chapter 4 poject analysis and findings

8/7/2019 Chapter 4 Poject Analysis and Findings

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CHAPTER 4

POJECT ANALYSIS AND FINDINGS

4.0 INTRODUCTIONIn this chapter, we will describe in detail the results and findings of the

project by way of critical analysis to present results from project that have been

made.

4.1 READING AND UNDERSTANDING THE SCHEMATIC CIRCUIT

To begin the project, our research should be made to the schematic circuit

to ensures that the circuit used are appropriate to the project which will be created.

This research is necessary for the project to ensure that there will be no problem

on the circuit and can operate as it is planned


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4.2 PURCHASING OF PROJECT COMPONENTS

In buying the components, it has to be refer to the schematic circuit, so

that there will no wasteful spending. After that, we need to list down all of the

components that we wanted to buy so that there will be no mistakes upon

purchasing them.

4.3 ETCHING PRINTED CIRCUIT BOARD

1. Choose your etching acid. Ferric chloride is a common choice for an etchant.However, you can use Ammonium Persulfate crystals or other chemical

solutions. No matter what choice for the chemical etchant, it will always be a

dangerous material, so besides following the general safety precautions

mentioned in this article, you should also read and follow any additional

safety instructions that come with the etchant.

2. Draw the PCB layout. For acid etching, you need to draw the circuitryusing an etchant resistant material. Special markers can be found easily for

this specific purpose if you intend to do the drawing by hand (not

appropriate for medium to large circuits). Laser printers' ink is the most

commonly used material however. The steps to use laser printers for

drawing the circuit layout is as follows:

3. Print the PCB layout on a glossy paper. You should ensure the circuit ismirrored before doing that (most PCB layouting programs have this as an

option when printing). This only works using a laser printer.

4. Put the glossy side, with the printing on it, facing the copper.

5. Iron the paper using an ordinary clothes iron. The amount of time thiswill take depends on the type of paper and ink used.


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6. Immerse the board and paper in hot water for a few minutes (up to 10minutes).

7. Remove the paper. If certain areas seem particularly difficult to peel off,you can try soaking a bit more. If everything went well, you will have a

copper board with your PCB pads and signal lines traced out in black

toner.

8. Prepare the acid etchant. Depending on the etchant you choose, there mightbe additional instructions. For example, some crystallized acids require

being dissolved in hot water, other etchants are ready to use.

9. Submerge the board in the acid.

10.Make sure to stir every 3-5 minutes.

11.Take the board out and wash it when all unnecessary copper is eaten awayfrom the board.

12.Remove the insulating drawing material used. There are special solventsavailable for almost all types of insulating drawing material used in

drawing PCB layouts. However, if you don't have access to any of these

materials, you can always use a sand paper (a fine one).


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4.4 SOLDERING PROCEDURE

4.4.0 Overview

Soldering is accomplished by quickly heating the metal parts to be joined,

and then applying a flux and a solder to the mating surfaces. The finished solder

joint metallurgically bonds the parts - forming an excellent electrical connection

between wires and a strong mechanical joint between the metal parts. Heat is

supplied with a soldering iron or other means. The flux is a chemical cleaner

which prepares the hot surfaces for the molten solder. The solder is a low melting

point alloy of non ferrous metals.

4.4.1 Solder and Flux

Solder is a metal or metallic alloy used, when melted, to join metallic

surfaces together. The most common alloy is some combination of tin and lead.

Certain tin-lead alloys have a lower melting point than the parent metals by

themselves. The most common alloys used for electronics work are 60/40 and

63/37. The chart below shows the differences in melting points of some common

solder alloys.

Tin/Lead Melting Point

40/60 460 degrees F (230 degrees C)






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Most soldering jobs can be done with fluxcored solder (solder wire with

the flux in a "core") when the surfaces to be joined are already clean or can be

cleaned of rust, dirt and grease. Flux can also be applied by other means. Flux

only cleans oxides off the surfaces to be soldered. It does not remove dirt, soot,

oils, silicone, etc.

4.4.2 Base Material

The base material in a solder connection consists of the component lead

and the plated circuit traces on the printed circuit board. The mass, composition,

and cleanliness of the base material all determine the ability of the solder to flow

and adhere properly (wet) and provide a reliable connection.

If the base material has surface contamination, this action prevents the

solder from wetting along the surface of the lead or board material. Component

leads are usually protected by a surface finish. The surface finishes can vary

from plated tin to a solder - dipped coating. Plating does not provide the same

protection that solder coating does because of the porosity of the plated finish.

4.4.3 The Correct Way to Solder

1. The selected temperature is too high. Thetin coating is burnt off rapidly and

oxidation occurs.

2. Oxidation may occur because of wrongor imperfect cleaning of the tip. E.G.:

when other material is used for tip

cleaning instead of the original damp

Weller sponge.


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3. Use of impure solder or solder with flux interruptions in the flux core.

4. Insufficient tinning when working with high temperatures over 665 degrees F(350 degrees C) and after work interruptions of more than one hour.

5. A "dry" tip, i.e. If the tip is allowed to sit without a thin coating of solderoxidation occurs rapidly.

6. Use of fluxed that are highly corrosive and cause rapid oxidation of the tip(e.g. water soluble flux).

7. Use of mild flux that does not remove normal oxides off the tip (e.g. no-cleanflux).

4.4.4 The Soldering Iron Tip

The soldering iron tip transfers thermal energy from the heater to the

solder connection. In most soldering iron tips, the base metal is copper or some

copper alloy because of its excellent thermal conductivity. A tip's conductivity

determines how fast thermal energy can be sent from the heater to the

connection.

Both geometric shape and size (mass) of the soldering iron tip affect the

tip's performance. The tip's characteristics and the heating capability of the heater

determines the efficiency of the soldering system. The length and size of the tip

determines heat flow capability while the actual shape establishes how well heat

is transferred from the tip to the connection.


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There are various plating processes used in making soldering iron tips.

These plating operations increase the life of the tip. The figure below illustrates

the two types of plating techniques used for soldering iron tips. One techniqueuses a nickel plate over the copper. Then an iron electroplate goes over the

nickel. The iron and the nickel create a barrier between the copper base material

and tin used in the solder alloy.

The barrier material prevents the copper and tin from mixing together.

Nickel-chrome plating on the rear of the tip prevents solder from adhering to the

back portion of the tip (which could cause difficulty in tip removal) and provides

a controlled wetted area on the iron tip. Another plating technique is similar but

omits the nickel electroless plating, leaving the iron to act as the barrier metal.


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4.4.5 What is a WellerTip - How Does It Work?

A Weller tip is made of a copper corewhich is electro-plated with iron to

extend the life of the tip. The non-working end of the tip is plated with nickel for

protection against corrosion and then chrome plated to prevent the solder from

adhering except where desired. The wettable part is tin covered.

The task of the tip is to store the heat which is produced by the heating

element and to conduct a maximum amount of this heat to the working surface of

the tip.

For fast and optimal heat transfer to the solder joint the tip mass should

be as large as possible. When choosing a soldering tip always select the largest

possible diameter and shortest reach. Use fine-point long reach tips only where

access to the work piece is difficult.

4.4.6 How to Care For Your Tip

Because of the electro-plating Weller tips should never be filed or

ground. Weller offers a large range of tips and there should be no need for

individual shaping by the operator. If there is a need for a specific tip shape

which is not in our standard range we can usually provide this on a special order

basis.

Although Weller tips have a standard pretinnng (solder coating) and are

ready for use, we recommend you pretin the tip with fresh solder when heating it

up the first time. Any oxide covering will then disappear. Tip life is prolonged

when mildly activated rosin fluxes are selected rather than water soluble or no-

clean chemistries.


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When soldering with temperatures over 665 degrees F (350 degrees C)

and after long work pauses (more than 1 hour) the tip should be cleaned and

tinned often, otherwise the solder on the tip could oxidize causing Unwettability

of the tip. To clean the tip use the original synthetic wet sponges from Weller (no

rags or cloths).

When doing rework, special care should be taken for good pretinnng.

Usually there are only small amounts of solder used and the tip has to be cleaned

often. The tin coating on the tip could disappear rapidly and the tip may become

unwettable. To avoid this the tip should be retinned frequently.

Rajah 4.4.6 soldering process


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4.4.7 Soldering Tips

1. Keep working surfaces tinned, wipe only before using, and retinimmediately. Care should be taken when using small diameter solder to

assure that there is enough tin coverage on the tip working surface.

2. If using highly activated rosin fluxes or acid type fluxes, tip life will bereduced. Using iron plated tips will increase service life.

3. If tips become unwettable, alternate applying flux and wiping to clean thesurface. Smaller diameter solders may not contain enough flux to adequately

clean the tips. In this case, larger diameter solder or liquid fluxes may be

needed for cleaning. Periodically remove the tip from your tool and clean

with a suitable cleaner for the flux being used. The frequency of cleaning will

depend on the frequency and type of usage.

4. Filing tips will remove the protective plating and reduce tip life. If heavycleaning is required, use a Weller WPB1 Polishing Bar available from your

distributor.

5. Do not remove excess solder from a heated tip before turning off the iron.The excess solder will prevent oxidation of the wettable surface when the tip

is reheated.

6. Anti-seize compounds should be avoided (except when using threaded tips)since they may affect the function of the iron. If seizing occurs, try removing

the tip while the tool is heated. If this fails, it may be necessary to return the

tool to Weller for service. Removing the tip from the tool on a regular basis

will also help in preventing the tip from seizing.


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7. We recommend using distilled water when wetting the cleaning sponge. Themineral content in most tap water may contaminate your soldering tips.

8. Storing tips after production use:-- Clean hot tip thoroughly with damp sponge.

-- Apply coating of solder to tip.

-- Turn unit off to allow tip to cool.

-- Put tip away in proper storage or in iron holder


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4.5 TESTING PROJECT

The result of a project should be tested to make sure that it is working. The

test can be done using the multi meter to chec every each connection of the

components. After checked and sure that all connection is connected, the text test

can be done which is connect the circuit to the power supply iether transformer,

adapter or 9V battery. This is to find any unoticed mistakes on the circuit and it is

also important to make sure that every connection is working and to avoid the

componets damage when the connection is wrong.

After that, the circuit can be tested with the components on. There will

only be 2 result ither the circuit is functioning caused by the short circuit. If the

circuit is not working, every each components need to be check weather the

component itself is damaged or it is because the other component.

4.6 CUTTING THE COMPONENTS LEG

After sure that there is no more mistakes on the circuit, the last process

can be done which is to cut-off the extra feet of the components. This process is

to make sure the completed circuit look tidy and can easily placed in the casing.


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4.7 PROGRAMMING CODES

// Pin definitions

const int knockSensor = 0; // Piezo sensor on pin 0.

const int programSwitch = 2; // If this is high we program a new code.

const int lockMotor = 3; // Gear motor used to turn the lock.

const int redLED = 4; // Status LED

const int greenLED = 5; // Status LED

// Tuning constants.

const int threshold = 3; // Minimum signal from the piezo to register as a

knock

const int rejectValue = 25; // If an individual knock is off by this percentage of a

knock we don't unlock..

const int averageRejectValue = 15;// If the average timing of the knocks is off

by this percent we don't unlock.

const int knockFadeTime = 150; // milliseconds we allow a knock to fade

before we listen for another one. (Debounce timer.)

const int lockTurnTime = 650; // milliseconds that we run the motor to get it

to go a half turn.

const int maximumKnocks = 20; // Maximum number of knocks to listen for.

const int knockComplete = 1200; // Longest time to wait for a knock before

we assume that it's finished.

// Variables.

int secretCode[maximumKnocks] = {50, 25, 25, 50, 100, 50, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0}; // Initial setup: "Shave and a Hair Cut, two bits."

int knockReadings[maximumKnocks]; // When someone knocks this array fills

with delays between knocks.


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int knockSensorValue = 0; // Last reading of the knock sensor.

int programButtonPressed = false; // Flag so we remember the programming

button setting at the end of the cycle.

void setup() {

pinMode(lockMotor, OUTPUT);

pinMode(redLED, OUTPUT);

pinMode(greenLED, OUTPUT);

pinMode(programSwitch, INPUT);

Serial.begin(9600); // Uncomment the Serial.bla lines for

debugging.

Serial.println("Program start."); // but feel free to comment them out

after it's working right.

digitalWrite(greenLED, HIGH); // Green LED on, everything is go.

}

void loop() {

// Listen for any knock at all.

knockSensorValue = analogRead(knockSensor);

if (digitalRead(programSwitch)==HIGH){ // is the program button pressed?

programButtonPressed = true; // Yes, so lets save that state

digitalWrite(redLED, HIGH); // and turn on the red light too so we

know we're programming.

} else {

programButtonPressed = false;

digitalWrite(redLED, LOW);

}


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if (knockSensorValue >=threshold){

listenToSecretKnock();

}

}

// Records the timing of knocks.

void listenToSecretKnock(){

Serial.println("knock starting");

int i = 0;

// First lets reset the listening array.

for (i=0;i


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do {

//listen for the next knock or wait for it to timeout.

knockSensorValue = analogRead(knockSensor);

if (knockSensorValue >=threshold){ //got another knock...

//record the delay time.

Serial.println("knock.");

now=millis();

knockReadings[currentKnockNumber] = now-startTime;

currentKnockNumber ++; //increment the counter

startTime=now;

// and reset our timer for the next knock

digitalWrite(greenLED, LOW);

if (programButtonPressed==true){

digitalWrite(redLED, LOW); // and the red one too if we're

programming a new knock.

}

delay(knockFadeTime); // again, a little delay to let the

knock decay.

digitalWrite(greenLED, HIGH);


digitalWrite(redLED, HIGH);

}

}

now=millis();

//did we timeout or run out of knocks?

} while ((now-startTime < knockComplete) && (currentKnockNumber 0){ //todo: precalculate this.

secretKnockCount++;

}

if (knockReadings[i] > maxKnockInterval){ // collect normalization data

while we're looping.

maxKnockInterval = knockReadings[i];

}

}

// If we're recording a new knock, save the info and get out of here.


for (i=0;i


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delay(1000);



delay(50);

for (i = 0; i < maximumKnocks ; i++){

digitalWrite(greenLED, LOW);

digitalWrite(redLED, LOW);

// only turn it on if there's a delay

if (secretCode[i] > 0){

delay( map(secretCode[i],0, 100, 0, maxKnockInterval));// Expand the

time back out to what it was. Roughly.



}

delay(50);

}

return false; // We don't unlock the door when we are recording a new

knock.

}

if (currentKnockCount != secretKnockCount){

return false;

}

int totaltimeDifferences=0;

int timeDiff=0;

for (i=0;i rejectValue){ // Individual value too far out of whack

return false;


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4.9.1 RESEARCH COSTS

After doing the calculations for the total cost of research, the research

found that the cost is very minimal because we only use methods that do not

require a cost. It is through the everyday problems of consumers and through

searches on the Internet.

4.9.2 EQUIPMENT COSTS

The equipment needed is equipment related to projects where all the

equipment is prepared by our self and some of them are purchased from suppliers

who sell related equipment. The cost of equipment and components involved are:

1. Solder2. Arduino3. LED4. Resistor5. Diode6. Transistor7. Gear8. Pizeo Speaker9. Push Button10.Acid11.Marker

4.9.3 OVERHEAD

Overhead costs are the other costs associated in the course of the

project. Among the costs involved are electricity and the materials used in the

construction of the prototype unlocking device.

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