Gesture vocalizer

                                        ABSTRACT

Gesture vocalizer is a large scale microcontroller based system being designed to facilitate the communication among the dumb and deaf communities and their communication with the normal people. This system can be dynamically reconfigured to work as a “smart device”. Gesture vocalizer discussed is basically a data glove and a microcontroller based system. Data glove can detect almost all the movements of a hand and microcontroller based system converts some specified movements into human recognizable voice. The data glove is equipped with two types of sensors: The bend sensors and accelerometers as tilt sensors. This system is beneficial for dumb people such that their hands will speak having worn the gesture vocalizer data glove.

                                   INTRODUCTION

“Speech” and “gestures” are the expressions, which are mostly used in communication between human beings. Learning of their use begins with the first years of life. Research is in progress that aims to integrate gesture as an expression in Human-Computer Interaction (HCI).

In human communication, the use of speech and gestures is completely coordinated. Machine gesture and sign language recognition is about recognition of gestures and sign language using computers. A number of hardware techniques are used for gathering information about body positioning; typically either image-based (using cameras, moving lights etc.) or device-based (using instrumented gloves, position trackers etc.).

However, getting the data is only the first step. The second step, that of recognizing the sign or gesture once it has been captured is much more challenging, especially in a continuous stream.

This project analyses the data from an instrumented data glove for use in recognition of some signs and gestures. A system is developed for recognizing these signs and their conversion into speech.

The results will show that despite the noise and accuracy constraints of the equipment, reasonable accuracy rates have been achieved.

                                                           Fig.1: gesture vocalizer system

                                  

                                    MOTIVATION

The motivation of this project is the problem faced when dumb people communicate with blind,deaf and normal communities.

Since all gestures used by dumb people are not understood by normal or blind people the gesture vocalizer comes into play. Where the gestures used by dumb people are converted into voice.

Likewise the gestures are also displayed on an LCD (Liquid crystal display), hence helping the communication between deaf and dumb people.

Therefore the aim of the project is to create a glove, which allows interaction of the dumb people with blind, deaf and normal people, with no greater effort than wearing a glove which can be part of one’s daily attire. 

  

SYSTEM DESCRIPTION

Block diagram of the system is shown in Fig.1.1. The system is consisted of the following modules:

• Data Glove

• Tilt detection

• Gesture detection

• Speech Synthesis

• LCD Display

Data glove is consisted of two sensors; bend sensors and tilt sensor. The output of the tilt sensors is detected by the tilt detection module, while the output of the bend sensors, and the overall gesture of the hand are detected by the gesture detection module. Gesture detection module gives low input to the voice record and playback module. The voice record and playback module outputs message with respect to each input from the gesture detection module. And the same output is also displayed on the LCD.

Fig.2: Block diagram of the system

DATA GLOVE

The main module of the project is the data glove. It mainly consists of two sensors; bend sensor and tilt sensor.

     FLEX SENSOR

In this project,the data glove is equipped with three bend or flex sensors, each of the bend sensor is meant to be fixed on one of the finger of the hand glove for the monitoring and sensing of static movements of the fingers of the hand.

One side of the sensor is printed with a polymer ink that has conductive particles embedded in it. When the sensor is straight, the particles give the ink a resistance of about 30k Ohms. When the sensor is bent away from the ink, the conductive particles move further apart, increasing this resistance (to about 50k Ohms when the sensor is bent to 90º as in the diagram below). When the sensor straightens out again, the resistance returns to the original value. By measuring the resistance, you can determine how much the sensor is being bent.

Fig.3: Bend sensor operation

 General features

- Angle Displacement Measurement

- Bends and Flexes physically with motion device

- Possible Uses

1.      Robotics

2.      Gaming (Virtual Motion)

3.      Medical Devices

4.      Computer Peripherals

5.      Musical Instruments

6.      Physical Therapy

- Simple Construction

- Low Profile

3.1.2 Mechanical Specifications

-Life Cycle: >1 million

-Height: 0.43mm (0.017")

-Temperature Range: -35°C to +80°C

3.1.3 Electrical Specifications

-Flat Resistance: 25K Ohms

-Resistance Tolerance: ±30%

-Bend Resistance Range: 45K to 125K Ohms (depending on bend radius)

-Power Rating : 0.50 Watts continuous. 1 Watt Peak

Fig.4 : Description of flex sensor

Fig.5: Different angles of the flex sensor

     TILT SENSOR

Accelerometer in the Gesture Vocalizer system is used as a tilt sensor, which checks the tilting of the hand. ADXL335 is the accelerometer used in the system. The accelerometer has an analog output, and this analog output varies from 1.5 volts to 3.5 volts.It uses a single structure for sensing the X, Y, and Z axes. As a result, the three axes’ sense directions are highly orthogonal and have little cross-axis sensitivity. Mechanical misalignment of the sensor due to the package is the chief source of cross-axis sensitivity. Mechanical misalignment can, of course, be calibrated out at the system level.

Fig.6: Different pins of ADXL335

.
The user can select the bandwidth of the accelerometer using the C_X, C_Y, and C_Z capacitors at the X_OUT, Y_OUT, and Z_OUT pins. Bandwidths can be selected to suit the application, with a range of 0.5 Hz to 1600 Hz for the X and Y axes, and a range of 0.5 Hz to 550 Hz for the Z axis.

The ADXL335 is available in a small, low profile, 4 mm × 4 mm × 1.45 mm, 16-lead, plastic lead frame chip scale package (LFCSP_LQ).It’s a cost sensitive and low power consumption device used for motion- and tilt-sensing measurement.

It’s applications are found in:

·         Mobile devices

·         Gaming systems

·         Disk drive protection

·         Image stabilization

·         Sports and health devices

                                                            Fig .7: Overview of ADXL335

                                          Fig.8: Functional block diagram of ADXL335

     THEORY OF OPERATION

The ADXL335 is a complete 3-axis acceleration measurement system. The ADXL335 has a measurement range of ±3 g mini-mum. It contains a polysilicon surface-micro-machined sensor and signal conditioning circuitry to implement an open-loop acceleration measurement architecture. The output signals are analog voltages that are proportional to acceleration. The accelerometer can measure the static acceleration of gravity in tilt-sensing applications as well as dynamic acceleration resulting from motion, shock, or vibration.

The sensor is a polysilicon surface micro-machined structure built on top of a silicon wafer. Polysilicon springs suspend the structure over the surface of the wafer and provide a resistance against acceleration forces. Deflection of the structure is measured using a differential capacitor that consists of independent fixed plates and plates attached to the moving mass. The fixed plates are driven by 180° out-of-phase square waves. Acceleration deflects the moving mass and unbalances the differential capacitor resulting in a sensor output whose amplitude is proportional to acceleration. Phase-sensitive demodulation techniques are then used to determine the magnitude and direction of the acceleration.

The demodulator output is amplified and brought off-chip through a 32 kΩ resistor. The user then sets the signal bandwidth of the device by adding a capacitor. This filtering improves measurement resolution and helps prevent aliasing.

    MECHANICAL SENSOR

The ADXL335 uses a single structure for sensing the X, Y, and Z axes. As a result, the three axes’ sense directions are highly orthogonal and have little cross-axis sensitivity. Mechanical misalignment of the sensor due to the package is the chief source of cross-axis sensitivity. Mechanical misalignment can, of course, be calibrated out at the system level.

    PERFORMANCE

Rather than using additional temperature compensation circuitry, innovative design techniques ensure that high performance is built in to the ADXL335. As a result, there is no quantization error or non-monotonic behaviour, and temperature hysteresis is very low (typically less than 3 mg over the −25°C to +70°C temperature range).

     PIN CONFIGURATION AND FUNCTION DESCRIPTION

Fig.9: Pin diagram of ADXL335

    PIN DESCRIPTION

Pin No.	Mnemonic	Mnemonic
1	NC	No Connect
2	ST	Self-Test
3	COM	Common.
4	NC	No Connect
5	COM	Common.
6	COM	Common.
7	COM	Common.
8	ZOUT	Z Channel Output.
9	NC	No Connect
10	YOUT	Y Channel Output.
11	NC	No Connect
12	XOUT	X Channel Output.
13	NC	No Connect
14	VS	Supply Voltage (1.8 V to 3.6 V)
15	VS	Supply Voltage (1.8 V to 3.6 V)
16	NC	No Connect
EP	Exposed Pad	Not internally connected. Solder for mechanical integrity

                   
                                          Table 1: Pin Description of ADXL 335

TILT DETECTION

The basic function of this module is to detect the tilting of the hand and to send the corresponding signal to the gesture detection module.The output, which is obtained from the accelerometer after amplification, is an analog output. To deal with this analog output, and to make it useful for further use, it is required to change it into some form, which is detectable by the microcontroller.Hence the analog output of the accelerometer is converted into digital form.

This tilt detection module in the gesture vocalizer system is a three axis system, which can detect the tilt of the hand in three axes. An inbuilt ADC in PIC18F25K20 microcontroller in the gesture detection module can be used to convert the outputs of accelerometer into digital form.

Microcontroller receives the data of the ADC, and saves them,for the further use. Next step for the microcontroller is to check the data from the ADC. The microcontroller checkswhether the data received from the ADC is some recognizable data, or useless one. Meaningful means that the tilt of the hand is some meaningful tilt and hand is signaling some defined gesture, or a part of the gesture, because gesture means a complete motion of the hand in which the bending of the finger is also involved. The microcontroller compares the values received from the ADC with the predefined values, which are present in the memory of the microcontroller and on the basis of this comparison the microcontroller decides that, if the gesture a meaningful gesture.

Fig.10: The gravity range with respect to different degrees

If the hand is signaling a meaningful gesture then the microcontroller moves towards the next step. The signal generated is different for every valid gesture. On the basis of this signal, which is, sent by the tilt detection module, the “gesture detection” module comprising of the microcontroller, checks the gestures as a whole, and takes some decisions. The “gesture detection module” comprising of the microcontroller, sends data to the voice record and playback module that knows the meaning of each data.

BEND DETECTION
The bend detection module is also an important part of the system. The bend sensors are fixed to 3 fingers of the data glove, and are basically responsible for the detection of the bend of the fingers.

Even a little bend of the finger is detected at this stage of the system. The bending of the finger has infinite levels of bends, and the system is very sensitive to the bending of the finger. Now the bending of each finger is quantized into ten levels. At any stage, the finger must be at one of these levels, and it can easily be determined how much the finger is bent. So that individual bending of each finger can be captured. System knows how much each finger is bent. Now the next step is to combine the movement of each finger and name it a particular gesture of the hand.

Now the system reads the movements of three fingers as a whole, rather than reading the individual finger. Having read bending of the fingers, the system checks whether the bend is some meaningful bend, or a useless or undefined bend. If the bending of the fingers gives some meaningful gesture, then system moves towards the next step.

In the next step the system checks the data, which was sent by tilt detection module at port one of the microcontroller. The data sent by this module shows whether the tilt of the hand is giving some meaningful gesture or it is undefined. If the tilt of the hand is also meaningful then it means that the gesture as a whole is a meaningful gesture.

So far it is detected by the system whether thegesture given by hand is some meaningful gesture, or auseless one. If the gesture is meaningful, the systemsends data to the voice record and playback module. This data can represent differentgestures.

GESTURE DETECTION

The Gesture detection module comprises of a microcontroller namely PIC18F25K20. This module processes the gestures detected by the tilt and bend detection modules to generate voice, by providing processed signal to voice record and playback IC,APR9600 and also to the alphanumeric LCD,JHD162A to display the same in text form.

     PIC18F25K20

PIC is a family of modified Harvard architecturemicrocontrollers made by Microchip Technology, derived from the PIC1650 originally developed by General Instrument's Micro-electronics Division. The name PIC initially referred to "Peripheral Interface Controller".

                                                        Fig.11: Pic microcontroller

PICs are popular with both industrial developers and hobbyists alike due to their low cost, wide availability, large user base, extensive collection of application notes, availability of low cost or free development tools, and serial programming (and re-programming with flash memory) capability.

The features of PIC18F25K20 are as follows:

      High-Performance RISC CPU:

• C Compiler Optimized Architecture: 

- Optional extended instruction set designed to optimize re-entrant code

• Up to 1024 bytes Data EEPROM

• Up to 64 Kbytes Linear Program Memory Addressing

• Up to 3936 bytes Linear Data Memory Addressing

• Up to 16 MIPS Operation

• 16-bit Wide Instructions, 8-bit Wide Data Path

• Priority Levels for Interrupts

• 31-Level, Software Accessible Hardware Stack

• 8 x 8 Single-Cycle Hardware Multiplier

      Flexible Oscillator Structure:

• Precision 16 MHz Internal Oscillator Block:

 - Factory calibrated to ± 1%

- Software selectable frequencies range of31 kHz to 16 MHz

- 64 MHz performance available using PLL –no external components required

• Four Crystal modes up to 64 MHz

• Two External Clock modes up to 64 MHz

• 4X Phase Lock Loop (PLL)

• Secondary Oscillator using Timer1 @ 32 kHz

• Fail-Safe Clock Monitor:

- Allows for safe shutdown if peripheral clockstops

- Two-Speed Oscillator Start-up

     Special Microcontroller Features:

• Operating Voltage Range: 1.8V to 3.6V

• Self-Programmable under Software Control

• Programmable 16-Level High/Low-VoltageDetection (HLVD) module:

- Interrupt on High/Low-Voltage Detection

• Programmable Brown-out Reset (BOR):

- With software enable option

• Extended Watchdog Timer (WDT):

- Programmable period from 4 ms to 131s

• Single-Supply 3V In-Circuit SerialProgramming™ (ICSP™) via Two Pins

• In-Circuit Debug (ICD) via Two Pins

    Extreme Low-Power Management with nanoWatt XLP:

• Sleep mode: < 100 nA @ 1.8V

• Watchdog Timer: < 800 nA @ 1.8V

• Timer1 Oscillator: < 800 nA @ 32 kHz and 1.8V

     Analog Features:

• Analog-to-Digital Converter (ADC) module:

- 10-bit resolution, 13 External Channels

- Auto-acquisition capability

- Conversion available during Sleep

- 1.2V Fixed Voltage Reference (FVR) channel

- Independent input multiplexing

• Analog Comparator module:

- Two rail-to-rail analog comparators

- Independent input multiplexing

• Voltage Reference (VREF) module:

- Programmable (% VDD), 16 steps

- Two 16-level voltage ranges using VREF pins

     Peripheral Highlights:

• Up to 35 I/O Pins plus 1 Input-only Pin:

- High-Current Sink/Source 25 mA/25 mA

- Three programmable external interrupts

- Four programmable interruptonchange

- Eight programmable weak pull-ups

- Programmable slew rate

• Capture/Compare/PWM (CCP) module

• Enhanced CCP (ECCP) module:

- One, two or four PWM outputs

- Selectable polarity

- Programmable dead time

- Auto-Shutdown and Auto-Restart

• Master Synchronous Serial Port (MSSP) module

- 3-wire SPI (supports all 4 modes)

- I2C™ Master and Slave modes with address mask

• Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART) module:

- Supports RS-485, RS-232 and LIN

- RS-232 operation using internal oscillator

- Auto-Wake-up on Break

-Auto-BaudDetect

    Advantages

The PIC architectures have these advantages:

• Small instruction set to learn
• RISC architecture
• Built in oscillator with selectable speeds
• Easy entry level, in circuit programming plus in circuit debugging PICKit units available from Microchip.com for less than $50
• Inexpensive microcontrollers

Wide range of interfaces including I²C, SPI, USB, USART, A/D, programmable comparators, PWM, LIN, CAN, PSP, and Ethernet.

6.1.8        Limitations

The PIC architectures have these limitations:

• One accumulator
• Register-bank switching is required to access the entire RAM of many devices
• Operations and registers are not orthogonal; some instructions can address RAM and/or immediate constants, while others can only use the accumulator

The following stack limitations have been addressed in the PIC18 series, but still apply to earlier cores:

• The hardware call stack is not addressable, so preemptivetask switching cannot be implemented

Software-implemented stacks are not efficient, so it is difficult to generate reentrant code and support local variables

Fig. 12:  PIC18F25K20 IC

     
AMICUS 18 BOARD

What does the name Amicus mean ? 

The name Amicus derives from the Latin word Amici, meaning friend. An Amicus is a person who speaks or performs on your behalf. The Amicus18 board will become your best friend, allowing a freedom to perform tasks that you never dreamed possible.

The IC, PIC18F25K20 is supported by Amicus 18 board.For programming simply connect the USB port of the Ami18 to a computer or connect a power supply / battery to get started. The Ami18 presents itself as a standard serial port on the PC. The Ami18 can be programmed directly from the USB port, so there is no need for a special programmer. The board can also be programmed directly from the In Circuit Serial Programming (ICSP™) adapter compatible with Microchip PICkit 2 or PICkit 3  programmers.

Fig 13: Different components of Ami18 board

Coming to the software the board can be programmed with any PIC® language like C18, Swordfish, PICbasic and the free Proton Amicus18 software. The PIC18F25K20 on the board is supplied pre-burned with a boot loader program that allows user to upload new code without the use of an external hardware programmer.         

VOICE RECORD AND PLAYBACK

This module of the system consists of APR9600 voice record and playback IC,amplifier circuitry. APR9600 is a low-cost high performance sound record/replay IC incorporating flash analogstorage technique. Recorded sound is retained even after power supply is removed from themodule. The replayed sound exhibits high quality with a low noise level. Sampling rate for a 60second recording period is 4.2 kHz that gives a sound record/replay bandwidth of 20Hz to 2.1 kHz.

However, by changing an oscillation resistor, a sampling rate as high as 8.0 kHz can be achieved.This shortens the total length of sound recording to 32 seconds. Total sound recording time can be varied from 32 seconds to 60 seconds by changing the value of asingle resistor.

The IC can operate in one of two modes: serial mode and parallel mode. In serial access mode, sound can be recorded in 256 sections. In parallel access mode, sound can berecorded in 2, 4 or 8 sections. It ispossible to control the IC using external digital circuitry such as micro-controllers and computers.The APR9600 has a 28 pin DIP package. And supply voltage is between 4.5V to 6.5V. Duringrecording and replaying, current consumption is 25 mA. In idle mode, the current drops to 1 mA.

Fig 14: APR9600 with speaker

The APR9600 experimental board is an assembled PCB board consisting of an APR9600 IC, anelectret microphone, support components and necessary switches to allow users to explore all functions of the APR9600 chip. The oscillation resistor is chosen so that the total recording periodis 60 seconds with a sampling rate of 4.2 kHz. The board measures 80mm by 55mm.

Fig 15: APR9600 Experimental board

During sound recording, sound is picked up by the microphone. A microphone pre -amplifier amplifies the voltage signal from the microphone. An AGC circuit is included in the pre-amplifier, the extent of which is controlled by an external capacitor and resistor. If the voltage level of a sound signal is around 100 mV peak-to-peak, the signal can be fed directly into the IC through ANA IN pin (pin 20). The sound signal passes through a filter and a sampling and hold circuit. The analog voltage is then written into non-volatile flash analog RAMs.

During sound replaying, the IC’s control circuit reads analog data from flash RAMs. The signal then passes through a low-pass filter, a power amplifier and output to an 8 to 16 Ohm speaker.

The function of this voice record and playback module is to produce voice against the respective gesture. APR9600 produces output when it receives a low input signal. Therefore each pin in APR9600 is recorded with a message and as and when the particular pin receives a low input signal the respective message is played back.

When the microcontroller receives the data from the “bend and tilt detection” module it compares the data with the predefined values. On the basis of this comparison the microcontroller comes to know that which gesture does the hand make. When a predefined gesture is recognized by the microcontroller it sends low input to the respective pin of APR9600. When APR9600 receives low signal it plays the message stored in the particular pin through the speaker.

 Features of APR9600

• Single-chip, high-quality voice recording & playback solution

- No external ICs required

- Minimum external components

• Non-volatile Flash memory technology

- No battery backup required

• User-Selectable messaging options

- Random access of multiple fixed-duration messages

- Sequential access of multiple variable-duration messages

• User-friendly, easy-to-use operation

- Programming & development systems not required

- Level-activated recording & edge-activated play back switches

• Low power consumption

- Operating current: 25 mA typical

- Standby current: 1 uA typical

- Automatic power-down

• Chip Enable pin for simple message expansion

     PIN CONFIGURATION

Fig.16: Pin-out of APR9600

7.2.1 Pin functions of APR9600

Pin	Name	Functions
1	-M1	Select 1st section of sound or serial mode recording and replaying control (low active)
2	-M2	Select 2nd section or fast forward control in serial mode (low active)
3	-M3	Select 3 rd section of sound
4	-M4	Select 4th section of sound
5	-M5	Select 5th section of sound
6	-M6	Select 6th section of sound
7	OSCR	Resistor to set clock frequency.
8	-M7	Select 7th section of sound or IC overflow indication
9	-M8	Select 8th section of sound or select mode
10	-BUSY	Busy (low active)
11	BE	=1, beep when a key is pressed =0, do not beep
12	VSSD	Digital circuit ground
13	VSSA	Analogue circuit ground
14	SP+	Speaker, positive end
15	SP-	Speaker, negative end
16	VCCA	Analogue circuit power supply
17	MICIN	Microphone input (electret type microphone)
18	MICREF	Microphone reference input
19	AGC	AGC control
20	ANA-IN	Audio input (accept a signal of 100 mV p-to-p)
21	ANA-OUT	Audio output from the microphone amplifier
22	STROBE	During recording and replaying, it produces a strobe signal
23	CE	Reset sound track counter to zero/ Stop or Start / Stop
24	MSEL1	Mode selection 1
25	MSEL2	Mode selection 2
26	EXTCLK	External clock input
27	CLK	=0 to record, =1 to replay
28	VCCD	Digital circuit power supply

Table 2: Pin description of APR9600

 LCD DISPLAY

By using the gesture vocalizer the dumb people can communicate with the normal people and with the blind people as well, but the question arises that how can the dumb people communicate with the deaf people. The solution to this problem is to translate the gestures, which are made by the hand, into some text form. The text is displayed on LCD.

The gestures are already being detected by the “Gesture Detection” module. This module sends signal to the voice record and playback  module, the same signal is sent to the LCD display module. The microcontroller is controlling the LCD. A signal against each gesture is received by LCD displaymodule. The LCD display module checks eachsignal, and compares it with the already storedvalues. On the basis of this comparison themicrocontroller takes the decision what should bedisplayed, having taken the decision the microcontroller send an four bit address to the LCD, this four bit address, tells the LCD, what should be displayed.

A liquid crystal display (LCD) is a flat panel,electronic visual or video display that uses the light modulating properties of liquid crystals (LCs).

Fig.17: Working of LCD

LCDs are used in a wide range of applications, including computer monitors, television, instrument panels, aircraft cockpit displays etc. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones.

LCDs have replaced cathode ray tube (CRT) displays in most applications. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphorus, they cannot suffer image burn-in. LCDs are, however, susceptible to image persistence.

The LCD is more energy efficient and offers safer disposal than a CRT. Its low electrical power consumption enables it to be used in battery-powered electronic equipment. It is an electronically modulated optical device made up of any number of segments filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome. The most flexible ones use an array of small pixels.

Fig. 18 : JHD162A LCD

Here a 16 x 2 alphanumeric LCD, namely JHD162A has been used. An alphanumeric LCD is one which can display both alphabets and numbers. Here 16 x 2 implies 16 characters x 2 rows. JHD162A LCD is reflective in nature and can have green,yellow or grey displays.

.

Fig.19: Functional block diagram of 16 x 2 alphanumeric LCD

Specifications

Important factors to consider when evaluating an LCD:

 Resolution versus range:

Fundamentally resolution is the granularity (or number of levels) with which a performance feature of the display is divided. Resolution is often confused with range or the total end-to-end output of the display. Each of the major features of a display has both a resolution and a range that are tied to each other but very different. Frequently the range is an inherent limitation of the display while the resolution is a function of the electronics that make the display work.

 Spatial performance:

LCD’s come in only one size for a variety of applications and a variety of resolutions within each of those applications. LCD spatial performance is also sometimes described in terms of a "dot pitch". The size (or spatial range) of an LCD is always described in terms of the diagonal distance from one corner to its opposite. This is an historical remnant from the early days of CRT television when CRT screens were manufactured on the bottoms of glass bottles, a direct extension of cathode ray tubes used in oscilloscopes. The diameter of the bottle determined the size of the screen. Later, when televisions went to a more square format, the square screens were measured diagonally to compare with the older round screens.

 Temporal/timing performance:

Contrary to spatial performance, temporal performance is a feature where smaller is better. Specifically, the range is the pixel response time of an LCD, or how quickly you can change a sub-pixel's brightness from one level to another. For LCD monitors, this is measured in btb (black to black) or gtg (gray to gray). These different types of measurements make comparison difficult. Further, this number is almost never published in sales advertising.

 Colour depth or colour support:

It’s is sometimes expressed in bits, either as the number of bits per sub-pixel or the number of bits per pixel. This can be ambiguous as an 8-bit colour LCD can be 8 total bits spread between red, green, and blue or 8 bits each for each colour in a different display. Further, LCDs sometimes use a technique called dithering which is time averaging colours to get intermediate colours such as alternating between two different colours to get a colour in between. This doubles the number of colours that can be displayed; however this is done at the expense of the temporal performance of the display. Dithering is commonly used on computer displays where the images are mostly static and the temporal performance is unimportant.
 Brightness and contrast ratio:

Contrast ratio is the ratio of the brightness of a full-on pixel to a full-off pixel and as such, would be directly tied to brightness if not for the invention of the blinking backlight (or burst dimming). The LCD itself is only a light valve, it does not generate light; the light comes from a backlight that is either a florescent tube or a set of LEDs. The blinking backlight was developed to improve the motion performance of LCDs by turning the backlight off while the liquid crystals were in transition from one image to another.

However, a side benefit of the blinking backlight was infinite contrast. The contrast reported on most LCDs is what the LCD is qualified at, not its actual performance. In any case, there are two large caveats to contrast ratio as a measure of LCD performance.

Advantages and disadvantages

Advantages

• Very compact and light.
• Low power consumption.
• No geometric distortion.
• Little or no flicker depending on backlight technology.
• Not affected by screen burn-in.
• Can be made in almost any size or shape.
• No theoretical resolution limit.

 Disadvantages

• Limited viewing angle, causing colour, saturation, contrast and brightness to vary, even within the intended viewing angle, by variations in posture.
• Bleeding and uneven backlighting in some monitors, causing brightness and distortion, especially towards the edges.
• Smearing and ghosting artifacts caused by slow response times (>8 ms) and "sample and hold" operation.
• Only one native resolution. Displaying resolutions either requires a video scaler, lowering perceptual quality, or display at 1:1 pixel mapping, in which images will be physically too large or won't fill the whole screen.
• Fixed bit depth, many cheaper LCDs are only able to display 262,000 colours. 8-bit S-IPS panels can display 16 million colours and have significantly better black level, but are expensive and have slower response time.
• Low bit depth results in images with unnatural or excessive contrast.
• Input lag
• Dead or stuck pixels may occur during manufacturing or through use.
• In a constant-on situation, thermalization may occur, which is when only part of the screen has overheated and looks discoloured compared to the rest of the screen.
• Not all LCDs are designed to allow easy replacement of the backlight.
• Cannot be used with light guns/pens.
• Loss of contrast in high temperature environments.

LOUDSPEAKER

A loudspeaker is used in this project to play the voice that has been recorded using voice record and playback IC APR9600. The analog output from the voice record and playback IC APR9600 is given to the loudspeaker.

A loudspeaker (or "speaker") is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful.

The most common form of loudspeaker uses a paper cone supporting a voice coil electromagnet acting on a permanent magnet, but many other types exist. Where accurate reproduction of sound is required, multiple loudspeakers may be used, each reproducing a part of the audible frequency range.

 Miniature loudspeakers are found in devices such as radio and TV receivers, and many forms of music players. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, and in public address systems.

Fig. 20:An inexpensive low fidelity 3.5 inch speaker

SOFTWARE

Proton Amicus 18 complier

      Proton Amicus18 is supported by an integrated development environment (Amicus IDE), and provides the user with:

• Proton BASIC source code editor - with colour syntax highlighter
• Compiler - Full version of Proton Basic for the PIC^® Microcontroller with full integration to MPLAB^® for debugging, if required.
• Programmer - automated USB programming of the Amicus18 Board - no external programmer is required.

                           Fig. 21: Amicus IDE
The Amicus18^tm IDE has been designed to maximize programmer productivity by providing highly integrated and intuitive interface to the tools required to develop on the Amicus 18 hardware. The Amicus18 IDE provides many features for authoring, modifying, compiling, deploying and debugging your programmes. Your program can be compiled while being written, providing instant feedback on syntax errors. This results in an uninterrupted workflow from writing the program code through compiling to downloading the program to the Amicus18 hardware.

Comprehensive documentation and a helpful and friendly support environment, make using Amicus18 an easy and enjoyable experience for beginners and seasoned programmers.

                                   CONCLUSION

This project describes the design and working of asystem which is useful for dumb, deaf and blind people to communicate with one another and with the normal people, and hence the project proves to be socially active. The dumb people use their standard sign language which is not easily understandable by common people and blind people cannot see their gestures. This system converts the sign language into voice which is easily understandable by blind and normal people.

The sign language is also translated into some text form, to facilitate the deaf people as

well. This text corresponding to the gesture is displayed on LCD.

The project is user friendly and cost-effective due to its simplicity. The hardware is easy to construct, the only challenging part being placing the accelerometer on the glove. The project works in real time environment by producing voice and text corresponding to the gestures made by the one wearing the glove.


regards ,

prem