Printed Circuit Board(PCB’S)

1http://saturnpcb.com/pcb_services.htm

OverviewWhat is a PCB?Why use a PCB?How do I make a PCB?

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Printed Circuit Board Circuit connects components through board Made of alternating layers of conducting

and insulating materials

3http://www.seilpcb.co.kr/products/images/2_1_img5.gif

Why PCB?• Features

• Surprisingly Affordable• Highly reliable• Compact

• Drawbacks• Requires more layout than other board types• Higher initial cost than wire wrap or point-to-

point construction

4http://en.wikipedia.org/wiki/File:Breadboard_complex.jpg

PCB Design Steps1 Design the circuit2 Place the components3 Route the wires4 Manufacture

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EDA Software• PCB design software package

• Design the circuit (Schematics editor)• Place the components (PCB editor)• Route the wires (Autorouter module)

• Examples:• Express Schematics• ExpressPCB• Proteus(ISIS)

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Schematic Capture Pin in/outs Components Interconnections Easily Readable High-Level Block

Diagram

7All pictures of schematics and EAGLE screenshots from http://www.sparkfun.com/tutorials/108 and http://www.sparkfun.com/tutorials/109

Placement of Components

• Rat’s Nest

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Placement of Components• Place big components first- e.g.

microcontroller• Place components in separate functional

groups• Put a ground plane under all components

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Signal Routing Component PlacementSurface mount

• Top and bottom planes• Minimal routing area

Through-hole mounted• All components on same side• Reduces routing area on all planes

10http://www.ehow.com/how_8306661_solder-mini-components.htmlhttp://blog.amal.net/?p=188

Signal RoutingTraces are wires connecting componentsTraces can be routed through multiple layers

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Vias and PadsVias are connections between layersPads are copper areas for pin connections

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Viewplot Check

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Cost Estimate

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•www.pcbfabexpress.com

THE 8051 MICROCONTROLLERPIN DIAGRAMIT’S COMPONENTSIT’S ADVANTAGESDISADVANTAGESCOMPARISON WITH DIFFERENT

MEMBERS

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8051 Basic Component4K bytes internal ROM128 bytes internal RAMFour 8-bit I/O ports (P0 - P3).Two 16-bit timers/countersOne serial interface64k external memory for code64k external memory for data210 bit addressable

Microcontroller

8051 Foot Print

1234567891011121314151617181920

4039383736353433323130292827262524232221

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7RST

(RXD)P3.0(TXD)P3.1

(T0)P3.4(T1)P3.5

XTAL2XTAL1

GND

(INT0)P3.2(INT1)P3.3

(RD)P3.7(WR)P3.6

VccP0.0(AD0)P0.1(AD1)P0.2(AD2)P0.3(AD3)P0.4(AD4)P0.5(AD5)P0.6(AD6)P0.7(AD7)EA/VPPALE/PROGPSENP2.7(A15)P2.6(A14)P2.5(A13)P2.4(A12)P2.3(A11)P2.2(A10)P2.1(A9)P2.0(A8)

8051(8031)(8751)(8951)

IMPORTANT PINS (IO Ports)IMPORTANT PINS (IO Ports)

Port 2 Port 2 （（ pins 21-28pins 21-28 （（ P2.0P2.0

～～ P2.7P2.7 ））8-bit R/W - 8-bit R/W -

General Purpose General Purpose I/OI/O

OrOr highhigh byte of byte of the the addressaddress bus bus for external for external memory designmemory design

IMPORTANT PINS (IO Ports)IMPORTANT PINS (IO Ports)

Port 3 Port 3 （（ pins 10-17 pins 10-17 （（ P3.0P3.0 ～～

P3.7P3.7 ）） General Purpose I/OGeneral Purpose I/O if not using any of the if not using any of the

internal peripherals internal peripherals (timers) or external (timers) or external interrupts.interrupts.

Registers

A

B

R0

R1

R3

R4

R2

R5

R7

R6

DPH DPL

PC

DPTR

PC

Some 8051 16-bit Register

Some 8-bitt Registers of the 8051

Data memory

XM

DMMOV A,62H

MOV R1,#62HMOV A@R1

MOV A,0A2H

MOV R1,#0A2HMOV A@R1

Comparison some of the 8051 Family Members

ROM RAM Timer8051 4k 128 28031 - 128 28751 4k

eprom128 2

8052 8krom 256 38032 - 256 38752 8k

eprom256 3

Comparison of the 8051 Family Members

ROM type 8031 no ROM 80xx mask ROM 87xx EPROM 89xx Flash EEPROM

89xx 8951 8952 8953 8955 898252 891051 892051

Example (AT89C51,AT89LV51) AT= ATMEL(Manufacture) C = CMOS technology LV= Low Power(3.0v)

Advantages of Microcontroller based SystemAs the peripherals are integrated into a single chip, the

overall system cost is very lessThe product is of small size compared to micro processor

based systemThe system design now requires very little effortsAs the peripherals are integrated with a microprocessor the

system is more reliableThough microcontroller may have on chip ROM,RAM and

I/O ports, addition ROM, RAM I/O ports may be interfaced externally if required

On chip ROM provide a software security

SJCET

Disadvantages of microprocessorThe overall system cost is highA large sized PCB is required for

assembling all the componentsOverall product design requires more

timePhysical size of the product is bigA discrete components are used, the

system is not reliable

SJCET