Introduction

In this week’s group assignment, our objective was to probe and understand the analog and digital signals generated by different input devices. We connected various sensors to a microcontroller board and observed their outputs using measurement tools. Analog sensors such as an DHT22 we used. Digital sensors such as an IR sensor were used to observe discrete HIGH and LOW signals when an object was detected. The sensors were connected to the ESP32-C3 and programmed using Arduino IDE. The output signals were monitored through the Serial Monitor, Serial Plotter, and an oscilloscope to analyze how the sensor signals change in real time. This helped us understand how microcontrollers read and interpret both analog and digital input signals from sensors.

Digital signal

Using IR sensor

Hardware components we used:-

• xiao ESP32C3
• IR sensor
• oscilloscope
• Connceting wires

Using ultrasonic sensor

Hardware components we used:-

• xiao ESP32C3
• Ultrasonic sensor
• oscilloscope
• Connceting wires

Link to view group assignmentGroup Assignment

Input Devices

An input device is a component that sends information or signals to a computer or microcontroller so that it can understand what is happening in the outside world. These devices detect physical changes such as light, temperature, sound, distance, or motion and convert them into electrical signals. The microcontroller reads these signals and processes them to perform a specific action. In simple words, an input device is something that gives data to the system.

What is sensor?

A sensor is a device that can detect or measure changes in the environment and send that information to a computer or microcontroller. These changes can be things like light, temperature, sound, distance, motion, or humidity. The sensor converts these physical changes into electrical signals so the system can read and process them.

Types of sensors:-

image from search engine

Digital signal

A digital signal is a type of signal that has only two possible values: ON or OFF. It is usually represented as 1 and 0. In electronics and microcontrollers, a digital signal means the device only understands whether something is high 1 or low 0.

Analog signal

An analog signal is a signal that changes continuously and can have many different values, not just two. It represents real-world measurements like light, temperature, sound, or pressure. Unlike digital signals (which are only 0 or 1), analog signals can have a range of values.

image from unison audio

Kicad software Schematic Diagram

First, I opened KiCad Schematic Editor to design my circuit. I selected the XIAO ESP32C3 microcontroller module as the main controller for my board. After placing the microcontroller, I added LEDs and resistors to the schematic. The resistors are connected with LEDs to limit the current and protect the LEDs.Then I connected each LED to different GPIO pins of the ESP32C3 so that they can be controlled individually through programming. I also added 3-pin connectors which include 3.3V, GND, and signal pins. These connectors can be used to connect external input sensors such as LDR, IR sensor, or sound sensor.

Kicad software diagram in PCB editor

Then I go to PCB Editor where I route my PCB board.after this I plot gerber files to a specific folder for future use.

Link to view group assignmentGroup Assignment

Starting with gerber to image conversion

I used Gerber2Image to convert my Gerber files into PNG format. In this software, I simply drag and drop the Gerber files, and the program automatically loads and converts them into image files.

I used Gerber2Image to convert my PCB Gerber file into a PNG image. First, I selected the F.Cu (Front Copper) file and dragged and dropped it into the software. After loading the file, I chose the black and white rendering option to clearly show the PCB traces. Then, I saved the rendered output as a PNG file, which can be used for PCB milling.

After that, I selected the Edge.Cuts file, which defines the outline of the PCB board, and similarly rendered and saved it as a PNG image.

Using mods for G-code generation

I opened mods ce then click on programs and select machine I am using for pcb making.

I used Mods CE to convert the PNG files into G-code for PCB milling.

First, I opened Mods CE and clicked on Select PNG file, then I uploaded the trace cut PNG file.

Since I was using a 1/64 milling bit for cutting the PCB traces, I selected the 1/64 tool option.

After that, I set the cutting speed to 4 mm/s and set the origin coordinates X = 0, Y = 0, Z = 0. Then I configured the settings by disabling the top button and enabling the bottom one to prepare the file for saving.

. Finally, I clicked on Calculate, and the software generated and saved the .rml file.

This file is then used for milling the PCB, and the generated preview shows how the PCB simulation will look after the milling process.

Similarly, I uploaded the Edge.Cuts PNG file into Mods CE to generate the toolpath for cutting the PCB outline. After selecting the PNG file, I chose the 1/32 cutout tool option since a 1/32 milling bit is used for cutting the board edges.

Then I set the speed to 4 mm/s and defined the origin coordinates as X = 0, Y = 0, Z = 0. After that, I configured the settings by turning off the top button and enabling the bottom one to prepare the file for saving. Finally, I clicked on Calculate, which generated the toolpath and saved the .rml file.

Before starting the milling process, the software displays a simulation preview, allowing us to check how the PCB outline will be cut on the machine.

Using V-Panel for tracing and cutting process:-

I set proper tool for tracecut(1/64 inch end mill) during milling process.

Then I set x,y origin to 0.

Also I set z axis to 0 by putting 1/64 inch end mill bit at proper position.

I set z origin to 0.

Then I click on cut option and select add to add tracecut file for tracing process.

After completing process I use vaccum cleaner to clean the part.

After this I change the bit to 1/32 inch end mill and put edgecut file for cutting purpose.

I add edgecut for for edge cutting purpose.

milling process get completed here.

And here is my milled board

Soldering Process:-

material required during soldering process:-

The soldering process is used to attach electronic components to the PCB after the board is milled. First, the milled PCB is cleaned properly to remove dust or copper particles. Then all the required components such as resistors, LEDs, microcontroller, and connectors are placed on their respective pads according to the schematic design. A soldering iron is heated and solder wire is applied to the joint where the component lead and copper pad meet. The heat melts the solder, allowing it to flow around the component lead and pad, creating a strong electrical and mechanical connection. This process is repeated for all components on the board. After soldering, the board is visually inspected to ensure there are no loose connections, excess solder, or short circuits between the pads.

Components used are as follows:-

• 1.XIAO ESP32-C3 microcontroller
• 2. one 4-pin connectors
• 3. one 3-pin connectors
• 4.5-LEDs
• 5.5-Resistors

Uploading code:-

1.aht2415c

The AHT2415C temperature and humidity sensor is a digital sensor used to measure temperature and humidity in different environments. It contains an integrated sensing chip that detects environmental conditions and converts them into digital data that can be read by microcontrollers such as Arduino or ESP32 using the I²C communication protocol. The sensor typically operates within a temperature range of about −30 °C to 80 °C and a humidity range of 0–100 % RH, with an accuracy of around ±0.5 °C for temperature and ±3 % RH for humidity. It is usually housed in a stainless-steel probe with a protective PTFE dust-proof membrane, which protects the sensor from moisture, dust, and environmental interference while ensuring stable and reliable measurements. Because of its high accuracy, fast response time, and digital output, the AHT2415C is commonly used in HVAC systems, industrial monitoring, weather stations, home appliances, and IoT projects where accurate environmental sensing is required.

Pin description

• VCC-This pin provides power to the sensor. It is typically connected to 3.3 V or 5 V from the microcontroller or power supply.
• GND-This pin is connected to the ground of the microcontroller to complete the electrical circuit.
• SDA-SDA is the data communication line used in the I²C protocol. It transfers temperature and humidity data between the sensor and the microcontroller.
• SCL-SCL is the clock signal line of the I²C communication. It synchronizes data transfer between the sensor and the microcontroller.

Internal structure of AHT2415C

The AHT2415 Temperature and Humidity Sensor is a digital environmental sensor used to measure temperature and humidity. Inside the sensor there are two main sensing elements: a humidity sensing capacitor and a temperature sensing thermistor.

The humidity sensor works by using a special moisture-sensitive material placed between two electrodes; when the air humidity changes, the material absorbs or releases water vapor, which changes the capacitance of the sensor

The temperature sensor (thermistor) changes its electrical resistance depending on the surrounding temperature. Inside the chip, a small signal processing circuit and ADC (Analog-to-Digital Converter) convert these changes into digital data that can be read by a microcontroller. The sensor module usually has four pins: VCC, GND, SDA, and SCL. VCC provides power to the sensor (usually 3.3V or 5V), GND is the ground connection, SDA is the data line used to send humidity and temperature data, and SCL is the clock line that synchronizes communication. The sensor communicates with microcontrollers like ESP32‑C3 XIAO or Arduino Uno using the I²C communication protocol, which allows temperature and humidity data to be transmitted through only two signal wires.

1.Using aht2415c temperature humidity sensor

VCC → 3.3 V,GND → GND, SDA → GPIO8, SCL → GPIO9

2.Sound sensor

A sound sensor is an electronic module used to detect sound levels in the surrounding environment. It usually contains a microphone that converts sound waves into electrical signals and a small amplifier circuit to process the signal. Sound sensors are commonly used in electronics and IoT projects with microcontrollers like Arduino or ESP32 to detect noise, claps, or music. They can be used in applications such as sound-activated lights, security systems.

Pin description

• VCC-This pin supplies power to the sound sensor module. It is usually connected to 3.3 V or 5 V from the microcontroller.
• GND-This pin is connected to the ground (GND) of the microcontroller to complete the circuit.
• OUT-This pin sends the sound signal to the microcontroller. In analog sound sensors, it provides varying voltage depending on the sound intensity. In digital sensors, it outputs HIGH or LOW when the sound crosses a preset threshold.

The structure of sound sensor

VCC → 3.3 V, GND → GND, OUT → GPIO 2

3.MQ2 Sensor

The MQ-2 gas sensor is a commonly used sensor for detecting flammable gases and smoke in the environment. It is widely used in safety and monitoring systems because it can sense gases such as LPG, propane, methane, hydrogen, alcohol, and smoke. The sensor works using a gas-sensitive material (tin dioxide – SnO₂) whose electrical resistance changes when it comes in contact with different gases. These changes are converted into electrical signals that can be read by microcontrollers like Arduino or ESP32. Due to its sensitivity and simple interface, the MQ-2 sensor is often used in gas leakage detection systems, fire alarms, air quality monitoring, and IoT safety projects.

Pin description

• VCC-This pin provides power to the MQ-2 sensor module. It is usually connected to 3V,5V from the microcontroller or external power supply.
• GND-This pin is connected to the ground (GND) of the microcontroller to complete the circuit.
• AO-The AO pin provides an analog voltage output that varies depending on the concentration of gas detected. This allows the microcontroller to measure the gas intensity level.
• DO-The DO pin provides a digital HIGH or LOW signal when the gas concentration crosses a preset threshold. The threshold level can usually be adjusted using a potentiometer on the sensor module.

VCC → 3V,GND → GND,AO → Analog input pin D2, DO → Digital input pin (optional)

Code files

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PNG and .rml files

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