Communication PIC-Microcontroller Lab Course by JAOM Center, Feb. 2013PIC Microcontroller Review Instructor: Mohsen Sarakbi
Definitions of Control Systems A control system is a collection of components working together under the direction of some machine intelligence. In most cases, electronic circuits provide the intelligence, and electromechanical components such as sensors and motors provide the interface to the physical world.
Parts of Control System Every control system has (at least) a controller and an actuator (also called a final control element). The Controller is the intelligence of the system and is usually electronic. The input to the controller is called the Set point, which is a signal representing the desired system output. The Actuator is an electromechanical device that takes the signal from the controller and converts it into some kind of physical action. Examples of typical actuators would be an electric motor, an electrically controlled valve, or a heating element. The last block is labeled Process and has an output labeled Controlled variable. The process block represents the physical process being affected by the actuator, and the controlled variable is the measurable result of that process.
Control System Classifications Open-Loop Control Systems:The controller never actually knows if the actuator did what it was supposed to. Closed-Loop Control Systems: The output of the process (controlled variable) is constantly monitored by a sensor.
Microcontrollers The microcontroller is simply a computer on a chip. A microcontroller differs from microprocessor; it usually includes a central processor (CPU), input and output ports, memory for program and data storage, an internal clock, and one or more peripheral devices such as timers, counters, analog-to-digital converters (ADC) and serial communication facilities.
PIC Microcontrollers PIC is the name for the Microchip microcontroller (MCU) family, consisting of a microprocessor, I/O ports, timers and other internal, integrated hardware. The main advantages are low external part count, a wide range of chip sizes great availability of compilers and source code and easy programming. In our course we’ll use the Microchip products (PIC16F877A) microcontroller.
PIC16F877A Featureso High-performance RISC CPUo 8 Kbytes of FLASH Program Memoryo 368 bytes of Data Memory (RAM)o 256 bytes of EEPROM Data Memoryo 33 I/O pins: (5 ports: A(6), B(8), C(8), D(8) and E(3))o 4-20 MHz operating speedo Wide operating voltage range: 2.0V to 5.5V.o Max. 25 mA current from an output pin.