Projector Functions And Uses Computer Science Essay

A projector is to display images from computer or laptop. The term ‘wireless’ is used to describe how the projector receives the signal. Presentation projector always having wire mess up here and there, this is where wireless projector comes in. It solves the problem of wiring by transmitting without wire using wireless technology such as Bluetooth, radio frequency and Wi-Fi. By eliminating wiring problem, it will speed up the time of setting up through wire. This will also allow multiple users to be connected to projector at a time to present their content from their laptop. Installation of projector using wire is very costly because VGA cable is quite expensive when it comes to using long length of wire. Currently there are many types of projectors such as image projector, movie projector and etc. This project is about sending data wirelessly using radio frequency from a transmitter to receiver. This project will be using microcontroller that is connected to a PC. There will have 2 circuit boards that have a microcontroller each.

The transmitting board will be the place where process the data that come from a PC that is an analog signal and it will be kept first in the memory that is a static ram. Then the data will pass through an encoder that will convert data information into a standard format or code and transmit by using radio frequency.

For receiver board, data that is receive from radio frequency receiver will be decoded using decoder to reverse the format to the original form of data information. Like at the transmitting board, data will be stored in memory first then only it will send to digital to analog conversion to convert it into analog form. Lastly the data will be send to a projector. As for this project, projector will be replaced to CRT monitor. This is because projector and monitor are having the same VGA pin out connector. The VGA pin out connector is a DE15.

Aim

The aim for this project is to design a device that will transmit signal from a laptop/desktop to a presentation projector through wirelessly.

Objectives

To design a device that will interface to PC and a projector wirelessly.

To research of RGB signaling and protocol.

To research of various types of wireless of technology.

To understand the functioning of the presentation projector.

Product specification

Specification

Project

Microcontroller

PIC 18F4550

Power Supply

9V

Type of Wireless

Radio Frequency Module

Wire

Single Core

Weight

300 Gram

Type of Memory

Static Ram

Table 1: Product Specification

CHAPTER 2: LITERATURE REVIEW

Marketing survey

Lindy Projector Server[1]

C:Documents and SettingsAdministratorDesktopprojector server.jpg

Figure 1.0: VGA Extender & Projector Server[1]

The wireless VGA extender & projector server allow connection to a projector either by using wire or wireless LAN. This is best application for PowerPoint and other presentation. It’s wireless connection support up to 100m. Do not need to swap VGA cable between laptops. Presenter just have to connect their computers to server access point through wireless. It is very convenient. [1]

Panasonic[2]

Panasonic PT-LB10NTU Projector

Figure 1.1: Panasonic PT-LB10NTU[2]

It support for most wireless cards and it has a great quality image when is in presentation mode. It is very easy to setup and friendly user. The disadvantage of this projector is that it comes with only 1 type of connection cable that is VGA. The projector can be connected up to 4 users at a time with broad support, fast and easy. [2]

Dell[3]

C:Documents and SettingsAdministratorDesktopdell.jpg

Figure 1.2: Dell S300wi[3]

It is very rare to find a projector that has a multimedia audio. It is a short-throw projector type that can be projected in a short distance. This product does not need to be calibrated before using. It is best to use in a small to medium size room. It has one wireless connector that is an embedded WiFi. [3]

Canon[4]

Canon LV-8215 Projector

Figure 1.3: Canon LV-8215[4]

This product has a few of advantages; one of them is audio quality. It is a multimedia projector that is why audio quality, image quality and resolution are its advantages. When it comes to such good features, there will always have a bad side that is its fan is noisy and also need maintenance once in a while. [4]

Casio[5]

Casio XJ-S46 Projector

Figure 1.4: Casio XJ-S46[5]

A DLP projector that uses a wireless adapter to connector between laptop and projector. It has a wireless adapter so that allow wireless connection. It is easy to carry to anywhere due to its light weight. The projector has digital zoom feature. [5]

Overall Product Cost and Specification

Product name

Lindy

Panasonic

Dell

Canon

Casio

Type

Projector server

LCD projector

DLP projector

LCD projector

DLP projector

Specification

-Compatible with all Windows but not Mac

-Up to 4 laptops can be connected

-Quick and easy setup

-Wireless connection

-Up to 4 laptops can be connected

-Quick and easy to shut down and start up

-For small to medium room

-Wireless connection

-Short-throw

-Has an interactive pen

-Short-throw projector

-HDMI input

-Up to 4-1 split-screen

-3D projection

-High contrast

-Has DVI input

-Blackboard mode

-Soft carrying case

-Very light weight

-USB port

-Soft carrying case

Weakness

-Only VGA connection

-Projection mode does not support wireless audio

-Presenting speed and image quality

-Overloaded and distorted at maximum volume

-Very heavy

-No digital zoom

-Very heavy

-No digital zoom

-Low contrast

-Uses high power consumption

Cost

RM1600.00

RM602.00

RM3000.00

RM1673.90

RM3526.60

Comments

-Not a projector but a server

-Fast setup

-Quite expensive

-Fast setup

-Quite cheap

-Simultaneously project up to 4 different user screens

-Very expensive

-not good image quality

-Very expensive

Table 2: Overall product cost and specification [1][2][3][4][5]

Component

D-Subminiature[6]

D-Subminiature or can be called D-Sub is universal type of electrical connector used in computer. D-Sub has a lot of series that every series has different number of pins. There are DA-15, DB-25, DC-37, DD-50 and DE-9.[6]

http://upload.wikimedia.org/wikipedia/commons/thumb/4/47/DSubminiatures.svg/250px-DSubminiatures.svg.png

Figure 2.0: Different Pins Connector[6]

Type

DA-15

DB-25

DC-37

DD-50

DE-9

Pins

15

25

37

50

9

Table 2.1: Different type of D-sub

From the table above, DB-25, DC-37 and DD-50 are not in consideration because laptop does not have this type of pin out. DE-9 has 9 pins and laptops do have the pin out but for monitor/projector, it only supports DA-15. That’s why for this project DA-15 will be used. DA-15 can be called DE-15 or also VGA connector is used because monitor and laptop both have pin in and pin out that support each other. [6]

Microcontroller[7]

Microcontroller is a device with hidden powerful ability to do a lot of thing. Nowadays most of electronic device has microcontroller inside them because it is use to process task. Due to its low voltage consumption and for its ability to run one specific program, it is usually chosen to use in project. The program generally is program by using a programmer and store in ROM (read-only memory). [7]

Microcontroller

PIC 16F877a

PIC 18F4550

Basic Stamp

I/O ports

33

35

16

RAM

368Bytes

2048 Bytes

32Bytes

Flash Program Memory

8K

16K

2K

Cost

RM21

RM35

RM70

Table 2.2: Different type of microcontroller[7]

From the table above, out of 3 comparisons basic stamp is the most not suitable for this project. This is because there are only a few I/O ports. It runs at a very slow speed and has small memory size.

PIC 16F877a and PIC18F4550 is the 2 microcontroller can take into consideration.

Memory[8]

There are 2 types of memory which are volatile and non-volatile memory. Volatile memory is storage where when power is off contents are erased. This is because of RAM’s volatile nature that is why user must use hard drive to keep their work as a permanent medium in order to avoid losing data. DRAM and SRAM are both volatile memory that currently have in market. Device like computer ram is a volatile.

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Non-volatile memory is storage where when power is off the contents that is stored previously will still be there. Devices like hard drive and CMOS chip are example of non-volatile memory. Currently in market, ROM, Flash memory, FeRAM, MRAM and PRAM that are non-volatile memory.

Memory

Volatile Memory

Non-Volatile Memory

Type

DRAM, SRAM

ROM, Flash memory, FeRAM, MRAM, PRAM

Advantages

-Mostly comes with a lifetime guarantee

-Automatically store data

-Data can be stored up to 10 years

-Less costly

-Data won’t lost when power off

Disadvantages

-Data will lost when power off

-Quite costly

-User need to manually store data

Table 2.3: Comparison of memory type[8]

As for this project after analysis, it is best to go for volatile memory because this project does not need to store memory and retrieve after power off. After analyze and decided to go for volatile memory, there are DRAM and SRAM to choose from. DRAM stands for dynamic random access memory and SRAM is static random access memory. In this project, SRAM is chosen because it does not need to keep refreshed over time which DRAM needs a constant refreshing. This I s because DRAM store its memory as charge leaks which information needs to be read and written every few milliseconds.

Memory

X28HC256PZ-15

CY62256LL-70PXC

AT29LV256-20JC

Type

EEPROM

SRAM

FLASH

Mounting

Through hole

Through hole

Surface mount

Density

256k

256k

256k

Operating Voltage

5V

5V

3.3V

Pin Count

28

28

32

Number of Bits per Word

8bit

8bit

8bit

Interface Type

Parallel

Parallel

Parallel

Manufacturer

Intersil

Cypress

Atmel

Table 2.4: Comparison of memory available[8]

From the table above, most of the specification above is nearly the same. Memory that is produce by Atmel is out of consideration because the operating voltage is 3.3V that is not suitable for this project. The mounting way is surface mount making this project not that suitable because there is no equipment to solder it onto PCB. This memory has too many pin count too which cannot be supported by PIC18F4550.

Cypress and Intersil memory are the exact same specification but the memory that is used in this project is Cypress memory. This is because Intersil memory is EEPROM type. In this project, it does not need to store any data after power down so making SRAM is the best choice due to its nature.

Wireless

Wireless is a transferring data method without using any wire over certain distance. Some distance is just a short distance and some can goes up to very far away. Nowadays wireless is the most communication way for telecommunication method.

There are a few ways of transmitting wirelessly such as:

Infrared(IR)

Radio Frequency(RF)

Bluetooth

Wi-Fi

Wireless Technology

Infrared

Radio Frequency

Bluetooth

Distance

Short

Vary

Medium

Line of sight

Yes

No

No

Table 2.5: Comparison of Different Technology

There are modules available for this technology. From table above, this project best technology fit to use is radio frequency.

Modules that available in market are:

Modules

Type

Security

Distance

Speed

Communication way

Price

IR module

Infrared

Medium

Short

Slow

1 Way

Cheap

RF module

Radio frequency

Medium

Medium

Medium

1Way

Medium

Zigbee

Radio frequency

Medium

Medium

Fast

2Ways

Expensive

Table 2.6: Comparing wireless modules

From the table above, this project will be using RF module. Zigbee has a faster speed than RF module but from price and communication aspect, it is quite expensive and this project does not need 2 ways communication. This project just needs to send data signal to the receiver only.

CHAPTER 3: Methodology

General Block Diagram

Microcontroller PIC 18F4550

RF module

Memory

Laptop

VGA cable

Monitor

Figure 3.0: General Block Diagram

Figure above showing the overall diagram of what this project has. Monitor will be device where it display whatever shown at the laptop. Before the display can be shown at monitor, the data signal need to pass through the output video graphic array (VGA) connector that has 15 pins which can also be called DB15. Memory is to store the data signal so that the data can be kept and synchronize before going to transmitting device. This is to make sure the data is send correctly. There will be also radio frequency module which will help transmitting data signal through wirelessly.

General Flow Chart

Start

Radio frequency module

Digital to Analog Conversion

PIC

Analog to Digital Conversion

Display at monitor

Get Laptop signal

Figure 3.1: General Flow Chart

The flow chart above is showing the way a laptop send its on screen image wirelessly to the receiver side which is a monitor. Laptop will constantly send image to microcontroller which will be kept in memory of its data to enable of synchronize when transmitting wirelessly. When it captures 7500 bits then it will send to encoder to convert into a standard format or code and transmit by using radio frequency.

At the receiver side, it will constantly receive the data signal then keep in the memory. When it store up till 7500 bits, microcontroller will automatically synchronize into a code and send to monitor to display.

Project Signal Overview

Digital

Digital

Digital

Digital

Digital

Digital

R, G, B, HSync, VSync

Analog/

Digital

Laptop

Microcontroller

Memory

Microcontroller

Encoder

Transmitter

Microcontroller

Decoder

Memory

Microcontroller

Monitor

Receiver

Digital

Digital

Digital

Analog/

Digital

Figure 3.2: Signal Overview

Basically this figure above showing an overview of what type of signal when it reaches at certain hardware. There are 2 places where analog signal can only be detected which are from laptop to microcontroller and before it show the screen of laptop user. This is because signal that comes out from VGA port has red, green, blue, Hsync, and Vsync. Hsync and Vsync are the only signal that runs at 5voltage which are transistor-transistor logic (TTL) signal. The color signals are analog. This signal will pass through analog to digital converter which microcontroller itself has the function. From microcontroller to RF module, all the signals are in digital. Before display the laptop on screen display at receiver side, it will pass through digital to analog converter because monitor is uses VGA port which are analog.

Microcontroller

Figure 3.3: PIC 18F4550

PIC 18F4550 is a low voltage and 40 pins microcontroller from Microchip. It is a flash high performance PIC which has two-speed oscillator start-up. It has 35 input and output ports and up to 13 ADC module. It has also 32kbytes flash program memory, SRAM of 2048bytes and EEPROM of 256bytes.

Early few months ago, this project started out with PIC 16F877a. After some intensive of testing out to get output of image from PIC 16F877a, there is no image shown. Hence PIC 18F4550 become the next PIC to act as a microcontroller. This is because 16F877a with oscillator of 20 MHz, the speed of microcontroller couldn’t match up with the speed of VGA cable signal. Now with this PIC 18F4550, oscillator of 40 MHz is used. In this project the port are use as follow:

Port A (1-5) and Port B (0-7):

This port A (1-5) and port B (0-7) connected to memory’s address lines which are A0-A12.

Port D (0-7):

This Port D (0-7) is connected to memory data lines which are the I/O port.

Port E (0-2):

This Port E (0-2) is connected to memory control lines which are chip enable, write enable and output enable. All of this control lines are active low.

Port C (4-5):

This Port C (4-5) are vertical sync and horizontal sync.

Port A (0):

This Port A is the input of either red, green or blue pin from laptop. The color pin out from laptop is connected to A0 of this PIC is because pin A0 and pin A1 are the only pin available for analog to digital converter (ADC).

VDD:

This pin is connected to a voltage regulator which is LM 7805. This has to be connected to LM7805 to make sure the voltage does not go over 5V.

Vss:

This pin surely has to be connected to ground if not the microcontroller will not work.

OSC1 and OSC2:

It is connected to a 40MHz crystal. Without this crystal, this project will not work.

Analog to Digital Conversion (ADC)

Analog to digital conversion is a way to convert a signal from analog to digital so that the microcontroller can read the signal. After converting to digital, the signal will become either logic ‘1’ or logic ‘0’.

Example on how to convert an analog signal input of 8 bit:

x 255 = Voltage value per step

Example RGB voltage

x 255 = 35.7

Then convert into binary

35 = 00100011 (binary)

Digital to Analog Conversion (DAC)

C:Documents and SettingsAdministratorMy DocumentsMy PicturesIMG_0405.jpg

Figure 3.4: Resistor Ladder

Resistor ladder can be constructed by using a set of resistors of 2 values while another resistor double. For this project, resistor ladder is used as digital to analog conversion. Figure above is the fully constructed resistor ladder. It is a R/2R resistor network. This resistor ladder can increase its number of bits by adding more resistor network. To prove the ADC and DAC formula match, here is the example of formula.

Example on how to convert digital to analog of 8bit:

= Voltage value per step

Step x Voltage value per step = Analog output voltage

So from the formula above, now to prove the formula is correct by using previous analog result:

= 0.0196V

36 x 0.0196 = 0.686V (approximate 0.7V)

From the calculation, it is proven that the formula for ADC and DAC is correct.

RGB Theory

Video

RGB and YCbCr are the typical digital signals. The typical order of decreasing video quality is:

HDMI (Digital YCbCr)

HDMI (Digital RGB)

Analog YPbPr

Analog RGB

Analog S-Video

Analog composite

Video is always considered as continuous picture motion but actually it is a sequence of still images due to rapid changing that it looks like nonstop picture motion. The typical video refresh rate is 50 or 60 times per second for consumer video and 70 to 90 times per second for computer.

The vertical and horizontal sync information is usually transferred in one of three ways:

Separate horizontal and vertical sync signals.

Separate composite sync signal.

Composite sync signal embedded within the video signal.

Most CRT based displays are still interlaced while LCD, plasma and computer displays are progressive. Enhanced-definition video is usually defined as having 480 or 576 progressive active scan lines and is commonly called “480p” and “576” respectively. Interlaced and enhanced-definition is progressive is standard-definition.

Figure 3.5: Progressive displays

Figure 3.6: Interlaced displays

Color spaces

A three dimensional, Cartesian coordinate system is use to represent Red, Green, Blue that are the three primary additive colors.

Figure 3.7: The RGB color cube

The figure above showing RGB values for 100% amplitude, 100% saturated color bars. It is use for common video test signal.

Table 3.0: RGB color bars

Video Timing Background

Every VGA connector consist of 5 main data signals which is needed to display an image. The following are the 5 data signals:

Red

Green

Blue

Horizontal sync

Vertical sync

Red, green and blue signals is an analog type of signal. This signals carry pixel data in it. Horizontal and vertical sync is to provide information of timing for the monitor so those monitors display the pixel data correctly.

Figure 3.8: Horizontal Timing

The figure above shows that the timing of the video data and horizontal data signal. The blanking interval means that there is no video data signal is been send. Every monitor will use horizontal blanking interval to check on horizontal sync pulse. There are 3 characteristics of horizontal pulse:

Front porch

Back porch

Pulse width

Front porch is to check on the delay of initial edge and the end of video signal of sync pulse. Delay of the first piece of data and the final edge of signal of sync pulse for the next scanline is back porch. Pulse width is the period of time that sync signal is asserted.

Figure 3.9: Vertical Timing

The figure above is video frame which also video data with vertical sync. It’s basically the same thing with horizontal except for vertical then is video frame.

VGA connector

Pin

Name

Signal Direction

Description

1

Red

→

Red data

2

Green

→

Green data

3

Blue

→

Blue data

4

ID2

←

Monitor ID bit 2

5

GND

−

Ground

6

RGND

−

Red ground

7

GGND

−

Green ground

8

BGND

−

Blue ground

9

Key

.

No pin

10

SGND

−

Sync ground

11

ID0

←

Monitor ID bit 0

12

ID1

←

Monitor ID bit 1

13

HSync

→

Horizontal sync

14

Vsync

→

Vertical sync

15

ID3

←

Monitor ID bit 3

Table 3.1: Pin Description

Output signal from laptop

Input signal to laptop

Figure above is showing the pin description and the direction of the signal is going.

Encoder & Decoder

Figure 3.10: Encoder 2262 Figure 3.11: Decoder 2272-L6

Encoder

Below is a table for encoder PTC 2262:

Pin Name

I/O

Description

A0~A5

I

Pin 0 to pin 5 is address. These pin is to encode and bit ‘0’ to bit ‘5’. Logic ‘0’, logic ‘1’ or floating is set by the pin

A6/D5~A11/D0

I

Address pin or data pin is 7,8,12,13. Bit 6 to bit 11 is to determine the encoded waveform. It can be set as logic ‘0’, logic ‘1’, or floating. When data pins is used then only logic ‘1’ or log ‘0’

TE’

I

Transmission Enable. Active low trigger. Encode when ground or plug out

OSC1

O

Oscillator Pin no.1( A resistor have to connected between OSC1 and OSC2 to determine the frequency)

OSC2

I

Oscillator Pin no.2

Dout

O

Data output pin. The encoded data is sent by serial transmitting through this pin.

Vcc

–

Voltage supply

Vss

–

Ground

Table 3.2: Encoder description

Decoder

Below is a table for decoder PTC 2272-L6

Pin Name

I/O

Description

A0~A5

I

Pin 0 to pin 5 is address. These pin is to decode and bit ‘0’ to bit ‘5’. Logic ‘0’, logic ‘1’ or floating is set by the pin

A6/D5~A11/D0

I

Address pin or data pin is 7,8,12,13. Bit 6 to bit 11 is to determine the decoded waveform. It can be set as logic ‘0’, logic ‘1’, or floating. When data pins is used then only logic ‘1’ or log ‘0’

VT

O

Transmission receive. Active high trigger. When logic ‘1’ means receive

OSC1

O

Oscillator Pin no.1( A resistor have to connected between OSC1 and OSC2 to determine the frequency)

OSC2

I

Oscillator Pin no.2

Dout

O

Data output pin. The encoded data will be serially transmitted through this pin.

Vcc

–

Voltage supply

Vss

–

Ground

Table 3.3: Decoder Description

Encoder is use to convert the data information into a standard format or code so that it is easier to send. This can allow the data information to be compress into a code word.

Signal Resistor Oscillator

Resistors have to be connected to osc1 and osc2 pin at both encoder and decoder so that the resistor will set the oscillation. Below is the recommended resistor value for both encoder and decoder:

Encoder 2262

Decoder 2272-L6

4.7MΩ

820kΩ

3.3MΩ

680kΩ

1.2MΩ

200kΩ

Table 3.4: Oscillator for encoder and decoder

F =

From this formula, the best suitable resistor value for fastest speed when transmit is 1.2MΩ and 200kΩ.

Code word

A code word is consisting of 8 address, 4 data and 1 sync. This adds up into 13 bits.

Figure 3.12: Code Word

Figure 3.13: Address/data bit waveform

The figure above is showing address bit waveform that has been encoded.

Radio Frequency Module

http://www.ananiahelectronics.com/pcr1a.gif http://www.ananiahelectronics.com/fs100a.gif

Figure 3.14: Receiver Figure 3.15: Transmitter

The radio frequency transmitter has 3 pins. From the figure above, the transmitter has 1 ground, 1 power supply pin and 1 data pin. Receiver has 1 ground, 1 power supply and 2 data pins. Both transmitting and receiving device have to be the same frequency so that the signals data can be send n receive. Every wireless transmission, there will be encoding and decoding technique that is vary from every device. Encoding is to ensure that the information that will be send wirelessly is secure as in security and not disturb by other same device that has same frequency.

Memory (RAM)

Memory which can be separated into 2 types which are volatile and non-volatile memory. In chapter 2 already explain what is volatile and non-volatile. This project uses 2 memory which are 1 at transmitting and 1 at receiving.

The following are the pin definitions for this memory:

Pin Number

Type

Description

1-10, 21, 23-26

Input

A0-A14 are address inputs.

11-13, 15-19

Input/Output

I/O0-I/O7 are data lines. It is used as inputs and output lines depending on the operation.

27

Input/Control

When WE is selected to be low, a write is conducted. When high is selected, a read is conducted.

20

Input/Control

When CE is low, chip is selected. When high, chip is selected.

22

Input/Control

Output enable. Controls the direction of the I/O pins. When low, the I/O pins behave as outputs. When deasserted high, I/O pins are three-stated and act as input data pins

14

Ground

Ground for device

28

Power Supply

Power supply for device

Table 3.5: Memory Description

Software Flow Chart

Transmitter

Start

Capture frame 8 times

Write into memory

Capture 7500 bits?

Transmit wirelessly

Yes

No

Figure 3.16: Transmitter

First the laptop will send out bit of red, green and blue with the sync bit. This bit that is in analog will convert into digital once it reach inside microcontroller. Then the microcontroller will write the frames that is capture 8 times into memory. It will check has it capture 7500 bits or not if not then the microcontroller will keep on capturing. After that once 7500 bits obtain then microcontroller will read from memory and send through wirelessly at transmitting side.

Receiver

Checking for wireless signal

Write into memory

Receive 7500 bits?

Display at monitor

End

Yes

No

Figure 3.17: Receiver

The receiver will keep on checking for wirelessly signal. Once it obtains the signal then will write into the memory. The microcontroller will constantly check whether it has receive 7500 bits. Once it reach 7500 bits then the monitor will display image.

CHAPTER 4: Analysis and Testing

RGB Timing