Mini Project

INTRODUCTION

Most of security system uses light or micro switch, magnetic sensor to detect the signal. Here is a new type of security system that uses infra-red rays to detect the signal. this signal is invisible signal. There fore once we install the circuit we need not require any setting expect to watch the power supply is ok.

Infrared security system is the ideal infrared (IR) light beam detector for access control of a door or window, and provides threshold crossing alert. It can also be used for "present" detection in automated manufacturing processes. A focused infrared (IR) light beam is projected from an emitter and bounced off of a reflector which is placed at the other side of the detection area. A retro-reflective photoelectric beam sensor built into the emitter detects when the infrared beam is broken by the passing of a person or the presence of an object in the path of the infrared beam. A separate speaker annunciates (included) can be set to chime or alarm to alert you that a security breech has occurred or that an object has entered or passed through the infrared beam.

Possible uses of the 74LS14 infrared access control / security system are many, ranging from notifying store operators that a customer has entered the store, home or commercial security system detector, to manufacturing process control "presence" detection of objects. With the optional74LS93, this infrared access control system can be used to count people passing through an entry gate, or objects moving over a conveyor, etc. Many other possible uses. 74LS14 is pre-assembled and ready to use.

BLOCK DIAGRAM:

Fig:1

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TRANSMITTER

Transmitter circuit uses 74LS14 IC.which is a Schmitt trigger IC. It is used to generate 40KHz. Signal IR transmit 40KHz .signal resistor R2,capacitor C1&diode D1 is used for exact 40KHz signal. Adjust P1 for maximum range .red led shows that power supply is on when the brightness of led decreases change the battery for power proper operation.

RECEIVER

Receiver circuit operated at 5V DC and it is derive from power supply circuit .transformer convert 230 V AC to 12V AC is converted into DC by diode D!&D2 it filtered by capacitor C1.IC3 gives regulated 5V DC to other circuit .infra-red receiver module detected 40KHz signal that is transmitted from transmitter circuit . when transmitter is on I/R sensor gets 40Khzsignal and its out put is low when some one breaks the signal I/R sensor does not get signal and its output go to high level . this output level is fed to smitt trigger IC2 at pin1. Output is available at pin 8 of IC2 that is used to drive the transistor . green LED show the on time period . out put is available means buzzer is on for approximately 10 sec . after 10 sec circuit is reset automatically and it ready to detect other object.

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CIRCUIT DIAGRAM

INFRARED TRANSMITTER:

Fig:2

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INFRARED RECEIVER:

Fig:3

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Parts list

Transmitter:

Resistors:

R1 -680

R2 -1000K

R3 -47

R5, R11 -18K

R6, R10 -10K

R7 -27K

R12 -47K

P (preset) -10K

R4, R8, R9 -NOT USE

Capacitor:

C1 -10f/50V

C2 -1Kpf

C3 -100Kpf

C4 -100Kpf

C5 -2.2f/50V

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Semiconductor:

T1 -2N2222A

IC1 -74LS14 OR 40106

Miscellaneous:

L1 -5mm (RED LED)

L2 -I/R LED

14 PIN SOCKET -1Pc

2 CELL HOLDERS -1Pc

RECEIVER

RESISTORS

R1 -220K

R2 -10M

R3 -1M

R4 -1K

CAPACITORS

C1 -1000f/25V

C2, C4, C5 -0.1f

C3 -100f/25V

C6 -10f/50V

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SEMI CONDUCTOR

D1, D2, D3 -IN 4007

D4 -IN 4148

D5 -5mm led green

IC1 -74LS93

IC2 -74LS14 OR 40106

IC3 -7805

T1 -CL100

MISCELLANEOUS

I/R Receiver module -1pc

14 Pin socket -2pc

Buzzer -1pc

Transformer -12-0-12/500ma

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COMPONENT DESCRIPTION

SCHMITT TRIGGER 74LS14 / 40106:

Invention:

The Schmitt trigger was invented by US scientist Otto H. Schmitt in 1934 while still a graduate student[1], later described in his doctoral dissertation (1937) as a "thermionic trigger"[2]. It was a direct result of Schmitt's study of nerve propagation in squid nerves[2].

Symbol

The symbol for Schmitt triggers in circuit diagrams is a triangle with a hysteresis symbol:

Fig:4

The benefit of a Schmitt trigger over a circuit with only a single input threshold is greater stability (noise immunity). With only one input threshold, a noisy input signal near that threshold could cause the output to switch rapidly back and forth from noise alone. A noisy Schmitt Trigger input signal near one threshold can cause only one switch in output value, after which it would have to move beyond the other threshold in order to cause another switch.

Schmitt trigger with two transistors

A Schmitt trigger is still frequently made using two transistors as shown. The chain RK1 R1 R2 sets the base voltage for transistor T2. This divider, however, is affected by transistor T1, providing higher voltage if T1 is open. Hence the threshold voltage for switching between the states depends on the present state of the trigger.

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Fig:5

For NPN transistors as shown, when the input voltage is well below the shared emitter voltage, T1 does not conduct. The base voltage of transistor T2 is determined by the mentioned divider. Due to negative feedback, the voltage at the shared emitters must be almost as high as that set by the divider so that T2 is conducting, and the trigger output is in the low state. T1 will conduct when the input voltage (T1 base voltage) rises slightly above the voltage across resistor RE (emitter voltage). When T1 begins to conduct, T2 ceases to conduct, because the voltage divider now provides lower T2 base voltage while the emitter voltage does not drop because T1 is now drawing current across RE. With T2 now not conducting the trigger has transitioned to the high state.

With the trigger now in the high state, if the input voltage lowers enough, the current through T1 reduces, lowering the shared emitter voltage and raising the base voltage for T2. As T2 begins to conduct, the voltage across RE rises, further reducing the T1 base-emitter potential and T1 ceases to conduct.

In the high state, the output voltage is close to V+, but in the low state it is still well above V−. This may not be low enough to be a "logical zero " for digital circuits. This may require additional amplifiers following the trigger circuit.

The circuit can be simplified: R1 can be omitted, connecting the T2 base directly to the T1 collector, and the connection of the T2 base to V- via R2 can be completely omitted. When T1 conducts, it connects the T2 base to the T2 emitter so that T2 does not conduct. When T1 does not conduct, RK1 pulls up the T2 base and T2 conducts.

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Fig:6

The effect of using a Schmitt trigger (B) instead of a comparator (A).

In electronics, a Schmitt trigger is a comparator circuit that incorporates positive feedback.

When the input is higher than a certain chosen threshold, the output is high; when the input is below another (lower) chosen threshold, the output is low; when the input is between the two, the output retains its value. The trigger is so named because the output retains its value until the input changes sufficiently to trigger a change. This dual threshold action is called hysteresis, and implies that the Schmitt trigger has some memory.

Comparator implementation

Today Schmitt triggers are typically built around comparators, connected to have positive feedback instead of the usual negative feedback. For this circuit the switching occurs near ground, with the amount of hysteresis controlled by the resistances of R1 and R2as shown in fig:7

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Fig:7

The comparator simply gives out the highest voltage it can, +VS, when the positive input ("+" on the above diagram) is at a higher voltage than the negative input (" − " on above diagram), and then switches to the lowest output voltage it can, −VS, when the positive input drops below the negative input.

For instance, if the Schmitt Trigger is currently in the high state, the output will be at the positive power supply rail (+VS). V+ is then a voltage divider between Vin and +VS. The comparator will switch when V+=0 (ground). Current conservation shows that this requires:

Vin/R1 = −VS/R2

so Vin must drop below −(R1/R2)VS to get the output to switch. Once the comparator output has switched to −VS, the threshold becomes +(R1/R2)VS to switch back to high.

Fig:8

So this circuit creates a switching band centered around zero, with trigger levels ±(R1/R2)VS. The input voltage must rise above the top of the band, and then below the bottom of the band, for the output to switch on and then back off. If R1 is zero or R2 is infinity (an open circuit), the band collapses to zero width, and it behaves as a standard comparator. The output characteristic is

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shown in the picture on the right. The value of the threshold T is given by (R1/R2)VS and the maximum value of the output M is the power supply rail.

A possible structure of a more realistic configuration is the following fig:9

Fig:9

The output characteristic has exactly the same shape of the previous basic configuration and the threshold values are the same as well. On the other hand, in the previous case the output voltage was depending on the power supply, while now it is defined by the Zener diodes: this way the output can be modified and it is much more stable. The resistor R3 is there to limit the current through the diodes, while R4 is there to minimize the input voltage offset caused by the op-amp's input bias currents (see Limitations of real op-amps).

Use as an oscillator

Schmitt triggers are sometimes used to implement a simple type of relaxation oscillator, or multivibrator. This is achieved by connecting a single resistor-capacitor network to an inverting Schmitt trigger — the capacitor connects between the input and ground and the resistor connects between the output and the input. The output will be a continuous square wave whose frequency depends on the values of R and C, and the threshold points of the Schmitt trigger. Since multiple Schmitt trigger circuits can be provided by a single integrated circuit (e.g. the 4000 series CMOS device type 40106 contains 6 of them), a spare section of the IC can be quickly pressed into service as a simple and reliable oscillator with only two external components.

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Devices that include a built-in Schmitt trigger

The following 7400 series devices include a Schmitt trigger on their input or on each of their inputs:

7413: Dual Schmitt trigger 4-input NAND Gate 7414: Hex Schmitt trigger Inverter 7419: Hex Schmitt trigger Inverter 74132: Quad 2-input NAND Schmitt Trigger 74221: Dual Monostable Multivibrator with Schmitt Trigger Input 74232: Quad NOR Schmitt Trigger 74240: Octal Buffer with Schmitt Trigger Inputs and Three-State Inverted Outputs 74241: Octal Buffer with Schmitt Trigger Inputs and Three-State Noninverted Outputs 74244: Octal Buffer with Schmitt Trigger Inputs and Three-State Noninverted Outputs 74310: Octal Buffer with Schmitt Trigger Inputs 747541 Octal Schmitt Trigger Buffer/Line Driver

A number of 4000 series devices include a Schmitt trigger on inputs, for example:

14093: Quad 2-Input NAND 40106: Hex Inverter 14538: Dual Monostable Multivibrator 4020: 14-Stage Binary Ripple Counter 4024: 7-Stage Binary Ripple Counter 4040: 12-Stage Binary Ripple Counter 4017: Decade Counter with Decoded Outputs 4022: Octal Counter with Decoded Outputs

Dual Schmitt input configurable single-gate CMOS logic, AND, OR, XOR, NAND, NOR, XNOR

NC7SZ57 Fairchild NC7SZ58 Fairchild SN74LVC1G57 Texas Instruments SN74LVC1G58 Texas Instruments

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Buzzer:

Electronic symbol for a buzzer:-

Fig:10

Fig:11

Metal disk with piezoelectric disk attached, as found in a buzzer

For the woodworking machine, see jointer.

For the radio station, see Radio Station UVB-76.

A buzzer or beeper is a signaling device, usually electronic, typically used in automobiles, household appliances such as a microwave oven, or game shows.

It most commonly consists of a number of switches or sensors connected to a control unit that determines if and which button was pushed or a preset time has lapsed, and usually illuminates a light on the appropriate button or control panel, and sounds a warning in the form of a continuous or intermittent buzzing or beeping sound. Initially this device was based on an electromechanical system which was identical to an electric bell without the metal gong (which makes the ringing noise). Often these units were anchored to a wall or ceiling and used the ceiling or wall as a sounding board. Another implementation with some AC-connected devices was to implement a circuit to make the AC current into a noise loud enough to drive a

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loudspeaker and hook this circuit up to a cheap 8-ohm speaker. Nowadays, it is more popular to use a ceramic-based piezoelectric sounder like a Sonalert which makes a high-pitched tone. Usually these were hooked up to "driver" circuits which varied the pitch of the sound or pulsed the sound on and off.

In game shows it is also known as a "lockout system," because when one person signals ("buzzes in"), all others are locked out from signaling. Several game shows have large buzzer buttons which are identified as "plungers".

The word "buzzer" comes from the rasping noise that buzzers made when they were electromechanical devices, operated from stepped-down AC line voltage at 50 or 60 cycles. Other sounds commonly used to indicate that a button has been pressed are a ring or a beep.

Some systems, such as the one used on Jeopardy!, make no noise at all, instead using light. Another example is the buzzer at the end of each stage in Sasuke, Kunoichi, and Viking. These buzzers do not make a sound or turn on a light; instead, they stop a nearby digital clock, briefly fire two smoke cannons on each side of the stage exit, and open the exit. However, at the end of the Heartbreaker in Viking, the buzzer is replaced with a sword that, when removed, causes two contacts to touch, closing the circuit and causing the latter two actions above to occur.

7805 Linear regulator:

In electronics, a linear regulator is a voltage regulator based on an active device (such as a bipolar junction transistor, field effect transistor or vacuum tube) operating in its "linear region" (in contrast, a switching regulator is based on a transistor forced to act as an on/off switch) or passive devices like zener diodes operated in their breakdown region. The regulating device is made to act like a variable resistor, continuously adjusting a voltage divider network to maintain a constant output voltage.

Overview:

The transistor (or other device) is used as one half of a potential divider to control the output voltage, and a feedback circuit compares the output voltage to a reference voltage in order to adjust the input to the transistor, thus keeping the output voltage reasonably constant. This is inefficient: since the transistor is acting like a resistor, it will waste electrical energy by converting it to heat. In fact, the power loss due to heating in the transistor is the current times the voltage dropped across the transistor. The same function can be performed more efficiently by a switched-mode power supply (SMPS), but it is more complex and the switching currents in it tend to produce electromagnetic interference. All said, most modern SMPSs have a performance that can be as good as or exceed that of linear regulators. Most [computer]s have an SMPS to power them. A SMPS can easily provide more than 30A of current at voltages as low as 3V, while for the same voltage and current, a linear regulator would be very bulky and heavy.

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Linear regulators exist in two basic forms: series regulators and shunt regulators.

Series regulators are the more common form. The series regulator works by providing a path from the supply voltage to the load through a variable resistance (the main transistor is in the "top half" of the voltage divider). The power dissipated by the regulating device is equal to the power supply output current times the voltage drop in the regulating device.

The shunt regulator works by providing a path from the supply voltage to ground through a variable resistance (the main transistor is in the "bottom half" of the voltage divider). The current through the shunt regulator is diverted away from the load and flows uselessly to ground, making this form even less efficient than the series regulator. It is, however, simpler, sometimes consisting of just a voltage-reference diode, and is used in very low-powered circuits where the wasted current is too small to be of concern. This form is very common for voltage reference circuits.

All linear regulators require an input voltage at least some minimum amount higher than the desired output voltage. That minimum amount is called the drop-out voltage. For example, a common regulator such as the 7805 has an output voltage of 5V, but can only maintain this if the input voltage remains above about 7V. Its drop-out voltage is therefore 7V - 5V = 2V. When the supply voltage is less than about 2V above the desired output voltage, as is the case in low-voltage microprocessor power supplies, so-called low dropout regulators (LDOs) must be used.

When one wants a voltage higher than the available input voltage, no linear regulator will work (not even an LDO). In this situation, a switching regulator must be used.

Simple zener regulator:

Fig:12 Simple zener voltage regulator

The fig:12 shows a simple zener voltage regulator. It is a shunt regulator and operates by way of the zener diode's action of maintaining a constant voltage across itself when the current through it is sufficient to take it into the zener breakdown region.

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The resistor R1 supplies the zener current IZ as well as the load current IR2 (R2 is the load). R1 can be calculated as -

where, VZ is the zener voltage, and IR2 is the required load current.

This regulator is used for very simple low power applications where the currents involved are very small and the load is permanently connected across the zener diode (such as voltage reference or voltage source circuits). Once R1 has been calculated, removing R2 will cause the full load current (plus the zener current) to flow through the diode and may exceed the diode's maximum current rating thereby damaging it. The regulation of this circuit is also not very good because the zener current (and hence the zener voltage) will vary depending on VS and inversely depending on the load current.

Simple series regulator:

Fig:13

Simple series voltage regulator

Adding an emitter follower stage to the simple zener regulator forms a simple series voltage regulator and substantially improves the regulation of the circuit. Here, the load current IR2 is supplied by the transistor whose base is now connected to the zener diode. Thus the transistor's base current (IB) forms the load current for the zener diode and is much smaller than the current through R2. This regulator is classified as "series" because the regulating element, viz., the transistor, appears in series with the load. R1 sets the zener current (IZ) and is determined as -

where, VZ is the zener voltage, IB is the transistor's base current and K = 1.2 to 2 (to ensure that R1 is low enough for adequate IB).

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where, IR2 is the required load current and is also the transistor's emitter current (assumed to be equal to the collector current) and hFE(min) is the minimum acceptable DC current gain for the transistor.

This circuit has much better regulation than the simple zener regulator, since the base current of the transistor forms a very light load on the zener, thereby minimising variation in zener voltage due to variation in the load. Note that the output voltage will always be about 0.65V less than the zener due to the transistor's VBE drop. Although this circuit has good regulation, it is still sensitive to the load and supply variation. It also does not have the capability to be adjustable. Both these issues can be resolved by incorporating negative feedback circuitry into it. This regulator is often used as a "pre-regulator" in more advanced series voltage regulator circuits.

Using a linear regulator:

Linear regulators can be constructed using discrete components but are usually encountered in integrated circuit form. The most common linear regulators are three-terminal integrated circuits in the P1d package/TO220 package. (The TO-220 package is the same kind that many medium-power transistors commonly come in: three legs in a straight line protruding from a black plastic molded case with a metal backplate which has a hole for bolting to a heatsink).

After one connects the appropriate pins to 0 V and incoming power, the regulated output voltage appears on the output pin.

Common solid-state series voltage regulators are the LM78xx (for positive voltages) and LM79xx (for negative voltages), and common fixed voltages are 5 V (for transistor-transistor logic circuits) and 12 V (for communications circuits and peripheral devices such as disk drives). In fixed voltage regulators the reference pin is tied to ground, whereas in variable regulators the reference pin is connected to the centre point of a fixed or variable voltage divider fed by the regulator's output. A variable voltage divider (such as a potentiometer) allows the user to adjust the regulated voltage.

Cautions:

It's important to follow all the datasheet's recommendations:

Use a heat-sink on the regulator if it is going to dissipate substantial power or it may get very hot without one.

Use the recommended capacitors on the input and output lines to avoid oscillations and poor regulation.

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Remember the regulator metal case is connected to one of the circuit pins on almost all regulators. The pin varies, the case is usually connected to the ground pin on most positive voltage regulators, connected to the output pin on most negative voltage regulators, but check each time to make sure.

Fixed regulators:

"Fixed" three-terminal linear regulators are commonly available to generate fixed voltages of plus 3 V, and plus or minus 5 V, 9 V, 12 V, or 15 V when the load is less than about 7 amperes.

The "78" series (7805, 7812, etc.) regulate positive voltages while the "79" series (7905, 7912, etc.) regulate negative voltages. Often, the last two digits of the device number are the output voltage; eg, a 7805 is a +5 V regulator, while a 7915 is a -15 V regulator.

Adjustable regulators:

Invention:The adjustable linear regulator first debuted on April 12, 1977 in an Electronic Design article entitled "Break Loose from Fixed IC Regulators". The article was written by Robert Dobkin, an IC designer then working for National Semiconductor. Because of this, National Semiconductor claims the title of "LDO inventor". Dobkin later left National in 1981 to found Linear Technology where he is currently chief technology officer.

Operation:

For output voltages not provided by standard fixed regulators and load currents of less than 7 amperes, commonly-available "adjustable" three-terminal linear regulators may be used. An adjustable regulator generates a fixed low nominal voltage between its output and its 'adjust' terminal (equivalent to the ground terminal in a fixed regulator). The "317" series (+1.2V) regulates positive voltages while the "337" series (-1.2V) regulates negative voltages.

The adjustment is performed by constructing a potential divider with its ends between the regulator output and ground, and its centre-tap connected to the 'adjust' terminal of the regulator. The ratio of resistances determines the output voltage using the same feedback mechanisms described earlier.

Complex power requirements (eg, op-amp circuits needing matched positive and negative DC supplies) are more difficult, but single IC dual tracking adjustable regulators are available. Some even have selectable current limiting as well. An example is the 419x series.Note that some regulators require a minimum load, like the 317.

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CONCLUSIONThe designed infrared alarming system works by sending out a beam of light, if this beam is broken by human across the path of the infrared sensor with a transistor output that activates an alarm and the buzzer will be sounded.

REFERENCE

http://www.medwelljournals.com/fulltext/?doi=ajit.2010.243.247

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