1.Sparkless and Contact Less Switching Increases Switches Life

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ABSTRACT

The purpose of this project is to operate any home appliance using Remote Control. The entire circuit works on the basis of Infrared rays(IR) .The output of the device becomes high or low in the presence or absence of IR rays. When no IR rays fall on the receiver module the output remains high. The circuit consists of two transistors t1 & t2 due to large base current ,the transistor t2 will remain in cut-off state .Thus the remaining circuit and the load is in off condition.

Remote operating distance upto 30 feet/10 meters.When IR rays fall on the receiver module the t2 will conduct energizing the relay2 thus ic2 triggers and output remains high.The main application of this project is to on or off any home appliance using any remote in schools, offices and industries.It has advantages of

1.Sparkless and contact less switching increases switches life.

2.Prevents children from risk of electric shock and short circuit.

3.It is a boon for physically handicapped persons.

4.Ideal for bed-ridden patients and aged people

CIRCUIT DIAGRAM:

CIRCUIT DESCRIPTION:

This circuit is designed to switch on/off any home or industrial appliance by using the TV/DVD remote controller. The circuit can be operated up to a distance of 5-10 metre depending on the remote used. The circuit consists of a step-down transformer X1 (6V-0-6V, 250mA secondary), 5V regulator 7805 (IC1), two 5V, 1 changeover (C/O) relay, a timer NE555 IC (IC2), an IR receiver module (IRX1 TSOP1738) and some discrete components. The circuit works on regulated 5V, which is derived from X1 and regulated by IC1. Home appliance is controlled either by pressing any key on the remote or by manually pressing switch s1 .

The TV/DVD remote controller produces 38kHz frequency. The IR receiver module operates at this frequency. It is used to control relay RL2. The relay triggers IC2, which is wired in a bistable mode to control the home appliance connected at the contacts of relay RL1. Timer IC2 toggles relay RL1 when switch S1 is pressed momentarily. Threshold and trigger input pins 6 and 2 of IC2 are held at one-half of the power supply voltage (5V) by resistors R2 and R3. When output pin 3 of IC2 is high, capacitor C4 charges..
When switch S1 is pressed, capacitor C4 voltage is applied to pins 2 and 6 of IC2, which causes the output of IC2 to change from low to high, or high to low. When switch S1 is released capacitor C4 charges or discharges to the original level at the output pin 3 of IC2. At normal condition, when IR rays are not incident on TSOP1738, its output at pin 3 remains high. When any TV remote key is pressed, IR rays fall on the TSOP1738 and its output goes low. At the same time relay RL2 energises for a few seconds through pnp transistor T2 (BC558). The working of the circuit is simple.
Initially, when there are no IR rays falling on the IR receiver module, its output remains high. Transistor T2 is in cut-off condition. Relay RL2 does not energise and hence IC2 does not toggle. As a result home appliance connected at the contacts of relay RL1 remains switched off. When you press any remote key for the first time, IR receiver module’s output goes low and collector of the transistor T2 goes high. Relay RL2 energises and triggers IC2. Output of IC2 goes high and relay RL1 energises to switch on the appliance. So the appliance which is connected at the contacts of relay RL1 remains switched on. Now when you press any remote key the second time, relay RL2 energises and re-triggers IC2. Output of IC2 goes low and relay RL1 de-energises to switch off the appliance. Once relay RL1 de-energises it remains in that state.

555 IC :

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package.

Introduced in 1971 by Signetics, the 555 is still in widespread use, thanks to its ease of use, low price and good stability, and is now made by many companies in the original bipolar and also in low-power CMOS types. As of 2003[update], it was estimated that 1 billion units are manufactured every year.

The IC was designed in 1971 by Hans R. Camenzind under contract to Signetics, which was later acquired by Philips.

Depending on the manufacturer, the standard 555 package includes 25 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8).[2] Variants available include the 556 (a 14-pin DIP combining two 555s on one chip), and the two 558 & 559s (both a 16-pin DIP combining four slightly modified 555s with DIS & THR connected internally, and TR is falling edge sensitive instead of level sensitive). There is no 557.

The NE555 parts were commercial temperature range, 0 °C to +70 °C, and the SE555 part number designated the military temperature range, −55 °C to +125 °C. These were available in both highreliability metal can (T package) and inexpensive epoxy plastic (V package) packages. Thus the full part numbers were NE555V, NE555T, SE555V, and SE555T. It has been hypothesized that the 555 got its name from the three 5kΩ resistors used within, but Hans Camenzind has stated that the number was arbitrary.

Low power versions of the 555 are also available, such as the 7555 and CMOS TLC555. The 7555 is designed to cause less supply glitching than the classic 555 and the manufacturer claims that it usually does not require a "control" capacitor and in many cases does not require a decoupling capacitor on the power supply. Such a practice should nevertheless be avoided, because noise produced by the timer or variation in power supply voltage might interfere with other parts of a circuit or influence its threshold voltages.

UsagePins :

The connection of the pins for a DIP package is as follows:

Pin / Name / Purpose
1 / GND / Ground, low level (0 V)
2 / TRIG / OUT rises, and interval starts, when this input falls below 1/3 VCC.
3 / OUT / This output is driven to +VCC or GND.
4 / RESET / A timing interval may be interrupted by driving this input to GND.
5 / CTRL / "Control" access to the internal voltage divider (by default, 2/3 VCC).
6 / THR / The interval ends when the voltage at THR is greater than at CTRL.
7 / DIS / Open collector output; may discharge a capacitor between intervals.
8 / V+, VCC / Positive supply voltage is usually between 3 and 15 V.

The 555 has three operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.

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 and so on. Selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor: the period of the output pulse is determined by the temperature. The use of a microprocessor based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.

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 bounce-free latched switches.

Monostable:

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 signal at the trigger input that falls below a third of the voltage supply. The width of the output pulse is determined by the time constant of an RC network, which consists of a capacitor (C) and a resistor (R). The output pulse ends when the voltage on the capacitor equals 2/3 of the supply voltage. The output pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C.

While using the timer IC in monostable mode, the main disadvantage is that the time span between the two triggering pulses must be greater than the RC time constant.

Bistable

In bistable mode, the 555 timer acts as a basic flip-flop. The trigger and reset inputs (pins 2 and 4 respectively on a 555) are held high via Pull-up resistors while the threshold input (pin 6) is simply grounded. Thus configured, pulling the trigger momentarily to ground acts as a 'set' and transitions the output pin (pin 3) to Vcc (high state). Pulling the reset input to ground acts as a 'reset' and transitions the output pin to ground (low state). No capacitors are required in a bistable configuration. Pin 5 (control) is connected to ground via a small value capacitor (usually 0.01 to 0.1 uF); pin 7 (discharge) is left floating.

Astable

In astable mode, the 555 timer puts out a continuous stream of rectangular pulses having a specified frequency. Resistor R1 is connected between VCC and the discharge pin (pin 7) and another resistor (R2) is connected between the discharge pin (pin 7), and the trigger (pin 2) and threshold (pin 6) pins that share a common node. Hence the capacitor is charged through R1 and R2, and discharged only through R2, since pin 7 has low impedance to ground during output low intervals of the cycle, therefore discharging the capacitor.

ICM7555 PIN DESCRIPTION:

The ICM7555 is a CMOS timer providing significantly improved performance over the

Standard NE/SE555 timer, while at the same time being a direct replacement for those devices in most applications. The ICM7555 is a stable controller capable of producing accurate time delays or frequencies.

PIN DIAGRAM :

OPERATION :

In this mode of operation, the timer functions as a one shot. Initially the external capacitor (C) is held discharged by a transistor inside the timer. Upon application of a negative TRIGGER pulse to pin 2, the internal flip-flop is set which releases the short circuit across the external capacitor and drives the OUTPUT high. The voltage across the capacitor increases exponentially with a time constant

t = RC.When the voltage across the capacitor equals 2/3 V+, the comparator resets the flip-flop, which in turn discharges the capacitor rapidly and also drives the OUTPUT to its low state.TRIGGER must return to a high state before the OUTPUT can return to a low state.

APPLICATIONS :

• Precision timing

• Pulse generation

• Sequential timing

• Time delay generation

• Pulse width modulation

• Pulse position modulation

• Missing pulse detector

RESISTORS :

Resistors (R), are the most commonly used of all electronic components, to the point where they are almost taken for granted. They are "Passive Devices", that is they contain no source of power or amplification but only attenuate or reduce the voltage signal passing through them. When used in DC circuits the voltage drop produced is measured across their terminals as the circuit current flows through them while in AC circuits the voltage and current are both in-phase producing 0 degrees phase shift. In all Electrical and Electronic circuit diagrams and schematics, the most commonly used resistor symbol is that of a "zig-zag" type line with the value of its resistance given in Ohms, Ω.

RESISTOR SYMBOL

The symbol used in schematic and electrical drawings for a Resistor can either be a "zig- zag" type line or a rectangular box.

RESISTOR TYPES

All modern resistors can be classified into four broad groups;

• Carbon Composition Resistor - Made of carbon dust or graphite paste, low wattage

values

•Film or Cermet Resistor - Made from conductive metal oxide paste, very low

wattage values

• Wire-Wound Resistors. - Metallic bodies for heat sink mounting, very high wattage ratings

•Semiconductor Resistors - High frequency/precision surface mount thin film technology

RESISTOR COLOUR CODE

The resistance value, tolerance, and watt rating of the resistor are generally printed onto the body of the resistor as numbers or letters when the resistor is big enough to read the print, such as large power resistors. When resistors are small such as 1/4W Carbon and Film types, these specifications must be shown in some other manner as the print would be too small to read. So to overcome this, small resistors use coloured painted bands to indicate both their resistive value and their tolerance with the physical size of the resistor indicating its wattage rating. These coloured painted bands are generally known as a Resistors Colour Code.

THE RESISTOR COLOUR CODE TABLE:

VARIABLE RESISTOR:

Variable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle. The track may be made from carbon, cermet (ceramic and metal mixture) or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available. Variable are often called potentiometers in books and catalogues.

RHEOSTAT:

This is the simplest way of using a variable resistor. Two terminals are used: one connected to an end of the track, the other to the movable wiper. Tuning the spindle changes the rheostat resistance between the two terminals from zero up to the maximum resistance.

CAPACITORS :

INTRODUCTION

Just like the Resistor, the Capacitor or sometimes referred to as a Condenser is a passive device, and one which stores energy in the form of an electrostatic field which produces a potential (Static Voltage) across its plates. When a voltage is applied to these plates, a current flows charging up the plates with electrons giving one plate a positive charge and the other plate an equal and opposite negative charge. This flow of electrons to the plates is known as the Charging Current and continues to flow until the voltage across the plates (and hence the capacitor) is equal to the applied voltage Vc. At this point the capacitor is said to be fully charged and this is illustrated below.

Capacitor Construction

Q = CxV

UNITS OF CAPACITANCE

• Microfarad (μF) 1μF = 1/1,000,000 = 0.000001 = 10^-6 F

• Nanofarad (nF) 1nF = 1/1,000,000,000 = 0.000000001 = 10^-9 F

• Picofarad (pF) 1pF = 1/1,000,000,000,000 = 0.000000000001 = 10^-12 F

TYPES OF CAPACITORS

1.DIELECTRIC :

Dielectric Capacitors are usually of the variable type such as used for

tuning transmitters, receivers and transistor radios. They have a set of fixed plates and a set of

moving plates that mesh with the fixed plates and the position of the moving plates withrespect to the fixed plates determines the overall capacitance. The capacitance is generally at maximum when the plates are fully meshed.

2.FILM CAPACITORS:

Film Capacitors are the most commonly available of all types of capacitors, consisting of a relatively large family of capacitors with the difference being in their dielectric properties. These include polyester (Mylar), polystyrene, polypropylene, polycarbonate, metallized paper, teflon etc. Film type capacitors are available in capacitance ranges from 5pF to 100uF depending upon the actual type of capacitor and its voltage rating.

3.CERAMIC CAPACITORS:

Ceramic Capacitors or Disc Capacitors as they are generally called, are made by coating two sides of a small porcelain or ceramic disc with silver and are then stacked together to make a capacitor. For very low capacitance values a single ceramic disc of about 3-6mm is used. Ceramic capacitors have a high dielectric constant (High K) and are available so that relatively high capacitances can be obtained in a small physical size.

4.ELECTROLYTIC CAPACITORS

Electrolytic Capacitors are generally used when very large capacitance values are required.Here instead of using a very thin metallic film layer for one of the electrodes, a semi-liquid electrolyte solution in the form of a jelly or paste is used which serves as the second electrode (usually the cathode). The dielectric is a very thin layer of oxide which is grown electrochemically in production with the thickness of the film being less than ten microns. This insulating layer is so thin that it is possible to make large value capacitors of a small size. The majority of electrolytic types of capacitors arePolarized, that is the voltage applied to the capacitor terminals must be of the correct polarity as an incorrect polarization will break down the insulating oxide layer and permanent damage may result.

TRANSISTOR :

A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal. Some transistors are packaged individually but many more are found embedded in integrated circuits.

TRANSISTOR CHARACTERISTICS:

ADVANTAGES

The key advantages that have allowed transistors to replace their vacuum tube predecessors in Most applications are

• Small size and minimal weight, allowing the development of miniaturized electronic Devices.

• Highly automated manufacturing processes, resulting in low per-unit cost.

• Lower possible operating voltages, making transistors suitable for small, battery powered applications.

• Lower power dissipation and generally greater energy efficiency.

• Higher reliability and greater physical ruggedness.

• Extremely long life. Some transistorized devices have been in service for more than 30 years.

LIMITATIONS:

• Silicon transistors do not operate at voltages higher than about 1,000 volts. In contrast electron tubes have been developed that can be operated at tens of thousands of volts.
• High power, high frequency operation, such as that can be used in over-the-air television broadcasting, is better achieved in electron tubes due to improved electron mobility in vacuum.

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Diode

A diode is a two-terminalelectronic component that conducts electric current in only one direction. A semiconductor diode is a crystalline piece of semiconductor material connected to two electrical terminals. A vacuum tube diode is a vacuum tube with two electrodes a plate and a cathode.