PIC Microcontroller

Hope you read about word length above. So based on the word length of a processor we can have 8-bit, 16-bit, 32-bit and 64-bit processors.RISC – Reduced Instruction Set Computer: RISC is a type of microprocessor architecture which uses small, general purpose and highly optimized instruction set rather than more specialized set of instructions found in others. RISC offers high performance over its opposing architecture CISC (see below). In a processor, execution of each instruction require a special circuit to load and process the data. So by reducing instructions, the processor will be using simple circuits and faster in operation.Simple instruction setLarger programConsists of large number of registersSimple processor circuitry (small number of transistors)More RAM usageFixed length instructionsSimple addressing modesUsually fixed number of clock cycles for executing one instructionCISC – Complex Instruction Set Computer:CISC is the opposing microprocessor architecture for RISC. It is made to reduce the number of instructions per program, ignoring the number of cycles per instruction. So complex instructions are directly made into hardware making the processor complex and slower in operation.This architecture is actually designed to reduce the cost of memory by reducing the program length.Complex instruction setSmaller programLess number of registersComplex processor circuitry (more number of transistors)Little RAM usageVariable length instructionsVariety of addressing modesVariable number of clock cycles for each instructionsSpecial Purpose ProcessorsThere are some processors which are designed to handle some specific functions.DSP – Digital Signal ProcessorsCoprocessors – processors used along with a main processor (8087 math-coprocessor used with 8086)Input/Output processorsTransputer – Transistor Computer : Microprocessor with its own local memory

A microprocessor is an integrated circuit (IC) which incorporates core functions of a computer’s central processing unit (CPU). It is a programmable multipurpose silicon chip, clock driven, register based, accepts binary data as input and provides output after processing it as per the instructions stored in the memory.A processor is the brain of a computer which basically consists of Arithmetical and Logical Unit (ALU), Control Unit and Register Array. As the name indicates ALU performs all arithmetic and logical operations on the data received from input devices or memory. Register array consists of a series of registers like accumulator (A), B, C, D etc. which acts as temporary fast access memory locations for processing data. As the name indicates, control unit controls the flow of instructions and data throughout the system.So basically a microprocessor takes input from input devices, process it as per instructions given in the memory and produces output.

In some of our projects, we may want to measure the distance of an object from a point. Ultrasonic Distance Sensors are the best sensor which provides stable, accurate, precise, non-contact distance measurements from 2cm to 4m. Ultrasonic Sensors can be used to measure distance between moving or stationary objects. Being very accurate and stable, these devices find large number of applications in robotics fields. For example it can be used as an excellent replacement for IR sensors in a Micromouse. In this tutorial we will lean to interface an Ultrasonic Distance Sensor with PIC Microcontroller.Here for demonstration we are using Rhydolabz Ultrasonic Distance Sensor with ASCII Output. It can be easily interfaced with a PIC Microcontroller using USART by just connecting the output pin of the sensor to RX pin of the microcontroller. In every 500ms this sensor transmits an ultrasonic burst and listens for its echo. The sensor sends out ASCII value corresponds to the time required for the ultrasonic burst to return to the sensor. The UART of the sensor is operates at a baud rate 9600 and the sensor can be powered by a 5V DC Supply. The ASCII output of the sensor will be equal to the distance to the obstacle in centimeter (cm).

The thirst for new sources of energy is unquenchable, but we seldom realize that we are wasting a part of the electrical energy every day due to the lagging power factor in the inductive loads we use. Hence there is an urgent need to avoid this wastage of energy.Before getting into the details of Power factor correction, lets just brush our knowledge about the term “power factor”. In simple words power factor basically states how far the energy provided has been utilized. The maximum value of power factor is unity. So closer the value of P.F to unity, better is the utility of energy or lesser is the wastage. In electrical terms Power factor is basically defined as the ratio of the active power to reactive power or it is the phase difference between voltage and current. Active power performs useful work while Reactive power does no useful work but is used for developing the magnetic field required by the device.Most of the devices we use have power factor less than unity. Hence there is a requirement to bring this power factor close to unity. Here we are presenting a prototype for automatic power factor correction using PIC Microcontroller.

HC-SR04 Ultrasonic Distance Sensor is a popular and low cost solution for non-contact distance measurement function. It is able to measure distances from 2cm to 400cm with an accuracy of about 3mm. This module includes ultrasonic transmitter, ultrasonic receiver and its control circuit.Provide TRIGGER signal, atleast 10μS High Level (5V) pulse.The module will automatically transmit eight 40KHz ultrasonic burst.If there is an obstacle in-front of the module, it will reflect the ultrasonic burst.If the signal is back, ECHO output of the sensor will be in HIGH state (5V) for a duration of time taken for sending and receiving ultrasonic burst. Pulse width ranges from about 150μS to 25mS and if no obstacle is detected, the echo pulse width will be about 38ms.PIC 16F877A is the heart of this circuit. VDD and VSS of PIC Microcontroller is connected to +5V and GND respectively which will provide necessary power for its operation. A 8MHz crystal is connected to OSC1 and OSC2 pins of PIC, to provide clock for its operation. 22pF capacitors connected along with the crystal will stabilize the oscillations generated by the crystal. 16×2 LCD is connected to PORTD which is interfaced using 4 bit mode communication. 10KΩ preset is used to adjust the contrast of the LCD. A 100Ω resistor is used to limit current through the LCD back-light LED.