Wednesday, 12 September 2012

Week 7: Block Diagram and Flow Chart



  Block Diagram Explanation

Solar radiance is the input and as the set point for this project. From the set point it sends error to the controller. The controller in this project is PID controller, to control the speed of the servo motor, PWM are needed to give a signal and control the speed of servo motor. Motion device or final control element here is servo motor. It received signal from controller and manipulated process of the solar panel direction by follow the direction of the sun and it minimize the angle of solar radiance. The output is the solar panel direction. LDR sensor will give a feedback to this system and the process will repeated until this project cannot detect the sun radiance.

 Light Dependent Resistor (LDR)

Light Dependent Resistor (LDR) is made of a high-resistance semiconductor. It can also be referred to as a photoconductor. If light falling on the device is of the high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance. Hence, Light Dependent Resistors (LDR) is very useful in light sensor circuits. LDR is very high-resistance, sometimes as high as 1000 000Ω, when they are illuminated with light resistance drops dramatically.

 LabView

The software is used to control and display the output. This will be connected with the DAQ card to transfer the data to the Lab View. The software is used to show data from the solar panel and to switch on the solar circuit. It also uses to control the motor movement.

The Data Acquisition/Interface Card (DAQ)

The main aim of the Data Acquisition/Interface Card is to provide testing functionality of the mains parts of the Solar Tracker. It should provide available ports for the sensors input, motor controlling output bits and also other interfaces to be controlled as simply as possible and in the shortest time. It must be within specifications and should be small enough to accommodate all the required components and not draw too much power. Popular choices for Data Acquisition/Interface Card are PCI-7334 and EMANT300.

Servo Motors

Servos contain a small DC motor, a gearbox and some control circuitry, and feed on 5 volts at about 100mA maximum, and about 10-20mA when idle. They have a three-wire connector, one common wire (0 volt, usually black), one +5v wire (usually red), and one signal wire. In normal use they are controlled by pulses of about 1 to 2 milli-seconds at a repetition rate of about 50 per second. A short pulse makes the servo drive to one end of the travel, a long pulse makes it drive to the other end, and a medium one puts it somewhere proportionally between. The speed though, is not greatly affected by the pulse repetition rate, as long as it is above about 30 per second. These pulses can easily be provided by an output port of just about any computer, for instance the data or control lines of a printer port or a serial port, or a simple addressed latch added to the memory circuits.

             Solar panel

Solar panel is the main point of the project. It involves solar panel to get the voltage output. This is renewable energy that needs to convert into voltage. This solar need more study and do the experimental to know the range of the output value. This solar panel will be controlled by software to switch on the circuit that will be converted the output and stabilize the voltage that be used in the project.

        Flow Chart


Flow chart show that the flow of the program that be used in the software graphical Labview. The programs start when this project sensor port, LDR port, detects the input from the sun. If the LDR port detects 1 and 0 or 0 and 1, the servo motor will move the solar panel until LDR port get 0 and 0. The DAQ card will receive the data voltage output from the hardware and display the output at the front panel labview. If the software cannot receive the data, there is no display output and the programs retry to get the data.

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