This project is about using PID controller control the DC motor’s speed.

For that purpose, four circuits are used. These circuits are FVC (frequency to

voltage converter), Encoder (motor driver), Subtractor, and PID. Different

components like, resistors, capacitors, motor and IC’s are used in this

project.

3.1

Proposed Design Methodology

Figure 1:

Proposed Design

+ –

–

PID

MOTOR DRIVER

FVC

Y(t)

The reference input was given to the summer which subtracts the

error amount which is coming from the output and then gives that signal to the PID controller as

input. PID controller generates the signal as input to the motor driver circuit.

Tachometer is used to measure the speed in rpm, then FVC was used which converts

frequency into voltage. LM2907

IC was used for conversion purpose, it gives output to summer which calculates the

error.

3.2

Analysis Procedure

We have to figure out a way

to control the speed of the small dc motor using 555 timers. Using a small

permanent magnet DC motor

to build small projects like, cars, robots, or quads, requires a speed controller

to make their work easier.

Figure 2:

Analysis Procedure

3.3

Design of the Project Hardware/ Software

The project has three main components for designing. All three of

them will combine to control the motor’s speed.

PID

controller

Encoder

(motor driver)

Frequency

to voltage converter circuit

3.3.1

PID controller

design

PID is combination of three different

controllers which are following:

1. Proportional controller

2. Integral controller

3. Differential controller

3.3.1.1

Proportional Controller

In this controller, the output is proportional

to the error which is equal to the difference of the set point and the process

variable. The proportional controller has constant variable kp which is called proportional

gain. The rise time increases by the increment of proportional gain, and thus steady

state error decreases but it doesn’t

remove it completely 5.

Figure 3: Proportional Controller

The circuit diagram of proportional controller

is

3.3.1.2

Integral controller

The

proportional controller did not remove steady state error completely. So for

removing steady state error integral controller is used, it removes the steady

error completely but it increases the rise time and induces the overshoot in

the system 5.

Figure 4:

Integral Controller

The circuit diagram of Integral

controller is

3.3.1.3

Derivative controller

The derivative controller is used to decrease the overshoot, and for reducing the settling

time. This can be achieved by:

Increasing kd reduces the

rising time.

Increasing kd reduces the

settling time.

Where Kd is the gain of the derivative controller 5.

The circuit of the derivative controller

is

Figure 5:

Derivative Controller

3.3.2

Encoder

A two wing fan is attached with the DC motor. A phototransistor

sensor is placed in front of a Led and the wings of the fan are in between the

sensor and led. Whenever fan wings cuts

the LED, the sensor counts the rotation 6.

Figure 6:

Encoder

3.3.3

Frequency to

voltage converter

The

circuit to convert the frequency to voltage is implemented by using IC LM 2907.

Figure 7: Frequency to

Voltage Converter

The input

frequency is coming from the tachometer and then the circuit converts that

frequency into voltage and gives it as feedback to the circuit 7.

3.4

Implementation

Procedure

Figure 8:

Implementation Procedure

FVC

Encoder

PID

Subtractor

3.5

Details about

Hardware

3.5.1

LM 2907

The LM2907,

LM2917 series works as a monolithic frequency to voltage converters with a high

gain operational amplifier aimed to operate a load when the input frequency is

equal or more than a specified rate. A charge pump technique is employed by the

tachometer which offers frequency doubling for low ripple, full input

protection in two versions (LM2907-8, LM2917-8) and for an input of zero

frequency, its output swings to ground.

Figure 9: LM2907

The

input is given on the pin 1 and

VCC is given on pin 6, pin 8 is grounded and output is taken from pin 4 7.

3.5.2

Photo Diode

It is a semiconductor device with a purpose of converting light

into current. When photodiode absorbs the photons, some current is generated. It

might consist of some optical filters, built-in lenses, and it comes with small

or large surface areas 8.

Figure 10:

Photo Diode

3.5.3

DC motor

We used a 12 volts DC motor. It belongs to any class of the electrical

machines which basically converts the direct current electrical power into

mechanical power 9.

Figure 11: DC

Motor

3.5.4

Resistors

It is an electrical component in a circuit with a basic working of limiting

or regulating the flow of electrical current. They can give an active device,

for example a transistor, some pre-specified voltage. Multiple resistors are

being deployed in this project 10.

Figure 12:

Resistor

3.5.5

Capacitors

It is a passive electronic component, whose main

job is to store the energy in the form of an electrostatic field. While there are

multiple variations out there, the simplest capacitor comprises of two conducting plates separated by an

insulating material called the dielectric 10.

Figure 13:

Capacitor

3.6

Details about Software/Algorithm

The software used in this project are:

Proteus

MATLAB

3.6.1

Proteus

The Windows

application of Proteus Design Suite is mostly used for schematic capture,

running the simulation of circuit and making a PCB layout design.

To draw the

schematics and simulate the circuits in real time, we use ISIS. We can access

the simulation during the run time, which provides us a real time hands-on

experience.

For PCB

designing, ARES is used. Some of its features include viewing the designed PCB

along with the components in 3D. It also allows developing 2D drawings of the

product 11.

3.6.2

MATLAB

MATLAB is a high-performance language for technical

computing. It has an easy-to-use environment which integrates computation,

visualization, and programming, where the problems and their solutions are presented

in simple mathematical notation 12.

3.7

Design of project hardware/ Simulations /

Mathematical Modeling

·

Schematic diagram of the circuit is:

Figure 14:

Schematic Diagram

·

PCB diagram of the circuit is:

Figure 15: PCB

Diagram

3.8

Summary

The speed of

motor can be controlled by using the PID controller. So, firstly by changing

P-factor or proportional factor it can be seen that how overshoot of the signal

can be changed and rise time of

the signal also changes. Then by changing I-factor (Integral) it can be

seen that overshoot value of the signal is decreased and rise time of the

signal also changed in

the last by changing D-factor (Differential). It can be seen that if there are some error occurs in the

signal it will show.