work station work

7/31/2019 Work Station Work

1/26

ABSTRACT

The field of electrical engineering cannot do without the soldering process. The digital

soldering workstation is a protion or piece of equipment in a given workshop that is

provided for use during any soldering operation in the laboratory and it is assigned

specially for soldering operation. The system consists of the soldering iron control system

that controlss the heating temperature of the temperature. When the system is put on, the

soldering iron gets heated the sensor ( heat sensor) monitors the temperature of the heater,

when the temperature gets within a certain preset treshold set on the system, the heating of

the heater is cut of by a relay provided inside the device. The device also provides an lcd

display that gives the alphanumeric value of the temperature of the heater. And also

displays the status of the system. The project consists of the LM35 temperature sensor

which is used to monitor the temperature of the soldering iron used in the work station.

The signal from the sensor is then passed to the ADC0804 that converts the signal int a

digital signal the digital signal is then passed to the MCU that now prforms the nessesary

calculations required for the operation of the project. The project finds a number of

apllications expecially in the workshops.

1


2/26

1.0 INTRODUCTION

A work station is a person's work area, including furniture, appliances, tools etc. where a

specific type of activity is carried out in the work area by one person at a time. It is a high

end mapped out section of a working area and includes everything that makes up such aplace. In computer systems, the workstation is a high-end microcomputer designed for

specific technical or scientific applications. Intended primarily to be used by one person at

a time, they are commonly connected to a local area network and run multi-user operating

systems. The term workstation has also been used to refer to a mainframe computer

terminal or a PC connected to a network.

The term soldering work station refers to a giving area in a work shop or any place were a

complete setup is established with all the materials required for soldering operation is putin place for soldering of electrical and electronics components during an electrical or

electronics maintenance or construction. Soldering is a process in which two or more metal

items are joined together by melting and flowing a filler metal (solder) into the joint, the

filler metal having a lower melting point than the work piece. Soldering differs from

welding in that soldering does not involve melting the work pieces. In brazing, the filler

metal melts at a higher temperature, but the work piece metal does not melt. Formerly

nearly all solders contained lead, but environmental concerns have increasingly dictated

use of lead-free alloys for electronics and plumbing purposes.. The soldering is a term that

is used to describe the joining together of two nor more metals at a junction with the use of

an alloy usually with a lower melting point in order to make up an electrical circuit or

putting together of one or more electrical components. It is used during maintenance to

maintain a continuous flow of electric current in an electrical circuit. The soldering work

station encompasses one or more devices and components put together to make up the

work station. These components includes

The Soldering Iron

The soldering iron is a thin handheld tool about 10 inches long or more. An electrical cable

connects it to the power supply. A heating element inside the soldering iron gets the metal2


3/26

barrel and tip hot. The iron has a plastic handle and soft grip to keep your fingers cool and

comfortable. The soldering iron is used to melt the lead alloy that is used for the soldering.

The soldering Stand

The soldering stand is usually a metal stand attached to the workstation provides a safe

place to park the hot iron when you're not soldering. A metal cage encloses the iron and

safely dissipates heat, preventing burns if touched.

The soldering Sponge

The soldering iron workstation has a holder for a small rectangular sponge. The soldering

iron operator uses the sponge to clean burnt rosin and oxides from the iron's tip.

Temperature control unit

The soldering work station usually requires a temperature regulation system that is used to

regulate the temperature of the heating element. This prevents overheating parts and speeds

the soldering of larger connections. In many cases, you can adjust the temperature from a

control on the power supply.

Power

Soldering irons for electronics fall in a power range of 5 to 30 watts. Some power supplies

let you control the power going to the iron. Less power is better for delicate work. More

power lets you solder components like power transistors and heavier-gauge wire.

The soldering work station that is implemented in this project is designed around the 8051

microcontroller which is the heart of the system. A temperature sensor LM35 is also

provided in the project whose sole function is to take the analog reading of the temperature

of the soldering iron. The ADC is interfaced with the microcontroller whose main function

is to convert the analog signal that is read from the LM35 temperature sensor into a digital

form. The ADC also converts the digital signal into an 8-bit digital data that is read by the

MCU (microcontroller unit) of the project. The project also provides an LCD (liquid crystal

3


4/26

display) display that is used to provide a digital read out of the alphanumeric value of the

temperature of the soldering iron in the work station. The project also provides an interface

of relays that are used to provide the control of the various accessories of the work station.

In the project, the relays acts as switches that put on the appliance whenever the MCU

requests that.

The operation is initiated upon the switching of the power supply into the system. As soon

as the power supply is turn on, the LM 35 temperature sensor reads the temperature of the

soldering iron and continuously sends the analog signal value of the temperature to the

ADC which in turn converts the analog signal into an 8-bit digital equivalent of the

temperature. This signal is then passed on to the MCU which interprets the signal and

sends the alphanumeric value of the temperature for the LCD to display. When the controlbuttons is pressed, the MCU records the value of the temperature that is selected and

ensures that the operating temperature of the soldering iron stays within that range. The

control of the heating of the soldering iron is done by a relay that is designed to trip off the

soldering iron when the temperature tries to go outside the operation range. The operation

of the appliances that make up the work station is simply carried out by pressing a button

that controls the required appliance and the MCU triggers the relay on thereby putting the

appliance on or off as the case may be.

1.1 BACKGROUND OF THE STUDY

Soldering, the art of connecting individual objects, is an age-old procedure. However, latest

innovations stress more on the use of eco-friendly materials besides the use of the best

physical and chemical components, especially that of the fluxes, for better results and

greater compatibility. In a quest to find more eco-friendly materials, research organizations

worldwide laid emphasis on the elimination of ozone-depleting chemicals and started

experimenting with a variety of new combinations with potential materials and alternative

processes. In the process, researchers tumbled upon a more reliable form of soldering,

better than the established conventional soldering process. The traditional process involved

the use of rosin flux. The landmark discovery in the field of soldering was the use of no-

clean flux for the soldering process. The main advantage being that it does away with the

4


5/26

laborious post-solder, which requires the use of CFCs or costly solvents for cleaning. This

process has helped in saving time and energy, compared to the age-old practice when

soldering was done manually. The introduction of the soldering work station also ensured

that cold joints and other forms of abnormal soldering is averted in a given soldering

operation.

1.2 AIMS AND OBJECTIVES

The main aim of embarking on the design and implementation of the soldering work station

in this project is to establish a platform with which soldering operation can be conveniently

conducted in any electrical establishment. The project is also embanked on with the

following objectives.

To investigate the issues soldering operations in the engineering field of study.

To combine the advantages offered by all types of soldering work stations that

exists in the implementation of a more reliable and efficient system.

To examine the best possible method of implementation of a digital work station

that provides all the necessary requirements that is required for easy soldering.

To design and implement an improved soldering work station that will give a

digital display of the status of the temperature of the soldering iron during thesoldering.

1.3 PROBLEM STATEMENT

Various problems may arise in the soldering process which lead to joints which are non

functional either immediately or after a period of use. This is because of abnormal

temperatures that are used for soldering in many cases of soldering operation. The most

common defect when hand-soldering results from the parts being joined not exceeding thesolder's liquids temperature, resulting in a "cold solder" joint. This is usually the result of

the soldering iron being used to heat the solder directly, rather than the parts themselves.

Properly done, the iron heats the parts to be connected, which in turn melt the solder,

guaranteeing adequate heat in the joined parts for thorough wetting. In electronic hand

5


6/26

soldering solders, the flux is embedded in the solder. Therefore heating the solder first may

cause the flux to evaporate before it cleans the surfaces being soldered. A cold-soldered

joint may not conduct at all, or may conduct only intermittently. Cold-soldered joints also

happen in mass production, and are a common cause of equipment which passes testing,

but malfunctions after sometimes years of operation. A "dry joint" occurs when the cooling

solder is moved, and often occurs because the joint moves when the soldering iron is

removed from the joint.

The use of the digital soldering work station that is presented in this thesis solves the

problems of temperature regulation that usually leads to abnormal soldering by providing

an automated way of temperature control during soldering.

1.4 SIGNIFICANCE OF THE STUDY

The digital soldering work station offers a wide range of advantages and applications in

electrical and electronics engineering discipline and the entire engineering at alarge. It

provides a platform where the user can automatically regulate the temperature at which he

performs a soldering operation and also provides a digital read out of the value of the

operating temperature of the soldering iron. The work station also allows the control of all

the tools and equipment that make up the work station set up such as control of the

soldering lights, the control of the sucker or the blower as the case may be. The soldering

work station is indeed the most reliable setup for soldering in any work shop as it integrates

all the materials used for soldering together in the workshop there by defining and

separating the section from any other section in the work shop.

6


7/26

1.5 SCOPE AND LIMITATIONS OF THE STUDY

The digital soldering work station that is implemented in this project cover a quite wide

area of application. It can be used in both home and industrial soldering or any scale of

soldering though its operation may depend on the size of material being soldered. Ifsoldering is required for larger size situations, all that is required is to change the size of the

soldering iron that is used for the soldering as the temperature regulation is not limited to

any size of soldering iron.

The project offers a wide range of advantages but it is also faced with several limitations

which includes;

High cost of purchase due to its uniqueness.

The use of the soldering work station requires a proper knowledge of the operating

principles making the use difficult for the lay man technician.

The project is only limited for people with knowledge of different temperature

requirements for soldering

The use of the system requires proper knowledge of the system and operation

requires a trained personnel.

7


8/26

2.0 LITERATURE REVIEW

2.1 Introduction

Soldering, the art of joining two or more metal items together by melting and flowing a

filler metal (solder) into the joint, the filler metal having a lower melting point than the

work piece, the soldering process is an age-old procedure. However, latest innovations

stress more on the use of eco-friendly materials besides the use of the best physical and

chemical components, especially that of the fluxes, for better results and greater

compatibility. In a quest to find more eco-friendly and efficient platform for soldering,

research organizations worldwide and various researchers laid emphasis on the meas of

providing an ease and reliable platform for soldering and the elimination of ozone-

depleting chemicals and started experimenting with a variety of new combinations withpotential materials and alternative processes during soldering. In the process, researchers

tumbled upon a more reliable form of soldering, better than the established conventional

soldering process. This has lead to the various evolutionary trend of soldering work

stations.

2.2 Historical Overview of the Work Station

The evolutionary trend on the development of the modern soldering iron work station has

passed through series of transformations. These began with the discovery of the soldering

itself. Soldering was invented in 1916 by a Holland company but the wording is a little

non-specific and gives no credit to the original inventor. "The company was founded in

1916 as a manufacturing company under the name ZEVA. This name had much to do with

the introduction of an innovative product: the electric soldering iron (as differing from

then-popular petrol and gas irons). Major customers included Philips Radio and Dutch

Telecom." Since the invention of the soldering, there have existed many methods by which

the soldering is being done. These methods include the use of the blowing lamp, the use of

the soldering gun and the use of the soldering irons which is the most popular today. The

soldering iron itself was invented about the same time as its original constituent metals -

Lead (Pb in Chemistry) and Tin (Sn in Chemistry) - were discovered several thousand

years ago. (www.wikiananswers.com). German inventor Ernst Sachs patented the first

8


9/26

electric soldering iron in 1921, according to ERSA Global Connectors, the company Sachs

founded later that year to produce his device. The company exists today and has its

headquarters in Wertheim, Germany. (www.answerbag.com). the modifications on this

great invention were made severally in a quest to develop more reliable soldering irons.

The introduction of the work station began with the soldering iron stand which is setting

where a hot soldering iron is places in the workshop. The soldering iron stands where

introduced in the late 18th century in the United States. Since then, the soldering iron stand

has being severally modified in various ways leading to the discovery of the work station in

the 19th century which can be used both as the stand and as a control station for the

soldering operation capable of controlling the temperature of the tools used for soldering

such as the soldering iron and the sucker.

2.3 An Overview of the Soldering Work Station

The soldering work station that is implemented in this project is designed around the 8051

microcontroller which is the heart of the system. A temperature sensor LM35 is also

provided in the project whose sole function is to take the analog reading of the temperature

of the soldering iron. The ADC is interfaced with the microcontroller whose main function

is to convert the analog signal that is read from the LM35 temperature sensor into a digital

form. The ADC also converts the digital signal into an 8-bit digital data that is read by theMCU (microcontroller unit) of the project. The project also provides an LCD (liquid crystal

display) display that is used to provide a digital read out of the alphanumeric value of the

temperature of the soldering iron in the work station. The project also provides an interface

of relays that are used to provide the control of the various accessories of the work station.

In the project, the relays acts as switches that put on the appliance whenever the MCU

requests that. The operation is initiated upon the switching of the power supply into the

system. As soon as the power supply is turn on, the LM 35 temperature sensor reads the

temperature of the soldering iron and continuously sends the analog signal value of the

temperature to the ADC which in turn converts the analog signal into an 8-bit digital

equivalent of the temperature. This signal is then passed on to the MCU which interprets

the signal and sends the alphanumeric value of the temperature for the LCD to display.

When the control buttons is pressed, the MCU records the value of the temperature that is

9


10/26

selected and ensures that the operating temperature of the soldering iron stays within that

range. The control of the heating of the soldering iron is done by a relay that is designed to

trip off the soldering iron when the temperature tries to go outside the operation range. The

operation of the appliances that make up the work station is simply carried out by pressing

a button that controls the required appliance and the MCU triggers the relay on thereby

putting the appliance on or off as the case may be.

10


11/26

3.0 DESIGN ANALYSIS

The techniques employed in investigating the application principles of the 8051

microcontroller is based on gathering observable, empirical and measurable evidence

through research of primary and secondary sources. Primary data acquisition is throughpractical experience on electrical engineering principles and through lecture notes.

Secondary data were collected from the internet and from textbooks. The design of the

project will be implemented by splitting the project into various sub-units, which are:

The power supply unit

The MCU Oscillations input unit

The reset circuit

The ADC unit

The output LCD display unit

The relaying unit

3.2 METHOD OF DESIGN AND IMPLEMENTATION

The design of this project is made by splitting the project into various sectional units in the

course of the design. This is to facilitate easy design and to enable the system to be easily

trouble shot at the end of the design and implementation of the project.

3.3 THE POWER SUPPLY UNIT

The power supply unit is designed to continuously supply power to all the sub-sections of the

board. The power supply design is carried out using the following circuit diagram;

11


12/26

Figure 3.1; Circuit Diagram for the Power Supply Unit

The power supply unit is designed using a 12V step-down transformer, which supplies the

bridge rectifier circuit in the unit. The rectified output voltage is passed through a set of

capacitors that filters off any unwanted ripples in the output. The filtered output is then

passed through a 5V linear regulator (7805) that keeps a constant 5v output on the unit.

Since the Transformer used for the power supply unit design takes a 220V input and gives an

output voltage of 12V, then the transformation ratio can be calculated as:

Ni/No = Ei/Eo = ,

Where

=transformation ratio

Ni=Number of primary turns

No=Number of secondary turns

Ei=primary voltage

Eo=secondary voltage.

From Ei/Eo = ,

12


13/26

220/12 = 18.33

Therefore, the transformation ratio is 18.33.

Output is given by: -

V (out) = 1/2 x V

V (out) = 0.71 X V

= 0.707 X 12V

= 8.48V

(This equation is similar for the negative rail as well)

The capacitor value for the power supply is given by

C=Q/V

Where C=capacitance

Q = Charge across the circuit

V = Voltage across the circuit

But Q = it

Where I = current

T = time. Also T = 1/f

Where f = frequency = 50Hz.

T= 1/50 = 0.02seconds

Hence Q = 0.02 x 500 x 10-3 (from transformer current rating.) = 0.01C

Therefore C = 0.01/12 = 0.000833Farads = 833uF. But capacitors of this range is not

obtainable thus we use 1000uf for the design.

13


14/26

3.4 THE MCU OSCILLATION INPUT UNIT

The 8051 requires the existence of an external oscillator unit. The oscillator circuit usually

runs around 12 MH2, although the 8051 (depending on which specific mode) is capable of

running at a maximum of 40MH2. Each machine cycle in the 8051 is a clock cycle givingan attentive cycle at IMH2 clock. The configuration circuit for the external clock of the

8051 can be illustrated as follows.

C3

33p

C4

33p

X1CRYSTAL

PIN 18

PIN 19

Fig 3.2; The Oscillation Circuit Of 8051

3.4.1 Finding the period circle

Find the period of the machine cycle for 11.0592 MHz crystal

Frequency for the crystal oscillator used we have;

11.0592/12 = 921.6 kHz;

Thus the machine cycle is given by

1/921.6 kHz = 1.085s

Therefore the machine circle for the microcontroller using a crystal oscillator of 11.0592

crystals is equal to 1.085s

3.5 THE RESET CIRCUIT

The RESET is an active high input when RESET is set to High, 8051 goes back to the

power on state. The 8051 is reset by holding the RST high for at least two machine cycles

and then returning it law. The circuit diagram for the rest cycle and returning it low is

illustrated below.

14


15/26

Figure 3.3; Circuit Diagram for the Reset

In the diagram, the reset is configured as power on reset and the manual rest. In the

poweron Rest mode, initially charging of the capacitor make RST High and when the

capacitor charge fully it blocks the DC. In the manual rest mode, the closing of the switch

momentarily will make RST High. After the rest in the both modes, the program counter is

loaded with 0000H but the content of on-chip RAM is not attested. (Ablilav .V. etal.)

3.6 The ADC Unit

Analog to digital converters find huge application as an intermediate device to convert the

signals from analog to digital form. These digital signals are used for further processing by

the digital processors. Various sensors like temperature, pressure, force etc. convert the

physical characteristics into electrical signals that are analog in nature. The ADC0804 that

is used in this project is used to convert the analog temperature into an 8-bit digital signal

that is read by the MCU.

ADC0804 is a very commonly used 8-bit analog to digital convertor. It is a single channel

IC, i.e., it can take only one analog signal as input. The digital outputs vary from 0 to a

maximum of 255. The step size can be adjusted by setting the reference voltage at pin9.

When this pin is not connected, the default reference voltage is the operating voltage, i.e.,

Vcc. The step size at 5V is 19.53mV (5V/255), i.e., for every 19.53mV rise in the analog

input, the output varies by 1 unit. To set a particular voltage level as the reference value,

15


16/26

this pin is connected to half the voltage. For example, to set a reference of 4V (Vref), pin9

is connected to 2V (Vref/2), thereby reducing the step size to 15.62mV (4V/255).

ADC0804 needs a clock to operate. The time taken to convert the analog value to digital

value is dependent on this clock source. An external clock can be given at the Clock IN

pin. ADC 0804 also has an inbuilt clock which can be used in absence of external clock. A

suitable RC circuit is connected between the Clock IN and Clock R pins to use the internal

clock.

Features

Compatible with 8080 P derivatives-no interfacing logic needed - access time - 135

Easy interface to all microprocessors, or operates "stand alone"

Differential analog voltage inputs

Logic inputs and outputs meet both MOS and TTL voltage level specificationsWorks with 2.5V (LM336) voltage reference

On-chip clock generator

0V to 5V analog input voltage range with single 5V supply

No zero adjust required

0.3[Prime] standard width 20-pin DIP package

20-pin molded chip carrier or small outline package

Operates ratiometrically or with 5 V DC, 2.5 VDC, or analog span adjusted voltage

reference

3.7 LM35 Precision Centigrade Temperature Sensor

The LM35 series are precision integrated-circuit temperature sensors, whose output voltage

is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an

advantage over linear temperature sensors calibrated in Kelvin, as the user is not required

to subtract a large constant voltage from its output to obtain convenient Centigrade scaling.

The LM35 does not require any external calibration or trimming to provide typical

accuracies of C at room temperature and C over a full -55 to +150C temperature

range. Low cost is assured by trimming and calibration at the wafer level. The LM35's low

output impedance, linear output, and precise inherent calibration make interfacing to

readout or control circuitry especially easy. It can be used with single power supplies, or

with plus and minus supplies. As it draws only 60 A from its supply, it has very low self-

16


17/26

heating, less than 0.1C in still air. The LM35 is rated to operate over a -55 to +150C

temperature range, while the LM35C is rated for a -40 to +110C range (-10 with

improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor

packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92

transistor package. The LM35D is also available in an 8-lead surface mount small outline

package and a plastic TO-220 package. In the project, the LM35 is used to sense the

temperature of the soldering iron in the project.

Calibrated directly in Celsius (Centigrade)

Linear + 10.0 mV/C scale factor

0.5C accuracy guaranteeable (at +25C)

Rated for full -55 to +150C range

Suitable for remote applicationsLow cost due to wafer-level trimming

Operates from 4 to 30 volts

Less than 60 A current drain

Low self-heating, 0.08C in still air

Nonlinearity only C typical

Low impedance output, 0.1 Ohm for 1 mA load

3.8 The Liquid Crystal Display (LCD) Unit

The liquid crystal display (LCD) is a device that is used to give an alphanumeric display of

data on a crystal screen. Frequently, an 8051 program must interact with the outside world

using input and output devices that communicate directly with a human being. One of the

most common devices attached to an 8051 is an LCD display. Some of the most common

LCDs connected to the 8051 are 16x2 and 20x2 displays. This means 16 characters per line

by 2 lines and 20 characters per line by 2 lines, respectively.

Fortunately, a very popular standard exists which allows us to communicate with the vast

majority of LCDs regardless of their manufacturer. The standard is referred to as

HD44780U, which refers to the controller chip which receives data from an external source

(in this case, the 8051) and communicates directly with the LCD. The 44780 standard

requires 3 control lines as well as either 4 or 8 I/O lines for the data bus. The user may

17


18/26

select whether the LCD is to operate with a 4-bit data bus or an 8-bit data bus. If a 4-bit

data bus is used the LCD will require a total of 7 data lines (3 control lines plus the 4 lines

for the data bus). If an 8-bit data bus is used the LCD will require a total of 11 data lines (3

control lines plus the 8 lines for the data bus).

The three control lines are referred to as EN, RS, and RW. That is the enable, register

select and the read write respectively.

The EN line is called "Enable." This control line is used to tell the LCD that you are

sending it data. To send data to the LCD, your program should make sure this line is low

(0) and then set the other two control lines and/or put data on the data bus. When the other

lines are completely ready, bring EN high (1) and wait for the minimum amount of time

required by the LCD datasheet (this varies from LCD to LCD), and end by bringing it low

(0) again.

The RS line is the "Register Select" line. When RS is low (0), the data is to be treated as a

command or special instruction (such as clear screen, position cursor, etc.). When RS is

high (1), the data being sent is text data which should be displayed on the screen. For

example, to display the letter "T" on the screen you would set RS high.

The RW line is the "Read/Write" control line. When RW is low (0), the information on the

data bus is being written to the LCD. When RW is high (1), the program is effectively

querying (or reading) the LCD. Only one instruction ("Get LCD status") is a read

command. All others are write commands--so RW will almost always be low.

Finally, the data bus consists of 4 or 8 lines (depending on the mode of operation selected

by the user). In the case of an 8-bit data bus, the lines are referred to as DB0, DB1, DB2,

DB3, DB4, DB5, DB6, and DB7.

As we've mentioned, the LCD requires either 4 or 7 I/O lines to communicate with. For the

sake of this project, we are going to use a 4-bit data bus--so we'll be using7 of the 8051's

I/O pins to interface with the LCD.

18


19/26

As seen, we've established a 1-to-1 relation between a pin on the 8051 and a line on the

44780 LCD. Thus as we write our assembly program to access the LCD, we are going to

equate constants to the 8051 ports so that we can refer to the lines by their 44780 name as

opposed to P0.1, P0.2, etc. Let's go ahead and write our initial equates:

DB4 EQU P1.4

DB5 EQU P1.5

DB6 EQU P1.6

DB7 EQU P1.7

EN EQU P3.7

RS EQU P3.6

RW EQU P3.5DATA EQU P1

Having established the above equates, we may now refer to our I/O lines by their 44780

name. For example, to set the RW line high (1), we can execute the following instruction:

RW=1

Handling The EN Control Line

As we mentioned above, the EN line is used to tell the LCD that you are ready for it to

execute an instruction that you've prepared on the data bus and on the other control lines. Itis Noted that the EN line must be raised/lowered before/after each instruction sent to the

LCD regardless of whether that instruction is read or write, text or instruction. In short, you

must always manipulate EN when communicating with the LCD. EN is the LCD's way of

knowing that you are talking to it. If you don't raise/lower EN, the LCD doesn't know

you're talking to it on the other lines.

Thus, before we interact in any way with the LCD we will always bring the EN line low

with the following instruction:

EN=0

And once we've finished setting up our instruction with the other control lines and data bus

lines, we'll always bring this line high:

19


20/26

EN=1

The line must be left high for the amount of time required by the LCD as specified in its

datasheet. This is normally on the order of about 250 nanoseconds, but check the datasheet.

In the case of a typical 8051 running at 12 MHz, an instruction requires 1.08 microseconds

to execute so the EN line can be brought low the very next instruction. However, faster

microcontrollers (such as the DS89C420 which executes an instruction in 90 nanoseconds

given an 11.0592 Mhz crystal) will require a number of NOPs to create a delay while EN is

held high. The number of NOPs that must be inserted depends on the microcontroller you

are using and the crystal you have selected.

The instruction is executed by the LCD at the moment the EN line is brought low with a

final CLR EN instruction.

The LCD interprets and executes our command at the instant the EN line is brought low. If

you never bring EN low, your instruction will never be executed. Additionally, when you

bring EN low and the LCD executes your instruction, it requires a certain amount of time

to execute the command. The time it requires to execute an instruction depends on the

instruction and the speed of the crystal which is attached to the 44780's oscillator input.

20


21/26

Checking the Busy Status of the LCD

As previously mentioned, it takes a certain amount of time for each instruction to be

executed by the LCD. The delay varies depending on the frequency of the crystal attachedto the oscillator input of the 44780 as well as the instruction which is being executed.

While it is possible to write code that waits for a specific amount of time to allow the LCD

to execute instructions, this method of "waiting" is not very flexible. If the crystal

frequency is changed, the software will need to be modified. Additionally, if the LCD itself

is changed for another LCD which, although 44780 compatible, requires more time to

perform its operations, the program will not work until it is properly modified.

A more robust method of programming is to use the "Get LCD Status" command to

determine whether the LCD is still busy executing the last instruction received.

The "Get LCD Status" command will return to us two tidbits of information; the

information that is useful to us right now is found in DB7. In summary, when we issue the

"Get LCD Status" command the LCD will immediately raise DB7 if it's still busy executing

a command or lower DB7 to indicate that the LCD is no longer occupied. Thus our

program can query the LCD until DB7 goes low, indicating the LCD is no longer busy. Atthat point we are free to continue and send the next command.

The LCD in this project is used for the display of the value of the temperature of the

soldering iron.

3.9 The Operation of the System

The digital soldering workstation is a protion or piece of equipment in a given workshop

that is provided for use during any soldering operation in the laboratory and it is assignedspecially for soldering operation. The system consists of the soldering iron control system




21


22/26



displays the status of the system.

The circuit diagram for the system is designed around the 8051 micrcontroller which is theheat of the system. The system also consists of an LM35 temperature which takes the

temperature of the heater and sends the output in an analogue form into the analog to

digital converter. The analog to digital digital converter (ADC) converts the anolog signal

received fron the sensor into a digital signal which is readeable by the microcontroller. The

ADC used for the system is and ADC0804 ADC which is an 8-bit system. It recieves the an

analog signal from the sensor and gives out an 8-bit digital output. The device also

provides a liquid crystal display (LCD) which anables the display of an alphanumeric

display of the value of the temperature of the system. The LCD used for the system is a

2*16 LCD. The device also consists of a relay which controls the switchin of the heater.

The relay controls the switching of the heater provided.

When the system is put on, the sensor starts the reading of the temperature of the heater and

sends the analog signal into the ADC input the ADC acts on the analog signal and converts

it into an 8-bit digital signal which it passes into the microcontroller. The microcontroller

performs necessary mathematical calculations on the signal and gives an alphanumeric

display of the value of the temperature on the LCD display. When the temperature is

beyond the preset valueu, the microcontroller actuates the relay which puts off the heater.

When the teprature falls bellow the preset value. The micrcontroller reconnects the heater.

3.10 The Circuit Diagram for the Project

The generalised circuit diagram for the design of the project can be illustarated by the

figure below.

22


23/26

F IL E N A M E :

:

g l

::

D E S I G N T I T L E :C :

V IN +6

V IN -7

V R E F /29

C L K IN4

A G N D8

R D2

W R3

IN T R5

C S1

D G N D1 0

D B 7 (M S B )11

D B 612

D B 513

D B 414

D B 315

D B 216

D B 117

D B 0 (L S B )18

C L K R1 9

V C C20

U 1

A D C 0 8 04

R 71 0 k

X T A L21 8

X T A L11 9

A L E3 0

E A3 1

P S E N2 9

R S T9

P 0 .0 /A D 03 9

P 0 .1 /A D 13 8

P 0 .2 /A D 23 7

P 0 .3 /A D 33 6

P 0 .4 /A D 43 5

P 0 .5 /A D 53 4

P 0 .6 /A D 63 3

P 0 .7 /A D 73 2

P 2 .7 /A 1 52 8

P 2 .0 /A 82 1

P 2 .1 /A 92 2

P 2 .2 /A 1 02 3

P 2 .3 /A 1 12 4

P 2 .4 /A 1 22 5

P 2 .5 /A 1 32 6

P 2 .6 /A 1 42 7

P 1 .01

P 1 .12

P 1 .23

P 1 .34

P 1 .45

P 1 .56

P 1 .67

P 1 .78

P 3 .0 /R X D1 0

P 3 .1 /T X D1 1

P 3 .2 /IN T 01 2

P 3 .3 /IN T 11 3

P 3 .4 /T 01 4

P 3 .7 /R D1 7

P 3 .6 /W R1 6

P 3 .5 /T 11 5

U 2

8 0 C 51

D7

14

D6

13

D5

12

D4

11

D3

10

D2

9

D1

8

D0

7

E

6

RW

5

RS

4

VSS

1

VDD

2

VEE

3

L C D 1L M 0 1 6L

X 1C R Y S T A L

C 4

3 3 p

C 5

3 3 pR 8

1 0 k

C 6

1 0 u

23456789 1

R P 1R E S P A C K -8

C 71 5 0 p

H

eater

T

O V 1O V E N

Q 1B C 5 48

R 1

4 k 7

R L 11 2 V

D 1D IO D E

s u p p l y

R 24 k 7

R 34 k 7

Q 2

B C 5 48

Q 3

B C 5 48

R L 2

1 2 V

R L 3

1 2 V

Figure 3.4: The Generalized Circuit Diagram for the Project

3.11 The Block Diagram for the Project

23


24/26

Figure 3.5: The Block Diagram for the Project.

24


25/26

4.0 SUMMARY AND CONCLUSION

4.1 Summary

The digital soldering workstation is a protion or piece of equipment in a given workshop

that is provided for use during any soldering operation in the laboratory and it is assigned








The design of the soldering ironwork station designed in this project is aimed at providing

a platform for an efficient and reliable soldering operation in a work shop.

The thesis is divided into four major chapters. The abstract of the project gives a

comprehensive summary of digital soldering iron work station. It highlights the problems

the objectives and the operating principles of the project in summary.

The chapter one of the project introduces the concept of access control systems, theexisting types and the background of digital soldering iron work station; it highlights the

problems, the aims and objectives of the research, the background and the scope of the

soldering iron work station. The chapter one of the project gives the reader an insight of

what the research is about.

The chapter two of the project presents the literature review of the project. It pre-examines

the historical background of the project and also reviews previous works done relating to

the same aims and objectives, reviewing their success and failures as well as the

modifications to be input on the works to achieve a more reliable system to make the

system more reliable and efficient.

The chapter three of the project presents the design analysis of the project it reviews the

various sections of the project there design procedures and the implementation process. It25


26/26

also presents the necessary calculations carried out in the course of the design. It also

presents the block diagram, the circuit diagram and the flow chart of the project.

The chapter four of this thesis presents the summary and conclusion of the entire work.

4.2 Conclusions

The field of electrical engineering cannot do without the soldering process. The digital

soldering workstation is a protion or piece of equipment in a given workshop that is

provided for use during any soldering operation in the laboratory and it is assigned








26

work station work

Documents