CONTENTS Introduction Block diagram Power supply PIC
Microcontroller BLDC Motor Opto-isolator MOSFET IR LED &
Photodiode Keypad LCD Schematic & Working of the project
Advantages Applications Future scope Conclusion
Slide 3
Project overview This project describes a message based
monitoring tool using the RS232 Rx Tx features of the MC to
communicate between 3 PIC MCs. In this project 3 motors are been
synchronized. The required speed is entered with a keypad fed
master controller which in turn controls the slave-1 which controls
slave-2. IR sensors are used to sense the speed.
Slide 4
Block diagram
Slide 5
Slide 6
Slide 7
Power supply Step down transformer Bridge rectifier Filter
Regulator
Slide 8
Contd.. The 230V AC supply is first stepped down to 12V AC
using a step down transformer. This is then converted to DC using
bridge rectifier. The AC ripples is filtered out by using a
capacitor and given to the input pin of voltage regulator 7805. At
output pin of this regulator we get a constant 5V DC which is used
for MC and other ICs in this project.
Slide 9
PIC (PIC16F877A) High-Performance RISC CPU: Only 35 single-word
instructions. All single-cycle instructions except for program
branches, which are two cycle. Operating speed: DC 20 MHz clock
input DC 200 ns instruction cycle Up to 8K x 14 words of Flash
Program Memory, Up to 368 x 8 bytes of Data Memory (RAM), Up to 256
x 8 bytes of EEPROM Data Memory. Pin out compatible to other 28-pin
or 40/44- pin, PIC16CXXX and PIC16FXXX microcontrollers.
Slide 10
Special Microcontroller Features: 100,000 erase/write cycle
Enhanced Flash program memory typical. 1,000,000 erase/write cycle
Data EEPROM memory typical. Data EEPROM Retention > 40 years.
Self-reprogrammable under software control. In-Circuit Serial
Programming (ICSP) via two pins. Single-supply 5V In-Circuit Serial
Programming. Watchdog Timer (WDT) with its own on-chip RC
oscillator for reliable operation. Programmable code protection.
Power saving Sleep mode. Selectable oscillator options. In-Circuit
Debug (ICD) via two pins.
Slide 11
Peripheral Features: Timer0: 8-bit timer/counter with 8-bit
prescaler. Timer1: 16-bit timer/counter with prescaler, can be
incremented during Sleep via external crystal/clock. Timer2: 8-bit
timer/counter with 8-bit period register, prescaler and postscaler.
Two Capture, Compare, PWM modules - Capture is 16-bit, max.
resolution is 12.5 ns - Compare is 16-bit, max. resolution is 200
ns - PWM max resolution is 10-bit Synchronous Serial Port (SSP)
with SPI (Master mode) and I2C (Master/Slave). Universal
Synchronous Asynchronous Receiver Transmitter (USART/SCI) with
9-bit address detection. Parallel Slave Port (PSP) 8 bits wide with
external RD, WR and CS controls (40/44-pin only). Brown-out
detection circuitry for Brown-out Reset (BOR).
Slide 12
PIN DIAGRAM OF PIC16F877
Slide 13
BLDC motor Standard DC motor -- Magnetic field is stationary in
stator, rotor poles switch polarity due to commutation to provide
constant rotation. Brushless DC motor -- Magnetic field of rotor is
fixed. Magnetic field in stator poles is electronically commutated,
provides rotating magnetic field. Motor contains internal position
encoder to provide position feedback to the control system.
Slide 14
Contd.. Applications - CPU cooling fans - CD/DVD Players -
Electric automobiles Pros (compared to brushed DC) - Higher
efficiency - Longer lifespan, low maintenance - Clean, fast, no
sparking/issues with brushed contacts Cons - Higher cost - More
complex circuitry and requires a controller.
Slide 15
Opto-isolator Opto coupler is a 6 pin IC. It is a combination
of 1 LED and a transistor. Pin 6 of transistor is not generally
used and when light falls on the Base-Emitter junction then it
switches and pin5 goes to zero. If input of the diode is zero and
other end of diode is GND then the output is one. When logic zero
is given as input then the light doesnt fall on transistor so it
doesnt conduct which gives logic zero as output. When logic 1 is
given as input then light falls on transistor so that it conducts,
that makes transistor switched ON and it forms short circuit this
makes the output is logic zero as collector of transistor is
connected to ground.
Slide 16
MOSFET The MOSFET (Metal Oxide Semiconductor Field Effect
Transistor) is a Voltage controlled device. This means that a
voltage at the gate control the current flows from the drain to the
source. There are three terminals: Gate - connected to the input
device. Drain - connected to the positive, since electrons drain
away to the positive. Source - the source of the electrons
Slide 17
Contd.. USES OF MOSFETS High power devices like motors and
light bulbs give a large current output for a very tiny current
input. So a MOSFET can act as the interface between an integrated
circuit that can give only a tiny current, and the motor that takes
a big current. In complimentary pairs they are used in hi-fi power
amplifiers. They produce less distortion as they are more linear
than bipolar transistors. Integrated circuits, as they can be made
very compact.
Slide 18
IR LED Here the IR transmitter is like a normal LED but
transmits the IR signals. These are infrared LEDs; the light output
is not visible by our eyes. They can be used as replacement LEDs
for remote controls, night vision for camcorders, invisible beam
sensors, etc.
Slide 19
Photodiode Here the photodiode is like a normal LED but
receives the IR signals. A photodiode is a type of photo detector
capable of converting light into either current or voltage,
depending upon the mode of operation.
Slide 20
Keypad A keypad is a set of buttons arranged in a block or
"pad" which usually bear digits, symbols and usually a complete set
of alphabetical letters. If it mostly contains numbers then it can
also be called a numeric keypad. In order to detect which key is
pressed from the matrix, the row lines are to be made low one by
one and read the columns. Assume that if Row1 is made low, then
read the columns. If any of the key in row1 is pressed then
correspondingly the column 1will give low that is if second key is
pressed in Row1, then column2 will give low.
Slide 21
Liquid Crystal Display-LCD Most common LCDs connected to the
microcontrollers are 16x2 and 20x2 displays. This means 16
characters per line by 2 lines and 20 characters per line by 2
lines, respectively. The standard is referred to as HD44780U, which
refers to the controller chip which receives data from an external
source (and communicates directly with the LCD.
Slide 22
Contd.. If an 8-bit data bus is used the LCD will require 11
data lines(3 control lines plus the 8 lines for the data bus) The
three control lines are referred to as EN, RS, and RW EN=Enable
(used to tell the LCD that you are sending it data) RS=Register
Select. When RS=0; data is treated as a command & When RS=1;
data being sent is text data. R/W=Read/Write. When RW=0; the data
written to the LCD & When RW=1; the data reading to the
LCD.
Slide 23
Working of project The speed of the motor is sensed by an IR
pair and is displayed on LCD and is also fed to the MC. The
required speed is entered using a keypad which is interfaced with
MC. The motor is interfaced to the MC through a opto-coupler &
a MOSFET which drives the motor. PWM pulses are generated from MC
according to the entered speed and the motor is adjusted to that
speed and maintained at that speed.