors wound in transverse slots. The slider has sets of

magnets, commutators, a bearing surface and it makes a path of magnetic flux

between the magnets.

Current Infrared Communication Systems

At present, most infrared links are of the directed-LOS or hybrid-LOS designs. The low

path loss of these designs minimizes the transmitter power requirement and permits the

use of a simple, low-cost receiver. Typically, these links transmit using a single light-

emitting diode (LED), which emits an average power of several tens of mW that is

concentrated within a semi angle of 15to 30The LED emission wavelength

typically lies between 850 and 950 nm. This wavelength matches the responsivity peak of

the silicon positive-intrinsic-negative (p-i-n) photodiode. The wavelength band between

about 780 and 950 nm is presently the best choice for most applications of infrared

wireless links, due to the availability of low-cost LEDs and laser diodes (LDs), and

because it coincides with the peak responsivity of inexpensive, low-capacitance silicon

photodiodes. Infrared radiation a type of invisible radiation for which the wavelengths are

longer and frequency lower than those for visible radiation.

A light emitting diode (LED) is a semiconductor device which emits visible,

infrared or ultraviolet radiation due to flow of electric current through it. Essentially it is

a p-n junction device with p- and n-regions made from the same or different

semiconductors. The color of the emitted light is determined by the energy of the

photons, and in general, this energy is usually approximately equal to the energy band

gap Eg of the semiconductor material in the active region of the LED. III-V

semiconductors such as GaAs, GaP, AlGaAs, InGaP, GaAsP, GaAsInP, AlInGaP, etc. are

the common constituents of an LED. However, which materials would be used for which

LED depends on the choice of color, performance and cost. Operating currents at a

forward voltage of about 2 V are usually in the range of 1-50 mA. Infrared (IR) and red

emission Eg should be less than 2 eV, a range possessed by GaAs AlGaAs and GaAsP.

The performance of LEDs is typically in the range of 1 to 10 W-1, although

performance as high as 20 W-1 can also be achieved. This is comparable with 10-15 W-1

performance of an incandescent bulb. LEDs are very suitable for room illumination

because, at the lower level, they can operate even at less than 0.1 W. Parallel to the

development of visible LEDs infrared (IR) LEDs also attracted interests. Instead of being

detected by eyes, these LEDs are detected by photodiodes or phototransistors. Therefore,

IR LEDs can function as important tools for transmitting data. How fast these data will be

transmitted depends on the switching speed of the IR LEDs. Therefore, this switching

speed is quite unimportant for visible LEDS, this is an important performance parameter

for IR LEDs [35].

3.9.1 The IR Light Emitter

Principle of Operation

Because they emit at wavelengths which provide a close match to the peak spectral

response of silicon photodetectors, both GaAs and GaAlAs. There are many off-the-shelf,

commercially available, IR LED emitters that can be used for a discrete infrared

transceiver circuit design. It should be mentioned here that there are also a number of

integrated transceivers that the designer can choose as well. In general, there are four

characteristics of IR emitters that designers have to be wary of:

Rise and Fall Time

Emitter Wavelength

Emitter Power

Emitter Half-angle

Description

In this system IR LED used is The QED233 / QED234 which is a 940 nm GaAs /

AlGaAs LED encapsulated in a clear untinted, plastic T-1 3/4 package.

QED234 Features

Wavelength=940nm

Chip material =GaAs with AlGaAs window

Package type: T-1 3/4 (5mm lens diameter)

Matched Photo sensor: QSD122/123/124, QSE 973.

Medium Emission Angle, 40°

High Output Power

Package material and color: Clear, untinted, plastic

Ideal for remote control applications

3.9.2 Semiconductor Light Detectors

Energy entering a semiconductor crystal excites electrons to higher levels, leaving behind

"holes". These electrons and "holes" can recombine and emit photons, or they can move

away from one another and form a current. This is the basics of semiconductor light

detectors. The basic optical receiver converts the modulated light coming from the space

back in to a replica of the original signal applied to the transmitter.

Types of optical detector

Anode Cathode

P-N photodiode

P-I-N photodiode

Avalanche photodiode

In P-N photodiode, electron hole pairs are created in the depletion region of a p-n

junction in proportion to the optical power. Electrons and holes are swept out by the

electric field, leading to a current. In P-I-N photodiode, electric field is concentrated in a

thin intrinsic layer. In avalanche photodiode, like P-I-N photodiodes, but have an

additional layer in which an average of M secondary electron –hole pairs are generated

through impact ionization for each primary pair. Photodiodes usually have a large

sensitive detecting area that can be several hundreds microns in diameter.

3.9.3 The IR Light Detector

The most common device used for detecting light energy in the standard data stream is a

photodiode, Photo transistors are not typically used in IrDA standard-compatible systems

because of their slow speed. Photo transistors typically have ton/toff of 2 µs or more. A

photo transistor may be used, however, if the data rate is limited to 9.6 kb with a pulse

width of 19.5 µs. A photodiode is packaged in such a way as to allow light to strike the

PN junction.

In infrared applications, it is common practice to apply a reverse bias to the

device. Refer to Figure 3.17 for a characteristic curve of a reverse biased photodiode.

There will be a reverse current that will vary with the light level. Like all diodes, there is

an intrinsic capacitance that varies with the reverse bias voltage. This capacitance is an

important factor in speed.

Description

The QSE973 is a silicon PIN photodiode encapsulated in an infrared transparent, black,

plastic T092 package.

1 2

+_

QSE 973 Features

Daylight filter

T092 package

PIN photodiode

Recepting angle 90°

Chip size = .1072 sq. inches (2.712 sq. mm)

Link Distance

To select an appropriate IR photo-detect diode, the designer must keep in mind the

distance of communication, the amount of light that may be expected at that distance and

the current that will be generated by the photodiode given a certain amount of light

AnodeCathode

energy. The amount of light energy, or irradiance that is present at the active-input

interface is typically given in µW/cm2. This is a convenient scale of light flux [36].

THE ELECTROMAGNETIC RELAY

The electromagnetic relay consists of a multi-turn coil, wound on an iron core, to form an

electromagnet. When the coil is energised, by passing current through it, the core

becomes temporarily magnetised. The magnetised core attracts the iron armature. The

armature is pivoted which causes it to operate one or more sets of contacts.

When the coil is de-energised the armature and contacts are released. The coil can

be energised from a low power source such as a transistor while the contacts can

switch high powers such as the mains supply. The relay can also be situated

remotely from the control source. Relays can generate a very high voltage across the

coil when switched off. This can damage other components in the circuit. To prevent

this a diode is connected across the coil.

555 timer IC

The 555 Timer IC is an integrated circuit (chip) implementing a variety of timer and

multivibrator applications. The IC was designed by Hans R. Camenzind in 1970 and

brought to market in 1971 by Signetics (later acquired by Philips). The original name was

the SE555 (metal can)/NE555 (plastic DIP) and the part was described as "The IC Time

Machine".[1] It has been claimed that the 555 gets its name from the three 5  kΩ resistors

used in typical early implementations,[2] but Hans Camenzind has stated that the number

was arbitrary.[3] The part is still in wide use, thanks to its ease of use, low price and good

stability. As of 2003, it is estimated that 1 billion units are manufactured every year.[3]

Depending on the manufacturer, the standard 555 package includes over 20 transistors, 2

diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package

(DIP-8).[4] Variants available include the 556 (a 14-pin DIP combining two 555s on one

chip), and the 558 (a 16-pin DIP combining four slightly modified 555s with DIS & THR

connected internally, and TR falling edge sensitive instead of level sensitive).

Ultra-low power versions of the 555 are also available, such as the 7555 and TLC555. [5]

The 7555 requires slightly different wiring using fewer external components and less

power.

The 555 has three operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot". Applications

include timers, missing pulse detection, bouncefree switches, touch switches,

frequency divider, capacitance measurement, pulse-width modulation (PWM) etc

Astable - free running mode: the 555 can operate as an oscillator. Uses include

LED and lamp flashers, pulse generation, logic clocks, tone generation, security

alarms, pulse position modulation, etc.

Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin

is not connected and no capacitor is used. Uses include bouncefree latched

switches, etc.

Usage

The connection of the pins is as follows:

Nr. Name Purpose

1 GND Ground, low level (0 V)

2 TRIG A short pulse high-to-low on the trigger starts the timer

3 OUT During a timing interval, the output stays at +VCC

4 RESETA timing interval can be interrupted by applying a reset pulse to low

(0 V)

5 CTRL Control voltage allows access to the internal voltage divider (2/3 VCC)

6 THRThe threshold at which the interval ends (it ends if the voltage at THR

is at least 2/3 VCC)

7 DISConnected to a capacitor whose discharge time will influence the

timing interval

8 V+, VCC The positive supply voltage which must be between 3 and 15 V

Monostable mode

The relationships of the trigger signal, the voltage on C and the pulse width in

monostable mode

In the monostable mode, the 555 timer acts as a “one-shot” pulse generator. The pulse

begins when the 555 timer receives a trigger signal. The width of the pulse is determined

by the time constant of an RC network, which consists of a capacitor (C) and a resistor

(R). The pulse ends when the charge on the C equals 2/3 of the supply voltage. The pulse

width can be lengthened or shortened to the need of the specific application by adjusting

the values of R and C.[6]

The pulse width of time t, which is the time it takes to charge C to 2/3 of the supply

voltage, is given by

where t is in seconds, R is in ohms and C is in farads. See RC circuit for an explanation

of this effect.