Difference between revisions of "S15: Hand Gesture Recognition using IR Sensors"

System Block Diagram:
The system consists of 9 IR proximity sensors, which are arranged in 3x3 grid. The output of the sensors is given to the Analog-to-Digital convertor on the SJOne Board to get the digital equivalent of the voltage given by the sensors. Since there are only 3 ADC channels exposed on the pins on the board, we cannot connect all the sensors directly to the board. For these we have used three multiplexers, which has 3 sensors each connected to its input. The output of the multiplexers is connected to ADC. SJOne board is connected to the laptop via UART-to-USB connection.

Proximity Sensor:
This sensor by Sharp measures the distance from an obstacle by bouncing IR rays off the obstacle. This sensor can measure distances from 10 to 80 cms. The sensor returns an analog voltage corresponding to the distance from the obstacle. Depending on which sensor returns valid values, validations could be made and hand movement can be determined. There is no external circuitry required for this sensor. The operating voltage recommended for this sensor is 4.5V to 5.5V.

Multiplexer:
The chip used in the project is M74HC4052 from STMicroelectronics. This is a dual 4-channel multiplexer/demultiplexer. Due to shortage of ADC pins to interface with the sensors, use of multiplexer is required. The multiplexer takes input from three sensors and enables only one of them at the output. The program logic decides which sensor’s output should be enabled at the multiplexer’s output. A and B control signals select one of the channel out of the four. The operating voltage for the multiplexer is 2 to 6V.

UART-to-USB convertor:
To communicate to SJONE board over UART there is a need an USB to serial convertor and a MAX232 circuit to convert the voltage levels to TTL, which the SJONE board understands. Instead it’s better to use a UART-to-USB convertor to avoid the multiple conversions. This is done using CP2102 IC, which is similar to a FTDI chip.

Pin connections for IR Sensor to Multiplexer:

Pin connections on SJOne board:

Connections between SJOne board and UART-to-USB Convertor:

Filter Algorithm

State Machine Diagram:

Application Development
QT Software
QT is a cross-platform application framework that is widely used in developing application software that can be run on various software and hardware platforms with little or no change in the underlying codebase while having the speed and the power of native application. [1] It is mainly used to make GUI based applications but there can be applications such as consoles or command-line applications developed in QT. QT is preferred by many application programmers as it helps in developing GUI applications in C++ as it uses the standard C++ libraries for backend. Platforms supported by Qt are:

• Android
• Embedded Linux
• Integrity
• iOS
• OSX
• QNX
• VxWorks
• Waylands
• Windows
• Windows CE
• Windows RT
• X11

QT applications are highly portable from one platform to other as QT first runs a Qmake function before compiling the source code. It is very similar to ‘cmake’ which is used for cross platform compilation of any source code. The qmake auto generates a makefile depending on the operating system and the compiler used for the project. So if a project is to be ported from windows to linux based system then the qmake auto generated a new makefile with arguments and parameters that the g++ compiler expects.