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Development of a Microcontroller Based DC Motor Speed Control System

Article in World Journal of Engineering and Technology · January 2019

DOI: 10.4236/wjet.2019.74046

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 World Journal of Engineering and Technology, 2019, 7, 634-639
https://www.scirp.org/journal/wjet
ISSN Online: 2331-4249
ISSN Print: 2331-4222

Development of a Microcontroller Based DC

Motor Speed Control System

O. O. Adejumo1*, W. A. Azeez2
1
Department of Physics and Solar Energy, Bowen University, Iwo, Nigeria
2
Department of Physics, The Polytechnic, Ibadan, Nigeria

How to cite this paper: Adejumo, O.O. Abstract

and Azeez, W.A. (2019) Development of a
Microcontroller Based DC Motor Speed This work reports the development of a microcontroller based control system
Control System. World Journal of Engi- to change the speed of a DC motor. Pulse Width Modulation (PWM) tech-
neering and Technology, 7, 634-639. nique was used to control the amount of power delivered to the load (the DC
https://doi.org/10.4236/wjet.2019.74046
motor) without dissipating any wasted power. The components and assembly
Received: August 26, 2019 of this microcontroller circuit are highlighted in this paper, and the con-
Accepted: November 12, 2019 structed circuit tested. This device was used to control the speed of a rotating
Published: November 15, 2019
fan attached to a DC motor. The DC motor speed variations were read from a
Copyright © 2019 by author(s) and
Tachometer connected to this motor and the results obtained show good
Scientific Research Publishing Inc. agreement with our expectations. DC Motor speed microcontroller devices
This work is licensed under the Creative find applications in many areas of life, and its applications in small scale in-
Commons Attribution International
dustrial settings will no doubt enhance the quest for development in a devel-
License (CC BY 4.0).
http://creativecommons.org/licenses/by/4.0/
oping nation like ours.
Open Access
Keywords
Microcontroller, DC Motor, Pulse Width Modulation, Circuit, Rotor

1. Introduction
Direct current (DC) motors find useful applications in many control systems [1].
DC motor speed control is about the change of the drive speed of the motor to a
value required to perform a work process [2]. DC motors are made up of two
basic parts namely the stator, which is the stationary part and the rotor, the in-
ner rotating part, usually called the armature. The rotational speed of a DC mo-
tor depends on the interaction between the two magnetic fields set up by the
stator’s stationary permanent magnets and the armature’s rotating electromag-
nets. By controlling this interaction, we can control the speed of rotation of the
DC motor [3]. This speed control can be achieved in many different ways. A

DOI: 10.4236/wjet.2019.74046 Nov. 15, 2019 634 World Journal of Engineering and Technology
 O. O. Adejumo, W. A. Azeez

simple and easy method is the use of pulse width modulation, PWM technique,
which can be achieved by driving the DC motor with a number of “on” and “off”
pulses and varying the duty cycle of the pulses while the frequency is kept con-
stant [4]. Changing or modulating the timing of these pulses, controls the speed
of the motor, i.e., the longer the pulse is “on”, the faster the motor will rotate and
the shorter the pulse is “on”, the slower the motor will rotate. Hence, the wider
the pulse width, the more average voltage applied to the motor terminals, the
stronger the magnetic flux inside the armature windings and the faster the mo-
tor will rotate. This way, the voltage across the terminals of the motor can be
regulated, and, hence the power applied to the motor can be controlled. In cases
“switching on” and “switching off” are done in quick succession, the motor ro-
tates at a slower speed between zero and full rated speed [5]. This is what a
PWM technique based controller does: it switches the motor “on” and “off” with
a pulse train. When the motor is “on” for a short period and “off” for a long one,
it will rotate slowly. When the motor is “on” for most of the time and “off” only
for a short while, it will rotate at higher speed, say, nearly at full or maximum
rated speed [6]. The aim of this work is to design and construct a circuit that will
generate a pulse width modulation signal to control the motor speed. Initiating
interrupt signals to the microcontroller using push switches (labelled as up- and
down-buttons in this circuit) produces speed increase and decrease of the DC
motor. This change in the motor’s speed was measured by a tachometer con-
nected to the motor’s shaft, and the observations were in agreement with our
expectations.

2. Materials and Methods

The circuit diagram shown in Figure 1 displays the DC motor speed controller
circuit.
The whole assembly is composed of three main units namely; 1) the power
source with its power-on reset switch sub-unit, 2) the main circuit (control unit)
which obtains signals through the interrupt input switches, and 3) switching
unit, incorporating the interrupt input switches and the switching power tran-
sistor for the DC motor.
The power supply unit of this circuit assembly is made up as: A transformer
labelled TRF which steps down, the mains 230 V alternating current, AC to de-
liver a secondary output of 12 V, 500 mA. This output is rectified by a full-wave
bridge rectifier circuit made up of four IN4001 diodes, labelled D1, D2, D3 and
D4, filtered by a 1000 µF, 25 V electrolytic capacitor, labelled C1. The circuit
regulator is a 7805, 5 V, integrated circuit IC, labelled IC1 in the circuit diagram.
This acts as power-on reset for the ATmega 328P microcontroller. From the
output terminal of IC1, a 0.1 µF capacitor labelled C2 is connected in series,
which serves as a filter for the output from IC1. Across C2 is connected to a 330
Ω resistor labelled R1 which regulates the current passing to the LED1. Switch,
S1 serves as the power-on-off for the circuit providing a manual control.

DOI: 10.4236/wjet.2019.74046 635 World Journal of Engineering and Technology

O. O. Adejumo, W. A. Azeez

Figure 1. DC motor speed control circuit.

From this power supply unit, connection was made to the main circuit via
switch S2. The oscillator circuit presented here to generate a pulse width mod-
ulation signal uses an 8-bit microcontroller, ATmega 328P labelled IC2, pro-
grammed by an ARDUINO C++ program. From the power supply pin, (1 of the
microcontroller) connection is made to the power source using a 10 KΩ resistor,
labelled R2, in series as a current limiter. Inputs to the appropriate pins of this
microcontroller are made as shown in the circuit diagram. Output from the mi-
crocontroller is connected to a 16 × 2 liquid crystal display, LCD which interfac-
es this microcontroller, having a total of 32 characters (16 on each line). For each
character there are 5 × 10 = 50 pixels, with all 50 pixels working together to dis-
play each character. The pixels are controlled by another controller (HD44780)
in the display unit. As the pin numbers are defined on the microcontroller, it
displays data on the LCD. Up and Down push buttons, serve as the speed incre-
ment and decrease switches. Two 10 KΩ resistors connected in series to these
switches, labelled R3 and R4 regulates the current supplied to them. Two 22 pF
non-electrolytic capacitors, labelled C4 and C5 are connected across the crystal
oscillator, labelled XRO, and connected to pins 9 and 10 of the microcontroller.

Circuit Explanation
The PWM wave for speed control is generated using the ARDUINO UNO
pre-programmed ATmega 328P microcontroller, which creates pulses of varying
width (using timer 0) for PWM and thereby controls the motor speed. Up and
Down push buttons are interfaced to interrupt the input to Pins 11 and 12 re-
spectively of the microcontroller, IC2, controlling the increment and decrement
respectively of the DC motor’s speed. By pressing any of these switches, an in-

DOI: 10.4236/wjet.2019.74046 636 World Journal of Engineering and Technology

 O. O. Adejumo, W. A. Azeez

terrupt is generated to change the duty cycle of the pulse train. The Up push
button is interfaced to interrupt and increase the duty cycle of the pulse train
while the Down push button is interfaced to interrupt and decrease the duty
cycle of the pulse train. The duty cycle of the pulse waveform is displayed on the
LCD. From Pin 5 of the microcontroller, connection is made to the base of an
npn TIP41C transistor, (labelled Q1), via a 1 KΩ resistor labelled R5. This tran-
sistor acts as a switch (in this case) for the 12 V D.C motor, labelled M, and from
the transistor’s collector, connection is made to the motor M, and from the mo-
tor to the Power source. Diode D5 is an IN4007 rectifier diode, connected in pa-
rallel across the motor to prevent reverse current flow. A tachometer was con-
nected to the D.C motor, M, which measures the speed of rotation of the motor.
Outputs from the microcontroller (data pins 13 through 18 or data pins D7
through D12) are connected to the LCD. The LCD displays 10% of the value of
the duty cycle, in other words, for a duty cycle of 10%, the LCD displays a value
1 and for a duty cycle 70%, the value displayed on the LCD is 7. The power for
the LCD is sourced from the regulator of the power source. The wired compo-
nents are shown in Figure 2.
After wiring the components together, the assembly is encased with switch S1,
labelled as power-on-off button, the Up and Down push buttons are labelled as
speed increase and speed decrease as shown on the case, the LCD and a fan
connected to the shaft of the motor are also displayed on the case as shown in
Figure 3.

Figure 2. Wired components assembly.

Figure 3. DC motor speed controller assemblyase.

DOI: 10.4236/wjet.2019.74046 637 World Journal of Engineering and Technology

O. O. Adejumo, W. A. Azeez

3. Result
Pressing the speed decrease button, led to corresponding reduction in the speed
of the DC motor and this is manifest in corresponding reduction of the speed of
the fan. By pressing the speed increase button to increase the speed of the DC
motor, corresponding increase of the speed of the fan was observed. The speed
of rotation of the motor as measured by the tachometer is displayed in Table
1.

4. Discussion and Conclusion

DC Motor speed controller devices find applications in many areas of life. It
finds good use in industrial automation systems, robotic motion control and in a
number of household appliances [7]. Its applications in small scale industrial
settings will no doubt enhance the quest for development in a developing nation
like ours. This developed microcontroller based control system to change the
speed of a DC motor reported in this work will definitely improve the need for
automation in small and medium scale industrial settings. The circuit compo-
nents for this circuit have been identified, and the constructed circuit tested.
This circuit was used to control the speed of an electric fan. It can also be used to
control the dimness of a lamp, movement of small toys and a number of other
applications. In this circuit, power loss is minimal consequent of using the PWM
technique to control the motor’s speed. The power loss in the switching transis-
tor is small because the transistor is either fully “on” or fully “off” giving it a li-
near type of control which results in better speed stability. Also, the voltage am-
plitude of the motor is constant, and hence the motor is at full strength always,
which means that the motor can be rotated much more slowly without stalling.

Table 1. Speed of rotation of motor.

Motor Speed (rpm)

Motor Speed Setting
Increase Decrease

0 0 0

1 682 682

2 1365 1365

3 2047 2047

4 2730 2730

5 3412 3412

6 4095 4095

7 4777 4777

8 5460 5460

9 6142 6142

DOI: 10.4236/wjet.2019.74046 638 World Journal of Engineering and Technology

 O. O. Adejumo, W. A. Azeez

Acknowledgements
This research did not receive any specific grant from funding agencies in the
public, commercial or not-for-profit sectors.

Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this
paper.

References
[1] Russel, Md.K. and Bhuyan, M.H. (2012) Microcontroller Based DC Motor Speed
Control Using PWM Technique. Proceedings of the International Conference on
Electrical, Computer and Telecommunications Engineering RUET, Rajshahi, Ban-
gladesh, 1-2 December 2012, 519-522.
[2] Bhuyan, M.H. (2007) Wireless Control System for DC Motor to Position a Dish An-
tenna Using Microcomputer. Daffodil International University Journal of Science and
Technology (DIUJST), 2, 44-49.
[3] Bhuyan, M.H., Rabby, M.A. and Tarik, M.M.G. (2010) Microcontroller Based Au-
tomatic Traffic Light Control System Design. Proceedings of the National Confe-
rence on Electronics and Telecommunications for Digital Bangladesh, Dhaka, 2-3
June 2010, 139-142.
[4] Siskind, C.S. (1959) Electrical Machines Direct and Alternating Current. McGraw
Hill Book Co., New York, USA.
[5] Shuler, C.A. and McNamee, W.L. (1986) Industrial Electronics and Robotics.
McGraw Hill Book Co., New York, USA.
[6] Rashid, M.H. (2010) Power Electronics Circuits, Devices and Applications. Prentice
Hall Inc., USA.
[7] Mathur, A. (2008) Microcontroller-Based DC Motor Speed Controller. Electro-
nicsForYou, March 2008, 92-96.

DOI: 10.4236/wjet.2019.74046 639 World Journal of Engineering and Technology

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