Multipurpose Absorbtion Rate Meter

8/9/2019 Multipurpose Absorbtion Rate Meter

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Multipurpose Absorption Rate MeterPROJECT 2009-2010

ABSTRACT

An ideal garment should remove excess liquid sweat & provide comfort to

the wearer. Fabrics with high liquid absorption and transport ability provide

substantial comfort. In textile and paper industries as well as related quality

testing laboratories, water absorbency tests are essentially performed. In the

conventional capillary travel method, to determine the absorption rate of a

material, sample strips of the material are suspended in the water, with a weight

tied at the bottom of each strip to keep the specimen straight . Then the rise of

water level in the strips, in ten-minute period, is recorded using a stopwatch.

Colored water can be used to clearly see the water rise in fabric strips.

The test is carried out under the standard atmospheric conditions of 270 C

temperatures and 65 % humidity. As the water rise in fabric strips is not easily

detectable by eyes, there is always the possibility of erroneous result while using

the capillary travel method. Fabrics have negligible electrical conductivity. Water,

being an excellent conductor of electricity, enhances the conductivity of fabric

after moisture absorption. The multipurpose absorption rate meter (MARM)described here works on electrical resistance principle to measure the absorption

rates of different types of fabrics (cotton, jute, wool, rayon, polyester, etc) &

towel samples. It can also make accurate measurements for yarns, writing &

computer papers, and 7 even commercial absorbents. The meter records the

vertical wicking height of the test sample, thereby automatically displaying its

absorption rate in seconds for 1cm wicking height.

Dept. of Electronics 1Don Bosco college,Mannuthy


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If one of the fibers absorbs moisture at a faster rate & activate start and stop

sensors. It doesnt require continuous monitoring.

Table of Contents

ABSTRACT............................................................................................................1

1.INTRODUCTION..................................................................................................3

2.DESIGN AND WORKING......................................................................................6

3.BLOCK DIAGRAM...............................................................................................8

3.1 OVERALL BLOCK DIAGRAM .......................................................................... 9

3.2 SECTIONAL BLOCK ..................................................................................... 11

4.BLOCK DIAGRAM ANALYSIS.............................................................................12

4.1 POWER SUPPLY SECTION ........................................................................... 13

4.2 WHEATSTONE BRIDGE ............................................................................... 14

1.1 COMMON EMITTER TRANSISTOR AMPLIFIER CONFIGURATION ...............15

1.2 OP-AMP POWER AMPLIFIER ...................................................................... 18

1.3 DIFFERENTIAL AMPLIFIER .......................................................................... 19

1.4 CLOCK GENERATOR ........................................................ 20

1.5 INVERTER .................................................................................................. 22

1.6 LATCH SECTION ......................................................................................... 24

1.7 DECODER, COUNTER AND DISPLAY ........................................................... 26

5.CIRCUITS.........................................................................................................27

6.CIRCUIT ANALYSIS...........................................................................................30

7.PCB LAYOUTS..................................................................................................33

7.1.1 DEVELOPING ....................................................................................... 35

7.1.2 ETCHING .............................................................................................. 36

7.1.3 STRIPPING ........................................................................................... 36

7.1.4 DRILLING ............................................................................................ 36

7.1.5 TIN-PLATING ........................................................................................ 36

7.1.6 SOULDERING ....................................................................................... 378.ADVANTAGES AND FUTURE EXPANSION..........................................................38



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9.APPLICATIONS.................................................................................................40

10.RESULT AND DISCUSSION.............................................................................42

11.CONCLUSION.................................................................................................44

12.COMPONENTS LIST........................................................................................47

13.REFERENCES.................................................................................................49

14.APPENDIX......................................................................................................50

1. INTRODUCTION



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The textile industry is becoming an increasingly competitive environment.

Differentiating products by quality is particularly important. Testing can be

performed both to improve product quality and achieve compliance to

international, regional or retailer specific standards. Fabric testing provides a

comprehensive review of the tests available for fabrics.

Multipurpose Absorption Rate Meter (MARM) has been designed and

developed for measuring the absorption rates of different fabrics and towel

samples. MARM, designed to measure absorbency by Capillary Travel Method,

works on electrical resistance principle. It records the vertical wicking height of

the test sample, thereby, displaying the absorption rate in seconds .Measurements

were made for 100% cotton, cotton/polyester and polyester/viscose blended

fabrics at 1, 2 and 3 cm heights. Results indicate that wicking slows down as

height increases. Absorption rates recorded for warp-wise and weft-wise strips

were found to be different. Fabric finishing, yarn count, thickness, crimp and

crease affect the wick ability. MARM can accurately make measurements for

yarns, writing and computer papers, and commercial absorbents.

Some important parameters related to fabric absorption are explained

below:

Absorption: The measure of amount of liquid (solvent) held in a fabric.

Extrinsic absorbency is stated in ml/m

2

, which represents the milliliters ofliquid held in a square meters of fabric. Intrinsic absorbency is stated in m

L/g, which represents the milliliters of liquid held in a gram of fabric .For

both intrinsic and extrinsic absorbency higher values indicates better

performance ;i.e. more liquid is held in the fabric. Typically, these tests are

performed with water.



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Absorption rate: The measure of how fast a quantity of liquid is absorbed

into a fabric. Extrinsic Rate is stated in L/m2/s, which represent how fast a

milliliter of liquid goes into a square meter of fabric. Intrinsic rate is stated

in L/g/s, which represents how fast a milliliter of liquid goes into a gram of

fabric. For both intrinsic and extrinsic rates higher values indicates better

performance.

Basis weight: The measure of the weight per unit area of a fabric.

Typically, basis weight is expressed as g/m2.Higher values indicate heavier

fabrics.



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2. DESIGN AND WORKING



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The circuit consists of two identical circuits, each comprising a resistive

Wheatstone bridge as shown in the figure. One of the arms of each of the

Wheatstone bridge is formed by a specific length of fibre under test, which is

connected to the circuit using needle like sensors. The sensor fabricated from

grade SS 304 stainless steel sense the conductivity of water and activates the

instrument.

The sensors are so mounted that these can be moved and fixed at any point

on a vertical stand with the help of a screw mechanism .The set distance on the

sensors can be read on the scale mounted on the stand. Orthophosphoric acid is

used to make solder joints between stainless steel sensors and conducting part of

the flexible feed wires.

MEASUREMENT

For making measurements one of the prepared sample strips is mounted on

the stand .Sensors A and B are fixed 1cm apart. Sensor C is fixed 2.5 cm away

from the lower end of the fabric strip. Now the lower end of the strip is dipped in

water .The instrument is switched on And its reset button is pressed to bring the

display to all zeros .The fabric strip starts wicking up water and soon as water

level reaches sensor B, LED 1 (start) glows to indicate the start counting When

water level reaches sensor A, LED 2 (stop) glows to indicate the completion of

counting. The number of one second pulses counted is displayed, which isequivalent to the time taken by the water to rise from point B to point A in fabric

strip .The four digit display thus shows the absorption rate of the fabric. The

display circuit shows the time taken for absorption per cm of the fabrics which

determines the quality of the fabric.



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3. BLOCK DIAGRAM



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3.1 OVERALL BLOCK DIAGRAM


RESET

START

LOGIC

STOP

LOGIC

TIME

GENERATO

R

COUNTER

USING

IC74C926

DISPLA

Y


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Block Diagram Description:

RESET: Used to reset the ARM (Absorption Rate Meter)

START LOGIC: Used to start the ARM. i.e. used to start the

counting.

STOP LOGIC: Used to stop the ARM. i.e. used to stop the

counting.

TIME GENERATOR: Used to generate Pulses of 0.1 Sec and/or

1Sec. for ARM

COUNTER: Used to count the pulses provided by Time Generator.

The pulses are counted between Start And Stop Signal

DISPLAY: Used to display the number of pulses counted by Arm in

terms of seconds


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3.2 SECTIONAL BLOCK


S

E

N

S

O

R

S

WHEATSTON

E BRIDGE

AMPLIFIE

RS

OP-AMP

AMPLIFIER

INVERTING

AND

SUMMING

AMPLIFIERS

CLOCK

GENERAT

OR

INVE

RTE

R

LATCHSECTIO

N

7

SEGME

NT

DECOD

ER

AND

COUNTE

R

DISPLA

Y

POWER SUPPLY

+ - 12 VOLT

POWER SUPPLY

5 VOLT


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4. BLOCK DIAGRAM ANALYSIS



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4.1 POWER SUPPLY SECTION

This low cost multipurpose power supply fulfills the requirements of almost all

laboratory experiments. A single transformer is used to build this power supply.

The dual +- 12v, 1A power supply is generated by regulators 7812 and 7912

.similarly dual +5V is generated by regulators 7805. Fixed power supply is used

for all digital, microprocessor and microcontroller experiments .Dual +-12V

power supply is used for op-amp based analogue circuit experiments. The basic

part of a power supply are rectifier, filter and regulator .The rectifier converts the

AC input voltage to pulsating DC voltage, and can be either half wave or fullwave rectifier, the one we use is the full wave rectifier which has the advantage

that it allows unidirectional current to the load during the entire cycle of the input

voltage and the result of the rectification is an output voltage with frequency twice

the input frequency that pulsated every half cycle of the input.

The second part of the power supply is the filter which eliminates the

fluctuations in the output of the full wave rectifier so as to produce a constant DC

voltage .The filter is simply a capacitor and it is chosen to be as large as possible

to minimize the voltage ripple in the output. The final part of the power supply is

the regulator and it is used to provide the desired constant DC output that is

basically independent of the input voltage.



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4.2 WHEATSTONE BRIDGE

The Wheatstone bridge is an arrangement of four resistances used for

measuring one of them in terms of the other three. It was first suggested by C.F

Wheatstone, a British physicist, in the 19th century The Wheatstone bridge being a

null method, is not affected by internal resistances, resistances of ammeters and

voltmeters .etc..It is the simplest example of an arrangement, variants of which are

used for a large number of electrical measurements .It can be made very accurate

with proper choice of standard and variable resistances.

Whetstones bridge can be used to measure any quantity which produces a

change in resistance. Strain gauges are device made from wire or metal foil. When

they are stretched their length increases, cross section area decreases and the

resistance increases. It is possible to measure quantities like force, pressure,

temperature, liquid level in a tank etc. The wheat stones bridge is used in

electronic arrangements in control devices in industry. If the resistance in the

fourth arm of the Whetstones bridge is replaced by an inductor then the bridge

can be used to measure wind speed. So here, in MARM, Whetstones bridge is

used to sense the small electrical resistance from the fabric piece and to amplify it

considerably.



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Wheatstones bridge

1.1 COMMON EMITTER TRANSISTOR AMPLIFIER

CONFIGURATION

A transistor raises the strength of a weak signal and thus acts as an amplifier.

The weak signal is applied between emitter base junction and output is taken

across the load connected in the collector circuit. Here the weak signal from the

whetstones bridge is fed to the common emitter circuit which increases the

overall strength of the signal. In this Multipurpose Absorption Rate Meter

(MARM), four stages of common emitter amplifier is used in order to

considerably increase the strength of the signal sensed by the sensors in the first

stage. Common-emitter amplifiers give the amplifier an inverted output and can

have a very high gain and can vary widely from one transistor to the next.

The gain is a strong function of both temperature and bias current, and so the

actual gain is somewhat unpredictable. Stability is another problem associated

with such high gain circuits due to any unintentional positive feedback that may

be present. Other problems associated with the circuit are the low input dynamic

range imposed by the small-signal limit; there is high distortion if this limit is

exceeded and the transistor ceases to behave like its small-signal model. One

common way of alleviating these issues is with the use of negative feedback,

which is usually implemented with emitter degeneration. Emitter degeneration

refers to the addition of a small resistor(or any impedance) between the emitter

and the common signal source (e.g., the ground reference or apower supply rail).This impedanceRE reduces the overall transconductanceGm =gm of the circuit by

a factor ofgmRE + 1, which makes the voltage gain

So, the voltage gain depends almost exclusively on the ratio of the resistors

RC /RE rather than the transistor's intrinsic and unpredictable characteristics. The

http://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/BIBO_stabilityhttp://en.wikipedia.org/wiki/Positive_feedbackhttp://en.wikipedia.org/wiki/Dynamic_rangehttp://en.wikipedia.org/wiki/Dynamic_rangehttp://en.wikipedia.org/wiki/Small-signal_modelhttp://en.wikipedia.org/wiki/Distortionhttp://en.wikipedia.org/wiki/Negative_feedbackhttp://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/Impedancehttp://en.wikipedia.org/wiki/Ground_(electricity)http://en.wikipedia.org/wiki/Power_supply_railhttp://en.wikipedia.org/wiki/Transconductancehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/BIBO_stabilityhttp://en.wikipedia.org/wiki/Positive_feedbackhttp://en.wikipedia.org/wiki/Dynamic_rangehttp://en.wikipedia.org/wiki/Dynamic_rangehttp://en.wikipedia.org/wiki/Small-signal_modelhttp://en.wikipedia.org/wiki/Distortionhttp://en.wikipedia.org/wiki/Negative_feedbackhttp://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/Impedancehttp://en.wikipedia.org/wiki/Ground_(electricity)http://en.wikipedia.org/wiki/Power_supply_railhttp://en.wikipedia.org/wiki/Transconductancehttp://en.wikipedia.org/wiki/Voltage


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sand stability characteristics of the circuit are thus improved at the expense of a

reduction in gain.



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Common emitter transistor amplifier



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1.2 OP-AMP POWER AMPLIFIER

After the weak signal absorbed from the sensors by the whetstones bridge is

amplified by the common emitter transistor amplifier stages, the signal is further

fed into an op-amp power amplification stage in order to further increase the

strength of the signal. For attaining high gain and power, voltage follower

configurations using op-amps are constructed. When the non inverting amplifier is

configured for unity gain, it is called a voltage follower because the output voltage

is equal to and in phase with the input .In other words .in the voltage follower the

output follows the input.

Although it is similar to discrete emitter follower, the voltage follower is

preferred because it has much high input resistance and the output amplitude is

exactly equal to the input.

Voltage follower



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1.3 DIFFERENTIAL AMPLIFIER

CIRCUIT

The differential amplifier has a unique feature that many circuits dont have

- two inputs. This circuit amplifies the difference between its input terminals.

Other circuits with one input actually have another input the ground potential.

But, in cases where a signal source (like a sensor) has both of its terminals biased

at several volts above ground, you need to amplify the difference between theterminals. What about noise that adds an unwanted voltage equally to both

terminals of a sensor? The differential amp rejects the noise and rescues the

signal. So MARM employs a differential amplifier circuit in its amplification

stage.

VOLTAGE GAIN

If you keep the following resistor ratios equal, R2/R1 = R4/R3, the voltage

gain looks like

What about signals common (or equal) at both inputs Vin+ and Vin-? The

equation above tells you the output Vo should be zero! This Common Mode



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Rejection (CMR) is useful but not perfect! It depends on the op amp device itself

and matching of the resistor values.

1.4 CLOCK GENERATOR

For this circuit, in order to generate the required clock pulse,the NE555 timer

in astable multivibrator configuration is used.

Pin configuration of 555 timer is shown below:

This circuit diagram shows how a 555 timer configured to function as an

astable multivibrator. An astable multivibrator is a timing circuit whose 'low' and

'high' states are both unstable. As such, the output of an astable multivibrator

toggles between 'low' and 'high' continuously, in effect generating a train of

pulses. This circuit is therefore also known as a 'pulse generator' circuit.



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In this circuit, capacitor C1 charges through R1 and R2, eventually building

up enough voltage to trigger an internal comparator to toggle the output flip-flop.

Once toggled, the flip-flop discharges C1 through R2 into pin 7, which is the

discharge pin. When C1's voltage becomes low enough, another internal

comparator is triggered to toggle the output flip-flop. This once again allows C1

to charge up through R1 and R2 and the cycle starts all over again.

C1's charge-up time t1 is given by: t1 = 0.693(R1+R2)C1. C1's discharge

time t2 is given by: t2 = 0.693(R2)C1. Thus, the total period of one cycle is t1+t2

= 0.693 C1(R1+2R2). The frequency f of the output wave is the reciprocal of this

period, and is therefore given by:f= 1.44/(C1(R1+2R2)), wherein f is in Hz if R1

and R2 are in megaohms and C1 is in microfarads.

In Multipurpose Absorption Rate Meter, an Astable Multivibrator

configuration is used to produce the clock pulses for the latch section.The output

pulse has a frequency of 1MHz and a time period of 1 sec.



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1.5 INVERTER

An inverter circuit outputs a voltage representing the opposite logic-level to its

input. Inverters can be constructed using a singleNMOS transistor or a single

PMOS transistor coupled with a resistor. Since this 'resistive-drain' approach uses

only a single type of transistor, it can be fabricated at low cost. However, because

current flows through the resistor in one of the two states, the resistive-drain

configuration is disadvantaged for power consumption and processing speed.

Alternately, inverters can be constructed using two complimentary transistors in aCMOS configuration. This configuration greatly reduces power consumption

since one of the transistors is always off in both logic states. Processing speed can

also be improved due to the relatively low resistance compared to the NMOS-only

or PMOS-only type devices. Inverters can also be constructed with Bipolar

Junction Transistors (BJT) in either aresistor-transistor logic (RTL) or a transistor-

transistor logic (TTL) configuration.

Digital electronics circuits operate at fixed voltage levels corresponding to a

logical 0 or 1 . An inverter circuit serves as the basic logic gate to swap between

those two voltage levels. Implementation determines the actual voltage, but

common levels include (0, +5V) for TTL circuits.

http://en.wikipedia.org/wiki/PMOShttp://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/CMOShttp://en.wikipedia.org/wiki/Bipolar_Junction_Transistorhttp://en.wikipedia.org/wiki/Bipolar_Junction_Transistorhttp://en.wikipedia.org/wiki/Resistor-transistor_logichttp://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/PMOShttp://en.wikipedia.org/wiki/Resistorhttp://en.wikipedia.org/wiki/CMOShttp://en.wikipedia.org/wiki/Bipolar_Junction_Transistorhttp://en.wikipedia.org/wiki/Bipolar_Junction_Transistorhttp://en.wikipedia.org/wiki/Resistor-transistor_logichttp://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/Digital


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This schematic diagram shows the arrangement of NOT gates within a

standard 4049 CMOS hex inverting buffer.

The digital inverter is considered the base building block for all digital

electronics. Memory (1 bit register) is built as a latch by feeding the output of two

serial inverters together. Multiplexers, decoders, state machines, and other

sophisticated digital devices all rely on the basic inverter.

The Hex Inverter is an integrated circuit that contains six inverters. For

example, the 7404 TTL chip which has 14 pins and the 4049 CMOS chip which

has 16 pins, 2 of which are used for power/referencing, and 12 of which are used

by the inputs and outputs of the six inverters (the 4049 has 2 pins with no

connection).

PERFORMANCE MEASUREMENT

Digital inverter quality is often measured using the Voltage Transfer Curve,

which is a plot of input vs. output voltage. From such a graph, device parameters

including noise tolerance, gain, and operating logic-levels can be obtained.

Ideally, the voltage transfer curve (VTC) appears as an inverted step-

function - this would indicate precise switching between on and off- but in real

devices, a gradual transition region exists. The VTC indicates that for low input

voltage, the circuit outputs high voltage; for high input, the output tapers off

towards 0 volts. The slope of this transition region is a measure of quality - steep

(close to -Infinity) slopes yield precise switching.

The tolerance to noise can be measured by comparing the minimum input

to the maximum output for each region of operation (on / off).

The output voltage, VOH, can be a measure of signal driving strength when

cascading many devices together.

http://en.wikipedia.org/wiki/Latch_(electronic)http://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logichttp://en.wikipedia.org/wiki/CMOShttp://en.wikipedia.org/wiki/Latch_(electronic)http://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logichttp://en.wikipedia.org/wiki/CMOS


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1.6 LATCH SECTION

In order for a logical circuit to "remember" and retain its logical state even

after the controlling input signal(s) have been removed, it is necessary for the

circuit to include some form of feedback. We might start with a pair of

inverters, each having its input connected to the other's output. The two

outputs will always have opposite logic levels.

The problem with this is that we don't have any additional inputs that we

can use to change the logic states if we want. We can solve this problem byreplacing the inverters with NAND or NOR gates, and using the extra input

lines to control the circuit.

The circuit shown below is a basic NAND latch. The inputs are generally

designated "S" and "R" for "Set" and "Reset" respectively. Because the

NAND inputs must normally be logic 1 to avoid affecting the latching action,

the inputs are considered to be inverted in this circuit.

The outputs of any single-bit latch or memory are traditionally designated

Q and Q'. In a commercial latch circuit, either or both of these may be

available for use by other circuits. In any case, the circuit itself is:

For the NAND latch circuit, both inputs should normally be at a logic

1 level. Changing an input to a logic 0 level will force that output to a

logic 1. The same logic 1 will also be applied to the second input of the

other NAND gate, allowing that output to fall to a logic 0 level. This in

turn feeds back to the second input of the original gate, forcing its output

to remain at logic 1.

Applying another logic 0 input to the same gate will have no further

effect on this circuit. However, applying a logic 0 to the othergate will

cause the same reaction in the other direction, thus changing the state of



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the latch circuit the other way.

Note that it is forbidden to have both inputs at a logic 0 level at the

same time. That state will force both outputs to a logic 1, overriding the

feedback latching action. In this condition, whichever input goes to logic

1 first will lose control, while the other input (still at logic 0) controls the

resulting state of the latch. If both inputs go to logic 1 simultaneously, the

result is a "race" condition, and the final state of the latch cannot be

determined ahead of time.

NAND gate latch



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1.7 DECODER, COUNTER AND DISPLAY

A decoder is a device which does the reverse of an encoder undoing the

encoding so that the original information can be retrieved. The same method used

to encode is usually just reversed in order to decode.

In digital electronics, a decoder can take the form of a multiple-input,

multiple-output logic circuit that converts coded inputs into coded outputs, where

the input and output codes are different. e.g. n-to-2n,binary coded decimal

encoders. Enable inputs must be on for the decoder to function, otherwise its

outputs assume a single "disabled" output code word. Decoding is necessary in

applications such as data multiplexing 7 segment display and memory address

decoding.

The example decoder circuit would be an AND gate because the output of anAND gate is "High" (1) only when all its inputs are "High." Such output is called

as "active High output". If instead of AND gate, the NAND gate is connected the

output will be "Low" (0) only when all its inputs are "High". Such output is called

as "active low output".

For multipurpose absorption rate meter , IC 74C926 is used as the counter and

display driver. The time taken for the fabric to absorb water / cm is sensed and is

fed to this circuit after several amplifying stages described earlier. The counter IC

decodes and counts the bits accordingly and displays the final result in time

through the multiplexed 7 segment circuits.



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5. CIRCUITS



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Amplifying section



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Display section



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6. CIRCUIT ANALYSIS



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The outputs of the two Whetstones bridges are amplified by high input

impedance transistorized differential amplifier stages built around transistor pairs

T1-T2 andT3-T4 .The output from the emitter of each transistor is buffered by op

amp buffers A1 and A2, and A5 and A6, before application to differential

amplifiers A3 and A7 .The outputs from op-amps A3 and A7n are further buffered

by op-amps A4 and A8, respectively, before application to the counter and display

circuit. Potentiometers VR1 through VR4 are used during calibration /adjustment.

These are so adjusted that when the common and start sensors are in contact

(through absorbed water), point P goes low, while point Q goes high .This cause

start LED1 to glow, while stop LED 2 goes off. Likewise, when all the three

sensors are in contact, point P should go low, while point P should go high. This

would cause stop LED2 to glow while causing LED 1 to go off. Thus the

adjustment of pot meters VR1 through VR4 can be done by looking at the LEDs

status.

When point P goes from high to low, the output of gate N5 goes high to

light up yellow start LED1.The differentiated output of gate N5 causes the

collector of transistor T5 and pin of NAND gate N1 to go low momentarily. This

cause the output at pin 3 of gate N1 to be latched high.(NAND gate N1and N2

constitute a NAND latch.)The latch output enables NAND gate N4 and takes LE

pin 5 of IC 6 (74c926) high. A high at pin 5 represents a flow through condition

for 74c926, while a low at pin 5 results in latching of the current count.

Now 1 Hz clock generated by timer NE 555 (configured as an Astable

multivibrator) is able to pass through gates N3 and N4 .The clock activity is

indicated by green LED 3.This lock is applied to pin12 of 74c926 and its

associated display keeps advancing with each clock pulse.



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When Q point goes from high to low state, stop LED2 (red) glows. At the

same time, the collector of the transistor T6 momentarily goes low to reset latch

pin 3 of NAND gate N3 low .This causes gate N4 to be inhibited, i.e. it stops

passing the clock. LE pin 5 of 74c926 also goes low to latch the current count.

Thus this count becomes stable in display D1S1-D4S4 to represent the time in

seconds taken by water level to travel 1cm from electrode B to electrode A

through capillary effect. A single side, actual-size PCB for the circuit and its

component layout is shown in the figures below.



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7. PCB LAYOUTS



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7.1. PCB MANUFACTURING PROCESS

There are many steps for fabricating a PCB:

1. Drawing a neat schematic of the circuit.

2. Designing the layout of that circuit.

3. Printing the layout on a copperclad or glass-epoxy sheet.

4. Etching.

5. Assembling the components.

6. Soldering.

The first step towards a PCB fabrication is drawing a neat schematic of the

circuit. This can be done either on paper or by any PCB design software. After

drawing the schematic layout should be designed. This can be also done manually

on paper or by using PCB design software. Here we have used easily applicable

graphical layout Editor (EAGLE) for our purpose. This layout is then drawn on a

copper-clad or glass-epoxy sheet either manually by using enamel paints or screen

printing the layout on it. Now the layout printed board undergoes a process called

etching.

The design of a printed circuit board (PCB) can be considered as the first

step in electronic circuit design as well as first major step in the production of

PCBs. It forms a distinct factor in electronic circuit performance and reliability.

The producibility of PCB and its assembly and serviceability also depends on thedesign. The entire factors finally get reflected in the price of the electronic

equipment of which PCBs take away approximately 20% of the cost.

Printed circuit boards (PCBs) are laminates. This means that they are made

from two or more sheets of materials stuck together; often copper and fiber glass.

Unwanted areas of the copper are etched away to form conductive lands or tracks

which replaced the wires carrying the electric currents in other forms of

construction. Some parts of the side with copper tracks are coated with solder



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resist (usually green colour) to prevent solder sticking to those areas where it is

not required. This avoids unwanted solder bridges between tracks. Soldering is

done by hand or by flow wave soldering where the PCB passes over a wave of

molten solder.

MAKING OF A PRINTED CIRCUIT BOARD (PCB)[DIAGRAMATIC

REPRESENTATION]

The connections on the PCB should be identical to the circuit diagram, but

while the circuit diagram is arranged to be readable, the PCB layout is arranged to

be functional, so there is any visible correlation between the circuit and the layout.

The design layout of the PCB is done on the computer using CAD. The layout is

printed out on a transparent A4 sheet called acetate, which is especially used for

this purpose. The print out mask of the image (on acetate) is put over the photo

resist side of the laminated board. Photo resist is positive working sensitive to UV

light with a developed image of blue / green tint .the copper clad laminate board

consist of a layer of copper ,covered over by a layer of green resin called photo

resist. The protective black plastic tape, that protects the copper laminate from

scratches, is removed to reveal green positive photo resist covering the copper.

7.1.1 DEVELOPING

A solution of liquid photo resist developer concentrate is mixed in a beaker

with one part developer to nine parts water, total 500mls and poured in to a basin

beeper will sound when the two minutes are up, the board is taken out of the UV

enclosure, and the acetate is not required anymore. The green photo-resist that

was exposed will appear as lighter color and the darker imprint of the PCB can be


Developi

ng Etching

Stripping

Drilling Tin-plati

ng

Solderin

g

Exposu

re


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seen when examined closely. The board is put into the solution and the liquid is

flowed over and back on the board. The lighter photo-resist will flow away

showing copper and the PCB layout will be revealed. it will be necessary to wash

the board under tap water and clean with tissue paper to ensure no traces of photo-

resist remain on the copper, otherwise etching would be difficult. A PCB marker

pen can be used to correct any errors such as Breaks in the track at this stage.

7.1.2 ETCHING

The PCB is put in the Ferric Chloride Hexa hydrate solution which is made

up of etchant granules dissolved in water, to away unwanted copper, forming the

track pattern. The bare copper PCB, with tracks and pads now finished, is cleaned.

7.1.3 STRIPPING

After etching the positive resist-9 (Photo-resist) be left on the copper to act

as protection. Solder is readily achieved through the resist. This green photo-resist

can be removed using a tube of photo-resist stripper, and the PCB washed clean

under tap water and dried using tissue paper.

7.1.4 DRILLING

After cutting the PCB to size around the perimeter using the guillotine,

drilling using a .9mm drill can now be performed in the workshop.

7.1.5 TIN-PLATING

This is done to provide a nice finish and to protect the copper from

oxidation; also soldering will appear neat. A solution made up of fine tin powder

mixed with water is poured into a basin. The copper is cleaned to shiny finished

be rubbing using a rubber supplied with the kit. The board is placed in the solution

for 10 minutes. The board should then have a silver finish.



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7.1.6 SOULDERING

The most important facture in building a system is soldering. clear the

component leads; wires etc with energy paper remove the rust and dust. Good

quality solders and resin flux should be used.

Solder intended for the electrical work is there for made in the form of

hollow wise, with core of flux chemical mixture that will dissolve the oxide film

at the soldering work. The heated bit of iron is applied to the surface to be joined

and a wise solder is applied to heated joint. The solder melts, allowing the flux to

remove all oxides. After soldering checks that the solder joint is around in

appearance and is shining.


PRECAUTIONS:

There is suitable socket for IC, The IC should plug into this socket only after

all the pin connections have been wired up correctly

Check the inquisitive voltages at the pins of the base and ensure that allconnections are wired before plugging the IC.

Always remove the IC from its socket when the pins are to be heated with a

soldering iron. Remember an IC is temperature sensitive and any excessive

heat on current damage the foil.


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8. ADVANTAGES AND FUTURE EXPANSION



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The Multipurpose ABSORPTION Rate meter offers many advantages to

the textile industry. By the quality testing method, the quality and purity of

materials can be ensured. Also duplication of fabrics can be controlled by this

means. This MARM is a low cost device which can effectively measure the

quality and performance of any material.This device is very easy to implementand can be used for a wide variety of fabric materials. The logic used for thisdevice is really simple.

This device has very scope in large textile environments. For industrial

purposes this devices can be implemented using Microcontrollers and advanced

techniques. For large bails of materials this can be effectively used. Automatic

testing devices can be implemented so as to detect any mix in the materials, when

dealing with large amount of materials.

Not only could the textile industry implement this technique, it can be used

in the medical fields and also in investigation purposes.

Mulitipourpose ABSORPTION Rate Meter Model



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9. APPLICATIONS



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It can be used to measure the absorption rate of liquid in textile and paper

Industries as well as related quality testing laboratories, water absorbency

tests.

The Absorption Rate Meter may be used to measure the absorption rate of

different types of fabrics like cotton, jute, wool, rayon, polyester etchant

towel samples.

It may also used to make accurate measurement for yarns, writing and

computer papers and even commercial absorbent.

Mulitipourpose ABSORPTION Rate Meter can be used as fabric filter leak

detection systems.

Its use may also be in fabric absorbency detection for dyeing purpose.



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Mulitipourpose ABSORPTION Rate Meter can be to measure the quality

of liquid bandages in medical field.

10. RESULT AND DISCUSSION



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Multipurpose Absorption Rate Meter (MARM) has been designed and

developed for measuring the absorption rates of different fabrics and towel

samples. MARM, designed to measure absorbency by Capillary Travel Method,

works on electrical resistance principle. It records the vertical wicking height of

the test sample, thereby, displaying the absorption rate in seconds.

In our project, we successfully designed and constructed a multipurposeabsorption rate meter to detect the quality of fabrics. The wicking of water and the

absorption rate was accurately sensed by the sensors and after different amplifying

stages the time taken / cm to absorb was detected by the system. The Amplifying

stages consisting of transistor amplifiers and op amp amplifiers played an

important role. The reset, start and stop logic was correctly conducted according

to the bit modes in the latch section.

The decoder and seven segment driver IC 74c926 may be called as the heart of

the circuit. The apparatus was tested for different types of fabrics and the

variations in absorbency rates were correctly detected.



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11. CONCLUSION



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One of the fast developing field of todays world is the material industry.

Fabrics of different types artificial and natural -are now in the role. But the

most important strategy given to rate a fabrics quality is its absorbency rate.

Fabrics with high liquid absorption and transport ability provide substantial

comfort. In textile and paper industries, as well as related quality testing

laboratories water absorbency tests are essentially performed. The importance

of a fabric absorption rate detector is, therefore, now observed.

The following conclusions can be drawn from this project:

Water is initially absorbed very quickly by terry fabrics. Depending on the

yarn type, around 26-40% of the total water absorption capacity is absorbed

in the first 10 seconds. The percentage of water absorption reaches up to

50% to 65% in the first 30 seconds. After 30 seconds, water absorption

continues at a decreasing speed. In the final 100 seconds, only 8-10% of

water is absorbed. Water absorption continues even after 300 seconds but at

a very low rate, which cannot be considered from the practical viewpoint.

Such a water absorption characteristic of terry fabrics matches the

logarithmic curves very well.

Warp density, weft density and pile height have only a small effect on the

percentage of the water absorption speed of fabrics, which is not worth

considering when designing them.

There are different methods of measuring dynamic water absorption. The results

obtained in this paper may not be useful for certain specific applications.

Therefore, conducting experiments using different methods will give a much

better understanding of the dynamic water absorption properties of fabrics.



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Warp density, weft density and pile height have only a small effect on the

percentage of the water absorption speed of terry fabrics, which is not worth

considering when designing them.



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12. COMPONENTS LIS T

TL 084 QUAD JFET INPUT QUAD Op amps _ (2)

NE 555 timer _(1)

CD4093 quad 2 input NAND gate Schmitt _(1)

7404 Hex inverter _(1)

IC 74C926 4 digit counter and 7 segment display driver _ (1)

BEL 188 pnp transistor _(4)

BC547 npn transistor _ (5)

5.1v,0.5 W zener diode _(2)

Yellow Red and Green LED (3)

RESISTORS (all watt ,+or ve 5% carbon unless stated otherwise)

1 M.,5 watt..(2)

220 k,.5 w (2)

10k (6)

2.2 k (2)

47 (4)

1k (2)

330 (2) 8.2k (1)

22k(1)

100 (1)

56k (3)

3.3k (3)

220 (7)

1 M potmeter (2)



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10k preset (2)

1 M preset (1)

50 k preset (1)

CAPACITANCE

10nf ceramic disc (2)

10 f, 16 v electrolytic (1)

.1f ,ceramic disc(1)

22 nf,ceramic disc (1)

Miscellaneous

Push to on switch (1)

Sensor stainless steel needle like electrode (3)



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13. REFERENCES

Text books:

Op Amps and linear integrated circuits _ Ramakant A. Gayakwad

Principles of electronics _V.K Mehta,Rohit Mehta

ISC Physics _ P.Vivekanandan, D.K Banrrjee

Electronics For You Magazine Vol 23

Chatterjee P.K., Absorbency, Elsevier Science B.V., Netherlands, 1985

Websites:

saitronics.org/saitronics/pdf/ABSORPTIONRateMeter.pdf

www.efymagonline.com/welcome.asp?id=007&m=7&y=2002

www.thermo.com/com/cda/.../0,10255,775,00.html

www.unitekproject.com/proj_power.html

http://www.efymagonline.com/welcome.asp?id=007&m=7&y=2002http://www.thermo.com/com/cda/.../0,10255,775,00.htmlhttp://www.unitekproject.com/proj_power.htmlhttp://www.efymagonline.com/welcome.asp?id=007&m=7&y=2002http://www.thermo.com/com/cda/.../0,10255,775,00.htmlhttp://www.unitekproject.com/proj_power.html


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14. APPENDIX

Multipurpose Absorbtion Rate Meter

Documents

Transcript of Multipurpose Absorbtion Rate Meter