1.LIST OF FIGURES
Proper water distribution is very important in today’s life. We cannot supply water to the entire city same time because of low pressure.
Therefore we have to supply the water separately to different areas. If we make the system manually then we require man power therefore cost will be increased as we have to pay man power.
Also if the system is manual , there may be chances for unequal water supply in the distribution.so in order to avoid this problem, we are designing project titled a “WIRELESS WATER DISTRIBUTION SYSTEM” is developed.
The objective of this project is to distribute the water in streets or many places without man power using RF transmitter and RF receiver at the particular time.
In this modern world, proper water distribution is very essential in today’s life. We have to supply water to the different areas. If the system is manual, large amount of man power is required and also there may be chances for unequal distribution. In order to avoid this problem our project “Wireless Water Distribution System” is developed.
The objective of this project is to distribute the water in streets or many places without man power using RF transmitter and receiver at the particular time.
In this project the Transmitter Unit consists, keypad and RF transmitter. At every particular time the transmitter section sends the signal in which valve getting ON and OFF status.
The receiver section consists of RF receiver, decoder driver circuit with relay. The receiver section receives the information by using RF receiver. The received signal is given to receiver module through decoder.
So whenever the RF receiver receives command it generates the pulse and gives to the corresponding relay through a driver circuit. This is very effective method for water distribution process.
Since the project has developed completely by wireless technology, it can be implemented in real time systems and equal distribution of water supply will be obtained.
4. BIOCK DIAGRAM
5. CIRCUIT DIAGRAM
6. CIRCUIT DIAGRAM DESCRIPTION
In this project the Transmitter Unit consists, keypad and RF transmitter. At every particular time the transmitter section sends the signal in which valve getting ON and OFF status.
The receiver section consists of RF receiver, decoder driver circuit with relay. The receiver section receives the information by using RF receiver. The received signal is given to receiver module through decoder.
So whenever the RF receiver receives command it generates the pulse and gives to the corresponding relay through a driver circuit. This is very effective method for water distribution process.
7.1RELAY WITH DRIVER CIRCUIT
A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off so relays have two switch positions and they are doublethrow (changeover) switches. Relays allow one circuit to switch a second circuit which can be completely separate from the first.
For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits; the link is magnetic and mechanical.The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can be as much as 100mA for relays designed to operate from lower voltages.
Most ICs (chips) cannot provide this current and a transistor is usually used to amplify the small IC current to the larger value required for the relay coil. The maximum output current for the popular 555 timer IC is 200mA so these devices can supply relay coils directly without amplification.
Relays are usually SPDT or DPDT but they can have many more sets of switch contacts, for example relays with 4 sets of changeover contacts are readily available. Most relays are designed for PCB mounting but you can solder wires directly to the pins providing you take care to avoid melting the plastic case of the relay.
The animated picture shows a working relay with its coil and switch contacts. A lever is present on the left being attracted by magnetism, when the coil is switched on.
This lever moves the switch contacts. There is one set of contacts (SPDT) in the foreground and another behind them, making the relay D PDT.
The relay's switch connections are usually labeled COM, NC and NO:
COM = Common, always connect to this, it is the moving part of the switch.
NC = Normally Closed, COM is connected to this when the relay coil is off.
NO = Normally Open, COM is c onnected to this when the relay coil is on.
7.1.3 CIRCUIT DESCRIPTION:
This circuit is designed to control the load. The load may be motor or any other load. The load is turned ON and OFF through relay. The relay ON and OFF is controlled by the pair of switching transistors (BC 547). The relay is connected in the Q2 transistor collector terminal.
A Relay is nothing but electromagnetic switching device which consists of three pins. They are Common, Normally close (NC) and normally open (NO).The relay common pin is connected to supply voltage. The normally open (NO) pin connected to load.
When high pulse signal is given to base of the Q1 transistors, the transistor is conducting and shorts the collector and emitter terminal and zero signals is given to base of the Q2 transistor. So the relay is turned OFF state.
When low pulse is given to base of transistor Q1 transistor, the transistor is turned OFF. Now 12v is given to base of Q2 transistor so the transistor is conducting and relay is turned ON.
Hence the common terminal and NO terminal of relay are shorted. Now load gets the supply voltage through relay.
Voltage Signal from
Microcontroller or PC
A ULN2803 is an Integrated Circuit (IC) chip with a High Voltage/High Current Darlington Transistor Array. It allows you to interface TTL signals with higher voltage/current loads.
In English, the chip takes low level signals (TLL, CMOS, PMOS, NMOS - which operate at low voltages and low currents) and acts as a relay of sorts itself, switching on or off a higher level signal on the opposite side.
A TTL signal operates from
The maximum power available on a TTL signal depends on the type, but generally does not exceed 25mW (~5mA @ 5V), so it is not useful for providing power to something like a relay coil.
Computers and other electronic devices frequently generate TTL signals. On the output side the ULN2803 is generally rated at 50V/500mA, so it can operate small loads directly.
Alternatively, it is frequently used to power the coil of one or more relays, which in turn allow even higher voltages/currents to be controlled by the low level signal.
In electrical terms, the ULN2803 uses the low level (TTL) signal to switch on/turn off the higher voltage/current signal on the output side. The ULN2803 comes in an
Pin details of uln 2803
A float switch is a device used to detect the level of liquid within a tank. The switch may be used in a pump, an indicator, an alarm, or other devices.
Float switches range from small to large and may be as simple as a mercury switch inside a hinged float or as complex as a series of optical or conductance sensors producing discrete outputs as the liquid reaches many different levels within the tank. Perhaps the most common type of float switch is simply a float raising a rod that actuates a micro switch.
Opened float switch from a sump pump
Float switch off
Opened float switch from a sump pump
Float switch ON
A very common application is in sump pumps and condensate pumps where the switch detects the rising level of liquid in the sump or tank and energizes an electrical pump which then pumps liquid out until the level of the liquid has been substantially reduced, at which point the pump is switched off again.
Float switches are often adjustable and can include substantial hysteresis. That is, the switch's "turn on" point may be much higher than the "shut off" point. This minimizes the
Some float switches contain a
A Float Switch is a device which is typically used to measure the depth/level of liquid in a container. As the water rises and reaches the level of the float switch, it begins to float going from the vertical to the horizontal. This closes an internal switch which can then be used to turn on/off a pump, alarm and relay.
Pictured above is a submersible water pump with an integrated float switch (the red part). If a pump is run dry, it will quickly burn out - therefore, all good quality pumps are sold with a
A float switch can be as simple as a mercury tilt switch fitted into watertight floatable case. Since mercury is very toxic, a far more common alternative is to use a reed switch which is triggered by a small
Pictured above is a typical
This particular float switch can manage a switching current of up to 1.5 Amps - plenty to trigger a relay or a light/alarm. Typically float switch switching currents range from 0.5 to 2Amps.
7.3.1Uses for Float Switches
Float switches can be set up to sense either rising or falling water levels - rising water to measure when a container is full or water has reached a certain maximum level, falling water to measure when a container is empty or has reached a certain minimum level.
One example is rainwater toilet flushing. If a pump is required to get collected rainwater up to toilet cistern from the main rainwater store, the pump can be automatically switched on when cistern is not full.
This ensures there is always water ready in the cistern to flush the toilet when required. This same technique can be used to safely fill a water tank in the loft so that there is decent
Another example is in garden irrigation. Water from a main rainwater/greywater storage tank can be pumped up to a smaller tank located near to a greenhouse or vegetable beds as and when it is required without the risk of overfilling.
7.3.2Alternative to a Float Switch - A Liquid Sensor
Float switches contain moving parts and are therefore prone to breakage - quite often failing before the pump they are designed to protect. One alternative is to use a liquid sensor such as the example pictured below.
The only moving part in such a device is the reed switch reducing its chance of mechanical failure. This particularly (typical) example can handle a switching current of 0.5 Amps.
More information about liquid sensors, their use and their limitations, is available in our new article Understanding Liquid Sensors
7.3.3 Simple Float Switch Circuit with Relay
In most cases when using a float switch, the current required by the device to be switched on is in excess of the switching current rating of the switch. Therefore, a relay* is used such as the 6 Volt example pictured above (and sold in the REUK Shop).
Since a relay is being used, a low power source such as a PV solar panel with battery back up can be used for the water level sensing circuit. This can then be used to connect a high power source such as mains electricity or a battery bank to drive the pump
The circuit diagram schematic above shows such a
When the (normally open) float switch is hanging in the air above the level of the water in the tank being filled, electricity flows through the float switch, and therefore through the LED (lighting up that PUMP ON indicator) and the relay coil.
That closes the relay contact connecting power to the water pump. When the float switch starts to float on top of the rising water, electricity stops flowing through the float switch, the LED turns off, and the pump stops.
NEW Click here to view full details of the implementation of a simple DIY Automatic Pump Shut Off Circuit.
7.3.4Hysteresis with Float Switches:
If the water in the container is at all turbulent at its surface, the float switch may turn on and off repeatedly (multiswitching), potentially damaging a pump attached to it.
Therefore a slightly more complicated electronic circuit can be used which introduces hysteresis - for example, when the pump is switched off it could be made to stay off for at least 10 seconds, or the sensor/switch has to detect water continuously for 10 seconds before the pump is switched on.
NEW Click here to view our new article Water Pump Hysteresis Circuit to find out more about how multiswitching can be prevented using a simple time delay circuit.
7.4 WATER PUMP
A pump is a device that moves fluids (liquids or gases), or sometimes slurries, b y mechanical action. Pumps can be classified into three majo r groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps.
Pumps operate by some mech anism (typically reciprocating or rotary), and consume energy to perform mechanical work by moving th e fluid. Pumps operate via many energy sources, including manual operation, electricity, engines, or wind power.
Pumps can be classified into positive displacement pumps, impulse pumps, velocity pumps, gravity pumps, steam pumps and valve less pum ps.
7.4.2 Velocity pumps
Rotor dynamic pumps (or dyna mic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is re duced prior to or as the flow exits the pump into the discharge pipe.
This conversion of kinetic ener gy to pressure is explained by the First law of thermodynamics, or more specifically by Bernoulli's principle. Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved.
These types of pumps have a number of characteristics:
2.Conversion of added energy to i ncrease in kinetic energy (increase in velocity)
3.Conversion of increased velocity (kinetic energy) to an increase in pressure head
A practical difference between d ynamic and positive displacement pumps is how they operate under closed valve conditions.
Positive displacement pumps physically displace fluid, so closing a valve downstream of a positive displacement pump produces a continu al pressure build up that can cause mechanical failure of pipeline or pump.
Dynamic pumps differ in that t hey can be safely operated under closed valve conditions (for short periods of time).
7.4.3 Centrifugal pump
Metering pump for gasoline and additives.
Pumps are used throughout society for a variety of purposes. Early applications include the use of the windmill or watermill to pump water.
Today, the pump is used for irrigation, water supply, gasoline supply, air conditioning systems, refrigeration (usually called a compressor), chemical movement, sewage movement, flood control, marine services, etc.
Because of the wide variety of applications, pumps have a plethora of shapes and sizes: from very large to very small.
From handling gas to handling liquid, from high pressure to low pressure, and from high volume to low volume.
8. TRANSMITTER & RECEIVER ARCHITECTURES
8.1Basic Building Blocks
8.1.1Block Diagram of Transmitter and Receiver
8.1.2Frequency Source (carrier)
In order to make the information signal (e.g. data) pass through the air, it must be modulated on to a carrier signal whose frequency is well suited to the propagation environment, conforms to the licensed operating bands, and is sufficiently stable to allow detection by a tuned receiver in the presence of interference.
Fig.8.1.2 Frequency Source
The method of imposing the information signal onto the carrier signal is termed modulation and must be accomplished cost effectively and accurately for maximum range and minimum interference.
The amplifier is a key part of the transceiver, and must be efficient (dc power in to RF power out), low cost,
The antenna is often the most poorly engineered part of a radio system. Good design will ensure maximum range, high amplifier efficiency (good matching), good selectivity, minimal pollution, good interference rejection, good sensitivity, reduced design headaches.
Key to the sensitivity, dynamic range and strong signal handling properties of the radio is the receiver ‘front end’. The main task is to boost weak wanted signals, often in the presence of strong unwanted signals whilst introducing minimal noise and distortion. In many cases, some selective filtering is required to assist this task.
The process of removing the information signal from the carrier is termed demodulation. The challenge is to design a circuit (or algorithm) that will achieve this task optimally in the presence of noise, interference and varying signal strength, frequency and phase, whilst being compact, power efficient and cheap.
8.1.7 Data processing
Pre and post processing of the information signal is often an afterthought for low power radio applications, usually implying some form of microprocessor or DSP engine with the presumed complexity, cost, power consumption and size penalties.
The benefits of matched filtering, error detection and correction (coding), channel equalization, etc., are however significant in terms of range, robust transmission, power conservation and data rate optimization.
The process of imposing the information signal onto the carrier is termed modulation and can be achieved in a wide variety of ways depending on the type of modulation required.
Essentially there are three basic ways of changing the properties of the carrier signal to convey information: Amplitude Modulation, Frequency Modulation and Phase Modulation. Modern low power radio devices use all three of these methods and some of the more recent designs use combinations to achieve improved data rate and range.
A detailed discussion of digital modulation formats and their merits, performance and implementation is covered in ‘Digital Communications – Design for the Real World’ published by Addison Wesley Longman, and in the Digital Modulation section of this course. For now, a brief overview of methods for modulating a carrier, independent of the data type, is given.
The simplest method of varying the frequency of a carrier it to include a voltage controlled impedance element in the oscillator circuit. The Varactor (voltage controlled capacitor) is most widely used, costing only a few pence, and providing reasonably linear variation in capacitance (and hence oscillator frequency) with applied voltage.
8.2.2 PLL Based Modulation
To achieve stability of the modulated source, the PLL is again widely used, with the varactor based oscillator acting as the VCO. Frequency modulation can be achieved in one of three ways:
a)Modulating the reference source (typically using a varactor based crystal oscillator or DDS source), in which case the modulation must not exceed the tracking bandwidth of the loop otherwise the modulation will not be recreated at the output. (Note: the output frequency shift, (modulation index), is N/M times the input frequency shift).
b)Adding the modulation signal to the VCO control voltage within the loop. This only works if the modulation rate exceeds the tracking bandwidth of the loop such that the loop is unable to track it out, which it will attempt to do!
Fig.8.2.2 Frequency Modulation using PLL
8.3RF POWER AMPLIFIER
An RF power amplifier is a type of electronic amplifier used to convert a
The basic applications of the RF power amplifier include driving to another high power source, driving a transmitting antenna, microwave heating, and exciting resonant cavity structures.
Among these applications, driving transmitter antennas is most well known. The transmitter– receivers are used not only for voice and data communication but also for weather sensing (in the form of a RADAR). Microwave or RF heating is an industrial application which is also benefiting our homes in the form of microwave ovens.
Exciting cavity resonators is quite a research lab and industrial application of an RF source. Particle accelerators utilize RF sources extensively.
8.3.2 RF Transmitter Module:
Radio frequency (RF) transmitters are widely used in radio frequency communications systems. With the increasing availability of efficient, low cost electronic modules, mobile communication systems are becoming more and more widespread. Wireless communications systems, including cellular phones, paging devices, personal communication services (PCS) systems, and wireless data networks, have become ubiquitous in society.
A mobile terminal apparatus used in the cellular radio communications system receives a radio frequency signal transmitted from a base station, by an antenna, inputs the signal to a receiving radio- frequency unit via an antenna duplexer, high frequency amplifies the signal, removes unnecessary waves outside the receiving band from the signal, converts the signal to an intermediate frequency signal, demodulates the intermediate frequency signal by a demodulator, and converts the signal into a baseband signal.
Generally, a radio transmitter and receiver is used for performing a radio transmission and receiving operation, whereby a high frequency signal outputted from a modulator is transmitted to an antenna of the radio transmitter and is transmitted therefrom to a remote radio transmitter and receiver, or the thusly transmitted signal is received through another antenna.
The transmitting baseband signal is subjected to a predetermined signal process, input to a modulator, which modulates a carrier wave signal. The modulated carrier wave signal is converted into a radio frequency by a transmitting
Such communication systems range from national and/or international cellular telephone systems to the Internet to
For indirect wireless communications, each wireless communication device communicates directly with an associated base station and/or an associated access point via an assigned channel. Compact radio frequency (RF) transmitters are widely employed to transmit radiating signals for use in connection with remote signal communication systems. RF transmitters are widely used in
A wide variety of compact transmitters are commonly used with automotive vehicle remote keyless entry systems for remotely controlling access to a vehicle in addition to controlling other vehicular functions such as alarm system features, trunk release, etc. Similarly, compact transmitters are also widely used for remotely controlling the operations provided with automatic garage door systems, electronic sound systems, televisions and VCRs.
In cellular systems, a plurality of base stations is distributed across the service area. Each base station services wireless communications within a respective cell. Both base stations and subscriber units include radio frequency transmitters and RF receivers, together they're called "RF transceivers." RF transceivers service the wireless links between the base stations and subscriber units. Transceivers are used in wireless communications to transmit and receive electromagnetic waves in free space. RF receivers generally either convert an input RF signal to an intermediate frequency, or directly mix an input signal to a direct current (DC) signal.
The transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The RF transmitter receives a baseband signal from a baseband processor, converts the baseband signal to an RF signal, and couples the RF signal to an antenna for transmission. In most RF transmitters, the baseband signal is first converted to an intermediate frequency (IF) signal and then the IF signal is converted to the RF signal.
The data modulation stage converts raw data into baseband signals in accordance with the particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
The function of the receiver is to detect signals in the presence of noise and interference, and provide amplification, downconversion and demodulation of the detected the signal such that it can be displayed or used in a data processor. The RF receiver receives an RF signal, converts the RF signal to an IF signal, and then converts the IF signal to a baseband signal, which it then provides to the baseband processor.
As is also known, RF transceivers typically include sensitive components susceptible to noise and interference with one another and with external sources. The RF receiver is coupled to the antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage.
The low noise amplifier receives an inbound RF signal via the antenna and amplifies it. The one or more intermediate frequency stages mix the amplified RF signal with one or more local oscillations to convert the amplified RF signal into a baseband signal or an intermediate frequency (IF) signal. Typical transmit circuitry includes a feedback loop (often a
Phase locked loops (PLLs) are becoming increasingly popular in integrated wireless transceivers as components for frequency generation and modulation. PLLs are typically used for one of a variety of functions, including frequency translation to
In general, the function of a radio frequency (RF) transmitter is to modulate, upconvert, and amplify signals for transmission into free space. An RF transmitter generally includes a modulator that modulates an input signal and a radio frequency power amplifier that is coupled to the modulator to amplify the modulated input signal. The radio frequency power amplifier is coupled to an antenna that transmits the amplified modulated input signal.
Power amplifiers are required in radio telecommunication systems to amplify signals before transmitting, because a radio signal attenuates on the radio path. For efficiency, the amplifier is often a non- linear amplifier operated near its peak capacity. To avoid distortion of the transmitted signals due to the non- linearity, the signals are
The predistortion is required to prevent transmitter from transmitting signals on channel bands other than the band assigned to the transmitter. Digitalpredistortion may be performed by multiplying the modulated signals prepared for transmission by a set of predistortion values. The predistortion values are chosen such that the product values entering the power amplifier will be distorted by the power amplifier to return to a substantially linear amplification of the modulated signals.
A direct conversion transmitter system to produce a transmission signal is generally comprised of a low oscillator (LO), a phase locked loop (PLL), a quadrature generator, a modulator, a power amplifier (PA), and one or more filters. The low oscillator, coupled to the PLL, produces a signal with a frequency that is substantially equal to the frequency of a desired RF transmission signal.
The amplified signal may go through a filter to reduce noise or spurious outputs outside of the transmission band. High quality RF transmitters typically include bandpass filters, such as surface acoustic wave (SAW) filters provide excellent performance. A typical cell phone may employ a bandpass filter following the power amplifier to reduce undesired noise present at the antenna in different portion of RF spectrum to meet various standards' regulations and specifications.
The optimal functioning of a transmitter in a telecommunications system depends upon the suitability of the bandwidth of the transmitted signal to its data rate and modulation type. Cellular phones are designed to operate within the environment of one of several mobile communications networks.
Transmitters and receivers for communication systems generally are designed such that they are tuned to transmit and receive one of a multiplicity of signals having widely varying bandwidths and which may fall within a particular frequency range.
8.3.3 RF Receiver Module:
How do radio receivers manage to communicate over huge distances? Here is a description of the fundamental mechanism used. The principle of the receiver is the same whatever the way you communicate; radio waves, sound waves, optical communications.
8.4. RADIO RECEIVER
A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filtersto separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions,etc.
Basic crystal set.
1.Basic Crystal Set:
The first receiver built by a hobbyist is usually the plain old crystal set. If you are unfamiliar with the design then check out the crystal set page.
2. T.R.F. Receiver:
The T.R.F. (tuned radio frequency) receiver was among the first designs available in the early days when means of amplification by valves became available. The basic principle was that all rf. stages simultaneously tuned to the received frequency before detection and subsequent amplification of the audio signal.
The principle disadvantages were (a) all rf. stages had to track one another and this is quite difficult to achieve technically, also (b) because of design considerations, the received bandwidth increases with frequency.
As an example - if the circuit design Q was 55 at 550 KHz the received bandwidth would be 550 / 55 or 10 KHz and that were largely satisfactory. However at the other end of the a.m. band 1650 KHz, the received bandwidth was still 1650 / 55 or 30 KHz.Finally a further disadvantage (c) was the shape factor could only be quite poor. A common error of belief with rf. filters of this type is that the filter receives one signal and one signal only.
If our signal sits in a channel in the a.m. radio band where the spacing is say 10 KHz e.g. 540 KHz, 550 KHz, 560 KHz.... etc and our signal, as transmitted, is plus / minus 4Khz then our 550 KHz channel signal extends from 546 KHz to 554 KHz. These figures are of course for illustrative purposes only.
Clearly this signal falls well within the
The rf filter of 10 KHz occupies the page width at the top of the page and the bottom of the page where the signal is only 3.16% of the original it is still the width of the page. In the real world this never happens. A shape factor of 2:1 would be good for an L.C. filter. This means if the bottom of your page was 20 KHz wide then the middle half of the top of the page would be 10 KHz wide and this would be considered good!.
Back to T.R.F. Receivers - their shape factors were nothing like this. Instead of being shaped like a page they tended to look more like a flat sand hill. The reason for this is it is exceedingly difficult or near impossible to build LC Filters with impressive channel spacing and shape factors at frequencies as high as the broadcast band. And this was in the days when the short wave bands (much higher in frequencies) were almost unheard of. Certain embellishments such as the regenerative detector were developed but they were mostly unsatisfactory.
3. Superhetrodyne Receiver:
A superheterodyne receiver works on the principle the receiver has a local oscillator called a variable frequency oscillator or V.F.O. This is a bit like having a little transmitter located within the receiver.
Now if we still have our T.R.F. stages but then mix the received signal with our v.f.o. we get two other signals. (V.F.O. + R.F) and (V.F.O. - R.F).In a traditional a.m. radio where the received signal is in the range 540 KHz to 1650 KHz the v.f.o. signal is always a constant 455 KHz higher or 995 KHz to 2105 KHz.
4. Reflex Receiver:
The reflex receiver uses the same transistors to amplify the RF and the audio independently, effectively doubling the transistor count
Several advantages arise from this and we will use our earlier example of the signal of 540 KHz:
(a) The input signal stages tune to 540 KHz. The adjacent channels do not matter so much now because the only signal to discriminate against is called the if. image. At 540 KHz the v.f.o. is at 995 KHz giving the constant difference of 455 KHz which is called the I.F. frequency. However a received frequency of v.f.o. + i.f. will also result in an i.f. frequency, i.e. 995 KHz + 455 KHz or 1450 KHz, which is called the i.f. image.
Put another way, if a signal exists at 1450 KHz and mixed with the vfo of 995 KHz we still get an i.f. of 1450 - 995 = 455 KHz. Double signal reception. Any reasonable tuned circuit designed for 540 KHz should be able to reject signals at 1450 KHz. And that is now the sole purpose of the r.f. input stage.
(b) At all times we will finish up with an i.f. signal of 455 KHz. It is relatively easy to design stages to give constant amplification, reasonable bandwidth and reasonable shape factor at this one constant frequency.
Radio design became somewhat simplified but of course not without its associated problems. On or off; in the case of a
8.5 RF TRANSMITTER:
The transmitter circuit is made up of two building blocks - the 303MHz RF oscillator and the 32 kHz crystal controlled oscillator.The 303MHz oscillator consists of a
Now we come to the purpose of the 15microhenry choke on the tank circuit.When the circuit oscillates, it takes a larger and small amount of current.This current passes through the choke and the turns produce a
The end effect is a voltage created atthe point where the choke is connected to the
The choke allows the
If the crystal is removed, the oscillator is seen as producing very narrow spikes with a frequency determined by the 2n2.When the crystal is added, the frequency increases (because the effect of the 2n2 and crystal in series creates a lower capacitance than 2n2) and as it rises, the amplitude of thefeedback signal increases until it reaches a maximum at the resonant frequency of the crystal.
The crystal exhibits the lowest impedance (the highest capacitance) at the resonant frequency. This is how the circuit stabilizes at the frequency of the crystal.When the device is turned on, the 150k on the base of the second transistor turns the transistor on.
The third transistor has 0.65v on the collector and the base also receives very close to 0.65v, via the 220k resistor.The third transistor is not fully turned on and it produces a small amount of noise. This noise is passed to the second transistor and appears on the collector.
The collector passes this noise to the base of the third transistor and the noise very rapidly increases to a maximum.It comes to a point where the waveform above is generated and the reason why the spikes are so narrow is easy to explain.
When the middle transistor changes from an OFF state to an ON state, the capacitor will be partially charged and the voltage on the end connected to the base of the third transistor will drop about 6v and put a negative voltage on the base of the third transistor.
This will keep it off and the middle transistor will be kept ON via the 150k
This causes the middle transistor to turn OFF and the collector voltage rises. This causes the capacitor to charge and create a
Both transistors are now turned ON and the capacitor charges very quickly via the 12k and base- emitter junction of the third transistor.
This creates the very narrow
8.6 RF RECEIVER:
The first stage is actually a 303MHz oscillator that is operating all the time.It produces a clean 303MHz signal and this frequency is too high to be detected or processed by the 4069 chip, as the chip will only operate to about 1MHz.The theory behind using this type of stage is quite simple.It is easier to "upset" or modify a stage that is already oscillating, rather than get a
The 303MHz oscillator is firstly set into operation by the noise produced by the transistor and this is passed to the tank circuit made up of the
The stage is actually a transmitter, but we will still call it the receiver circuit. Yes, it is a very weak transmitter and it fills the surrounding with a clean 303MHz signal. When the 303MHz signal from the transmitter enters this space, the signals interfere with one another and the receiver takes more and less current as it tries to maintain the signal strength.
When the 32 kHz signal is present, the receiver takes a varying current that corresponds to the 32 kHz signal and this is how the receiver circuit produces the waveform to correspond to the 32 KHz. A low- impedance path to the 0v rail is provided for the emitter by using a 82uH choke and a 2n2 capacitor across a 560R resistor.This low impedance path is needed so that the transistor has a high gain.The circuit is put into very delicate oscillation by using a 1k5 from the positive rail.It operates from 3v and the current taken by this stage is less than 1mA.
The first inverter has a 1M connected between the output and input to set it to mid rail so it becomes a
9. SOLENOID VALVE
A solenoid valve is an electromechanically operated valve. The valve is controlled by an electric current through a solenoid: in the case of a
Solenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix fluids. They are found in many application areas.
Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.
The valve body must be compatible with the fluid; common materials are brass, stainless steel, aluminum, and plastic. The seals must be compatible with the fluid.
To simplify the sealing issues, the plug nut, core, springs, shading ring and other components are often exposed to the fluid, so they must be compatible as well. The requirements present some special problems. The core tube needs to be
The plug nut and core need a material with good magnetic properties such as iron, but iron is prone to corrosion. Stainless steels can be used because they come in both magnetic and
Many variations are possible on the basic,
direct current or alternating current powered;
different number of ways and positions;
The illustration below depicts the basic components of a solenoid valve. The valve shown in the picture is a
Coil / Solenoid
The media controlled by the solenoid valve enters the valve through the inlet (Part 2 in the illustration above). The media must flow through the orifice (9) before continuing into the outlet port(3). The orifice is closed and opened by the plunger (7).
The valve pictured above is a
(8) which presses the plunger tip against the opening of the orifice. The sealing material at the tip of the plunger keeps the media from entering the orifice, until the plunger is lifted up by an electromagnetic field created by the coil.
The video animation below shows the operation sequence for a
example, has 2 ports; if the valve is closed, then the two ports are connected and fluid may flow between the ports; if the valve is open, then ports are isolated.
valve is open when the solenoid is not energized, then the valve is termed normally
Similarly, if the valve is closed when the solenoid is not energized, then the valve is
termed normally closed. There are also
9 .4 Common uses
Solenoid valves are used in fluid power pneumatic and hydraulic systems, to control cylinders, fluid power motors or larger industrial valves. Automatic irrigation sprinkler systems also use solenoid valves with an automatic controller. Domestic washing machines and dishwashers use solenoid valves to control water entry into the machine.
Solenoid valves are used in chairs to control air and water flow. In the paintball industry, solenoid valves are usually referred to simply as "solenoids." They are commonly used to control a larger valve used to control the propellant (usually compressed air or CO2). In addition to this, these valves are now been used in household water purifiers (RO systems).
Besides controlling the flow of air and fluids, solenoids are used in pharmacology experiments, especially for
10. POWER SUPPLY
The AC voltage, typically 220V rms, is connected to a transformer, which steps that AC voltage down to the level of the desired DC output. A diode rectifier then provides a
A regulator circuit removes the ripples and also remains the same DC value even if the input DC voltage varies, or the load connected to the output DC voltage changes. This voltage regulation is usually obtained using one of the popular voltage regulator IC units.
10.1 Block diagram
10.2 circuit diagram
10.1.1 BLOCKS OF ROWER SUPPLY UNIT:
A transformer is a static device that transfers electrical energy from one circuit to another without any change in frequency through inductively coupled
Fig. Transformer Model
Fig. Step down Transformer
This is a very useful device, indeed. With it, we can easily multiply or divide voltage and current in AC circuits. Indeed, the transformer has made
At either end (both the generator and at the loads), voltage levels are reduced by transformers for safer operation and less expensive equipment. A transformer that increases voltage from primary to secondary (more secondary winding turns than primary winding turns) is called a
This is a
The ratio of the number of turns on each coil, called the turns ratio, determines the ratio of the voltages. A
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which is in only one direction, a process known as rectification.
Rectifiers have many uses including as components of power supplies and as detectors of radio
10.3 Half Wave Rectifier
In half wave rectification, either the positive or negative half of the AC wave is passed, while the other half is blocked.. Because only one half of the input waveform reaches the output, it is very inefficient if used for power transfer.
Fig: 10.3Half Wave Rectifier
10.4 Full Wave Rectifier
One method to improve on this is to use every
Like the half wave circuit, a full wave rectifier circuit produces an output voltag e or current which is purely DC or has some specified DC component. Full wave rectifiers have some fundamental advantages over their half wave rectifier counterparts. The average (DC) output voltage is higher th an for half wave, the output of the full wave rectifier has much less ripple than that of the half wave rectifier producing a smoother output waveform.
In a Full Wave Rectifier circuit two diodes are now used, one for each half of the cycle. This configuration results in each diode conducting in turn when its anode terminal is positi ve with respect to the transformer center point C producing an output during both
Fig: 10.4Full Wave Rectifier
The full wave rectifier circuit consists of two power diodes connected to a singl e load resistance (RL) with each diode taking it in turn to supply current to the load. When point A of the transformer is positive with respect to point B, diode D1 conduc ts in the forward direction as indicated by the arrows.
When point B is positive (in the negative half of the cycle) with respect to point A, diode D2 conducts in the forward direction and the current flowing through resistor R is in the same direction for both circuits.
10.5 Bridge rectifier
Fig: 10.5Bridge rectifier
When four diodes are connected as shown in figure, the circuit is called as bridg e rectifier. The input to the circuit is applied to the diagonally opposite corners of the network, and the output is taken from the remaining two corners. Let us assume that the transformer is working properly and there is a positive potential, at point A and a negative potential at point B. the positive potential at point A will forward bias D3 and reverse bias D4.
The negative potential at point B will forward bias D1 and reverse D2. At this time D3 and D1 are forward biased and will allow current flow to pass through them; D4 and D2 are rev erse biased and will block current flow. The path for current flow is from point B through D1, up throu gh RL, through D3, through the secondary of the transformer back to point B. this path is indicated by the solid arrows. Waveforms (1) and (2) can be observed across D1 and D3.
One advantage of a bridge rectifier over a conventional
The maximum voltage that appears across the load resistor is
Therefore, the peak output voltage across the load resistor is nearly 1000 volts. With both circuits using the same transformer, the bridge rectifier circuit produces a higher output voltage than the conventional
10.6 Smoothing capacitor
In the previous section that the single phase
We can therefore increase its average DC output level even higher by connecting a suitable smoothing capacitor across the output of the bridge circuit.
The smoothing capacitor converts the
However, there are two important parameters to consider when choosing a suitable smoothing capacitor and these are its Working Voltage, which must be higher than the
To low a value and the capacitor has little effect but if the smoothing capacitor is large enough (parallel capacitors can be used) and the load current is not too large, the output voltage will be almost as smooth as pure DC.
10.7 Voltage regulator
Fig: 10. Voltage regulator
Voltage regulators comprise a class of widely used ICs. Regulator IC units contain the circuitry for reference source, comparator amplifier, control device, and overload protection all in a single IC. IC units provide regulation of either a fixed positive voltage, a fixed negative voltage, or an adjustable set voltage.
The regulators can be selected for operation with load currents from hundreds of mille amperes to tens of amperes, corresponding to power ratings from mille watts to tens of watts.
The series 78XX regulators provide fixed positive regulated voltages from 5 to 24 volts. Similarly, the series 79XX regulators provide fixed negative regulated voltages from 5 to 24 volts.
Electronic voltage regulators operate by comparing the actual output voltage to some internal fixed reference voltage. Voltage Regulator (regulator), usually having three legs, converts varying input voltage and produces a constant regulated output voltage. They are available in a variety of outputs.The most common part numbers start with the numbers 78 or 79 and finish with two digits indicating the output voltage. The number 78 represents positive voltage and 79 negative one.
The 78XX series of voltage regulators are designed for positive input. And the 79XX series is designed for negative input.
5V DC Regulator Name: LM7805 or MC7805
6V DC Regulator Name: LM7806 or MC7806
12V DC Regulator Name: LM7812 or MC7812
The multiple machines can be used for many projects important for humanitarian and economic development in developing countries:
Agriculture: Building and repairing irrigation pumps and farm implements
Water supplies: Making and repairing water pumps and
Food supplies: Building
Transportation: Anything from making cart axels to rebuilding vehicle clutch, brake, and other parts.
Education ; Building simple
Job creation: A group of specialized but easily built multiple machines can be combined to form a small, very low cost, metal working factory which could also serve as a trade school. Students could be taught a single skill on a specialized machine and be paid as a worker while learning other skills that they could take elsewhere.
Manual work is reduced.
Proper water distribution is achived.
More Econamical in cost.
Simple & Robust in construction.
Less hardware circuits are required.
One project has been idenfied and developed in order to obtain proper and efficient water distribution system using wireless technology.
Since the project has been developed using electronic components technology for wireless, it can be implemented in all red time system.
Microprocessor by NagoorKani
Control of Electrical machines.- bhaltacharya
Embedded C by jerk
Electronics for you
Electronics for you plus
14 COST OF ESTIMATION
Driver IC ULN2803
Basics of Entrepreneurship
It is a
The employment so generated covers only a segment of the unemployed. The private sector is also offering very little opportunity to the young unemployed people due to various reasons. In such adverse situation the Indian youth has to wage a bitter fight to solve the problem of unemployment.
The plan document of our country lays emphasis on
A country may be rich in material resources and capital, but if entrepreneurship is lacking, the utilization of resources would not be as expected. The developing economics of resources would not be as expected.
Entrepreneurship prevails environment in a country. Entrepreneurship being an innovator who introduces something new into the economy, a method of protection not yet tested by experience in the branch of manufactured concerned, a product with which the consumes are not familiar, a new source or raw materials, or a new market higher exploited and similar other innovations.
An entrepreneur is one who starts an industrial venture or a business of his own. Entrepreneurship would include undertaking manufacturing activities, business or crafts etc., Entrepreneurship is also associated with a risk assuming function.
An entrepreneur is said to be a person who organizes, manages and issue the risk for a business or enterprise. Commonly entrepreneur is understood to be those persons who start build their own enterprise rather than taking up a job. Entrepreneurship is the trait taking up own enterprises.
Role of entrepreneurship
An entrepreneur is a part of industrial society. He is responsible for not only making his own source of live hood but also for creating avenues of employment for others and making additions to the gross national product. If a larger number of entrepreneurs set up enterprise of their own, there is a great deal of transformation of an area. The industrial entrepreneurs are thus the agents of charge in removing back wardens and disparities of an area. An entrepreneur has a great social responsibility.
An enterprise consists of not only those who manage it but a host other segments of society, workers, consumers, the state and the surrounding community.
Some of the qualities are inherent but the others are mostly acquired. Broody speaking four qualities are the most important one, e.g. intelligence, motivation, knowledge and opportunity. While the first one is inherent, a continuous process generally gains the knowledge, the qualities of entrepreneurs further be sub- divided as under
Capacity to take risk
Capacity to work hard
Desire for deferred consumption
Capacity to take advantage of an external situation
Sociability and flexibility
Inventive ability and
Knowledge, both informative and technical.
Increase number of industries is expected from the entrepreneurs that they will help to.
Earn foreign exchange through exports
Develop the underdeveloped parts of the country.
Small – scale industries facilitate production of consumer goods locally and help reduction of prices. Some of the important measures of assistance now available are briefly noted below:
1.Technical assistance: complete technical, economic and managerial consultancy services are provided to SSO through Small Industries Services Institute (SISI) and Industrial Extension centers.
2.Assistance for obtaining raw materials: small – scale units are helped to obtain controlled indigenous raw materials through state director of industries and imported raw materials through State Trading Corporation of India (STC).
3.Supply of machinery Hire Purchase: The National Small Industries Corporation (NSIC) is giving assistance to small scale units by supplying machinery to them on deferred credit basis.
4.Marketing assistance: SS units are helped to market their products through Trade centers and by participating in government’s Stores Purchase Programme.
5.Assistance to small entrepreneurs: Entrepreneurial Development programmer is conducted by SSI and Small Industries Development Organization (SIDO) to give necessary training to young entrepreneurs. District Industries Centre (DIC) provides under a single – roof all the services and support required by the small and village industries at pre – investment, investment, investment and post investment stages.
6.Financial assistance : SS units are helped by providing various financial assistance like loans, subsides, and hire – purchase scheme through various agencies like State Finance Corporation NSIC, State Directorates of Industries, commercial banks, Industrial Development Bank of India (IDBI) , and National Bank for Agricultural and Rural Development (NABARD) .
7.Special incentives: Special inducements like the following are offered by the government for development of entrepreneurship.
a.Capital subsidy up to 15% in backward areas
b.Income Tax exemption for five years.
c.Exemption from Central excise duty.
d.Deduction of depreciation from net profit.
e.Concessions in Stamp duty.
f.License to import raw material.
The following are the four important government schemes for prompting
i.District Manpower Planning and Employment Generation Council
The Council prepares a list of investment opportunities in the
A special Vocational Guidance Unit functioning in every Employment Exchange with the object of giving guidance and motivation to unemployed persons to take up self employment ventures. In addition to furnishing information on
iii.The Prime Minister Scheme for providing
The objective of the scheme is to encourage the educated unemployed youth to undertake
The scheme covers all unemployed youth who are matriculates and above, and in the age group of 18 to 35 years. District Industries Centers (DIC) are assigned the operational responsibility of the scheme.
iv.Self employment scheme for TRYSEM – trained youth
TRYSEM stands for “Training of Rural Youth for
The Scheme is implemented by a Task Force under the Chairmanship of District Collector and with District Employment Officer as Member Secretary and Project officer (DRDA). DDO and Lead Bank Manager as members.
A prospective entrepreneur should first prepare a shore list of product lines that he wants to establish. Then, he should select the product to be manufactured based upon market survey and demand survey, financial implementations involved, technical
Market survey involves the following:
Study similar product available in the market that can be probable Competitors.
Analyze them in regards to their utility, quality and cost.
Check whether it is a seasonal product or needed throughout the year.
Find the probable extend of the market.
Find whether the product can be exported.
Explore the possibility of manufacturing in collaboration with a foreign company.
A demand survey is made to determine
Whether survey demand for the product is or inelastic.
The trend of the demand.
The composition and pattern of the potential users.
The important factors to be considered in selecting the site for an industry are given below.
Nearness to raw material: It will reduce the cost of transportation of raw materials to the factory.
Nearness to market: It will reduce transportation cost of the finished products and also help to catch the share of the market.
Easy availability of labor: If highly skilled workmen are required, it is better to locate the plant near a large town.
Availability of power and fuel: Electrical power and fuel required for the plant should be easily obtainable in the area, Reliability of power supply must be ensured.
Availability of water: Water for drinking and for other purposes should be easily available. If the process requires large quantity of water, then the plant should be located near a major water source.
Industrial areas: Notified industrial areas will be advantageous due to the availability of ready infrastructure and other benefits.
Other major factors: Presence of related industries, facilities for expansion, housing facilities, and nearness of public amenities like hospitals and schools, security problems, local and attitude of local people.
Plant layout means the disposition of the various (equipments, material, manpower, etc) and services of the plant within the area of the site selected. Plant layout begins with the design of the factory building and goes up lathe location and movement of a worktable. All the facilities like equipments, raw material, machinery, tools fixtures, Workers, etc, are given a proper place. In deciding the place for equipment, the supervisors and workers who nave to operate them should be consulted.
There are three types of plant layout:
1.Process Layout (functional layout) in which all machines or process of the same types is grouped together in the same area.
2.Product Layout (line layout) in which equipments regardless of process is arranged as per the sequence of operations in which a given product will be manufactured.
3.Layout by fixed position (static product layout) in which the product is too big (e.g. ship, airplane) or too heavy to be moved from one place to another and is consequently fixed in one place, and men and machines are brought to the product to perform the required operations. Whatever by the type required, certain basic principles must be observed. While preparing the plant layout.
1.Placement of facilities in a logical and balanced manner.
2.Minimum movements for workers and materials
3.Smooth and continuous flow of operations
4.Optimum space utilization.
i.Private Limited Company
ii.Public Limited Company
Each one has its own advantages and disadvantages. An entrepreneur’s choices of the type of the organization will primary depend upon the nature of the business to be started and his own preferences together with the amount of capital he can contribute.
The prospective entrepreneur in the small – scale sector need not obtain any Industrial Licenses, provided the item of manufacture is not governed by special regulations. However, to facilitate identification, the Directorate of Industries (through District Industries Center - DIC) issues certificates registering a unit as a Small Scale / Ancillary / Tiny Unit.
Registration is done is two stages, Via, provisional and permanent. The issue of Provisional certificate almost automatic, with Unit / ail validity of 6 months and with a further extension for another 6 months.
With a view to ensure adequate of funds, the small scale Industrial frame work for the flow of Financial Assistance to small Scale sector comprises of banks (Commercial Banks,
The NSIC and SSID’S provide Financial Assistance in the form supply of Machinery and hire purchase basis.A National Bank of Agriculture and Rural Development (NABARD) has recently been setup to meet the financial requirements of artisans, Small Scale Industries, Industries those engaged in the field of Handicraft and other rural craft.
The Reserve Bank of India issued instructions that no worth wile proposals of the Small scale unit should be rejected merely on the ground that these are not supported by adequate security. The commercial Banks have been advised by the Reserve Bank of India to give special Attention to the needs of the priority sector borrowers, particularly of the weaker section.
Small scale Industrial units also being charged lower rates of interest on their borrowings from commercial Banks.
State Financial Corporations
Provide medium and
The Scheme is designed to enable the bank to work effectively as an Instrument of development. Under the scheme, the district in the country have allocated to different commercial banks each of whom is expected to act as a consortium and as a leader of the financial institutions operating in allotted districts in matters relating to deposit mobilization, identifying of prospective avenues for financial assistance and ensuring adequate credit flow for the various development programs of the districts.
The success of Small Scale industries depends solely on the well – established institutional setup. In order to accelerate the small industries development, government at the central and state levels has setup a number of development agencies / institutions. Functions of some these are mentioned.
District Industries Center (DIC)
Each district has a DIC at its headquarters. The main responsibility of DIG is to act as the chief coordinator or multi functional agency in; respect of various governments can get all assistance from DIC for setting up and running the industry in rural areas. Each DIC has one General Manager in the rank of Joint Director of industries as the head and seven managers each looking after separate functional area.
Identification of Entrepreneurs.
Selection of Projects
Provisional registration under SSI
Purchase of fixed Assets
Clearances from Various Departments.
Assistance of Raw Material supplies.
Interest – Free Sales Tax Loan
Self – employment for Unemployed Educated Youth.
District Industries Centers are supposed to provide pre – investment and post – investment assistance to entrepreneurs under one roof.
Small Industries Development Organization
SIDO is a
The main functions of the SIDCD are
a.To assess the requirements of indigenous and imported raw materials and components for the small- scale sector and to arrange their supplies.
b.To collect data on consumer items, which are imported and encourage the setting up of new units giving them coordinate assistance.
c.To prepare model schemes, projects reports and other Technical literature for prospective entrepreneurs.
d.To assist and advise the Controller of Capital issues in regard to the issue of import licenses and the imposition of import restrictions on various products whose manufacture has already been undertaken indigenously be the existing or new units.
e.To secure reservations of certain products for the SSIS.
National Small Industries Corporation Limited (NSIC)
The NSIC was setup in 1955 with the objective of supplying machinery and equipment to small enterprise on a
3.The main functions of NSIC are
To develop small scale units as ancillary units to large scale industries.
To provide SSIS with machine on
To assist small enterprises to participate in the stores purchase Programme of the Central Government.
To assist small industries with marketing facilities.
To distribute basic raw materials through their depots
To import ad distribute components and parts actual small scale users in specific industries and
To construct industrial estates and establish and run prototype
4. Directorates of Industries of the State Governments
Each directorate is staffed with administration and small scale industries in particular. Each directorate is staffed with administration and technical officers at State staff in each district.
Forms of Business Enterprise Topics
Ownership when applied to an industrial enterprise means title to and possessions of the assets of the enterprise, the power to determine the policies of operation, and the right to receive and dispose of the proceeds.
It is called a single ownership when an individual exercise and enjoys these rights in his own interest.
A business owned by one man is called single ownership.
Single ownership does well for those enterprises, which require little capital and lend themselves readily to control by one person.
Examples of enterprise run by single owner are printing press, auto retail trades, service industries and small engine forms.
In single ownership, one person contributes the original assets to start the business, maintains and controls business operation, reaps full benefits in terms of profit and full liable for all debts associated with the business.
A single owner becomes inadequate as the size of the business enterprise grouse. He may not be in a position to do away with a1 the duty and responsibilities of the grown business.
At this stage the individual owner may associate with him more persons who have either capital to
invest or possess special skill and knowledge to make the existing business still more profitable.
Such a combination of individual traders is called partnership.
Partnership may be defined as the relation between persons who have agreed to share the profits of a business carried on by all or any of them acting for all. Individuals with common purposes join and partners and they put together their property, ability, skill, knowledge, etc, for the purpose of making profits.
In brief, partnership is an association of two or more (up to 20) persons to carry an as
Partnerships are based upon a partnership agreement which i.e. generally reduced to writing.
It should cover all areas of disagreement among the partners. It should define the authority, right and duties of each partner.
It should specify how profit and losses will be divided among the partners, etc.
The capital is collected from the private partners; some of them may be active while others are sleeping.
Private limited restrict the right to transfer shares, avoids public to take up shares or debentures.
The number of members is between two and 50, excluding employee and
The company need not file document such consent of directors, list of directors, etc. the register of joint stock companies.
The company need not obtain from the register, a certificate of commencement of business.
The company need not circulate the balance sheet, profit and loss account etc, among its members, but it should hold its annual general meeting and place such financial state rents in the meeting.
A private company must get its accounts audited.
A private company has to send a certificate along with the annual return to the register of joint stock companies stating that it does not have shareholders more than 50 excluding the employee and employee shareholders.
Actually, a private joint stock company resumes much with partnership and has the advantage that big capital can be collected than could be done so in partnership.
In public limited company, the capital is collected from public by issuing shares having small face value (Rs. 50, 20, 10).
The number of share holders should not be less than 7, but there is no limit to their maximum number.
The main aim of the
Members pay fees or buy shares the
Since each member has only one (unlike in joint stock companies), this avoid the concentration of control in few hand.
There are periodic meetings of share also.
Special laws deal with the formation and taxation of