Download Lab 3

Lab 3: Manual Rotary Potentiometer
Group Names
Name
Jaron Work
Iosefo Naketeca
Robert Mario
Tevita Sowane
ID Number
A00228670
A00226156
A00221330
A00165825
Date of the Experiment: 02/05/2024
Course Name & Number: Introduction to Automation systems (MCD-657)
Instructor: Ratu Tui Toutou
Abstract
The experiment investigated the variation of output voltage with the rotation of a rotary potentiometer in a voltage
divider circuit. The main findings revealed that the output voltage changed linearly with the potentiometer's rotation
within certain ranges, but non-linear behavior was observed, particularly at extreme positions. Sources of error such
as potentiometer non-linearity and contact resistance influenced the accuracy of the results. While the objectives of
exploring the relationship between potentiometer position and output voltage and verifying theoretical predictions
were achieved, future research directions include characterizing potentiometer non-linearity, mitigating contact
resistance, optimizing circuit design, exploring advanced potentiometer technologies, and conducting applicationspecific studies.
Introduction
A manual rotary potentiometer, commonly referred to as a potentiometer or pot, is a crucial component in electronics,
offering variable resistance controlled by rotating a knob or shaft. Its basic structure comprises a resistive element,
typically made of carbon or conductive plastic, with three terminals: the input terminal, and two output terminals. The
user manipulates the potentiometer by turning a shaft or knob, causing the wiper—a contact point attached to the shaft—
to move along the resistive element. This movement alters the resistance between the input terminal and each output
terminal.
The versatility of potentiometers stems from their ability to precisely adjust electrical parameters in circuits. In audio
systems, for example, potentiometers regulate volume by varying the resistance in the circuit controlling the audio
signal. By adjusting the potentiometer, users can increase or decrease the volume output. Likewise, in lighting systems,
potentiometers control the brightness of lamps or LEDs by modifying the current flowing through them. This feature is
essential for creating ambiance or conserving energy in various settings.
Potentiometers also find applications in motor control circuits, where they regulate motor speed by adjusting the voltage
or current supplied to the motor. This functionality is crucial in machinery and robotics, where precise control over
motor speed is necessary for optimal performance.
Moreover, potentiometers serve as adjustable voltage dividers, providing variable output voltages based on the position
of the wiper. This feature is valuable in electronic circuits requiring adjustable reference voltages or biasing.
In addition to these primary applications, potentiometers aid in calibration and tuning processes in electronic devices.
Technicians use them to fine-tune parameters such as frequency, amplitude, or sensitivity, ensuring accurate and reliable
performance.
The operation of a manual rotary potentiometer can be understood through various theories and concepts in electronics
and electrical engineering. Ohm's Law states that current flow through a conductor is directly proportional to voltage
across two points and inversely proportional to resistance between them. The voltage divider rule states that voltage
across any resistor in series is proportional to its resistance. In a potentiometer circuit, the resistive element acts as a
voltage divider, determining the output voltage by the ratio of resistance between the wiper and one output terminal to
the total resistance of the potentiometer. Potentiometers can have linear or logarithmic resistance profiles, with linear
potentiometers suitable for uniform adjustment and logarithmic potentiometers used in audio equipment for volume
control. In feedback control systems, potentiometers are often integrated into motor speed control to monitor and adjust
system parameters based on feedback signals.
Overall, the manual rotary potentiometer's simplicity, versatility, and effectiveness make it an indispensable component
in electronics, serving a wide range of applications from audio and lighting control to motor regulation and circuit
calibration. Its intuitive operation and precise adjustment capabilities empower users to tailor electrical parameters to
meet specific needs and preferences.
Objectives:

Plot the Variation of Output voltage with control Setting of Rotary Potentiometer
Materials and Method
Apparatus required:
 DIGIAC 1 7 5 0 Transducer a n d instrumentation Trainer.
 4 mm Connecting leads.
 Digital Multi meter
Procedure




I Connected the circuit as shown in Fig using the power supply facilities at the bottom of the panel and the
20V D C rang e of a digital multimeter.
Set the 10 0kΩ rotary resistor control fully counter - clockwise to setting 1 as shown in Fig. Note that the dial
is not marked with numbers on the printed page l.
After ensuring that the voltage adjustment is correct l y set, I switched ON the power supply.
I noted down the output voltage as indicated on the digital multimeter and recorded them in Table
Control Setting
Output Voltage



1
V
2
V
3
V
4
V
5
V
6
V
7
V
8
V
9
V
I Set the rotary control to “2” and repeated the readings, recorded the result in table again.
I Repeated the reading and recording for all other settings of the rotary control.
From the results I recorded in Table above plotted the characteristic of the 100kΩ.
Data from the experiment was obtained from wiper when it switches ON the power supply after making sure the
voltage adjustment is properly adjusted, examine the voltage output as displayed by the digital multimeter.
Results
Control Setting
Output Voltage
1
0V
2
0V
3
1V
4
1.2V
5
1.5V
6
2V
7
2.7V
8
4V
9
9V
10
11V
Discussion
The experiment offers valuable insights into the behavior of rotary potentiometers in voltage divider circuits,
revealing practical implications for controlling voltage levels in electronic circuits. The voltage divider formula
compares experimental results to theoretical predictions, indicating that output voltage should vary linearly with
potentiometer rotation under ideal conditions, but deviations may occur due to factors like non-linearity, contact
resistance, or circuit loading effects.
Uncertainty in the Experiment:

Potentiometer Non-linearity: Rotary potentiometers may exhibit non-linear behavior, especially at the
extremes of their rotation range.

Contact Resistance: Poor contact between the wiper and the resistive track can introduce additional
resistance, affecting the accuracy of voltage division.

Circuit Loading Effects: If the load connected to the output of the voltage divider circuit draws significant
current, it can affect the voltage across the potentiometer and lead to inaccuracies.

Measurement Errors: Errors in measurement instruments or techniques, such as inaccuracies in voltmeter
readings or misalignment of potentiometer markings, can contribute to uncertainty in the results.
Conclusion
The voltage divider circuit's output voltage fluctuated with the rotary potentiometer's rotation, with linear
relationships within the operational range. However, non-linear behavior was observed at extreme rotations, and
sources of error like potentiometer non-linearity, contact resistance, and circuit loading effects impacted results
accuracy. The experiment aimed to determine the relationship between potentiometer position and output voltage,
explore linearity or non-linearity of output voltage variation, and verify theoretical predictions using the voltage
divider formula. Results confirmed linear relationships within certain ranges and highlighted potential deviations due
to various factors, providing insights into potentiometer behavior in voltage divider circuits. Further research is
needed to understand the non-linear behavior of potentiometers, particularly at extreme positions, to develop more
accurate models for voltage control applications. Research on reducing contact resistance between the wiper and
resistive track could improve the accuracy and reliability of potentiometer-based circuits. Alternative circuit designs
or compensation techniques can also be explored. Advanced potentiometer technologies, such as conductive plastic or
cermet materials, may offer improved linearity and reliability.