Ehw Project

8/6/2019 Ehw Project

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EXPERIMENTALPROJECT:

UJT AS RELAXATIONOSCILLTOR


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MARKET RESEARCH

Our topic for the experimental project is UJT ASRELAXATION OSCILLATOR.

We have chosen this topic since it is interesting and easy

to perform. We have selected this topic from our EDC-I

file of Sem III. We have also searched for some more

information on it in a book called ELECTRONICS

CIRCUITS AND DEVICES written by BOLYSTED.

After the selection of Topic we were provided PCB from

College on which we have to make our projects. So now

our work begins.

We went to the shop to purchase basic things required

such as graph paper, trace paper, carbon paper, nail paint,

nail paint remover etc. we went to vashi, mulund and

lamington road to purchase things such as resistor,

capacitor, ujt and the components required for our

project. And hence finally we started to make our project

with great enthusiasm.


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PROCEDURE TO MAKE

A CIRCUIT1. LAYOUT SKETCH

These complete instructions on making the PCB is how I made mine. There are

many ways to make PCB's now-a-days, but if you would prefer to go a very

inexpensive route and yet very accurate, the below layout will indeed suffice. From

beginning to end, these step-by-step procedures will get you on your way to warm

up that soldering iron when the time comes for soldering all of the components onthe 'finished' PCB. Let's we begin:

Print out the drawing of IC first on the graph paper. It should come out exactly like

the posted measurements. Measure it to be sure it is, in fact, 116 mm's by 80 mm's.

If not exact, send the document to a Paint or Graphics Program and stretch or

squeeze to adjust for said measurements. This is extremely important. Make sure

the measurements (length and width) are no more 'off' then 1mm.

Now trace the diagram on the trace paper. Take the PCB. Place a carbon paper on it

and then turn the trace and keep it on the carbon paper so that we can trace our

diagram accurately on the PCB. Darken the lines so that get gets properly traced on

the PCB. We should note that the Ground line and the Vcc line should always

be thicker than the rest of the connecting lines.

After this remove the carbon and the trace paper from PCB and observe the

diagram. IF diagram is traced properly then use a permanent marker or a nail paint

to draw the lines on the PCB. Then take a pair of scissors and cut out the 116 mm's

by 80 mm's printed-out template. Once the markings are dried then go for the

itching process.


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2. ETCHING

In all the subtractive PCB process, Etching is the one of the most important step.

The final copper pattern is formed by selective removal of all the unwanted

copper, which is not protected by an etch resist.

There are two developers you can use, Ferric Chloride and Hydrochloric

Acid/Hydrogen-peroxide

Hydrochloric

(very clean)

One part Hydrochloric Acid One part Hydrogen

Peroxide Four parts water NEVER store it Etches in 3 - 5 minutes Available cheap from paint

shops

Ferric Chloride One part Hydrochloric Acid One part Hydrogen

Peroxide

Four parts water NEVER store it Etches in 3 - 5 minutes Available cheap from paint

shops


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If making a single sided PCB then you only have one side of copper to worry

about. The PCB should at least be kept in the solution for 1hour or as per

requirement. During etching you will normally see the PCB tracks begin to

appear through the board.

Etching may be speeded up by warming the solution or adding a little salt to it.

Do not use a metal vessel for etching as the etchant will attack If using the

Hydrochloric etchant then just drop the board in the etchant until it is finished.

If you insist on using the ferric Chloride then stick one or two strips of sticky tape

to the back of the board to form one or two handles so that you can pick up the

board without putting your fingers in the etchant. Lay the board on the surface of

the etching solution so that it floats with the COPPER SIDE DOWN.

Remove the board after a few seconds to inspect the surface of the copper. All the

exposed copper should turn a deep "shitty brown" color. Specks of unwanted

resist or even bubbles will leave copper spots where it should not be. Remove

bubbles by gently stroking the board with a paper tissue wetted with etchant.

If there are specks of resist then wash and dry the board then scrape the resist of

before trying again

Etching may be done during full daylight or with UV present; no harm will come

to the board at this stage.

After the itching is completely done, remove the PCB from the solution and wash

it with water.

Then use a nail remover or a blade to peel off the nail paint applied on it.

ERRORS

Scratches will cause wanted copper to disappear. Splashes of Ferric Chloride will stain clothes, skin, metals and even the

sink.

Unwanted copper remains - not etched for sufficient time.

3.DRILLING


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The lacquer (photo-resist) on the copper tracks may be used as a protective cover

to prevent oxidization of the copper during storage and also gives a little

mechanical protection during drilling / handling.

Drilling should always be done with a high-speed drill and very little force should

be applied to the drill to press it through the board. Doing so would cause the drill

bit to become blunt prematurely, especially if drilling fibre-glass PCBs.

It will also cause a rough edge to the board where the drill bit comes through the

board. Use good sharp drill bits up to 1mm diameter. Use a stable drill

instrument.

ERRORS

Drill bit wandering with small or absent etched guide hole.

Moving the board or drill during drilling can break drill bits. Using the wrong drill bit for the job. Injury to eyes - use protective shield or spectacles. Drilling the wrong places - use good lighting and count the holes. Forgetting holes - drill from one end of the board to the other. Count the

holes.


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4.SOLDERING

Soldering is the only permanent way to fix components to a circuit. However,

soldering requires a lot of practice as it is easy to destroy many hours

preparation and design work by poor soldering. If you follow the guidelines

below you have a good chance of success.

1. Use a soldering iron in good condition. Inspect the tip to make sure that itis not past good operation. If it looks in bad condition it will not help you solder a

good joint. The shape of the tip may vary from one soldering iron to the next but

generally they should look clean and not burnt.

2. The heated soldering iron should then be placed in contact with the trackand the component and allowed to heat them up. Once they are heated the solder

can be applied. The solder should flow through and around the component and

the track.

3. Having completed soldering the circuit the extended legs on thecomponents need to be trimmed using wire clippers. The circuit is now ready for

testing.


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INTRODUCTION

A unijunction transistor (UJT) is an electronic semiconductor device that has only

one junction. The UJT has three terminals: an emitter (E) and two bases (B1 andB2). The base is formed by lightly doped n-type bar of silicon. Two ohmic

contacts B1 and B2 are attached at its ends. The emitter is of p-type and it is

heavily doped. The resistance between B1 and B2, when the emitter is open-

circuit is called interbase resistance.

Circuit symbol

There are two types ofunijunction transistor:

The original unijunction transistor, or UJT, is a simple device that is essentiallya bar of N type semiconductor material into which P type material has been

diffused somewhere along its length, defining the device parameter . The

2N2646 is the most commonly used version of the UJT.

The programmable unijunction transistor, or PUT, is a close cousin to thethyristor. Like the thyristor it consists of four P-N layers and has an anode and

a cathode connected to the first and the last layer, and a gate connected to one

of the inner layers. They are not directly interchangeable with conventional

UJTs but perform a similar function. In a proper circuitconfiguration with two
http://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Dopedhttp://en.wikipedia.org/wiki/N-type_semiconductorhttp://en.wikipedia.org/wiki/P-type_semiconductorhttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Thyristorhttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Gatehttp://en.wikipedia.org/wiki/File:UJT_symbol.JPGhttp://en.wikipedia.org/wiki/File:Unijunction_transistors.jpghttp://en.wikipedia.org/wiki/Gatehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Thyristorhttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/P-type_semiconductorhttp://en.wikipedia.org/wiki/N-type_semiconductorhttp://en.wikipedia.org/wiki/Dopedhttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Electronics


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"programming" resistors for setting the parameter , they behave like a

conventional UJT. The 2N6027 is an example of such a device.

The UJT is biased with a positive voltage between the two bases. This causes apotential drop along the length of the device. When the emitter voltage is

driven approximately one diode voltage above the voltage at the point wherethe P diffusion (emitter) is, current will begin to flow from the emitter into the

base region. Because the base region is very lightly doped, the additional

current (actually charges in the base region) causes conductivity modulation

which reduces the resistance of the portion of the base between the emitter

junction and the B2 terminal. This reduction in resistance means that the

emitter junction is more forward biased, and so even more current is injected.

Overall, the effect is a negative resistance at the emitter terminal. This is what

makes the UJT useful, especially in simple oscillator circuits.

Unijunction transistor circuits were popular in hobbyist electronics circuitsin the 1970s and early 1980s because they allowed simple oscillators to be

built using just one active device. Later, as Integrated Circuits became

more popular, oscillators such as the 555 timer IC became more commonly

used.

In addition to its use as the active device in relaxation oscillators, one ofthe most important applications of UJTs or PUTs is to trigger thyristors

(SCR, TRIAC, etc.). In fact, a DC voltage can be used to control a UJT or

PUT circuit such that the "on-period" increases with an increase in the DC

control voltage. This application is important for large AC current control.
http://en.wikipedia.org/w/index.php?title=Conductivity_modulation&action=edit&redlink=1http://en.wikipedia.org/wiki/Negative_resistancehttp://en.wikipedia.org/wiki/Oscillatorhttp://en.wikipedia.org/wiki/Integrated_Circuitshttp://en.wikipedia.org/wiki/555_timer_IChttp://en.wikipedia.org/wiki/Relaxation_oscillatorhttp://en.wikipedia.org/wiki/Thyristorhttp://en.wikipedia.org/wiki/Silicon_controlled_rectifierhttp://en.wikipedia.org/wiki/TRIAChttp://en.wikipedia.org/wiki/TRIAChttp://en.wikipedia.org/wiki/Silicon_controlled_rectifierhttp://en.wikipedia.org/wiki/Thyristorhttp://en.wikipedia.org/wiki/Relaxation_oscillatorhttp://en.wikipedia.org/wiki/555_timer_IChttp://en.wikipedia.org/wiki/Integrated_Circuitshttp://en.wikipedia.org/wiki/Oscillatorhttp://en.wikipedia.org/wiki/Negative_resistancehttp://en.wikipedia.org/w/index.php?title=Conductivity_modulation&action=edit&redlink=1


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CIRCUIT DIAGRAM

Where,

C1, C2, C3=Charging & discharging capacitor

RE=Charging & discharging resistorVBB=Power supply

B1=Base1

B2=Base2

R1=Output resistor

R2=Temperature compensation resistor

S=Switch for selecting capacitor


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COMPONENTS LIST

SR.NO NAME OF

COMPONENT

NAME OF

MANUFACTURER

QUANTITY COST

1 UJT2646 Premier advertiser 1 Rs.24

2 Resistance - 3 Rs.1(each)

3 capacitor - 2 Rs.1(each)

4 potentiometer - 1 Rs.4

5 Connecting

wires

- 4-5 -


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WORKING OF UJT

Although a unijunction transistor is not a thyristor, this device can trigger largerthyristors with a pulse at base B1. A unijunction transistor is composed of a bar

of N-type silicon having a P-type connection in the middle. See Figure below(a).

The connections at the ends of the bar are known as bases B1 and B2; the P-type

mid-point is the emitter. With the emitter disconnected, the total resistance RBBO,

a datasheet item, is the sum of RB1 and RB2 as shown in Figure below(b). RBBO

ranges from 4-12k for different device types. The intrinsic standoff ratio is the

ratio of RB1 to RBBO. It varies from 0.4 to 0.8 for different devices. The schematic

symbol is Figure below(c).

Unijunction transistor: (a) Construction, (b) Model, (c) Symbol

The Unijunction emitter current vs voltage characteristic curve (Figure below(a)) shows that as VE increases, current IE increases up IP at the peak point. Beyond

the peak point, current increases as voltage decreases in the negative resistance

region. The voltage reaches a minimum at the valley point. The resistance of RB1,

the saturation resistance is lowest at the valley point.

IP and IV, are datasheet parameters; For a 2n2647, IP and IV are 2A and 4mA,

respectively. [AMS] VP is the voltage drop across RB1 plus a 0.7V diode drop; see

Figure below(b). VV is estimated to be approximately 10% of VBB.
http://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03504.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03504.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03504.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03508.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#AMS.bibitemhttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03508.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03508.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#AMS.bibitemhttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03508.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03504.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03504.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03504.png


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Unijunction transistor: (a) emitter characteristic curve, (b)

model for VP .The relaxation oscillator in Figure below is an application of the unijunction

oscillator. RE charges CE until the peak point. The unijunction emitter terminal

has no effect on the capacitor until this point is reached. Once the capacitor

voltage, VE, reaches the peak voltage point VP, the lowered emitter-base1 E-B1

resistance quickly discharges the capacitor. Once the capacitor discharges below

the valley point VV, the E-RB1 resistance reverts back to high resistance, and the

capacitor is free to charge again.
http://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03506.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03506.png


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Unijunction transistor relaxation oscillator and waveforms.

Oscillator drives SCR.During capacitor discharge through the E-B1 saturation resistance, a pulse may

be seen on the external B1 and B2 load resistors, Figure above. The load resistor

at B1 needs to be low to not affect the discharge time. The external resistor at B2

is optional. It may be replaced by a short circuit. The approximate frequency is

given by 1/f = T = RC. A more accurate expression for frequency is given in

Figure above.

The charging resistor RE must fall within certain limits. It must be small enough

to allow IP to flow based on the VBB supply less VP. It must be large enough to

supply IV based on the VBB supply less VV. [MHW] The equations and an

example for a 2n2647:
http://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03506.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03506.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#MHW.bibitemhttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#MHW.bibitemhttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03506.pnghttp://www.allaboutcircuits.com/vol_3/chpt_7/8.html#03506.png


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Hence after completion of layout sketch, etching, drilling and soldering of PCB,

our project look like as given below :

SOLDERING SIDE:

COMPONENT SIDE:


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SUMMARY

A unijunction transistor consists of two bases (B1, B2) attachedto a resistive bar of silicon, and an emitter in the center. The E-

B1 junction has negative resistance properties; it can switch

between high and low resistance.

A PUT (programmable unijunction transistor) is a 3-terminal 4-layer thyristor acting like a unijunction transistor. An external

resistor network programs .

The intrinsic standoff ratio is =R1/(R1+R2) for a PUT;substitute RB1 and RB2, respectively, for a unijunction

transistor. The trigger voltage is determined by . Unijunction transistors and programmable unijunction

transistors are applied to oscillators, timing circuits, and

thyristor triggering.


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DIGITAL PROJECT:

8-BIT PARITY GENERATOR


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MARKETING RESEARCH

Our topic for the digital project is 8-BIT PARITY

GENERATOR USING IC74180.

We have chosen this topic since it is interesting and easy

to perform.

We have selected this topic from textbook named

DIGITAL ELCTRONICS by R.P. JAIN. We havealso searched for some more information on it on URL

like www.google.com.After the selection of Topic

College has provided us the PCB on which we have to

make our projects. So now our work begins.

We went to the shop to purchase basic things required

such as graph paper, trace paper, carbon paper, nail

paint, nail paint remover etc. we went to vashi, mulund

and lamington road to purchase things such as resistor,

capacitor, ujt and the components required for our

project. And hence finally we started to make our project

with great enthusiasm.


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PROCEDURE TO MAKE

A CIRCUIT1.LAYOUT SKETCH

These complete instructions on making the PCB is how I made mine. There are


inexpensive route and yet very accurate, the below layout will indeed suffice.

From beginning to end, these step-by-step procedures will get you on your way to

warm up that soldering iron when the time comes for soldering all of thecomponents on the 'finished' PCB. Let's we begin:

Print out the drawing of IC first on the graph paper. It should come out exactly

like the posted measurements. Measure it to be sure it is, in fact, 116 mm's by 80

mm's. If not exact, send thedocument to a Paint or Graphics Program and stretch

or squeeze to adjust for said measurements. This is extremely important. Make

sure the measurements (length and width) are no more 'off' then 1mm.

Now trace the diagram on the trace paper. Take the PCB. Place a carbon paper on

it and then turn the trace and keep it on the carbon paper so that we can trace our

diagram accurately on the PCB. Darken the lines so that get gets properly traced

on the PCB. We should note that the Ground line and the Vcc line should

always be thicker than the rest of the connecting lines.


diagram. IF diagram is traced properly then use a permanent marker or a nail

paint to draw the lines on the PCB. Then take a pair of scissors and cut out the116 mm's by 80 mm's printed-out template. Once the markings are dried then go

for the itching process.


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2. ETCHING

In all the subtractive PCB process, Etching is the one of the most important step.

The final copper pattern is formed by selective removal of all the unwanted




Hydrochloric

(very clean)

One part Hydrochloric Acid One part Hydrogen

Peroxide

Four parts water NEVER store it Etches in 3 - 5 minutes Available cheap from paint

shops

Ferric Chloride One part Hydrochloric Acid One part Hydrogen

Peroxide Four parts water NEVER store it Etches in 3 - 5 minutes Available cheap from paint

shops


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requirement. During etching you will normally see the PCB tracks begin to

appear through the board.













before trying again




it with water.


ERRORS


sink.



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3.DRILLING









instrument.

ERRORS

Drill bit wandering with small or absent etched guide hole. Moving the board or drill during drilling can break drill bits. Using the wrong drill bit for the job. Injury to eyes - use protective shield or spectacles. Drilling the wrong places - use good lighting and count the holes. Forgetting holes - drill from one end of the board to the other. Count the

holes.


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4.SOLDERING





1. Use a soldering iron in good condition. Inspect the tip to make sure that itis not past good operation. If it looks in bad condition it will not help you solder a

good joint. The shape of the tip may vary from one soldering iron to the next but

generally they should look clean and not burnt.

2. The heated soldering iron should then be placed in contact with the trackand the component and allowed to heat them up. Once they are heated the solder

can be applied. The solder should flow through and around the component and

the track.

3. Having completed soldering the circuit the extended legs on thecomponents need to be trimmed using wire clippers. The circuit is now ready for

testing.


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INTRODUCTIONThe first step in implementing any circuit is to represent its operation in terms of

a Truth or Function table. The function table for an 8-bit data as input has 28 has

256 input combinations, which becomes unmanageable. Therefore, for the sake

of simplicity a 4-bit data with odd parity is assumed. The receiver circuit is also

based on the 4-bit data. The function table for the 4-bit data is shown.

The function table represents the 16 possible combinations of 4 data bits. The 4

data bits are represented by variables D3, D2, D1 and D0. The output P

represents the state of the Parity bit. Since Odd-Parity is being used therefore the

4-bit data and the parity bit should add up to give odd number of 1s. The functiontable shows the Parity bit set to 1 when the 16, 4-bit data input combinations have

no 1s or an even number of 1s.

The information in the function table is mapped directly to a four variable K-map

to simplify the Boolean expression represented by the Odd-Parity generator

function. None of the 1s mapped in the K-map are adjacent to each other thus the

function mapped to the K-map can not be simplified.

The 2 input AND and OR gates and how many inverters would be required toimplement the equation you got for P.

AND: OR: NOT:

This circuit can be implemented with the chips in your lab kit, but that would

leave only 1OR gate and no AND gates to implement our entire parity detection

circuit !(not to mention that it would be a pain to wire up!). So, how can we

simplify this further? This is one of those examples where you see why engineers

can't be replaced by computers (yet - but we're working on it). The K-map

guarantees us M.S.O.P. form, but that's not the simplest form for this problem.
http://free-books-online.org/tag/function/http://free-books-online.org/tag/function/http://free-books-online.org/tag/odd-parity/http://free-books-online.org/tag/receiver-circuit/http://free-books-online.org/tag/function/http://free-books-online.org/tag/function/http://free-books-online.org/tag/data-bits/http://free-books-online.org/tag/data-bits/http://free-books-online.org/tag/parity-bit/http://free-books-online.org/tag/parity-bit/http://free-books-online.org/tag/function/http://free-books-online.org/tag/parity-bit/http://free-books-online.org/tag/function/http://free-books-online.org/tag/boolean-expression/http://free-books-online.org/tag/function/http://free-books-online.org/tag/function/http://free-books-online.org/tag/function/http://free-books-online.org/tag/function/http://free-books-online.org/tag/boolean-expression/http://free-books-online.org/tag/function/http://free-books-online.org/tag/parity-bit/http://free-books-online.org/tag/function/http://free-books-online.org/tag/parity-bit/http://free-books-online.org/tag/parity-bit/http://free-books-online.org/tag/data-bits/http://free-books-online.org/tag/data-bits/http://free-books-online.org/tag/function/http://free-books-online.org/tag/function/http://free-books-online.org/tag/receiver-circuit/http://free-books-online.org/tag/odd-parity/http://free-books-online.org/tag/function/http://free-books-online.org/tag/function/


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Neither is the M.P.O.S. form we'd get from grouping the zeroes. This K-map

shows a checkerboard pattern (every other square), meaning it implements either

an XOR or XNOR function. If you look at the equation you got for P, if you did

it right it can be rewritten as:

P = (x'y'+xy)z' + (x'y+xy')z

we can implement this function as an XNOR of the four input variables,

Because of this property, XNOR is also known as the even function, and XOR is

also known as the odd function (If we changed our truth table so that our output

was 1 whenever there was an odd number of 1s, the resulting function would be

an XOR; the K-map would still look like a checkerboard, but the first one would

be in square 0001 instead of 0000).

Create your parity detection circuit using the equation for E above as a macro in

Digital Works with 4 inputs and 1 output, and wire it up on your breadboard (this

will require 3 more XOR gates and one more inverter - you should have 2 7486

chips). Hook your parity generator to your parity detector and verify that it works

correctly both in lab and in simulation. To test your simulation, embed your

generator and detector macros in the same circuit as shown in the figure below:


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Test your parity detector separately by disconnecting the P input from the parity

generator circuit and hooking it to a switch instead.

The equations in a way that we can implement with the parts we have. Certainly

we have enough parts to implement A and B with just AND and OR gates, so let'sjust take a look at C (have to give you the answer here):

C = y'z + xy

We need to reformulate this equation to use something other than AND gates or

OR gates. We've already used our XOR gates in part 1 of the lab. The two AND

operations and one OR operation in the equation for C with NAND operations.

Remember, x NAND y = (xy)'

C=((y'z)'(xy)')'

Using DeMorgan's Theorem, we can simplify C to:

C= ((y'z)'(xy)')' = (y'z)''+(xy)'' = y'z +xy, which is our original equation for C!

This means we can implement C as shown below, without changing the function

at all:


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PIN ARRANGEMENT


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PIN DESCRIPTION

Pin No. Description1 Input

2 Input

3 Even input

4 Odd input

5 Even output

6 Odd output

7 Gnd

8 Input9 Input

10 Input

11 Input

12 Input

13 Input

14 VCC


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FUNCTION TABLE

LOGICAL DIAGRAM

of H at A

through H

Even

(Pe)

Odd

(Po)

Even

(E)

Odd

(O)

Even H L H L

Odd H L L H

Even L H L H

Odd L H H L

X H H L L

X L L H H


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Hence after completion of layout sketch, etching, drilling and

soldering of PCB, our project look like as given below

COMPONENT side

SOLDERING side


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ANALOG PROJECT:

FIRE ALARM


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MARKET RESEARCHOur topic for the mini project is FIRE ALARM.

We have chosen this topic since it is interesting and used

for many applications.

We have selected this topic from magazine named as

ELECTRONICS FOR YOU. We have also searched for

some more information on URLs like www.google.com,

www.circuitstoday.com and www.efymag.com .

After the selection of Topic, College has provided us the

PCB on which we have to make our projects. So now our

work begins.

We went to the shop to purchase basic things required such

as graph paper, trace paper, carbon paper, nail paint, nail

paint remover etc. we went to vashi, mulund and lamington

road to purchase things such as resistor, capacitor, diode

and the components required for our project. And hence

finally we started to make our project with great enthusiasm

and excitement.
http://www.google.com/http://www.circuitstoday.com/http://www.efymag.com/http://www.efymag.com/http://www.circuitstoday.com/http://www.google.com/


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PROCEDURE OF HOW TO

MAKE A CIRCUIT

1. LAYOUT SKETCHThese complete instructions on making the PCB is how I made mine. There are


inexpensive route and yet very accurate, the below layout will indeed suffice.

From beginning to end, these step-by-step procedures will get you on your way to

warm up that soldering iron when the time comes for soldering all of the

components on the 'finished' PCB. Let's we begin:

measurements. Measure it to be sure it is, in fact, 116 mm's by 80 mm's. If not

exact, send the document to a Paint or Graphics Program and stretch or squeeze

to adjust for said measurements. This is extremely important. Make sure the

measurements (length and width) are no more 'off' then 1mm.

Now trace the diagram on the trace paper. Take the PCB. Place a carbon paper on

it and then turn the trace and keep it on the carbon paper so that we can trace our

diagram accurately on the PCB. Darken the lines so that get gets properly tracedon the PCB. We should note that the Ground line and the Vcc line should

always be thicker than the rest of the connecting lines.


diagram. IF diagram is traced properly then use a permanent marker or a nail

paint to draw the lines on the PCB. Then take a pair of scissors and cut out the

116 mm's by 80 mm's printed-out template. Once the markings are dried then go

for the itching process.


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2.ETCHING

In all the subtractive PCB process, Etching is the one of the most important step.The final copper pattern is formed by selective removal of all the unwanted




Hydrochloric

(very clean)

One part Hydrochloric Acid One part Hydrogen Peroxide Four parts water NEVER store it Etches in 3 - 5 minutes Available cheap from paint shops

Ferric Chloride One part Hydrochloric Acid One part Hydrogen Peroxide Four parts water NEVER store it Etches in 3 - 5 minutes Available cheap from paint shops



requirement. During etching you will normally see the PCB tracks begin toappear through the board.


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before trying again




it with water.


ERRORS


sink.


3. DRILLING








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instrument.

ERRORS

Drill bit wandering with small or absent etched guide hole. Moving the board or drill during drilling can break drill bits. Using the wrong drill bit for the job. Injury to eyes - use protective shield or spectacles. Drilling the wrong places - use good lighting and count the holes. Forgetting holes - drill from one end of the board to the other. Count the

holes.

4. SOLDERING





1. Use a soldering iron in good condition. Inspect the tip to make sure that it isnot past good operation. If it looks in bad condition it will not help you solder

a good joint. The shape of the tip may vary from one soldering iron to the

next but generally they should look clean and not burnt.

2. The heated soldering iron should then be placed in contact with the track andthe component and allowed to heat them up. Once they are heated the solder


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can be applied. The solder should flow through and around the component

and the track

3. Having completed soldering the circuit the extended legs on the componentsneed to be trimmed using wire clippers. The circuit is now ready for testing.


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INTRODUCTIONAn automatic fire alarm system is designed to detect the unwanted presence of

fire by monitoring environmental changes associated with combustion. In

general, a fire alarm system is either classified as automatically actuated,

manually actuated, or both. Automatic fire alarm systems can be used to notify

people to evacuate in the event of a fire or other emergency, to summon

emergency services, and to prepare the structure and associated systems to

control the spread of fire and smoke.

Design

After the fire protection goals are established - usually by referencing the

minimum levels of protection mandated by the appropriate model building code,

insurance agencies, and other authorities - the fire alarm designer undertakes to

detail specific components, arrangements, and interfaces necessary to accomplish

these goals. Equipment specifically manufactured for these purposes are selected

and standardized installation methods are anticipated during the design. In theUnited States, NFPA 72, The National Fire Alarm Code is an established and

widely used installation standard.
http://en.wikipedia.org/wiki/Firehttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/National_Fire_Protection_Associationhttp://en.wikipedia.org/wiki/National_Fire_Protection_Associationhttp://en.wikipedia.org/wiki/National_Fire_Protection_Associationhttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/Fire


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FUNDAMENTAL CONFIGURATION

A Honeywell DeltaNet FS90 fire alarm control panel.

Fire alarm control panel: This component, the hub of the system, monitorsinputs and system integrity, controls outputs and relays information.

Primary Power supply: Commonly the non-switched 120 or 240 VoltAlternating Current source supplied from a commercial power utility. In non-

residential applications, a branch circuit is dedicated to the fire alarm system

and its constituents. "Dedicated branch circuits" should not be confused with"Individual branch circuits" which supply energy to a single appliance.

Secondary (backup) Power supplies: This component, commonly consisting ofsealed lead-acid storage batteries or other emergency sources including

generators, is used to supply energy in the event of a primary power failure.

Initiating Devices: This component acts as an input to the fire alarm controlunit and are either manually or automatically actuated.

Notification appliances: This component uses energy supplied from the firealarm system or other stored energy source, to inform the proximate persons of

the need to take action, usually to evacuate.

Building Safety Interfaces: This interface allows the fire alarm system tocontrol aspects of the built environment and to prepare the building for fire and

to control the spread of smoke fumes and fire by influencing air movement,

lighting, process control, human transport and exit.
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NOTIFICATION APPLIANCES

A Honeywell speaker and a Space Age Electronics V33 remote light.

Audible, visible, tactile, textual or even olfactory stimuli (odorizer).[1]

to alertthe occupants. Audible or visible signals are the most common and may utilize

speakers to deliver live or pre-recorded instructions to the occupants. In the

United States, fire alarm evacuation signals are required to use a standardized

interrupted four count temporal pattern to avoid confusion with other signals

using similar sounding appliances. Other methods include:

Audible textual appliances, which are employed as part of a fire alarm systemthat includes Emergency Voice Alarm Communications (EVAC) capabilities.

High reliability speakers are used to notify the occupants of the need for action

in connection with a fire or other emergency. These speakers are employed inlarge facilities where general undirected evacuation is considered

impracticable or undesirable. The signals from the speakers are used to direct

the occupant's response. The system may be controlled from one or more

locations within the building known as Fire Wardens Stations, or from a single

location designated as the building Fire Command Center. Speakers are

automatically actuated by the fire alarm system in a fire event, and following a

pre-alert tone, selected groups of speakers may transmit one or more

prerecorded messages directing the occupants to safety. These messages may

be repeated in one or more languages. Trained personnel activating and

speaking into a dedicated microphone can suppress the replay of automated

messages in order to initiate or relay real time voice instructions.[2]
http://en.wikipedia.org/wiki/Honeywellhttp://en.wikipedia.org/wiki/Space_Age_Electronicshttp://en.wikipedia.org/wiki/Odorizerhttp://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-NFPA_805-0http://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-NFPA_805-0http://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-NFPA_805-0http://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-18th_Edition-1http://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-18th_Edition-1http://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-18th_Edition-1http://en.wikipedia.org/wiki/File:Honeywellspeakerv33.JPGhttp://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-18th_Edition-1http://en.wikipedia.org/wiki/Fire_alarm_system#cite_note-NFPA_805-0http://en.wikipedia.org/wiki/Odorizerhttp://en.wikipedia.org/wiki/Space_Age_Electronicshttp://en.wikipedia.org/wiki/Honeywell


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BUILDING SAFETY INTERFACES

S.H. Couch F5GX non-coded fire alarm pull station below a Couch 10" bell.

Magnetic Smoke Door Holders: Wall or floor mounted solenoids orelectromagnets controlled by a fire alarm system or detection component that

magnetically secures spring-loaded self-closing smoke tight doors in the open

position. Designed to de-magnetize to allow automatic closure of the door on

command from the fire control or upon failure of the power source,

interconnection or controlling element. Stored energy in the form of a spring or

gravity can then close the door to restrict the passage of smoke from one space

to another in an effort to maintain a tenable atmosphere on either side of thedoor during evacuation and fire fighting efforts.

Duct Mounted Smoke Detection: Smoke detection mounted in such a manneras to sample the airflow through duct work and other plenums specifically

fabricated for the transport of environmental air into conditioned spaces.

Interconnection to the fan motor control circuits are intended to stop air

movement, close dampers and generally prevent the recirculation of toxic

smoke and fumes produced by fire into occupiable spaces.
http://en.wikipedia.org/wiki/S.H._Couchhttp://en.wikipedia.org/wiki/Fire_alarm_pull_stationhttp://en.wikipedia.org/wiki/File:Couchpull.JPGhttp://en.wikipedia.org/wiki/Fire_alarm_pull_stationhttp://en.wikipedia.org/wiki/S.H._Couch


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UK fire alarm system categories

There are many types of fire alarm systems each suited to different building types

and applications. A fire alarm system can vary dramatically in both price and

complexity, from a single panel with a detector and sounder in a smallcommercial property to an addressable fire alarm system in a multi-occupancy

building. Systems have to protect both buildings and occupants.

The categories of fire alarm systems are L if they are designed to protect life, P to

protect buildings and M if they are manual systems.[3]

M

Manual systems, e.g. hand bells, gongs, etc. These may be purely manual or

manual electric, the latter may have call points and sounders. They rely on the

occupants of the building discovering the fire and acting to warn others byoperating the system. Such systems form the basic requirement for places of

employment with no sleeping risk.

P1

The system is installed throughout the building - the objective being to call

the fire brigade as early as possible to ensure that any damage caused by fire

is minimized. Small low risk areas can be excepted, such as toilets and

cupboards less than 1m.

P2

Detection should be provided in parts of the building where the risk of

ignition is high and/or the contents are particularly valuable. Category 2

systems provide fire detection in specified parts of the building where there iseither high risk or where business disruption must be minimised.

L1

A category L1 system is designed for the protection of life and which has

automatic detectors installed throughout all areas of the building (including

roof spaces and voids) with the aim of providing the earliest possible

warning. A category L1 system is likely to be appropriate for the majority of

residential care premises. In practice, detectors should be placed in nearly all

spaces and voids. With category 1 systems, the whole of a building is covered

apart from minor exceptions.

L2

A category L2 system designed for the protection of life and which has

automatic detectors installed in escape routes, rooms adjoining escape routes

and high hazard rooms. In a medium sized premises (sleeping no more than

ten residents), a category L2 system is ideal. These fire alarm systems are

identical to an L3 system but with additional detection in an area where there

is a high chance of ignition, e.g., kitchen) or where the risk to people is

particularly increased (e.g., sleeping risk).

L3

This category is designed to give early warning to everyone. Detectors should

be placed in all escape routes and all rooms that open onto escape routes.

Category 3 systems provide more extensive cover than category 4. The
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objective is to warn the occupants of the building early enough to ensure that

all are able to exit the building before escape routes become impassable.

L4

Category 4 systems cover escape routes and circulation areas only. Therefore,

detectors will be placed in escape routes, although this may not be suitable

depending on the risk assessment or if the size and complexity of a building isincreased. Detectors might be sited in other areas of the building, but the

objective is to protect the escape route.

L5

This is the "all other situations" category, e.g., computer rooms, which may

be protected with an extinguishing system triggered by automatic detection.

Category 5 systems are the "custom" category and relate to some special

requirement that cannot be covered by any other category.


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FIRE DEPARTMENTS

The Roman emperor Augustus is credited with instituting a corps of fire-fighting

vigiles (watchmen) in 24 bc. Regulations for checking and preventing fires

were developed. In the preindustrial era most cities had watchmen who sounded

an alarm at signs of fire. The principal piece of fire-fighting equipment in ancient

Rome and into early modern times was the bucket, passed from hand to hand to

deliver water to the fire. Another important fire-fighting tool was the ax, used to

remove the fuel and prevent the spread of fire as well as to make openings that

would allow heat and smoke to escape a burning building. In major

conflagrations long hooks with ropes were used to pull down buildings in the

path of an approaching fire to create firebreaks. When explosives were available,

they would be used for this same purpose. Following the Great Fire of London in

1666, fire brigades were formed by insurance companies. The government was

not involved until 1865, when these brigades became London's Metropolitan Fire

Brigade. The first modern standards for the operation of a fire department were

not established until 1830, in Edinburgh, Scotland. These standards explained, for

the first time, what was expected of a good fire department.

After a major fire in Boston in 1631, the first fire regulation in America was

established. In 1648 in New Amsterdam (now New York) fire wardens were

appointed, thereby establishing the beginnings of the first public fire departmentin North America.


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A Fire Departments in the United States

In the modern sense, fire departments constitute a comparatively recent

development. Their personnel are either volunteer (nonsalaried) or career

(salaried). Typically, volunteer fire fighters are found mainly in smaller

communities, career fire fighters in cities. The modern department with salaried

personnel and standardized equipment became an integral part of municipal

administration only late in the 19th century.

A1 Organization

In some cities a fire commissioner administers the department; other cities have a

board of fire commissioners with a fire chief as executive officer and head of the

uniformed force; in still other cities a safety director may be in charge of both

police and fire departments. The basic operating unit of the fire department is the

company, commanded by a captain. A captain may be on duty on each shift,

although in some fire departments lieutenants and sergeants command companies

when the captain is off duty. Fire companies are usually organized by types of

apparatus: engine companies, ladder companies, and squad or rescue companies.

A2 Fire Alarms

Fire-alarm systems came into existence with the invention of the telegraph.

Today many communities are served either with the telegraph-alarm system or

with telephone call boxes. Most fires, however, are reported from private

telephones. Many large cities have removed all or many of their street alarm

boxes because of problems associated with maintenance and with false alarm

transmissions. Some boxes have been replaced with telephones. All alarms are

then transmitted to the fire stations. In large cities, alarms are received at a central

dispatch office and then transmitted to fire stations, frequently with the use of

mobile teleprinters and computers. Apparatus is dispatched according to the

nature of the alarm and location of the fire. Many modern departments are now

equipped with computer-aided dispatch systems that can track the status of all

units and provide vital information about the buildings where fires occur.

Typically, on a first alarm, more apparatus is sent to industrial sections, schools,

institutions, and theaters than to neighborhoods of one-family dwellings.

Additional personnel, volunteer or off duty, is called as needed. Fires that cannot

be brought under control by the apparatus responding to the first alarm are called

multiple-alarm fires, with each additional alarm bringing more fire fighters and


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Forest Fire and Line Crew

A line crew gathers shovels and axes to make a trench to stop the oncoming forest fire. Inextremely dry or remote areas, firefighters often try to contain a fire by separating it from new

sources of fuel with such a firebreak, instead of attempting to extinguish it. Despite efforts tolimit and prevent forest fires, millions of acres of trees are lost to fire every year.

A4 Emergencies

Many modern fire departments spend a decreasing amount of overall activity in

fighting fires. Instead, fire fighters typically respond to all kinds of emergencies.

For example, in the U.S. approximately 70 percent of all emergency medical calls

are handled by the fire service. The same is true in many other countries.

The enormous increase in transportation of hazardous materials or dangerous

goods has resulted in intensified training for fire fighters, and their departments

often provide them with chemical protective clothing and monitoring equipment.

Fire departments also prepare and equip their members to handle emergencies

that result from earthquakes, plane crashes, and violent storms. In addition, fire

fighters handle incidents that require extricating trapped people from fallen

structures, from cave-ins, and from other situations.


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B Fire Departments Outside the United States

Although fire fighting is largely a matter of local jurisdiction in the U.S., many

countries have more centralized fire departments. Italy has a national fire service

(Corpo Nazionale-Vigili del Fuoco) organized into 92 provinces, administeredfrom 12 regional centers. In the United Kingdom, local fire departments are

organized into county, borough, and special district departments, all under a chief

inspector of fire services. In France, fire protection is administered in sectors,

except in Paris, where the fire department is operated by the Sapeurs-Pompiers, a

brigade of the French= army, and in Marseille, where it is administered by the

navy. The Japanese government administers 43 regional and 3 metropolitan fire

departments. In Denmark, local governments contract for fire-fighting services

with companies under supervision of the Ministry of Justice. In Germany,professional fire brigades operate in large cities; volunteer brigades serve the

small towns.

In all industrial countries fire fighters undergo training, beginning with

probationary fire fighters' school and continuing throughout a fire fighter's career.

Great Britain has several fire training centers. In Russia, fire schools are in

Moscow and Saint Petersburg; Sweden and Denmark have similar schools. In

some European countries fire protection and fire fighting are among the courses

included in teaching safety engineering.


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International fire service and fire protection associations bring together leaders of

the fire services of many nations. In Europe Comit Technique International de

Prevention et d'Extinction du Feu (CTIF) has over 30 member nations, including

Russia. The Organizacin Iberoamericana de Proteccin Contra Incendios

(OPCI) brings together the fire service leaders of all Latin American countries.

The Asia-Pacific region is served by the Asian Pacific Fire Safety Association

(APAC).

III FIGHTING THE FIRE

Most fire fighting consists of applying water to the burning material, cooling it to

the point at which combustion is no longer self-sustaining. Fires involving

flammable liquids, certain chemicals, and combustible metals often requirespecial extinguishing agents and techniques. With some fuels the use of water

may actually be dangerous.

A Fire Engines

The first fire engines, which appeared in the 17th century, were simply tubs

carried on runners, long poles, or wheels; water was still supplied to the fire site

by bucket brigade. The tub functioned as a reservoir and sometimes housed a

hand-operated pump that forced water through a pipe or nozzle to waitingbuckets. The invention of a hand-stitched leather hosepipe in the Netherlands

about 1672 enabled fire fighters to work closer to the fire without endangering

their engines and to increase the accuracy of water placement. At about the same

time the development of pumping devices made it possible to draw water from

rivers and ponds.


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In the early 19th century copper rivets replaced the stitching on hoses, and 15-m

(50-ft) lengths coupled with brass fittings enabled fire fighters to convey water

through narrow passages, up stairways, and into buildings, while the pumps

operated in the street. Cotton-covered rubber hose was developed around 1870.

The steam-pump fire engine, introduced in London in 1829 by John Ericsson and

John Braithwaite, was used in many large cities by the 1850s. Most steam

pumpers were equipped with reciprocating piston pumps, although a few rotary

pumps were used. Some were self-propelled, but most used horses for propulsion,

conserving steam pressure for the pump. Steam fire engines were used in fighting

the Chicago fire of 1871.

With the development of the internal-combustion engine early in the 20th

century, pumpers became motorized. Because of problems in adapting gearedrotary gasoline engines to pumps, the first gasoline-powered fire engines had two

motors, one to drive the pump and the other to propel the vehicle. The first

pumper using a single engine for pumping and propulsion was manufactured in

the United States in 1907. By 1925 the steam pumper had been completely

replaced by motorized pumpers. The pumps were originally of the piston or

reciprocating type, but these were gradually replaced by rotary pumps and finally

by centrifugal pumps, used by most modern pumpers.

At the same time, the pumper acquired its main characteristics: a powerful pump

that can supply water in a large range of volumes and pressures; several thousand

feet of fire hose, with short lengths of large-diameter hose for attachment to

hydrants; and a water tank for the initial attack on a fire while fire fighters

connect the pump to hydrants, and for areas where no water supply is available.

In rural areas, pumpers carry suction hose to draw water from rivers and ponds.

Current standards for pumper fire apparatus require that a fire pump have a

minimum capacity of 2840 liters (750 gallons)per minute at a pump pressure of10.35 bar (150 psi). They also call for a water tank capacity of at least 1893 liters

(500 gallons).

B Auxiliary Equipment

Auxiliary vehicles are equipped with specialized equipment for effecting rescue,

ventilating buildings, and salvage. Aerial ladders that typically extend to 30.5 m

(100 ft) are carried on hook and ladder vehicles that also hold various kinds of

tools and equipment, including heavy-duty jacks and air bags, extrication tools,


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oxyacetylene torches, self-contained breathing apparatus, and resuscitators. Other

more basic equipment includes axes, shovels, picks, battering rams, power saws,

hooks, and wrenches. Elevating platform trucks can raise fire fighters and

equipment, including the water delivery system, as high as 30.5 m (100 ft).

Rescue trucks carry a wide assortment of specialized emergency equipment,

including the type that might be used in building collapses and cave-ins. Field

communications units carry sophisticated electronic equipment for use in

managing fire and emergency operations. Salvage trucks carry implements for

reducing water damage, including large waterproof covers, dewatering devices,

and tools for shutting off water flow from sprinkler heads. Hazardous materials

response units are staffed with specially trained personnel equipped with

protective clothing and monitoring devices for use at chemical spills and similar

incidents.

C Fireboats

Shipboard fires present special problems ranging from small fires in cabin

cruisers to tanker fires involving thousands of metric tons of oil. Some of the

special problems include complicated ship layouts, the danger of capsizing, and

the difficulty of pinpointing and gaining access to the source of the fire.

Fireboats, in sizes ranging from small, high-speed, jet-propelled rescue craft to

large fire tugs, carry substantially all the fire-fighting equipment found on land

apparatus. These include pumps, ladders, and rescue equipment, as well as

special equipment necessary for marine fire fighting and water rescues, including

rotating and angled nozzles, portable pumps, floating booms, foam-making

apparatus, and special extinguishers such as carbon dioxide systems.

D At the Fire

The basic tactics of fighting a fire can be divided into the following categories:rescue operations, protection of buildings exposed to the fire, confinement of the

fire, extinguishing the fire, and salvage operations. The officer in charge, usually

designated as the fireground commander, surveys the area and evaluates the

relative importance of these categories. The commander also estimates what

additional assistance or apparatus may be needed. Rescue operations are always

given priority. Fire fighter safety has assumed increasing importance.

Once the fireground commander has appraised the situation, fire fighters and

equipment are deployed. Pumper, ladder, and other truck companies, as well as


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rescue squads, are assigned to different areas of the fire, usually in accordance

with the number and types of hose streams the fireground commander considers

necessary to control the fire and prevent its spread.

In accordance with standard procedure for first alarms, fire companies goimmediately to their assigned locations without waiting for specific orders.

Special plans cover contingencies such as a fire covering a large area, a large

building, or a particularly hazardous location. Usually on a first alarm one of the

pumpers attacks the fire as quickly as possible, using preconnected hose lines

supplied by the water tank in the truck, while larger hose lines are being attached

to the hydrants. Members of the ladder and rescue companies force their way into

the building, search for victims, ventilate the structurebreak windows or cut

holes in the roof to allow smoke and heat to escapeand perform salvageoperations. Ventilating the structure helps to advance the hose lines with greater

safety and ease, and also serves to safeguard persons who may still be trapped in

the building.

Temperatures within a burning building may exceed 815 C (1500 F). Brightly

burning fires principally generate heat, but smoldering fires also produce

combustible gases that need only additional oxygen to burn with explosive force.

The hazards to which fire fighters and occupants of a burning building are

exposed include the breathing of superheated air, toxic smoke and gases, and

oxygen-deficient air, as well as burns, injuries from jumping or falling, broken

glass, falling objects, or collapsing structures. Handling a hose is difficult even

before the line is charged with water under pressure. Nozzle reaction forces can

amount to several hundred pounds, requiring the efforts of several people to

direct a stream of water.

D1 Types of Nozzles

Various nozzles are capable of projecting solid, heavy streams of water, curtains

of spray, or fog. Fire trucks carry a selection of nozzles, which are used according

to the amount of heat that must be absorbed. Nozzles can apply water in the form

of streams, spray, or fog at rates of flow between 57 liters (15 gallons) to more

than 380 liters (more than 100 gallons)per minute. Straight streams of water have

greater reach and penetration, but fog absorbs heat more quickly because the

water droplets present a greater surface area and distribute the water more widely.

Fog nozzles may be used to disperse vapors from flammable liquids, although

foam is generally used to extinguish fires in flammable liquids.


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D2 Water Additives

A variety of chemicals may be added to water to improve its ability to extinguish

fires. Wetting agents added to water can reduce its surface tension. This makes

the water more penetrating and facilitates the formation of small drops necessaryfor rapid heat absorption. By adding foam-producing chemicals and liquids to

water, a fire-blanketing foam is produced. Foam is used to extinguish fires in

combustible liquids, such as oil, petroleum, and tar, and for fighting fires at

airports, refineries, and petroleum distribution facilities.

A chemical additive can expand the volume of foam 1000 times. This high-

expansion foam-water solution is useful in fighting fires in basements and other

difficult-to-reach areas because the fire can be smothered quickly with relatively

little water damage.

D3 Salvage

This term refers to the methods by which fire fighters protect merchandise,

household goods, and the interiors of buildings from smoke and water damage.

Objects are covered with waterproof covers, and water is removed by water

vacuums, mops, squeegees, water chutes, and portable pumps. Almost all fire

departments carry salvage equipment in their apparatus. Fire departments in somelarge cities maintain special salvage companies.

E Forest Fires

Forest fires, often called wildland fires, are spread by the transfer of heat, in this

case to grass, brush, shrubs, and trees. Because it is frequently difficult to

extinguish a forest fire by attacking it directly, the principal effort of forest fire

fighters is often directed toward controlling its spread by creating a gap, or

firebreak, across which fire cannot move. Firebreaks are made, and the fire crewsattempt to stop the fire by several methods: trenching, direct attack with hose

streams, aerial bombing, spraying of fire-retarding chemicals, and controlled

back-burning. As much as possible, advantage is taken of streams, open areas,

and other natural obstacles when establishing a firebreak. Wide firebreaks may be

dug with plows and bulldozers. The sides of the firebreaks are soaked with water

or chemicals to slow the combustion process. Some parts of the fire may be

allowed to burn themselves out. Fire-fighting crews must be alert to prevent

outbreaks of fire on the unburned side of the firebreaks.


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Fire-fighting crews are trained and organized to handle fires covering large areas.

They establish incident command posts, commissaries, and supply depots. Two-

way radios are used to control operations, and airplanes are employed to drop

supplies as well as chemicals. Helicopters serve as command posts and transport

fire fighters and their equipment to areas that cannot be reached quickly on the

ground. Some severe wildfires have required more than 10,000 fire fighters to be

engaged at the same time.

The U.S. Forest Service maintains research laboratories, which develop improved

fire-fighting equipment and techniques, and a school that trains fire fighters in the

latest fire-fighting techniques. International conferences on wildland fire

prevention and fire fighting have been held with greater frequency in recent

years.

IV PRIVATE FIRE PROTECTION

Commercial and industrial buildings usually have some sort of internal, or

private, fire-protection system installed.

A Sprinkler Systems

A sprinkler system is an integrated system of underground and overhead piping,

designed in accordance with fire protection engineering standards, and connected

to one or more automatic water supplies. The system is usually activated by heat

from a fire, and the sprinkler heads then discharge water over the fire area.

Sprinkler systems are nearly 100 percent effective. Many sprinkler systems are

supervised electrically from a central station, and alarms are transmitted to a fire

department whenever the sprinklers operate or when a valve in the sprinkler

system closes for any reason. If a fire-fighting unit arriving at a fire finds that the

sprinkler system is not receiving sufficient water and pressure, a pumper is

connected to the sprinkler system to supply additional water.

B Standpipe Systems

Many high-rise or other large buildings have an internal system of water mains

(standpipes) connected to fire-hose stations. Trained occupants or employees of

the building management operate the hoses until the fire department arrives. Fire

fighters can also connect their hoses to outlets near the fire.


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C Alarm Systems

Buildings may also be equipped with detection systems that will transmit an

alarm. Some detectors are designed to respond to smoke, and others to heat. In

many jurisdictions, detection systems are required in public buildings, apartmenthouses, and sometimes even in private homes.

Two major types of smoke detectors are available. One is an ionization device

that contains a small radioactive source for ionizing the air molecules between a

pair of electrodes, permitting a very small current to flow between the pair. If

smoke particles from a fire enter this space, they reduce the flow of current by

adhering to the ionized molecules. The drop in current sets off a buzzer or other

alarm. The second type of smoke detector uses a photoelectric cell. In some of

these detectors, smoke that enters obscures a steady beam of light; in others, the

smoke scatters a light ray from a diode so that the cell can detect it. In either case

the change sets off an alarm. The alarm may sound locally, or it may be designed

to alert a central station with notification to the fire department. Photoelectric

detectors are slower than ionization detectors, and sometimes both principles are

combined. Both types can be run by batteries or by building current.


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CIRCUIT DIADRAM

SPECIFICATIONS

1) ResistorR1 =1KER2=4.7KE

R3=1K

R4=47KE

VR1=100KE

2) Capacitors-C1,2-0.01uFC3100 uF/16v

3)IC1555

4)T1- BC548

5) Loud Speaker8 ohm

6)Diode- IN4148


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CIRCUIT DESCRIPTION

The circuit consists of one NE555 IC, resistors, capacitors,diode (thermistor) and loud speaker. The 555 has three

operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection,

bouncefree switches, touch switches, frequency divider,

capacitance measurement, pulse-width modulation (PWM)

etc Astable - free running mode: the 555 can operate as an

oscillator. Uses include LED and lamp flashers, pulse

generation, logic clocks, tone generation, security alarms,

pulse position modulation, etc.

Bistable mode or Schmitt trigger: the 555 can operate as aflip-flop, if the DIS pin is not connected and no capacitor is

used. Uses include bouncefree latched switches, etc. Diode control the speaker where diode is dependent on the

temperature.
http://en.wikipedia.org/wiki/Monostablehttp://en.wikipedia.org/wiki/Astablehttp://en.wikipedia.org/wiki/Oscillatorhttp://en.wikipedia.org/wiki/LEDhttp://en.wikipedia.org/wiki/Pulse_position_modulationhttp://en.wikipedia.org/wiki/Bistablehttp://en.wikipedia.org/wiki/Schmitt_triggerhttp://en.wikipedia.org/wiki/Flip-flop_%28electronics%29http://en.wikipedia.org/wiki/Flip-flop_%28electronics%29http://en.wikipedia.org/wiki/Schmitt_triggerhttp://en.wikipedia.org/wiki/Bistablehttp://en.wikipedia.org/wiki/Pulse_position_modulationhttp://en.wikipedia.org/wiki/LEDhttp://en.wikipedia.org/wiki/Oscillatorhttp://en.wikipedia.org/wiki/Astablehttp://en.wikipedia.org/wiki/Monostable


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WORKING OF FIRE ALARM

Many fire alarm circuits are presented here,but this time a new

circuit using a thermistor and a timer to do the trick. The circuit isas simple and straight forward so that , it can be easily

implemented.The thermistor offers a low resistance at high

temperature and high resistance at low temperature. This

phenomenon is employed here for sensing the fire.

The IC1 (NE555) is configured as a free running oscillator at audio

frequency. The transistors T1 drive IC1. The output(pin 3) of IC1

is couples to base of transistor T1which drives the speaker to

generate alarm sound. The frequency of NE555 depends on the

values of resistances R5 and R6 and capacitance C2.When

thermistor becomes hot, it gives a low-resistance path for the

positive voltage to the base of transistor T1 through diode D1 and

resistance R2. Capacitor C1 charges up to the positive supply

voltage and increases the the time for which the alarm is ON. The

larger the value of C1, the larger the positive bias applied to thebase of transistor T1 (BC548). As the collector of T1 is coupled to

the base of transistor , the transistor provides a positive voltage to

pin 4 (reset) of IC1 (NE555). Resistor R4 is selected s0 that NE555

keeps inactive in the absence of the positive voltage. Diode D1

stops discharging of capacitor C1 when the thermistor is in

connection with the positive supply voltage cools out and provides

a high resistance path. It also inhibits the forward biasing of

transistor T1.


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USESFire-alarm systems came into existence with the invention of the telegraph.

Today many communities are served either with the telegraph-alarm system or

with telephone call boxes. Most fires, however, are reported from private

telephones. Many large cities have removed all or many of their street alarm

boxes because of problems associated with maintenance and with false alarm

transmissions. Some boxes have been replaced with telephones. All alarms are

then transmitted to the fire stations. In large cities, alarms are received at a central

dispatch office and then transmitted to fire stations, frequently with the use of

mobile teleprinters and computers. Apparatus is dispatched according to the

nature of the alarm and location of the fire. Many modern departments are now

equipped with computer-aided dispatch systems that can track the status of all

units and provide vital information about the buildings where fires occur.

Typically, on a first alarm, more apparatus is sent to industrial sections, schools,

institutions, and theaters than to neighborhoods of one-family dwellings.

Additional personnel, volunteer or off duty, is called as needed. Fires that cannot

be brought under control by the apparatus responding to the first alarm are called

multiple-alarm fires, with each additional alarm bringing more fire fighters and

apparatus to the scene. Special calls are sent for specific types of equipment.

Mutual aid and regional mobilization plans are in effect among adjacent fire

departments for assisting each other in fighting fires.


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Hence after completion of layout sketch, etching, drilling and soldering of PCB,

our project look like as given below

Soldering side

Component side


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BIBLIOGRAPHY

1. www.circiutstoday.com2. www.wikipedia.com3.

www.google.com4. www.allaboutcircuits.com

5. Microsoft Encarta encyclopedia6. www.datasheetarchive.com7. R.P. Jain, Modern digital electronics8. www.hitachi.com9. National Geographic
http://www.circiutstoday.com/http://www.circiutstoday.com/http://www.wikipedia.com/http://www.wikipedia.com/http://www.google.com/http://www.google.com/http://www.allaboutcircuits.com/http://www.allaboutcircuits.com/http://www.datasheetarchive.com/http://www.datasheetarchive.com/http://www.hitachi.com/http://www.hitachi.com/http://www.hitachi.com/http://www.datasheetarchive.com/http://www.allaboutcircuits.com/http://www.google.com/http://www.wikipedia.com/http://www.circiutstoday.com/

Ehw Project

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