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HARDWARE MODULES (Flagship Projects) · Case study

Zephyr Station

Zephyr Station is an ESP32 indoor monitor combining environmental sensors, OLED feedback, RTC timestamping, SD-card CSV logging, and buzzer alerts. Its initialization logic keeps the monitor running when an individual sensor is unavailable.

Aug 2025 - Nov 2025
01

System map

Architecture path

ESP32
[I2C Bus 0: OLED]
[I2C Bus 1: BME280]
[I2C Bus 2: RTC]
[SPI: SD Card]
[1-Wire: DS18B20]
[Analog: MQ-135]
[Digital: Buzzer]
WiFi Cloud Upload
02

Engineering design

Subsystem breakdown

Environmental sensing

The BME280 measures temperature, humidity, and pressure. A DS18B20 is listed as a backup temperature sensor, while an MQ-135 monitors air-quality gases.

Local records and feedback

A DS3231 real-time clock and MicroSD module support timestamped CSV logging. An SSD1306 OLED provides a local readout, and an active buzzer is listed for threshold alerts.

Peripheral integration

The documented design assigns the OLED, BME280, and RTC to separate I²C buses, with SPI for the SD card, 1-Wire for the DS18B20, analog input for the MQ-135, and a digital output for the buzzer.

03

Bill of materials

Hardware inventory

11 listed componentsEstimated total: ₹1,202

ESP32 DevKit V1

×1

Main Controller & WiFi

Interface
WiFi/Bluetooth
Voltage
3.3V/5V
Listed price
₹300
Dual-core Xtensa processor, built-in WiFi and Bluetooth

SSD1306 OLED Display

×1

Real-time Visualization

Interface
I2C (0x3C)
Voltage
3.3V
Listed price
₹150
0.96" 128x64 monochrome display on I2C Bus 0

BME280

×1

Environmental Sensor

Interface
I2C (0x76/0x77)
Voltage
3.3V
Listed price
₹200
Temperature, humidity & pressure sensor on I2C Bus 1

DS18B20

×1

Backup Temperature Sensor

Interface
1-Wire
Voltage
3.3V-5V
Listed price
₹120
Waterproof digital temperature sensor with 4.7kΩ pull-up

DS3231 RTC Module

×1

Real-Time Clock

Interface
I2C
Voltage
3.3V-5V
Listed price
₹80
High precision RTC with battery backup on I2C Bus 2

MicroSD Card Module

×1

Data Logging Storage

Interface
SPI
Voltage
3.3V-5V
Listed price
₹50
SD card reader for CSV data logging via SPI interface

MQ-135 Gas Sensor

×1

Air Quality Monitor

Interface
Analog
Voltage
5V
Listed price
₹100
Detects NH3, NOx, alcohol, benzene, smoke, CO2

Active Buzzer 5V

×1

Audio Alerts

Interface
Digital Output
Voltage
5V
Listed price
₹20
Alert buzzer for threshold violations

4.7kΩ Resistor

×1

DS18B20 Pull-up

Interface
Passive
Voltage
N/A
Listed price
₹2
Pull-up resistor for 1-Wire communication

Breadboard & Jumper Wires

×1

Prototyping

Interface
N/A
Voltage
N/A
Listed price
₹80
For circuit connections and testing

5V 2A USB Power Supply

×1

System Power

Interface
USB
Voltage
5V
Listed price
₹100
Powers ESP32 and all peripherals