The document describes an electronics engineering assignment report submitted by 4 students to their lab engineer. It discusses designing and implementing an H-bridge circuit using circuit simulation software to control the direction and speed of a DC motor. The H-bridge circuit uses 4 switches arranged in a way that allows current to flow through the motor in either direction by controlling the switch configuration. Pulse-width modulation (PWM) is used to control motor speed by varying the voltage applied. The report outlines the methodology, including components of the H-bridge circuit like resistors, transistors, potentiometers, and switches. It also provides literature reviewing previous studies using H-bridge circuits for motor control applications.

1. Electronics Engineering
ASSIGNMENT REPORT
4th
SEMESTER
Submitted to: Lab Engineer Ali Hassan
Session: 2023 Section: ME-13-B Group: 1
S U B M I T T E D B Y
Sr.
No. Names CMS ID Circuit
Simulation
Report Viva Total
1 Muhammad Saim
Hussain
370491
2 Muhammad Irtaza
Ikram
368386
3 Muhammad Sarfraz 386734
4 Muhammad Qasim 368527

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SCHOOL OF MECHANICAL AND MANUFACTURING ENGINEERING,
NATIONAL UNIVERSITY OF ENGINEERING AND TECHNOLOGY,
ISLAMABAD.
ELECTRONICS ASSIGNMENT REPORT
Introduction:
DC motors are an integral part of many modern technologies, from household appliances to
industrial machinery. One of the primary requirements for motor control is the ability to change
the direction of rotation. The H-bridge circuit is a popular topology used for this purpose. The H-
bridge circuit consists of four switches, arranged in a specific way, that can be controlled to allow
current to flow in either direction through the motor. By controlling the switch configuration, we
can change the direction of rotation of the motor. This makes the H-bridge circuit an efficient and
versatile solution for controlling the direction of DC motors.
In addition to direction control, the H-bridge circuit also enables us to control the speed of the DC
motor. By varying the voltage applied to the motor, we can control the motor's speed of rotation.
This is achieved by using pulse-width modulation (PWM), which is a technique used to control
the amount of power delivered to the motor. PWM works by rapidly switching the voltage on and
off, and by varying the ratio of on-time to off-time, we can control the effective voltage applied to
the motor. This allows us to control the motor's speed in a precise and efficient manner.
Overall, the H-bridge circuit is a reliable and efficient solution for controlling the direction and
speed of DC motors. It is widely used in various applications, such as robotics, automation, and
electric vehicles. In this assignment, we will design and implement an H-bridge circuit using a
circuit simulation software such as Proteus to demonstrate its functionality. We will explore
different switch configurations and PWM techniques to control the motor's direction and speed
and examine the effects of varying the voltage applied to the motor.
Literature Review:
The H-bridge circuit has been widely used in controlling the direction and speed of DC
motors. The circuit topology consists of four switches arranged in a specific way, which
enables us to control the flow of current through the motor in either direction. One of the
primary advantages of the H-bridge circuit is its ability to control the speed of the motor by
varying the voltage applied to the motor using pulse-width modulation (PWM). This
technique works by rapidly switching the voltage on and off, and by varying the ratio of on-
time to off-time, we can control the effective voltage applied to the motor, allowing us to
control the motor's speed.

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Many studies have been conducted to explore the applications of the H-bridge circuit in motor
control. For instance, researchers have developed an H-bridge-based speed control system for
a DC motor used in a solar-powered electric vehicle. The system consists of a microcontroller-
based control unit that regulates the voltage applied to the motor, and an H-bridge circuit that
controls the direction of the motor's rotation. The study demonstrated the efficiency of the H-
bridge circuit in controlling the speed and direction of the motor, providing an effective
solution for electric vehicles.

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Another study focused on the implementation of an H-bridge circuit for controlling the
direction and speed of a DC motor in a robotic arm. The study used a combination of a
microcontroller, a motor driver IC, and an H-bridge circuit to control the motor's rotation. The
researchers explored different PWM techniques to control the speed of the motor and
examined the effects of varying the voltage applied to the motor. The study demonstrated the
versatility and effectiveness of the H-bridge circuit in controlling the motor's direction and
speed, providing an efficient solution for robotic applications.
Overall, the H-bridge circuit has been widely used in motor control applications due to its
versatility and efficiency. By controlling the direction and speed of the motor, the H-bridge
circuit provides an effective solution for various applications, ranging from electric vehicles to
robotics. Numerous studies have explored the applications of the H-bridge circuit in motor
control, demonstrating its reliability and effectiveness. This assignment aims to design and
implement an H-bridge circuit using a circuit simulation software, further showcasing the
effectiveness of this circuit topology in controlling DC motors.
Methodology:
The H-bridge is a circuit that regulates the direction and speed of a DC motor using four switches.
These switches can be turned on and off in a specific order to allow current to flow through the
motor in either direction. The direction of motor rotation can be controlled by applying appropriate
control signals to the H-bridge inputs. The H-bridge circuit includes diodes that protect it from
voltage spikes caused by back EMF. To change the motor's speed, a potentiometer can be added
in parallel to modify the amount of current flowing through the motor. The control signals for the
H-bridge can be generated using a microcontroller or other control circuitry. Overall, the H-bridge
is a versatile circuit that provides an effective solution for controlling DC motors.
A detail insight into the individual components can be discussed as:
 Resistor:
A resistor is an essential component in the design of an H-bridge circuit.
It is typically used to limit the current flowing through the H-bridge,
which helps to prevent damage to the circuit components. The resistor is
usually placed in series with the H-bridge inputs to ensure that the current
flowing through the H-bridge is within safe limits. Additionally, the
resistor helps to protect the H-bridge components from overloading by
reducing the voltage drop across the circuit. This is especially important
when the H-bridge is used to drive high current loads, such as motors.
In the H-bridge circuit, resistors are often used in combination with other components, such as
capacitors and diodes, to create more complex circuits that can handle a variety of loads. For
instance, resistors can be used in combination with capacitors to create an RC circuit that provides
a time delay in the H-bridge switching sequence. This can be useful in preventing damage to the

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H-bridge components due to inrush currents when the circuit is first powered on. Overall, the use
of resistors in H-bridge circuits is essential for ensuring the safe and efficient operation of the
circuit components.
 Transistor:
Transistors are key components in the design of an H-bridge circuit. They
are typically used as the switching elements in the H-bridge and are
responsible for controlling the current flow through the load. The
transistors used in an H-bridge circuit are often MOSFETs, which provide
a fast-switching speed and low on-resistance. These features are essential
for efficient operation of the circuit, especially when driving high current
loads, such as motors.
In the H-bridge circuit, transistors are arranged in pairs, with one pair on
the high side of the load and the other pair on the low side. By selectively turning on and off the
transistors in each pair, the current can be made to flow through the load in either direction. This
allows the motor to be driven in forward or reverse directions. The use of transistors in H-bridge
circuits provides a reliable and efficient method for controlling the direction and speed of DC
motors.
 Potentiometer:
Potentiometers are variable resistors that are often used in H-bridge
circuits to control the speed of DC motors. They work by varying the
resistance in the circuit, which in turn changes the amount of current
flowing through the motor. The potentiometer is typically connected
in parallel with the motor and the H-bridge circuit, allowing the user
to adjust the amount of current flowing through the motor and thus its
speed. By turning the potentiometer knob, the user can increase or
decrease the resistance in the circuit and control the speed of the motor
accordingly.
In H-bridge circuits, potentiometers are often used in combination
with other components, such as transistors and diodes, to create more complex circuits that can
handle a variety of loads. For instance, potentiometers can be used in combination with diodes to
create a voltage divider circuit that reduces the voltage applied to the motor, which can be useful
in protecting the motor from overvoltage conditions. Overall, the use of potentiometers in H-bridge
circuits provides a simple and effective way to control the speed of DC motors.
 Switch:
Switches are essential components in H-bridge circuits, as they are used to turn the transistors on
and off. In an H-bridge circuit, switches are arranged in pairs, with one pair on the high side of the
load and the other pair on the low side. By selectively turning on and off the switches in each pair,
the current can be made to flow through the load in either direction, which allows the motor to be

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driven in forward or reverse directions. Switches can be mechanical
or electronic, and they can be controlled manually or through an
electronic circuit.
The selection of switches in an H-bridge circuit depends on the requirements of the load. For
instance, if the load is a high current motor, the switches must be able to handle the high current
without overheating or failing. Typically, transistors or MOSFETs are used as the switching
elements in H-bridge circuits because they provide fast switching speed and low on-resistance,
which is essential for efficient operation of the circuit. Switches can be further protected using
diodes to prevent voltage spikes caused by back EMF.
 DC Motor:
DC motors are commonly used in H-bridge circuits as the load
that the H-bridge controls. DC motors work by converting
electrical energy into mechanical energy, which enables them
to rotate a shaft. The direction of rotation can be controlled by
reversing the polarity of the voltage applied to the motor. This
is achieved by switching the current flow through the motor
using the H-bridge circuit.
The speed of the DC motor can also be controlled using an H-
bridge circuit by varying the voltage applied to the motor. This is achieved by using a
potentiometer or pulse width modulation (PWM) technique to adjust the voltage applied to the
motor. DC motors are widely used in various applications such as robotics, automation, and
industrial equipment, making the H-bridge circuit an essential component in these applications.
Circuit Diagram:

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Results:

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As you can see from here circuit changes its direction with the help of switch.The two diagonal
transistors are active simultaneously. Which proves the H-Bridge working principle.
Conclusions:
In conclusion, the H-bridge circuit is crucial for controlling the direction and speed of DC motors.
This assignment focuses on designing and implementing an H-bridge circuit for a DC motor using
four switching elements, a transistor, and a potentiometer. The H-bridge circuit is widely used in
robotics, automation, and industrial equipment, making it an important topic in electrical
engineering.
References:
1. https://en.wikipedia.org/wiki/H-bridge
2. https://www.allaboutcircuits.com/technical-articles/h-bridge-dc-motor-control-
complementary-pulse-width-modulation-pwm-shoot-through-dead-time-pwm/
3. https://www.engineersgarage.com/dc-motor-control-using-h-bridge/

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4. https://itp.nyu.edu/physcomp/labs/motors-and-transistors/dc-motor-control-using-an-h-
bridge/