Chapter 3THE DESIGN SYSTEMThis chapter deals with the discussion of methods used in the development of the system. It included the procedure, technical specifications of components of the design and all necessary information needed for study.3.1 Data Gathering ToolsThe effective instruments for gathering data used in the study.Observation. Was used by the proponents to collect information through observing things, the proponents were able to describe and analyse current problems of the society , and come up with to a design a system. Library Research. The proponents researched for relevant topics and studies to aid up the study. Scan and review unpublished and published materials to design a original concept for the system. Internet-based Research. Through the use of computer network, the internet, the researchers acquired a vast variety of relevant information from local to international sources to identify the existing systems and not override the design system. The proponents also used this tool to check availability of materials needed for the construction of the design system.

3.2 Functional Block Diagram

Figure 3.2 Functional Block Diagram of the Designed System3.2.1 Hardware Operation Description of the Block Diagram Power Supplies a power source of 220V was required to power up the system with an ac-dc converter output voltage of 5V. Microcontroller - a small computer on a single Integrated Circuit for embedded application, it has the program codes that run the system automatically. LCD Display used as a visual interface between user and the system, verifying that the microcontroller works properly. 4 Digit 7 Segment used as a visual interface also. LED used also as a visual interface verifying the system works properly.3.3 Process FlowProgrammable Interface Controller model 16F628A has an 18-pin interface. Divided into Four (4) groups, Vss, Vdd, Port A and Port B. Knowing Vss is the ground and Vdd is for the 5V supply. Most of the time, Port B is being used for output and Port A is for input but if ever Port A is needed, disabling the comparator is the solution. The system came up with different examples with different visual interface. RA5/MCLR/Vpp needs to be held high so putting a 10k in series to it will make this work. For application wanting the LCD to be used as an output, Pins 1/GND and 5/R/W of LCD should be grounded and Pin 2/Vcc is connected to source. For backlight enabling, Anode should be in VCC and Cathode in ground. For the Potentiometer, 10k is a good variable resistor. For outputs D4-D7 should be connected to RB4-RB7 respectively. Four Digit Seven Segment works also as a visual interface, it has 12 pins, for 4 Digit, it has D1, D2, D3 and D4, a,b,c,d,e,f,g and h. For D1, D2, D3 and D4 to function it is needed to be connected to VCC but 4 Digit 7 Segment cannot handle 5V using of BC547 would best fit. Switches are used mostly for increment and decrement. It is connected to Port A for input. 3.4 Component ListTable 3.5.1 Parts List - Processing DevicesMaterial/sSpecificationQuantity

PICPIC16F628A5

Protoboard4X5 protoboard4

PCB2X2 PCB5

PCB1X1 PCB5

ProgrammerK1501

BreadboardBreadboard5

Table 3.5.2 Parts List - Output deviceMaterial/sSpecificationQuantity

LCD16X2 LCD Display Module5

7-segment4-digit common cathode 7-segment display5

LEDRed LED25

LEDGreen LED5

LEDYELLOW LED5

Table 3.5.3 Parts List - Switching componentsMaterial/sSpecificationQuantity

TransistorBC54720

Tact switchPush button20

Resistor4.7k Ohms40

Resistor10 k Ohms5

Resistor330 Ohms40

Resistor470 Ohms35

Trimmer10k potentiometer for LCD contrast5

Crystal4.0MHz crystal5

Capacitor22 pF10

Capacitor104 pF10

TransistorLM78055

HeaderFemale Header285

HeaderMale Header30

HolderIC Holder5

Connecting wiresSolid

Breadboard wiresStranded

Table 3.5.4 Parts List - miscellaneous componentsMaterial/sSpecificationQuantity

File caseRectangular5

Fiber glassRectangular1X1 foot

3.6 Bills of MaterialsTable 3.6.1 Bill of Materials - Processing DevicesMaterial/sSpecificationQuantityUnit price (PHP)Total amount

PICPIC16F628A5150750

Protoboard4X5 protoboard590450

PCB2X2 PCB51050

PCB1X1 PCB5525

ProgrammerK1501800800

BreadboardBreadboard5140700

Total:2775

Table 3.6.2 Bill of Materials - Output deviceMaterial/sSpecificationQuantityUnit price (PHP)Total amount

LCD16X2 LCD Display Module52501250

7-segment4-digit common cathode 7-segment display5

70350

LEDRed LED25375

LEDGreen LED5315

LEDYELLOW LED5315

Total:1705

Table 3.6.3 Bill of Materials - Switching componentsMaterial/sSpecificationQuantityUnit price (PHP)Total amount

TransistorBC54720480

Tact switchPush button2010200

Resistor4.7k Ohms40140

Resistor10 k Ohms515

Resistor330 Ohms40140

Resistor470 Ohms35135

Trimmer10k potentiometer for LCD contrast51050

Crystal4.0MHz crystal520100

Capacitor22 pF10110

Capacitor104 pF10110

TransistorLM780551575

HeaderFemale Header820160

HeaderMale Header12525

HolderIC Holder520100

Connecting wiresSolid3030

Breadboard wiresStranded65200200

Power supplyPower supply5150750

Totat:1820

Table 3.6.4 Bill of Materials - miscellaneous componentsMaterial/sSpecificationQuantityUnit price (PHP)Total amount

File caseRectangular5116580

Fiber glassRectangular1X1 foot360360

Screw70170

Washer70170

Knot70170

Total:1150

3.7 PCB Layout 3.7.1Below is the PCB layout of the PIC16F628A

Figure 3.7.1 PCB Layout of PIC16F628A3.7.2Below is the schematic of the step down circuit

Figure 3.7.2 PCB Layoout of Voltage Step-Dpwn Regulator3.7.3Below is the schematic of the whole system

Figure 3.7.3PCB Layout of Application Circuit3.7.4 Actual Pictures

Fig. 3.7.4a Complete Image

Fig. 3.7.4b Application Circuit

Fig. 3.7.4c PIC Circuit

Fig. 3.7.4d Step Down Regulator

Fig. 3.7.4e AC-DC Converter