The document outlines a project for controlling the speed of Brushless DC (BLDC) motors using a microcontroller, which improves industrial automation by accurately managing motor speed for various applications. It includes hardware components like an 8051 microcontroller, IR sensors for RPM detection, and MOSFETs for controlling motor power, along with software requirements for programming. The proposed system demonstrates effective speed control through PWM duty cycle adjustments and displays real-time RPM data on an LCD, proving its utility in practical scenarios such as aerospace and electric vehicle propulsion.

1. BLDC Motor Speed
Control with RPM Display

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Introduction
BLDC Motor Speed Control
with RPM Display
 The main objective of this project is controlling speed of BLDC motors with
the help of microcontroller. To make the industry automation the
equipment and machineries should be controlled automatically. So control
of the machineries which involving this motor can be done accurately. It
displays its speed using an IR method of speed sensor mechanism. The DC
motor has various application used in industries like in drilling, lathes,
spinning, elevators and etc.

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BLDC Motor Speed Control
with RPM Display
Why Controlling the Speed of Motor is Essential
 The speed control of a DC motor is very essential in industries.
 Controlling the speed has many applications such as drilling, spinning,
elevators, etc.
 To control the speed of the BLDC motor by varying duty cycles of the
power fed to it.
 This proposed system provides a very precise and effective speed
control system.
 The user can increase or decrease the speed as per the requirement.

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BLDC Motor Speed Control
with RPM Display
Block Diagram

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BLDC Motor Speed Control
with RPM Display
Hardware Components
• 8051 Microcontroller
• Level Shifter IC
• GSM modem
• LCD
• LED
• Crystal
• Relay driver IC
• Resistors
• Capacitors
• Diodes
• Transformer
• Voltage Regulator
• Opto Isolator
• Digital Energy Meter
• Lamp

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BLDC Motor Speed Control
with RPM Display
Software Requirement
 Keil compiler
 Language: Embedded C or Assembly

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BLDC Motor Speed Control
with RPM Display
Power supply
 The system requires a regulated +5v supply for the semiconductors.
These can be delivered from the 230V domestic supply. Before applying
this to the system we must step down this high voltage to an appropriate
value. After that it should be rectified. To achieve +5 V DC we should
regulate this.
 A step down transformer and a bridge rectifier is used here to convert AC
to DC. A regulator IC is also used here to give constant supply.7805 IC is
used for power supply.

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BLDC Motor Speed Control
with RPM Display
Power supply

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BLDC Motor Speed Control
with RPM Display
BLDC Motor
 BLDC motors have a rotor and a stator.
 BLDC motors are a type of synchronous motor.
 The magnetic field generated by the stator and the magnetic field generated
by the rotor rotates at the same frequency.
 BLDC motors do not experience the“slip” that is normally seen in induction
motors.

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BLDC Motor Speed Control
with RPM Display
Opto - Isolator
 Opto coupler or Opto Isolator is a 6 pin IC. It is a combination of 1 LED
and a diac. Pin 5 is not generally used and when light falls on the diac
then it switches ON the diac.

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BLDC Motor Speed Control
with RPM Display
MOSFET
 The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-
FET, or MOS FET) is a type of transistor used for amplifying or switching
electronic signals.

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BLDC Motor Speed Control
with RPM Display
Voltage Regulator (LM 7805)
 A voltage regulator is designed to automatically maintain a fixed
voltage level.
 7805 is a voltage regulator integrated circuit.
 It is a member of 78xx series of fixed linear voltage regulator ICs.
 The xx in 78xx indicates the fixed output voltage it is designed to
provide.
 7805 provides +5V regulated power supply.

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BLDC Motor Speed Control
with RPM Display
IR Sensor
 The IR Sensor is a general purpose proximity sensor.
 Here we use it for collision detection.
 The module consists of a IR emitter and IR receiver pair.
 The high precision IR receiver always detects a IR signal.

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BLDC Motor Speed Control
with RPM Display
Three Stages Of Controlling Speed of BLDC Motors
 The Input stage
 The Processing Stage
 The Output Stage

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BLDC Motor Speed Control
with RPM Display
The Input stage
 The input stage consists of entering the required speed through switches.
The Processing Stage
 The processing stage provides RPM reference of the motor. A shaft mounted IR
sensor interfaced to the microcontroller in the circuit.
The output stage
 The output stage uses a MOSFET being driven by the microcontroller output.

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BLDC Motor Speed Control
with RPM Display
Working Principle
 The proposed system uses a microcontroller of the 8051 family and a rectified
power supply. A set of IR transmitter and photodiode is connected to the
microcontroller for counting the number of rotations per minute of the DC motor
as a speed sensor. Opto-coupler is connected to trigger the MOSFET for driving the
BLDC motor which is duly interfaced to the microcontroller. Two switches are
interfaced to the microcontroller for controlling the speed.
 The speed control of the DC motor is achieved by varying the duty cycles (PWM
Pulses) from the microcontroller as per the program. The microcontroller receives
the percentage of duty cycles from the switches and delivers the desired output to
switch the driver IC to control the speed of the DC motor. The speed sensed by the
IR sensor is given to the microcontroller to display it on the LCD display.

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BLDC Motor Speed Control
with RPM Display
Application
 BLDC machines are used in applications of vital importance such as
aerospace industry, tool drives, actuators and electric vehicle
propulsion system.

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BLDC Motor Speed Control
with RPM Display
Conclusion
 The circuit was designed and implemented. Desired rpm was entered
through matrix keyboard. Speed of motor was displayed on LCD display.
IR sensor feedback the actual rpm. Motor rotates with 100% accuracy.
Different rpm values were checked and corresponding displays were
obtained on the LCD screen. The proposed method is very useful for
speed control of BLDC motor.

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