4. Industries are the backbone of the modern era and so it is of utmost importance
that they always run with the highest possible efficiency. And for this reason
many industrial applications require dc voltage sources, some by force and some
by choice. However many of them perform better when they are fed from a
variable dc source as compared to fixed voltage sources. These include battery
operated vehicles, subway cars, battery charging etc. The conversion of fixed dc
voltage to variable dc can be obtained by using semiconductor devices
this project aims to simulate and analyze a model of dc chopper using power
Transistor and study the speed control characteristics and the advantages and
limitations of using a Transistor.
Introduction :
5. Theory -
The PWM pulses are fed to the gate of a transistor which
reacts and controls the connected motor current in
response to the setting of the pot. The current level
through the motor decides it speed and thus implements
the controlling effect via the pot.
Here the Transistor are switched at a constant frequency with
a control signal having variable duty cycle. This allows the
average voltage across the motor to vary and thus control the
rotor angular speed
7. • 139 Transistor: :;;:
The BD139 is a NPN complementary low voltage NPN transistor in 3
pin SOT-32 package.
This device is designed for audio amplifiers and drivers utilizing
complementary or quasi-complementary circuits.
Products are pre-selected in DC current gain. Collector to emitter
voltage (Vce) is 80V.
• Resistor :
22K Ohm 1W High Quality Carbon Film Resistor (CFR) with ±5%
Tolerance and Tin Plated Copper Leads. 22K Ohm Resistor Color
Code: Red, Red, Orange, Golden. Resistance: 22K Ohm, Power Rating:
1 Watt, Approximate Maximum Current: 6.74mA .
8. • variable resistor:
Trimpot is a high accuracy variable resistor and pcb mountable
with 3 terminal pins. The voltage between the terminal varies
as the trimpot is rotated. The Variable resistors are used for
variating voltage as per the need in a circuit.
• BLDC Motor/Fan:
Machines ranging from simple devices like drills to complex
equipment like industrial robots all make use of brushless DC
motors that convert electrical energy into rotational motion.
BLDC motors offer many advantages over their brushed
counterparts.
9. • Printed Circuit Board (PCB):
A printed circuit board (PCB) is a laminated sandwich structure
of conductive and insulating layers. PCBs have two
complementary functions. The first is to affix electronic
components in designated locations on the outer layers by
means of soldering. The second is to provide reliable electrical
connections (and also reliable open circuits) between the
component's terminals in a controlled manner often referred to
as PCB design.
• Connecting Wires :
Connecting wires allows an electrical current to travel from one
point on a circuit to another because electricity needs a
medium through which it can move. Most of the connecting
wires are made up of copper or aluminum.
10.
11. In the above DC motor controller design, the pot adjustment creates a varying
potential difference across the gate of the transistor, and the source pin of the
transistor simply follows the value of this potential difference and adjusts the
voltage across the motor accordingly.
It implies that the source will be always 4 or 5V lagging behind the gate
voltage and vary up/down with this difference, presenting a varying voltage
between 2V and 7V across the motor.
When the gate voltage is around 7V, the source pin will supply the minimum
2V to the motor causing a very slow spin on the motor, and 7V will be
available across the source pin when the pot adjustment generates the full
12V across the gate of the transistor. above configuration helps to enforce a
smooth speed control on the motor, and the design could be built quite
cheaply
Working:
12. • We can built this project at very low price.
• Time requirement for making this project is approximately 1-
2 hour
• Component required for this are easily available .
• this is one of the simplest method of controlling DC motor
speed
13. • They have very susceptible to overload
voltage, hence due to installation
special handling is to be required.
• Required repeated calibration for
accurate dose measurement
Disadvantages:
14. The purpose of this project is to control the speed of DC motor
using TRANISTOR to explore its use and suggest other areas of application
DC (Direct current imotorhave been widely used in many industrial.
application due to its precise and continuous control characteristics in
theory, the DC motor is directly Proportional to the supply voltage, so if the
voltage reduce from 12 to 6 volts the speed decrease by half in practice the
supply voltage cannot be change all the time to control the motor speed so
the MOSFET. As the switching the switching device will turn supply ON and
OFF. where switching is done so fast that the only notices average voltage
effect and not the switching PWM (pulse width modulation) circuit to
control voltage output at the motor and the uned TRANSISTOR as the
switching device
Conclusion
15. • In this project we learn the how speed control DC motor using
TRANSISTOR work Working of each functional part of the speed
control DC motor using TRANSISTOR Also get knowledge about
how prepared model of speed control DC motor using
TRANSISTOR.
• knowledge of basic operation of the speed control DC motor
using TRANSISTOR
• Knowledge of the basic operation of the speed control DC motor
using TRANSISTOR.
• Knowledge of the group work.
Outcomes of Project
