A Wireless Transmission Projection Computer Science Essay

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A projector is to display images from computer or laptop. The term 'wireless' is used to describe how the projector receive the signal. Presentation projector always having wire mess up here and there, this is where wireless projector comes in. It solve the problem of wiring by transmitting without wire using wireless technology such as Bluetooth, radio frequency and Wi-Fi. Currently there are many types of projectors such as image projector, movie projector and etc.

Aims

The aim for this project is to design a device that will transmit signal from a laptop/desktop to a presentation projector through wirelessly. It will be using radio frequency to transmit the data.

1.3 Objective

There are few of objectives in this project. The main objective is to design a transmitter and receiver device that will work with a PC and a presentation projector. Before can achieve the main objective there are minor objective that is important to achieve the main objective. It is to understand RGB protocol and signaling. Then next is to understand various types of wireless technology that is available to transmit and receive the data. After that understand how a presentation projector receive data and decode the data.

Chapter 2: Literature review

2.1 Wireless

Wireless is a transferring data without using any wires over a distance, it can be short like few meters or long distance like kilometers. Wireless is one of the most famous telecommunication branches.

Nowadays wireless is widely used by a lot of devices, such as two-way radio, cellular phone, TV, GPS, mouse, keyboard, and wireless networking .

There are few ways of doing wireless transmission:

a) Radio frequency(RF)

b) Infrared

c) Bluetooth

d) Wi-Fi

2.1.1Radio Frequency (RF)

Radio frequency is frequency that lower than 300Ghz with a wavelength of 100km to 1mm. This range of electromagnetic range constitute a radio spectrum with refer to the part of electromagnetic spectrum.

Figure 1: Radio spectrum[1]

Radio waves are way longer compare to other of the electromagnetic spectrum, radio waves are divided to few bands according to their wavelength and serve different purpose and different kind of telecommunication. [1]

Band

Frequency

Wavelength

Uses

VLF

3-30kHz

100km-10km

Long range navigation and marine radio

LF

30-300kHz

10km-1km

Aeronautical and marine navigation

MF

300kHz-3MHz

1km-100m

AM radio  and radio telecommunication

HF

3-30MHz

100m-10m

Amateur radio bands, NRC time signal

VHF

30-300MHz

10m-1m

TV, FM, cordless phones, air traffic control

UHF

300MHz-3GHz

1m-10cm

UHF TV, satellite, air traffic radar

SHF

3-30GHz

10cm-1cm

Mostly satellite TV and other satellites

EHF

30-300GHz

1cm-1mm

Remote sensing and other satellites

Table 1: Characteristics of different bands [1]

2.2 Video[2]

The most common digital signals used are RGB and YCbCr. 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 series of still images due to fast changing that it looks like continuous 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. Standard-definition is interlaced and enhanced-definition is progressive.

Figure 2: Progressive displays "Paint" the lines of an image consecutively one after another

Figure 3: Interlaced displays "Paint" first one-half of the image (Odd Lines) then the other half(Even Lines)

2.3 Color spaces[2]

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

Figure 4: The RGB color cube[2]

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

Table 2: RGB color bars[2]

2.4 RS-232

Recommended Standard 232 that is commonly known is RS-232 is a standard for serial binary single-ended data and control signals connecting between a Data Terminal Equipment and a Data Circuit-terminating Equipment. It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals and the physical size and pinout of connectors.[3] There are 3 types of pin available that is 4, 9 and 25. This port is use to let a PC communicate with microcontroller.

Figure 5: 9-Pin "AT" Style[4]

2.5 Encoding technique[5]

In order to exchange data between 2 devices, a signal encoding technique is needed to make sure that the 2 devices can send and receive the data correctly. A digital signal is a sequence of discrete, discontinuous voltage pulses, each pulses is a signal element. Binary data will be transmitted by encoding each data into signal elements. The simplest way to encoding is one-to-one correspondence between bits and signal. However there are a lot more complex encoding technique to improve the performance and security to ensure the data is exchange fast and safe. There is a lot of encoding scheme that we can use but we need to compare each encoding scheme and select the most suitable scheme.

These are the few specification of the scheme that we need to compare:

a) Signal spectrum-the higher the frequency, more bandwidth require, providing isolation

b) Clocking-used to synchronize the data exchange between transmitter and receiver to provide the correct timing.

c) Error detection-to ensure the data is send and receive correctly; higher performance of error detection=better security

d) Cost and complexity-higher signal rate cause higher cost, some codes require more signal rate than data rate.

There are 4 types of encoding schemes:

a) NRZ-L (nonreturn to zero level)

b) NRZ-I (nonreturn to zero inverter)

c) Manchester coding

d) Differential Manchester

Among the 4 encoding scheme, Manchester coding have the most security and higher clock. Therefore it is the commonly use for encoding and decoding scheme.

2.6 Comparing similar products

Product Name

Specification

Panasonic PT-LB10NTU Projector

Panasonic PT-LB10NTU[6]

Pros: Support for most wireless cards, great image quality - even for presentations in wireless mode, easy to setup and use.[6]

Cons: Projector ships with just one type of connection cable - VGA. [6]

Summary: Panasonic takes wireless to a new level with broad support and fast and easy connection of up to 4 PCs, user-friendly features and high brightness in a slim 4.9 lb. [6]

Dell S300wi ProjectorDell S300wi[7]

Pros: It's interactive. No calibration. Short throw. Good data image quality. Acceptably bright image for a small to mid-size room. Good connectivity. Good audio.[7]

Cons: Sluggish interactive response. Below par brightness uniformity. Usable but low quality video. Moderately obvious rainbow artifacts. Limited 3D. [7]

Canon LV-8215 ProjectorCanon LV-8215[8]

Pros: Image Quality. Resolution. Audio Quality. Portability. Lamp Life. 3-Year Warranty.[8]

Cons: Fan noise. No User Memory. Maintenance. [8]

Table 3:Comparison with various products

2.7 Critical analysis

Most of the products have some special feature. All of the 3 are wireless projector that has various features and come from different manufacturer. Dell S300wi's interactive feature is very good feature because it has a remote and pen. The pen can move the mouse cursor when presentation. Basically all wireless projector is easy to setup and use so there will be no wiring problem.

Chapter 3: Methodology

3.1 System

Figure 6: System block diagram

The figure above is showing how this project system works. It starts off from a PC that will generate signal source then the signal will be send to microcontroller by using RS-232 port. In the microcontroller, it will encode the signal so that it can send the signal using radio frequency. When the receiver receive signal it will decode and send it to projector.

3.2 Flow chart

Figure 7: RF transmitter

A PC will send data through RS232 port to microcontroller then microcontroller will send it to RF transmitter. Figure above is showing how the RF transmitter process the data.

Figure 8: RF receiver

Figure above is showing how RF receiver process the data. It will receive the data wirelessly by using radio frequency.

3.3 Costing

No.

Components

Quantity

Unit price

Total price

1

PIC microcontroller

2

RM 30

RM 30

2

Printed circuit board

1

RM 20

RM 20

3

ETC

 

RM 200

RM 200

Grand total

2

RM 250

RM 280

Table 4: Costing for components

In the table, ETC under components is resistors, capacitors, diode and more.

3.4 Software

Software that will be needed for this project is MPLAB. MPLAB is a software that is free to use. It is an integrated toolset for the development of embedded applications consist of PIC.

Chapter 4: Limitation of project

There are 2 types of projectors that is 'Real time' projector and 'Upload' projector. The limitation for 'Real time' projector is that it has a slight delay between the transmitter and receiver due to processing speed involved in encoding and decoding the wireless signal. Mostly the effect has little effect but if it is playing video and audio then the effect can be clearly seen. This is due to the limited bandwidth of connection. 'Upload' projector limitation is that it need a PC within the range of the projector. All of the projector need a power supply so the limitation is that it always has to be has a cable connecting to the projector. The projector can't be mobilize although it is wireless.

Chapter 5: Conclusion

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