This presentation consists the speed control of a dc motor using hardware (microcontroller) by changing the reference voltages logically and minimising errors.
DC MOTOR SPEED CONTROL USING ON-OFF CONTROLLER BY PIC16F877A MICROCONTROLLER
1. HARDWARE IMPLEMENTATION OF DC
MOTOR SPEED CONTROL USING ON-OFF
CONTROLLER BY VARYING REFERENCE
VOLTAGE OF PIC16F877A
MICROCONTROLLER
DEPARTMENT OF ELECTRICAL ENGINEERING
JALPAIGURI GOVT. ENGG. COLLEGE
JALPAIGURI-735102, WEST BENGAL
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2. THE PROJECT SUBMITTED IN
THE FULFILLMENT OF THE
REQUIREMENTS FOR THE
DEGREE OF BACHELOR OF
TECHNOLOGY IN ELECTRICAL
ENGINEERING
BY
TRIDIB BOSE(13101102042)
ARPITA KUNDU(13101102057)
SUSANTA PAL(13101102089)
UNDER THE GUIDANCE OF:-
PROF. DR. G.K. PANDA
HEAD
ELECTRICAL ENGINEERING
DEPARTMENT
JALPAIGURI GOVT. ENGG. COLLEGE
WITH UNDENIABLE HELP FROM:-
MR. MOUSAM GHOSH
ASSISTANT PROFESSOR
ELECTRICAL ENGINEERING
DEPARTMENT
NIT MEGHALAYA
4. ABSTRACT
DIRECT CURRENT (DC) MOTOR HAS
ALREADY BECOME AN IMPORTANT
DRIVE CONFIGURATION FOR MANY
APPLICATIONS ACROSS A WIDE
RANGE OF POWERS AND SPEEDS.
THE EASE OF CONTROL AND
EXCELLENT PERFORMANCE OF THE
DC MOTORS WILL ENSURE THAT THE
NUMBER OF APPLICATIONS USING
THEM WILL CONTINUE GROW FOR
THE FORESEEABLE FUTURE.
5. ABSTRACT
This project is mainly concerned on DC motor speed control system by using microcontroller PIC 16F877A.
It is a closed-loop real time control system, where the motor to be controlled is coupled to a generator (as a
tacho-generator) shaft to provide the feedback speed signal to controller. Pulse Width Modulation (PWM)
technique is used where its signal is generated in microcontroller to check the feedback.
The PWM signal will be send to motor driver to vary the voltage supply to motor to maintain at constant
speed. Through the project, it can be concluded that microcontroller PIC 16F877A can control motor speed
at desired speed although there is a variation of load.
6. THEORY AND
LITERATURE
REVIEW
THIS PART INCLUDES THE STUDY OF
DIFFERENT TYPES OF DC MOTORS,
SPEED MEASUREMENT OF DC
MOTOR, MODEL OF SEPARATELY
EXCITED DC MOTOR, SEVERAL
TYPES OF DC MOTOR SPEED
CONTROLLER. IT ALSO DISCUSSES
BRIEFLY ABOUT
MICROCONTROLLER, RS232 SERIAL
PORT, MPLAB IDE AND HI-LINK.
7. THEORY AND LITERATURE
REVIEW
Introduction to DC Motor
DC Motor Speed Controller
PWM Technique
Microcontroller
RS232 Serial Port
MPLAB IDE
WinPic800
Hi-Tech C Compiler
9. Speed Measurement of DC Motor
There are several methods which can use to measure the speed
of motor. Here, we use tachometer for speed measurement of dc
motor.
Tachometer is an instrument that measure the speed of the
motor based on the concept of back EMF induced in motor while
it is running. The EMF is voltage, appeared on the commutator
segments, caused by the rotation in the magnetic field by some
external force. The magnitude of the EMF is given by [1],
EMF=KφN ……………….[1]
Where,
K = a constant based on motor construction
φ = magnetic flux
N = speed of motor (in rpm)
The actual relationship between motor speed and EMF follows
and is derived from equation
N=(EMF)/Kφ ……………………[2]
DC motor Speed Controller
For precise speed control of servo
system, closed loop-control is normally
used.
11. Vavg= (Ton/T)*Vin
Where, Vavg= average voltage supply to DC motor
Ton= time ON of switches
T = period of PWM
Ton/T= duty cycle
There are several controllers that can used to control the speed of the motor such as by using
thyristor, phase-locked-loop control, chopper circuit, Fuzzy Logic Controller and etc. Here, we will
discuss only at the speed control system by using PWM technique.
This on-off switching is performed by power MOSFETs. A MOSFET (Metal-Oxide-Semiconductor Field
Effect Transistor) is a device that can turn very large currents on and off under the control of a low
signal level voltage.
The average of voltage that supply to DC motor is given by,
PWM TECHNIQUE
12. METHODOLOGY
IN THIS PROJECT, MICROCONTROLLER WILL BE
USED AS THE CONTROLLER TO CONTROL DC
MOTOR SPEED AT DESIRED SPEED.
THE ACTUAL SPEED OF DC MOTOR WILL BE
FEEDBACK TO MICROCONTROLLER. IN
MICROCONTROLLER, IT WILL CALCULATE THE
ERROR BETWEEN THE DESIRED SPEED WITH
THE ACTUAL SPEED. THE ERROR WILL
DETERMINE DUTY CYCLE OF PULSE-WIDTH-
MODULATION (PWM) IN MICROCONTROLLER.
THEN, THE DUTY CYCLE WILL SEND TO DC
MOTOR DRIVER EITHER ACCELERATE OR
DECELERATE DC MOTOR TO MAINTAIN IT AT
DESIRED SPEED.
ALTHOUGH THE VARIATION IS CHECKED IN
OPEN LOOP USING A POT.
13. Hardware Implementation
DC Motor
Figure below shows the DC motor that will
be used in this project. It is a permanent
magnet 12V,200 RPM DC motor.
Power Supply +5 volts:
Most digital logic circuits and processors need
a +5 volt power supply. To use these parts we
need to build a regulated +5 volt source.
Usually we start with an unregulated power
supply ranging from 9 volts to 24 volts DC. To
make a +5 volt power supply, we use a LM7805
voltage regulator IC
14. Hardware Implementation
IRF540 is an n-channel MOSFET. It has a
insulated gate.
LM324 is a 14 pin IC consisting of 4
independent Op-amps compensated in a
single package. It is a 14 pin IC.
15. Hardware Implementation
OPTOCOUPLER
MCT2E is the optocoupler.In electronics, an
opto-isolator, also called an optocoupler,
photocoupler, or optical isolator, is a
component that transfers electrical signals
between two isolated circuits by using
light.Opto-isolators prevent high voltages
from affecting the system receiving the
signal. Commercially available opto-isolators
withstand input-to-output voltages up to
10 kVand voltage transients with speeds up
to 10 kV/μs.
16. Hardware Implementation
Microcontroller PIC 16F877A
The microcontroller acts like the brain of the DC motor speed control system. The microcontroller
chip that has been selected for the purpose of controlling the speed of DC motor is PIC16F877A
manufactured by Microchip. This chip is selected based on several reasons:
Its size is small and equipped with sufficient output ports without having to use a decoder
ormultiplexer.
Its portability and low currentconsumption.
It has PWM inside the chip itself which allow us to vary the duty cycle of DC motordrive.
It is a very simple but powerful microcontroller. Users would only need to learn 35 single word
instructions in order to program thechip.
It can be programmed and reprogrammed easily (up to 10,000,000 cycles) using the universal
programmer in robotics lab.
17. Pin name Pin no Description Application
VDD 11,32 Positive supply (+5v) Power supply to chip
VSS 12,31 Ground Reference Ground Reference
OSC1 13 For oscillator or resonator Connected to resonator
20MHz with 22pF
OSC2 14 For oscillator or resonator Connected to resonator
20MHz with 22pF
MCLR 1 Reset input Always connected to
+5V
RA0 2 Input/Output pin Input of Vout from LM324 as
speed counter
RB1 34 Input/Output pin Output to control CW/CCW of
left motor
RB2 35 Input/Output pin Output to control CW/CCW of
left motor
CCP2 16 Capture/Compare/PWM Output of duty cycle(PWM) to
control motor speed
Table: Pin connection of PIC16F877A for DC motor speed control system
18. Hardware Implementation
RS232 Serial Communication:
SCI is an abbreviation for Serial Communication Interface and, as a special
subsystem of microcontroller PIC16F877A. It provides RS232 serial communication with PC
easily.
As with hardware communication, we use standard NRZ (Non Return to Zero) format
also known as 8 (9)-N-1, or 8 or 9 data bits, without parity bit and with one stop bit. Free line
is defined as the status of logic one. Start of transmission - Start Bit, has the status of logic
zero. The data bits follow the start bit (the first bit is the low significant bit), and after the bits
we place the Stop Bit of logic one.
The duration of the stop bit 'T' depends on the transmission rate and is adjusted
according to the needs of the transmission. For the transmission speed of 9600 baud,
Tis104μs.In order to connect a microcontroller to a serial port on a computer, we need to
adjust the level of the signalssocommunicatingcantakeplace.ThesignallevelonaPCis-
10Vforlogiczero and+10Vforlogic one. Since the signal level on the microcontroller is +5V for
logic one and 0V for logic zero, we need an intermediary stage that will convert the levels.
One chip specially designed for this task is MAX232. This chip receives signals from -10 to
+10V and converts them into 0 and5V.
19. Hardware Implementation
RESISTORS
In this hardware implementation, we use
several resistors of values 47ohm,
330ohm, 1 Kohm, 2.2 Kohm, 5.6
Kohm, 10Kohm. We also made several
series and parallel connections of these
resistors to make different values of
resistor.
CAPACITORS
In this hardware implementation, we use
several capacitors of values 0.1
microfarad, 1 microfarad, 10 microfarad,
47 microfarad and 22 picofarad.
20. Hardware Implementation
DIODE
Here we use 1N4007 diode. Here diode is
mainly used for protection purpose.
TRANSISTORS
CL100 is connected in the circuit in
common emitter mode o increase both
voltage and current rating and TIP127 is
connected in common collector mode to
increase the current rating further.
21. Hardware Implementation
POT
A potentiometer, informally a pot, is a
three-terminal resistor with a sliding or
rotating contact that forms an adjustable
voltage divider. If only two terminals are
used, one end and the wiper, it acts as a
variable resistor or rheostat.
TRIMPOT
A trimpot or trimmer potentiometer is a
small potentiometer which is used for
adjustment, tuning and calibration in
circuits. When they are used as a variable
resistance (wired as a rheostat) they are
called preset resistors.
22. Hardware Implementation
HEAT SINK
A heat sink is a passive heat exchanger that
transfers the heat generated by an electronic or a
mechanical device to a fluid medium, often air or a
liquid coolant, where it is dissipated away from the
device, thereby allowing regulation of the device's
temperature at optimal levels. In computers, heat
sinks are used to cool central processing units or
graphics processors. Heat sinks are used with
high-power semiconductor devices such as power
transistors and optoelectronics such as lasers and
light emitting diodes (LEDs), where the heat
dissipation ability of the component itself is
insufficient to moderate its temperature.
Heat sink incorporated with MOSFET
24. RESULT AND
DISCUSSION
THE PWM MODULE IS PROGRAMMED IN THE
MICROCONTROLLER THEN TRIGGERED WITH A
POTENTIOMETER. THE TRIGGERING IS VARIED
AND DATA COLLECTION (GENERATOR
TERMINAL VOLTAGE) IS DONE AT EACH SPEED
FOR DC MOTOR SPEED CONTROL SYSTEM TO
OBSERVE PERFORMANCE OF THE SYSTEM.
LASTLY THE MICROCONTROLLER IS
PROGRAMMED AGAIN FOR A CLOSED LOOP
FEEDBACK WHICH IN TURNS MINIMIZES THE
ERROR. A PROVISION IS MADE TO VARY THE
REFERENCE VOLTAGE OF THE
MICROCONTROLLER (D-PORT). THUS, ACTING
AS AN ON-OFF CONTROLLER.
25. EXPERIMENT
Some experiments had been conducted for the project. First and foremost, an experiment is conducted to
find its feasibility in implementation of an open loop system. The PWM module is programmed in the
microcontroller then triggered with a potentiometer. The triggering is varied and data collection (generator
terminal voltage) is done at each speed for DC motor speed control system to observe performance of the
system. Lastly the microcontroller is programmed again for a closed loop feedback which in turns
minimizes the error. A provision is made to vary the reference voltage of the microcontroller (D-port).
Thus, acting as an on-off controller.
Experiment:
Determination of Voltage Supply and Motor Speed for open loop. An experiment is conducted to determine
the voltage supply and speed using digital multimeter and tachometer. The procedures and the result will be
discussed in following sections. For closed loop system, a feedback path is provided and a reference voltage
is changed.
26. PROCEDURE
For open loop,
The circuit was connected as Figure.
Voltage was supplied to motor and was varied.
Value of rpm at tachometer was recorded in Table(Next Slide).
For closed loop,
The initial procedure reflects that of open loop with,
A feedback loop is connected with pin 2.
3 outlet is provided for changing the reference voltage from pin 27, 28, 29 that is RD6, RD7, RD8 of port D.
The reference voltage is changed by taking RD6 as master switch and varying the logic of the remaining 2 i.e. 00, 01, 10, 11.
For 00 logic, rpm was set at 80.
For 01 logic, rpm was set at 110.
For 10 logic, rpm was set at 140.
For 11 logic, rpm was set at 170.
27. RESULT
For closed loop system, Microcontroller acts as
On-Off controller in the DC motor speed control
system. At each speed, the result was collected by
applying different condition that is reference
voltages.
28. CONCLUSION AND
RECOMMENDATION
IN CONCLUSION, WITH THE ON-OFF CONTROLLER
AT MICROCONTROLLER PIC 16F877A, THE MOTOR
SPEED RESPONSE CAN BE MAINTAINED AT
DESIRED VALUE ALTHOUGH THERE IS A
VARIATION OF LOAD BUT CAN BE VARIED BY
CHANGING THE REFERENCE VOLTAGE OF
MICROCONTROLLER. THE OBJECTIVE OF THIS
PROJECT IS SUCCESSFULLY FULFILLED.
MATHEMATICAL MODEL CAN BE OBTAINED FROM
THE GRAPH OF MOTOR SPEED RESPONSE. THEN,
FROM THE MATHEMATICAL MODEL, IT CAN BE
SIMULATED USING SOFTWARE SUCH AS MATLAB
TO GET THE IMPROVED MOTOR SPEED
RESPONSE BY USING CONTROLLER PACKAGES
SUCH AS PID CONTROLLER, FUZZY LOGIC
CONTROLLER AND OTHERS
29. CONCLUSION
Recent developments in science and technology provide a wide range scope of applications of high
performance DC motor drives in area such as rolling mills, chemical process, electric trains, robotic
manipulators and the home electric appliances require speed controllers to perform tasks. DC motors have
speed control capabilities, which means that speed, torque and even direction of rotation can be changed at
any time to meet new condition.
The goal of this project is to design a DC motor speed control system by using microcontroller PIC16F877A. It
is a closed-loop real time control system. The controller will maintain the speed at desired speed when there is
a variation of load. By varying the PWM signal from microcontroller (On-Off controller) to the motor driver,
motor speed can be controlled back to desired value easily.
In conclusion, with the On-Off controller at microcontroller PIC 16F877A, the motor speed response can be
maintained at desired value although there is no variation of load but can be varied by changing the reference
voltage of microcontroller. The objective of this project is successfully fulfilled.
Although the controller can function as we expected, but the performance is slightly sluggish where it takes
about 2 or 3 second to react properly. A delay is also provided in the coding to incorporate the effect of motor
inertia.
30. RECOMMENDATION
The performance of the system is slightly sluggish. For future works, some recommendations have been
listed based on the problems in order to improve the performance.
Mathematical model can be obtained from the graph of motor speed response. Then, from the
mathematical model, it can be simulated using software such as Matlab to get the improved motor speed
response by using controller packages such as PID controller, Fuzzy Logic Controller and others.
Besides, it will reduce the total hardware complexity and cost at the same time. We have done Fuzzy
Logic Controller in software simulation in our previous project, but its implementation is hard for a
Mamdani type FLC, thus this can be taken under consideration. Use fuzzy logic microcontroller which
combine the idea of fuzzy logic in microcontroller to obtain a DC motor speed control system with
excellent regulation and high robustness
31. REFERENCES
MUHAMMAD H. RASHID. POWER ELECTRONICS
CIRCUITS, DEVICES AND APPLICATIONS.
3RDEDITION. UNITED STATES OF AMERICA:
PRENTICE HALL. 2004.
P.C. SEN AND M. L. MACDONALD.
THYRISTORIZED DC DRIVES WITH
REGENERATIVE BRAKING AND SPEED
REVERSAL. IEEE TRANSACTIONS ON ENERGY
CONVERSION, 1978, VOL. IECI-25, NO. 4:347-
354.
HTTP://HOMEPAGES.WHICH.NET/PAUL.HILLS/SP
EEDCONTROL/SPEEDCONTROLLERSBODY.HTM
L
IOVINE JOHN. PIC MICROCONTROLLER
PROJECT BOOK. 2NDEDITION. MC. GRAW-HILL.
121-123;2000.
MPLAB IDE, SIMULATOR, EDITOR USER’S GUIDE
HTTP://WWW.MICROCHIP.COM
HTTP://WWW.WIKIPEDIA.COM
