Assignment 9: Input Devices

For this week 9 assignment, I am documenting my learning on Input Devices, covering their types, working principles, and how they interface with different microcontroller boards including the custom board I designed for this week.
I have detailed how I integrated both input and output devices with my board, along with the troubleshooting process I went through. Successfully, I managed to program my board and connect both an ultrasonic sensor and a Hall Effect sensor.
Additionally, my documentation includes reflections on what worked well, the challenges I faced, how I resolved them, and the improvements I would make in future assignments. I am also summarizing my key learning outcomes from this experience.

Highlight Moments of the Week

Basics of Input Devices

Input devices are essential components in electronics and computing, allowing systems to collect real-world data and interact with their environment. These devices convert physical parameters like motion, temperature, light, or sound into electrical signals that can be processed by microcontrollers or computers. They are widely used in automation, robotics, smart systems, and industrial applications to enhance functionality and responsiveness. The need for input devices arises from the requirement to monitor conditions, enable user interaction, and automate processes. Their advantages include improved accuracy, real-time data collection, and efficient control, while challenges may include calibration issues, environmental interference, and power consumption. Understanding input devices is crucial for designing responsive and intelligent electronic systems.

References:, Reference:1, Reference:2.

Types of Sensors:

Sensors are classified based on the type of physical quantity they detect. Common types include temperature sensors (e.g., thermocouples, RTDs) that measure heat, proximity sensors (e.g., infrared, ultrasonic) that detect object presence, and light sensors (e.g., LDR, photodiodes) that respond to light intensity. Magnetic sensors (e.g., Hall effect sensors) detect magnetic fields, while pressure sensors measure force or pressure variations. Every sensor generates a signal that corresponds to the measured quantity, ensuring accurate data collection for processing.

How a basic sensor works:

Characteristics of Sensors:

Sensors possess certain key characteristics that determine their performance and accuracy in measuring physical parameters. Some of the most important characteristics include:

Sensitivity – The ability of a sensor to detect small changes in the measured quantity and produce a proportional output.

Accuracy – The degree to which a sensor’s measurement matches the actual value of the physical quantity.

Resolution – The smallest detectable change in the measured value that the sensor can differentiate.

Linearity – The extent to which the sensor’s output signal is directly proportional to the input quantity over a given range.

Repeatability – The ability of a sensor to produce the same output when subjected to the same input conditions multiple times.

Response Time – The time taken by a sensor to react to a change in the measured parameter and produce a stable output.

Drift – The gradual change in sensor output over time due to factors like temperature, aging, or environmental conditions.

Range – The minimum and maximum values of the physical quantity that a sensor can measure accurately.

Hysteresis – The difference in output when the input quantity is increased versus when it is decreased, affecting measurement precision.

Stability – The ability of a sensor to maintain consistent performance over time and under varying conditions.
Each of these characteristics plays a crucial role in determining the effectiveness of a sensor in real-world applications

Classification of Sensors:

1. Based on the Quantity Being Measured Sensors are categorized according to the type of physical parameter they detect:

* Temperature Sensors – Devices like Resistance Temperature Detectors (RTD), Thermistors, and Thermocouples measure temperature variations.

* Pressure Sensors – Instruments such as Bourdon tubes, Manometers, Diaphragms, and Pressure Gauges detect pressure changes.

* Force/Torque Sensors – Examples include Strain Gauges and Load Cells, which measure force or torque.

* Speed/Position Sensors – Devices like Tachometers, Encoders, and Linear Variable Differential Transformers (LVDT) help measure speed or position.

* Light Sensors – Components such as Photodiodes and Light Dependent Resistors (LDRs) detect light intensity.

2. Based on Power Requirement Sensors are also classified based on their need for an external power source:

* Active Sensors – These sensors generate their own electrical output without requiring an external power source. They operate using the energy derived from the measured parameter. For instance,piezoelectric crystals produce an electrical charge when exposed to acceleration or pressure.

* Passive Sensors – These require an external power supply to function. Mostresistive, inductive, and capacitive sensors fall into this category, similar to how resistors, inductors, and capacitors are considered passive components.

3. Analog and Digital Sensors

* Analog Sensors – These sensors provide output in a continuous signal format corresponding to the measured parameter. Examples include Thermocouples, RTDs, and Strain Gauges.

* Digital Sensors – These sensors produce output in discrete pulses or digital signals, rather than a continuous range. Encoders are a common example of digital sensors.

4. Inverse Sensors - Some sensors have a unique ability to convert a physical quantity into another form and also reverse the process. For instance, piezoelectric crystals generate a voltage when subjected to vibrations. Conversely, when an alternating voltage is applied to them, they begin to vibrate. This dual nature makes them highly suitable for applications like microphones and speakers.

Types of Sensors

Before documenting my work for this week on input devices, I will first discuss some of the sensors that I plan to test and analyze for my Assignment.

1.Ultrasonic Sensor

An ultrasonic sensor is a device that measures distance by using sound waves beyond the range of human hearing. It works by emitting high-frequency sound pulses and calculating the time taken for the echo to return after bouncing off an object. The sensor consists of a Transmitter that generates the ultrasonic waves and a Receiver that detects the reflected signals. The time delay between transmission and reception helps determine the distance of the object. These sensors are commonly used in Robotics, automation, and obstacle detection systems due to their reliability in detecting objects without physical contact. Ultrasonic sensors work well in various environments, including dark or dusty conditions, where optical sensors may fail. However, they can be affected by soft surfaces that absorb sound instead of reflecting it. They are widely used in applications like parking sensors, liquid level monitoring, and proximity detection. The accuracy of measurement depends on factors such as sensor placement, object material, and environmental conditions.

Humans can hear sound waves that vibrate in the range of about 20 times a second (a deep rumbling noise) to 20,000 times a second (a high-pitched whistle). However, ultrasound has a frequency of more than 20,000 Hz and is therefore inaudible to humans.

References:, Reference,

Technical Specifications for ultrasonic sensor

Below, we will look at the pin diagram of the ultrasonic sensor, which shows the different pins and their functions.

The ultrasonic sensor has the following four connections:
VCC – This is the 5 Volt positive power supply.
Trig – This is the “Trigger” pin, the one driven to send the ultrasonic pulses.
Echo – This is the pin that produces a pulse when the reflected signal is received. The length of the pulse is proportional to the time it took for the transmitted signal to be detected.
GND – This is the Ground pin.

The Device Operates as Follows:
1. To operate, a 5V pulse of at least 10 microseconds is sent to the Trigger pin, prompting the HC-SR04 to emit a burst of eight 40 kHz ultrasonic pulses. This unique pattern helps the receiver differentiate the signal from background noise.

2.The Echo pin goes high as the pulses travel through the air. If no object reflects the signal, the Echo pin remains high for 38 milliseconds before timing out, indicating no obstacle within range. If an object is detected, the Echo pin goes low when the reflected pulse is received.

3. The duration of the Echo pulse (ranging from 150 microseconds to 25 milliseconds) corresponds to the time taken for the signal to travel to the object and return. Since this value represents the total time, the actual distance is calculated by dividing it by two.

References:, Reference,

The distance is calculated using the formula based on the time taken for the ultrasonic waves to travel to the object and back. Below, we will see an image illustrating this calculation.

2.Hall Effect Sensor

A Hall Effect sensor is a device that detects the presence and strength of a magnetic field. It operates based on the Hall Effect, which states that when a conductor carrying current is exposed to a perpendicular magnetic field, a voltage (Hall voltage) is generated across the conductor.

What is Hall Effect?

When a voltage source is applied to a conductor plate, electrons and holes move toward their respective opposite polarity terminals. In the presence of a magnetic field, these charge carriers experience a force known as the Lorentz Force, which causes them to deviate from their usual path. However, in the absence of a magnetic field, the charge carriers travel in a nearly straight-line trajectory. This deviation due to the magnetic field results in the Hall Effect within the conductor plate.

Block Diagram of Hall Effect Sensor

A typical Hall Effect sensor consists of three key components: the Hall plate, Voltage Regulator , and Chopper circuit.

Hall Effect sensors are categorized into two types: Linear Output Sensors and Digital Output Sensors. In linear sensors, the output signal is directly taken from an operational amplifier, which amplifies the Hall voltage generated by the Hall plate. However, in digital sensors, a Schmitt trigger circuit is included, which processes the Hall voltage and converts it into a binary ON/OFF output. This means the digital sensor provides a clear switching response depending on the presence or absence of a magnetic field.

Working Principle of a Hall Effect Sensor:

AHall Effect sensor operates based on the Hall Effect, which occurs when an electric current flows through a conductor or semiconductor placed in a perpendicular magnetic field. As the magnetic field interacts with the moving charge carriers (electrons and holes), they experience a force called the Lorentz Force, which pushes them to one side of the material. This results in a voltage difference across the sensor, known as the Hall voltage.

This small Hall voltage is then amplified and processed using signal conditioning circuits. Depending on the type of sensor:
1.Linear Hall sensors provide an analog voltage output proportional to the strength of the magnetic field.
2.Digital Hall sensors use a Schmitt trigger to convert the signal into a binary ON/OFF output, switching states when the magnetic field crosses a threshold.

Hall Effect sensors are widely used in applications such as position sensing, speed detection, and current measurement, as they provide a reliable, contactless method for detecting magnetic fields.

References:, Reference,

Connecting Hall Effect Sensor

Individual Assignment

Objective of the Individual Assignment:

-Integrate a sensor with a custom-designed microcontroller board.
-Capture data from the sensor and interpret the readings.

Plan for My Individual Assignment:

I carefully arranged the components and routed the connections to create an efficient layout. After that, I performed edge cutting to finalize the board shape and saved my design in the appropriate file location. Once the design was completed, I thoroughly reviewed it to identify and correct any potential errors before moving forward with fabrication. This setup will enable me to effectively test and analyze various input devices.

Before cutting my board, I converted my Gerber file to SVG to define the edge cut (outer cut) and inside cut. I used the Gerber2img website for this conversion, ensuring that the design was accurately prepared for fabrication.

After preparing the SVG file, I needed to generate the G-code for cutting my board. To do this, I used the MODS website, where I converted the SVG file into G-code. This step ensured that the milling machine could accurately follow the designated cutting paths.
I carefully checked the generated G-code to confirm that the edge cuts and inside cuts were correctly defined. Once verified, I saved the G-code file and prepared it for use with the milling machine. This process ensured precise board fabrication, allowing for accurate assembly and testing of input devices.