The Hong Kong Polytechnic University

The Hong Kong Polytechnic University

Industrial Training Centre

Department of Electronic and Information EngineeringDegree 2 Summer Term Project

The Hong Kong Polytechnic University

Industrial Training Centre

Department of Electronic and Information Engineering

Degree 2 Summer Term Project

Project Title: LED Thermometer

Project Report

Supervisor Name:Edward Cheung

Group Number:01N05

Group Member:Chung Kai Man (99000964D)

Fan Hoi Wang (99274797D)

Fung Hon San (99195707D)

Ho Ka Wai (99189069D)

Table of Contents

1. Introduction

1.1 Project Objectives

1.2 About Our Project

2. Product Features and Specifications

2.1 Descriptions

2.2 Technical Data (specifications)

3. Project Requirement

4. Project Planning

4.1 Job responsibilities

4.2 Time scheduling

4.3 Materials and development tools

5. Cost Analysis

5.1 Material costs

5.2 Manufacturing cost

5.3 End-product cost

6. Market Research

6.1 Target market segment

6.2 Similar products in the market

6.3 Comparison between your product and those in the market

6.4 Selling price level

7. Design philosophy

7.1 Hardware

7.2 Software

7.3 Material, casing and finishing

8. Manufacturing Process philosophy

8.1 Choice of processes

9. Testing strategies

9.1 Hardware

9.2 Software

9.3 Mechanical

10. Mass Production Recommendations

10.1 Production Methodology

10.2 Production tools, fixtures and machines

10.3 Production Flow

11. Conclusion

12. Recommendation and future enhancement

13. References

14. Appendix

14.1 Material & Parts List

14.2 Production Planning Chart (PCB)14.3 Production Planning Chart (Casing)14.4 Manufacturing Process Instruction (PCB)14.5 Manufacturing Process Instruction (Casing)14.6 Cost & Delivery Estimation Form

1. Introduction

1.1 Project Objectives:

Manufacturing and development projects are gradually important. They are becoming integral part in the working lives that virtually all engineers will come across at various stages in their career path.

For effective training, the manufacturing project work is structured that both staff of IC and parent department act as the company top management, student project teams act as project groups within a company. Each project is in the form of a prototype model and includes component selection, layout of circuits, making parts, assembly and testing a prototype. Finally, the stage is to document and present audiences the project. In this year, the presentation style is changed from oral presentation, to web site presentation in the Internet. Useful materials and presentation video clips should be found on the web site.

The project is structured that we can bring our previous knowledge and experience together into one coherent activity. It is based on the assumption that students have already undertaken and completed successfully the required basic IC training programs. Also it gives us a chance to develop teamwork.

After completing this manufacturing project exercise, students will be expected to gain hand-on experience of modern computer aids and equipment used in design, advance machine used in manufacturing. Students will be also expected to gain a good understanding of the importance of costs related to any decisions making, the methods used and factors considered in the selection of the manufacturing process and materials. Finally, this training is designed to develop students product development and manufacturing capability in their immediate career after their graduation.

1.2 About Our Project:

The ordinary types of thermometers are using alcohol or mercury for displaying temperature values. However, due to the development technology, electrical thermometers are said to be the new trend of thermometers.

In general, people prefer using 7 segment LED thermometers. It is because the display can show the readings in numerical form so that the temperatures can be read more easily.

In our project, we had created a LED thermometer with an innovative idea that using many individual LEDs for displaying temperature values. Such number of LEDs is the main feature of this product. It is because the displaying style is completely different from that of 7 segment LEDs thermometers.

Our product is designed to measure room temperature. By the use of cell battery, it can be portable.

Our project is divided into six stages, including design and planning, costing and parts manufacture, PCB and casing assembly, testing, documentation, and final evaluation. Further descriptions of each part will be found in the following paragraphs. If you would like to know more about the manufacturing process and the operation of our product, LED thermometers, you can refer to the Technical Manual and the User Manual.

2. Product Features and Specifications

2.1 Product Features

The product name is called LED thermometer, it is used for measuring room temperature. As mentioned in the introduction part, digital LED thermometer using 7 segment LED display is the most common type in the digital thermometer world. And our product does not use 7 segment LED display, in contrast, we use a certain number of LEDs for displaying the temperature values. Although 7 segment LED display can show numerical values, which can be more easily to read, our product can be more attractive since there are more LEDs for displaying the room temperature.

2.2 Technical Data (specifications):

LED thermometer uses AT89C51 as the micro-controller and DS1620 as the thermal sensor. Although the sensor is work from 55oC to +125oC, the temperature range of it is limited from 0oC to +59.5oC with the resolution 0.5oC since this product is designed for measuring room temperature. The error over temperature range is 0.5oC. If the temperature exceeds +59.5oC, all the LEDs will turn off.

For convenient referencing, a specification table is provided as below:

Sensor Workable range55oC to +125oC

Display range0 to +59.5oC

Resolution0.5oC

Error over temperature range0.5oC

Supply voltage9V

Dimension150mm ( 60mm ( 310mm

3. Project requirement

Students were required to form a project group. Group members had to divide their works themselves. Within the training period, the group member were expected to complete the project as per project specification and deliver the project in the form of a set of documentation. Documentation includes project report, user manual and technical manual.

Furthermore, time management is important. In general, the members decide to do the specification, planning, components costing in the first week. For the second and third weeks, they decide to do the design, drawing, manufacturing and assembly. Next, for the fourth week, they decide to do the testing and evaluation, and documentation and preparation of presentation in the last week.

With the above requirements, in general, the group members are divided into three groups. The first one is for hardware producing which included designing, manufacturing and testing the PCB. Another group is responsible for software programming which included deciding what functions needed and testing whether the program work or not. The last group is for casing which included designing of outlook and manufacture of the case.

However, these regulations are only for reference, for different project groups, they can adjust their plan and job responsibilities according to their needs.

4. Project Planning

4.1 Job responsibilities

For our group, there were only four members, the job responsibilities should be carefully divided to each member.

Chung Kai Man:focusing on casing manufacturing, finally assembling

Fan Hoi Wang:focusing on schematic design, printed circuit board manufacturing

Fung Hon San: focusing on AT89C51 programming and web site development

Ho Ka Wai:focusing on photographing, documentation and miscellaneous work

All the tasks and responsibilities are listed below:

Tasks:Responsible by:

Market Research, Project Planning and SchedulingHo Ka Wai

AT89C51, DS1620 and Serial Communication StudyingFung Hon San, Ho Ka Wai

Breadboard EmulationFung Hon San, Ho Ka Wai

AT89C51 ProgrammingFung Hon San

PowerLogic, PowerPCBFung Hon San, Fan Hoi Wang

Film MakingFan Hoi Wang

Printed Circuit Board ManufacturingChung Kai Man, Fan Hoi Wang,

Fung Hon San, Ho Ka Wai

Casing DesignChung Kai Man, Fung Hon San,Ho Ka Wai

AutoCADChung Kai Man

Casing Manufacturing and Finally AssemblingChung Kai Man, Fan Hoi Wang

Web Site Design and DevelopmentFung Hon San

PhotographingHo Ka Wai

DocumentationChung Kai Man, Fan Hoi Wang,

Fung Hon San, Ho Ka Wai

Video PresentationChung Kai Man, Fan Hoi Wang,

Fung Hon San, Ho Ka Wai

4.2 Time scheduling

Overall scheduling table:

Week No.Workout

Week 44Specifications, Market Research, Project Planning

Week 45Studying, including AT89C51 Programming, Sensor DS1620 Properties, Serial Communication

Week 46AT89C51 Programming Design, PowerLogic and PowerPCB Schematic Design, Casing Design

Week 47, 48WINICE 8051~52-E Emulator Demonstration and Functional Testing

Week 48, 49Film Making, PCB Production and Casing Assembling and Final Evaluation

Week 50, 51Documentation, Web Site Development

Week 44:Specifications, Market Research, Project Planning

In this week, our group designed the specification of the LED thermometer and also planned the overall workflow of the whole project. The original period of this project was from 3rd July to 2nd August (from week 44 to week 48), and the original schedule was planned at shown in the following Gantt Chart.

However, this was an ideal plan. As there were some unexpected problems, we could not follow this plan to do our project.

However, this was the ideal plan, and the following was the actual schedule that we had achieved:

On the other hand, we surfed the Internet to find information of some relevant products. More detailed descriptions can be found from the Market Research part in this report.

Week 45:Studying, including AT89C51 Programming, Sensor DS1620 Properties, serial communication

In this week, our group studied how to control the AT89C51 and learned how to access the sensor DS1620. We surfed the Internet to get useful information, studied the data sheet of both AT89C51 and DS1620, and also borrowed some books from library and studied them so that we could be more familiar with its command sets. On the other hand, we spent some time to study serial communication between AT89C51 and DS1620 since it was not included in the training course last year. So, it was necessary to do some extra efforts.

Week 46:AT89C51 Programming Design, PowerLogic and PowerPCB Schematic Design, Casing Design

In this week, we separated our group members into two main teams, the first one was responsible for AT89C51 programming design, and the other team was responsible to use the software PowerLogic and PowerPCB to design and draw the PCB circuit and also to use AutoCAD to design the casing.

In fact, the programming and the schematic layout should be designed at the same time, and they were highly related to each other. Each of them would affect the other one. For example, if one line of the schematic layout was changed, the programming should be adjusted correspondingly.

Week 47, 48:Hardware Demonstration using WINICE 8051~52-E Emulator

After studying the AT89C51 and DS1620 in week 45 and the design stage of week 46, we started to write the program in this week. There were totally three stages:

1) accessing DS1620,

2) programming for display, and

3) combining the transferred data with the display program to make the thermometer workable.

We used breadboard and the WINICE 8051~52-E emulator to do the hardware demonstration. Firstly, we tried to access the sensor DS1620. However, we spent much time in this stage since the serial communication between two ICs was not covered in the training course last year. Although we had studied the books, we still had some problems to do this task. So, we tried many times and finally we succeed. After that, we wrote the program for displaying LEDs. In this stage, we have found some problem for effective display. So we simply adjusted the PCB layout.

Lastly, we wrote the overall AT89C51 program. This program used 3 wires of AT89C51 to communicate with the sensor DS1620, one was data communication, one was clock pulse, and the last one was RESET. By suitable settings, the AT89C51 could serially communicate with the sensor, and we used some internal memory registers to store the temperature values. Using the displaying program we just written, the temperature values could be visualized by LEDs.

Week 48, 49:Film Making, PCB Production and Casing Assembling and Final Evaluation.The hardware manufacturing processes, including film making, PCB production, casing production and casing assembling were done within these two weeks. We applied the knowledge and skill we had learnt in last to perform the hardware production. After finished the hardware product, we used the WINICE 8051~52-E emulator to do an evaluation. After this, we burnt the programme to the micro-controller AT89C51 and performed the final evaluation.

Week 50, 51:Documentation, Web Site Development

In this week, we focused on doing documentation work and also web site development. However, in fact, we started to do documentation work at the very beginning. Since we knew that documentation should be done in certain progress.

We used MS Word, MS Excel, MS Project to make different reports, tables, and charts. All the contents and format of these documents were fully followed the project guide. On the other hand, we used Dreamweaver and Flash to create our web site. The content of the web site was said to be simplified version of the report and manuals. It also contained soft copy of the report, manuals, PCB layout, programme source code for downloading. Thus, customers could browse to our web site, then they would have brief idea of our project. If they were interested, they could download the files provided, and read them, then they would know more details about the idea, manufacturing process and also the operations of our product.

4.3 Materials and development tools

Components List:

Resistors:

R1R8, R11R14 = 220(R9 = 100k(R10 = 2k(7

Capacitors:

C1 = 82pF

C2, C3 = 100nF

C4 = 100mF 16V radial

Semiconductors:

D1D29 = LED, high efficiency, red

D30, D31, D32 = LED, high efficiency, yellow

D33 = IN4148

IC1 = DS1620

IC2 = AT89C51

IC3, IC4 = 74LS244

IC5 = 7805

Miscellaneous:

PC1, PC2 = solder pins

Development tools list:

Cathode-Ray Oscilloscope

WINICE 8051~52-E Emulator

Photo Film Making Machine

UV Exposure UnitPower Supply

Multi-meter ( 2

Breadboard ( 2

Lathe Machine

Cutting Machine

Drilling Machine

NC Drilling Machine

Hand tools (Drilling & tapping, solder iron, etc.)

5. Cost Analysis

For detailed information, please refer to the Cost & Delivery Estimation Form in the appendix.

5.1 Material costs

From the Cost & Delivery Estimation Form, we can see that the material cost for manufacturing a LED thermometer is $161.76.

5.2 Manufacturing cost

In the manufacturing process, we found that the total man-hour should be 3 hours. These 3 hours are the period of mass manufacturing, so, the period is much shorter than that we manufacture the product manually. The rate of a man-hour is $30, so the labour cost in manufacturing is $90.

5.3 End-product cost

From the MS EXCEL file, we can see that the total cost of manufacturing is $368.76. So we considered that the selling price of the LED thermometer would be $442.51.

6. Market Research

6.1 Target market segment

The product is LED thermometer, and it is mainly used to measure the room temperature. On the other hand, it can be used as decoration, it is suitable placing at office and home.

So, the target market is very large, everybody wanted to have a room temperature thermometer are the target market of our product.

6.2 Similar products in the market

From the Internet, many same kinds of products can be found. LED thermometers using 7 segment LED for displaying temperature values are very common. However, we could not find any examples using as much LEDs as our product.

Product NamePriceDescriptions

Economical and versatile LED Digital Thermometer

HK $544Large, brightly lit display easily readable from long distances. 5connector tubing to air probe for sensing air temperature in remote location (longer lengths available; contact us for pricing).

Designed to be surface mounted with two #4 screws through case; to flush mount, simply cut a 0.875 ( 1.75opening on a panel and fasten with two screws.

Optional flush mount on stainless steel electrical box cover plate, which installs on conventional electrical box, found at local hardware stores

Display: LED red in color 0.56 high.

Range: Available in either: -40 to +120oF or -40 to +50oC.

Power: 12 VAC or 12 VDC, recognized transformer included.

Calibration screw located on back of unit to allow for easy adjustment of temperature reading.

Accuracy: ( 2oF

Dimensions: 0.85 ( 1.75 ( 2(W ( L ( H)

Digital Solar Powered Air Thermometer

HK $232Can mount on outside of room to read inside air temperature or directly in room. 56 connector tubing to air probe for sensing air temperature in remote location. Solar powered with a battery (AAA) back-up system enables instrument to operate in low light levels. Estimated battery life is 3-4 years.

Accuracy: 2 F

Range: -50 to +158F (-50 to +70C, available by special order)

Dimensions: 4 wide x deep x 1 high

One year warranty

Digital LED Thermometer

HK $240This high bright LED digital thermometer uses an LM35 National Semiconductor IC as its temperature sensor. It shows the temperature with an accuracy of 0.5C on its digital display. The thermometer's range is from 0 - 99C.

Digital Thermometer Sensor With LED Display

HK $450It is well suited for use as a conventional thermometer. The digital display gives the current temperature, the minimum temperature and

the maximum temperature consecutively. When a 'rest' key is pressed the highest and lowest temperatures measured are stored and, if necessary, adjusted. An aluminum case is supplied with the kit, to allow the thermometer/sensor to be mounted on a wall. The sensor can be mounted anywhere with plain telephone wire. Minimum: 6 inches long, Maximum: 5 feet long. Use a switch to flip back and forth between inside temperature and outside temperature. Extra sensors are sold separately.

Range: -50C to + 150C

Linearity from -10to +50: better than 05%

Accuracy: better than 2%

Adjustable to degrees Fahrenheit

Display: 31/2 digits (01 display accuracy)

Supply voltage: 12 to 15V DC/I50mA

Dimensions: 144 ( 50 ( 22mm

Indoor/Outdoor Thermometer

HK $284Great for measuring temperature variances of walk-in coolers, ripening rooms, any refrigerated area, or home inside / outside temperatures.

10' sensor cord allows for easy remote monitoring.

Max/Min memory records the high and low temperatures.

1.25" LCD Display

-58 to +158F (C model available by special order)

1.5 volt battery included

Hangs or Stands

6.3 Comparison between your product and those in the market

As mentioned before, the main difference between our product and those in the market is the display style. Most of the products in the market are using 7 segment LEDs for displaying the temperature values, and our product uses large number of LEDs for the display.

Secondly, the size of our product is larger than that of those in the market. The reason is that, our product is a standalone LED thermometer and it can be used as decoration too. In contrast, those digital LED thermometers in the market can be used as add-ons to other electronic products.

In general, the 7 segment LED thermometers can be used as room temperature thermometers, clinical thermometer, and also can be used as add-ons accessory to other electronics products such as computer motherboards.

6.4 Selling price level

From the above table, the thermometers selling prices are generally from about $200 up to about $600.

7. Design philosophy

The hardware should match with the software. Either one of them had been changed, the other one should also be adjusted. This showed the importance of the relationship between hardware and software.

In order to give out an impression that the product is a thermometer, the arrangement of LEDs is limited, the best way for displaying temperature values is one single vertical line. This arrangement can provide clear view for reading. Besides, it also can give an impression that the temperatures rise from low to high.

7.1 Hardware

At the heart of the circuit is a AT89C51 micro-controller. The micro-controller reads temperature data from a sensor IC. The micro-controller has the job of displaying the measured value on 32 LEDs.In order to minimize the number of connections for a large number of display elements, the 32 LEDs are driven in a multiplexed fashion. Four additional LEDs are permanently lit and indicate the tens of degrees, making the display easier to read.

However, since so many LEDs should be connected to the 40 pins AT89C51 micro-controller, and we should arrange the LEDs in a single vertical line, the circuit lines would be tight.

On the other hand, the AT89C51 should communicate with the sensor DS1620 and control two buffers 74LS244, the circuit would be complicated and it was impossible to cover all the lines without shorting in single side. As a result, we used double sides PCB at our board. By this method, the circuit could be routed without shorting.

7.2 Software

As the AT89C51 microprocessor is used for controlling the temperature sensor DS1620, all data are communicated over an I2C bus. By serial communication, the data generated from the sensor DS1620 will be sent to the AT89C51 for calculation. And the number of light LEDs will show the corresponding temperature values.

By the use of AT89C51 programming, we can drive 32 LEDs through 14 ports only. The LED matrix is divided into four groups, the first and second columns consisting of 10 LEDs, the third column consisting of 9 LEDs and the last column consisting of 3 LEDs. These groups are driven from port pins 1417 in sequence, so that at most ten LEDs are ever lit simultaneously. The LEDs are turned on by setting port pins 21, 22, and 3239 to high. With a low level of port pins 1417, the appropriate group of LEDs is enabled. Although only at most ten LEDs are on at any one time, the multiplexing happens so fast that the visual appearance is that up to 32 LEDs are lit.

The overall temperature range from 0oC to +59.5oC is divided into two ranges (0 to +29oC and +30 to +59oC), as indicated by the two LEDs D31 and D32 respectively. The odd 0.5oC is indicated by the remaining range LED D30. So, for example, at 20.5oC, the LED D30 turns on, and also the LED D31 lit for indicating a temperature between 0oC and 29oC. If the temperature exceeds the minimum and maximum limits, i.e. 0oC and +59.5oC, all the LEDs will turn off. So, it was necessary to consider the temperature values during calculation. By separating the values into 2 parts, we could use different LEDs for indication.

7.3 Material, casing and finishing

7.3.1 Material

Our product comprise of there parts, they are the acrylic surfaces, aluminum frames and PCB. The surfaces are made of two piece of acrylic sheets, we choose this material to make the surface is because acrylic sheet is tough enough to avoid breaking, and it is relatively lighter than the others materials, such as aluminum sheet, stainless steel sheet etc. Also, acrylic sheet is easy to be cut and drilled when compare with the other materials, and the surface of acrylic sheet is clean and smooth for a good appearance, so it is a good material to use as a surface part of our product. Furthermore, after the sheets are cut and drilled, we want to add some colors on the back of the acrylic surfaces to improve the appearance. Since acrylic sheet is transparency, so prints the colors on the back of the surfaces will provide a brighten surfaces, and the effect are really good.

And about the frame of our product, we have chosen aluminum bar to support the acrylic surfaces. The reason for us to choose aluminum bars and do not use the acrylic bars or the other materials is if we use acrylic bars to support the surfaces, then our product will be totally used plastic to accomplish, since we had chosen acrylic sheet to use as our products surfaces, so we have chosen the other materials to used as our products frame. When comparing the common used materials, we think aluminum is the best material to do as our frame, since it is lighter than the other materials, such as brass, copper, stainless steel, etc. Also, it is easy to cut on the lathe, and the appearance of the surface of the aluminum bar is very good and bright. Moreover, the combination of acrylic sheet and aluminum bar can give an attractive appearance.

7.3.2 Casing

Since our fellows want to use one piece of PCB for circuit design, so the size of our case will be based on the size of the PCB. Also the shape of the case is based the application of the product to design, since our product is a LED Thermometer, so we will design a thing that can impress the user think it is related to temperature. As the result, we decided to use a cactus diagram as the shape of our products casing, since cactus is a plant grown in desert area, so it can impress the user think of temperature. Apart from this, designing our surface as a cactus shape can also provide a decorative purpose. And since we will place the PCB on the casing, so we decide to produce four aluminum bars to attach the PCB on the casing. And the four aluminum bars are used as a bolts and nuts, so that they can attach the surfaces and the PCB.

Furthermore, our product is a thermometer, so the sensor must be placed in a good ventilated area. In order to overcome this problem, we attach the PCB between the two same shape surfaces like a sandwiches, thus the sensor can directly contact the surrounding, and this can improve the accuracy of the thermometer. Moreover, since the back of the surfaces will be printed with oil, so in order to let the LEDs can be shown clearly, we decide to cut a gap and drill some holes on the front surface to let the LEDs expose on the surface.

8. Manufacturing Process philosophy

8.1 Choice of processes

a. PCB layout design

b. Film Making

c. Production of PCB board

d. Casing Production

a. Procedures of PCB layout design

We applied the knowledge we learnt last year to produce the PCB layout.

Firstly, we used the software PowerLogic to design the circuit. And then we used the auto route function of software PowerPCB to design the layout.

b. Procedures of Film Making

In last year, we attended a class talking about how the film could be made. However, we did not have hand-on experiences. In this year, technicians arranged a brief talk to remind us about the film making procedures. After that, we followed the procedures to make the film. The procedures are listed below.

1. prepare a piece of paper that the required circuit was printed on it, the layout should be printed as the actual circuit size of the product

2. bring this PCB layout to the dark room

3. put the layout copy on the photo film making machine

4. adjust the focus of the machine so that we can make photo film at 1:1 scale (in general, the scale should be 2:1 so that the film can be more accurate, however, since our PCB layout was too large, the scale is limited and we finally used the scale of 1:1)

5. turn off the light and place the film on the machine

6. undergo the exposure film

7. undergo developing and fixing

8. dry out the film

c. Procedures of PCB Production

Our group applied the skill that we learned in last year to produce the printed circuit board, the procedures are listed below.

1. use NC drilling machine to drill required holes of the PCB

2. use sand paper to make both sides of the PCB smooth

3. clean the board and put it in the oven at 60oC for few minutes

4. after the board is cooled down, cut dry film to size (the size of dry film has to be equal to or smaller than the size of the PCB)

5. remove unnecessary skin of the dry film

6. use a heat rolling machine to attach the dry film on the copper side of the board

7. by the UV light machine, the circuit layout could be printed on the dry film

8. repeat step 4 to step 7 for another side of the PCB

9. remove another skin of the dry films and then drill a hole, tighten a wire on it

10. put the board into developer so that only the circuit layout is remained, repeat step 3 again

11. check the circuit lines clear or not, if the lines are not clear, use PCB marker to fill them

12. put the board into the etching tank (ferrous chloride) to corrode unnecessary copper

13. put it into the stripper to remove the remaining dry film and then repeat step 3

14. chop the board in size and debur edges

15. assemble required components and wires on the board

16. apply voltage the circuit and test whether it is work or not

d. Procedures of Casing Production

Surface Production:

1. use pencil to draw the desired cactus diagram on the acrylic sheet2. cut it out by using saws3. then file the edges of the surface until the edge become smooth and accurate enough4. place the polished surface on the other piece of acrylic sheet5. use pencil to copy the shape on the sheet6. then repeat the above procedure until two surfaces have been polished7. use pencil to mark the desired gap on the front surface8. drill two holes on the upper and lower part of the gap by using a suitable twist drill9. then use a saw to cut the gap out of the surface10. file the edge of the gap until it reaches the marked pencil line and become smooth enough11. for the other holes, using appropriate twist drills to drill after using pencil markedFrame Production:

1. use some cutting tools in the lathe to cut the bar into suitable diameter2. drill holes on the lathe by using appropriate twist drills3. use cutting knife to cut the parts out of the aluminum bar4. to produce a bolt, cramp the parts on the vice5. then turn the die clockwise to cut the axis with screw6. to produce a nut, cramp the parts on the vice7. turning the tap clockwise to cut the hole with screwOil printing:

1. draw the desired diagrams on the paper of the surface2. cut the paper out by using a knife3. use oil sprayer to spray the suitable color onto the exposed surfaces4. then repeat the above process until the whole surfaces are filled with colors9. Testing strategies

9.1 Hardware

Firstly, having etched, use a multi-tester to check any open or short circuit of the PCB circuit board. Secondly, using multi-tester to check the accurate values of the resisters and capacitors. Thirdly, the correct model numbers of the ICs. With a power supply +5V connected to the ICs on the breadboard, we use a CRO to test the wave forms of the signals from ICs. Checking whether there is signal in the ports required.

Finally, as incorrectly fitted LED, capacitors or ICs may be hard to track down, the polarities of those components should be correctly oriented in the copper board.

The sensor device should be positioned at the bottom of the circuit, allowing remote mounting if it is desired to measure the temperature outside. Also it should be positioned far away from IC5 (7805) which is very hot if the device operates for a long time to avoid affecting the temperature measured by the sensor.

9.2 Software

We used the emulator to test the software. First, we separated the program into 2 parts, the sensor communication part and LED display part, and test both part one by one.

For the sensor communication part, we use the testing board to simulate the hardware and use the CRO to test the input and output signal.

For the LED display part, we use the emulator and the final hardware product to test the program. We set the port value of the emulator to test the program and the LED display.

Finally, we combine 2 parts together and get the final program.

9.3 Mechanical

In fact, the mechanical testing strategies were not complicated. What we necessary to do was checking whether the aluminum frame could tightly mount the acrylic sheet and PCB or not.

10. Mass Production Recommendations

10.1 Production Methodology

PCB:

To begin with mass production, we first prepare the PCB circuit file, NC drilling file and film. The production department should be divided into 5 main sections in sequence: PCB Board Section, Assembling Section, Circuit Testing Section, Casing Section and Quality Control Section:

1. In the PCB Board Section:

It aims to produce drilled PCB boards. To prepare copper board, it is desirable to prepare copper board with the sizes are multiple of the standard board.

The copper boards are drilled by NC drilling machines before exposing UV light. The copper boards wrapped with dry film are exposed by UV light in UV light Unit to produce PCB artworks layout onto the copper board before etching. In the process of etching, a number of copper boards are etched together. At the end of etching process, there is visual checking for any incomplete etching boards or damaged traces on the circuit.

Finally, a number of etched copper boards are transported to the Assembling Section.

2. In the Assembling Section:

It aims to assemble all the required components onto the etched copper boards. For the sake of convenience of assembling components, all the resistors are bend with size fitted with the size of holes. All the components are randomly tested by CRO or multitester to minimize the possibility of malfunction of the components. Having placed all the components onto the copper boards by robot arms, those boards are transported to the wave soldering machines for soldering. At the end of soldering, there is visual checking for any incomplete soldering components.

3. In the Circuit Testing Section:

It aims to test the function of the device (LED Thermometer) with power supply provided and investigate any infects. The ICs are tested by CRO to check their signal functions. This process is done by labour. Any failed devices will be disposed into Recycle Unit.

4. In the Casing Section:

Having tested, the painted cases are assembled with the circuit boards together by robot arms.

5. In the Quality Control Section:

The LED Thermometers are randomly picked up for QC checking. Any failed LED Thermometers are transported to the Circuit Testing Section for further investigation. Finally the LED Thermometers are packed by machines that will be distributed to retailers.

Casing:

The fabrication process of the product LED Thermometer can be divided into three parts; they are (1) Surfaces production, (2) Frame production and (3) Oil printing. Then we will describe each part briefly as follows:

1. Surface production

To produce the surfaces of the LED thermometer, for the mass production, we want to draw the desired diagram in the AutoCAD in a suitable scale, then save this file. Then import this file into the computer cutting machines, and then the cutting machine will cut and polish the surfaces automatically and accurately. Finally, import the same file into the computer drilling machines, the drilling machine will drilling the holes with appropriate diameters.

2. Frame production

To produce the frames of the LED thermometer, for the mass production, we want to draw the desired dimensions of the frame in the AutoCAD, then save this file. Then import this file into the computer lathes, and then adjust the cutting priorities, then the lathes will cut, drill and tapping the frames automatically and accurately.

3. Oil printing

To add some colors onto the surfaces of the casing, for mass production, we want to set up a program to control the oil printing machines. First, we use the oil printing machine built-in program to design which areas will want which color, then the machine will be print the desired colors onto the surfaces.

10.2 Production tools, fixtures and machines

PCB Production tools:

1. NC Drilling Machine

2. UV Exposure Unit3. Image Maker

4. Etching Tank

5. Wave Soldering Machine

6. Cutting Machine

7. Cathode-Ray Oscilloscope

8. Multi-meter

Casing Production tools:

1. Lathe Machine

2. Drilling Machine

3. Cutting Machine

10.3 Production Flow

11. Conclusions

11.1 Problem Encountered

There were several problems encountered within the manufacturing processes. In fact, the original LED thermometer used COP8782 as the micro-controller. It was a 20-pin integrated circuit that had many features that make it particularly well suited to this project:

1.1 4096 8 (OTP) EPROM

1.2 128 bytes RAM

1.3 1 ms cycle time at 10 MHz

1.4 16 bit timer with automatic reload, external event counter and capture functions

1.5 16 I/O pins, 14 of which can be individually programmed as inputs or outputs

1.6 Selectable tri-state, push-pull or pull-up I/O pin configuration

1.7 Microwire interface

1.8 Timer, software, and external interrupt sources, with programmable polarity

And the original schematic design is shown as following diagram.

This was designed by the Elektor Electronic Company. As we can see from the diagram, COP8782 was used as the micro-controller to control the thermal sensor DS1621. Because of the limitation of development tools, we use the AT89C51 as the micro-controller and the DS1620 as the thermal sensor.

However, AT89C51 is 40-pin integrated circuit, the original schematic design used in Elektor Electronics project should be revised. We changed the design by setting the number of each column from 8 to 10.11.2 Experience gained

After this industrial training programme, we had gained much valuable experiences. We had refreshed our memory of assembly programming, PCB manufacturing procedures. We also learnt how to use the cutting machine and lathe machine to produce the casing.

Besides, manufacturing process, we know the importance of project planning. If a good schedule was made before doing any process, the efficiency will be much better than no schedule and no planning.

12. Recommendation and future enhancementSince decoration can be subjective, no suggestions can be provided. However, focusing on the functions, we have thought about several recommendations or future enhancement.

Although our production can function properly, the temperature display is flashing during measuring the temperature values. To overcome this, the delayed function of the programme and the frequency of the crystal should be considered and changed.

By adding extra components to the PCB and design computer programme with an interface, the thermometer can communicate with computer. By the use of this programme, maximum temperature record and minimum temperature record of the whole day can be displayed. Memory refresh should be done within the programme too.

On the other hand, if available, adding a microphone and extra circuit design, the thermometer can be used to measure and display sound noise. A switch can activate this function. By pressing the same switch, the product will measure temperature again.

13. References

1. Dallus Semiconductor

http://www.dalsemi.com2. Elektor Electronic Company

http://www.elektor-electronics.co.uk3. RS Components Ltd.

http://www.rswww.com.hk4. METAL Design and Fabrication / David and Susan Frisch, New York : Whitney Library of design, 1998.

5. The 8051 microcontroller and embedded systems / Muhammad Ali Mazidi, Janice Gillispie Mazidi, Upper Saddle River, N.J. : Prentice Hall, c2000.

6. The 8051 microcontroller : architecture, programming, and applications / Ayala, Kenneth J., Minneapolis/St. Paul : West Pub., c1997.Recycle Unit or

Investigation Unit

Retailer

Quality Control Section

Casting Section

Circuit Testing

Assembling Section

PCB Board Section

Oil printing

Color selections

Design the graphics of the surfaces

Holes drilling

Acrylic sheet cutting

Draw the desired design on the AutoCAD

Consideration of the surfaces dimension

Design the outlook of the surfaces

Tapping

Holes drilling

Aluminum bars cutting

Draw the desired design on the AutoCAD

Consideration of the frames dimension

Design the outlook of the frames

Surface Production

Frame Production

Oil Printing

PCB Production

In case of failure

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