2-Layer IoT Data Acquisition PCB

This repository contains the design files and schematics for a custom 2-layer Printed Circuit Board (PCB) designed for high-efficiency IoT data acquisition. The board is engineered to interface high-precision analog and digital sensors with an ESP32 microcontroller, facilitating real-time data logging and output expansion.

Features

• 2-Layer Optimized Design: Compact PCB layout with dedicated signal and power planes to minimize noise.
• High-Precision Analog Sensing: Integrated ADS1115 (or ADC121C021) 16-bit I2C ADC for superior data resolution.
• Buffered Signal Conditioning: MCP6002 Op-Amp integrated for stable, low-noise signal amplification from the MQ-6 sensor.
• On-board Data Logging: Dedicated Micro SD card slot (optimized for Transcend cards) for local data redundancy.
• Robust Power Management: Dual-stage regulation providing dedicated 5V and 3.3V rails for mixed-voltage sensor arrays.

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Technical Specifications

Component	Specification
Microcontroller	ESP32-WROOM-32
Gas Sensor	MQ-6 (LPG, Butane, Propane Detection)
Temp/Humidity	BME280 (I2C Interface)
External ADC	ADS1115 / ADC121C021 (16-bit I2C)
Signal Amplifier	MCP6002 Dual Operational Amplifier
Local Storage	Micro SD Card Slot (Transcend supported)
Voltage Rails	12V → 5V (LM2596) & 5V → 3.3V (AMS1117-3.3)

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Hardware Connections & Pinout Guide

This document provides a comprehensive mapping of the electrical connections for the 2-Layer IoT Data Acquisition Board, derived from the IoT_Data.kicad_sch design.

1. Main Controller: ESP32-WROOM-32

The ESP32 manages all data acquisition and communication tasks.

Function	ESP32 Pin	Logic Level	Connection Details
I2C SDA	GPIO21	3.3V	Shared data line for BME280 & ADS1115
I2C SCL	GPIO22	3.3V	Shared clock line for BME280 & ADS1115
SPI MOSI	GPIO23	3.3V	SD Card Data Input
SPI MISO	GPIO19	3.3V	SD Card Data Output
SPI SCK	GPIO18	3.3V	SD Card Clock
SPI CS	GPIO5	3.3V	SD Card Chip Select
Analog In	SENSOR_VP	0V - 3.3V	Buffered signal from MQ-6 via MCP6002
VCC	3V3	3.3V	Power input from AMS1117-3.3
GND	GND	0V	Common system ground

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2. Sensor & ADC Connections

Environmental Sensor (BME280)

• Interface: I2C (Address: 0x76 or 0x77)
• VCC: 3.3V
• SDA/SCL: Connected to ESP32 Pins 21/22 with 4.7kΩ pull-up resistors.

Gas Sensor (MQ-6) & Signal Buffer (MCP6002)

• Heater Power: 5V (from LM2596)
• Signal Path: MQ-6 Output → MCP6002 Op-Amp (Voltage Follower/Buffer) → ESP32 SENSOR_VP.
• Purpose: The MCP6002 ensures high-impedance buffering to prevent the ESP32 ADC from loading the sensor signal.

External ADC (ADS1115 / ADC121C021)

• Interface: I2C (Address: 0x48)
• VCC: 3.3V
• Purpose: Used for 16-bit high-resolution sampling of critical analog telemetry.

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3. Storage: Micro SD Card Slot

• Interface: SPI
• Power: 3.3V
• Compatibility: Optimized for Transcend Micro SD cards (FAT32).
• Connection: Uses standard ESP32 SPI pins (GPIO 18, 19, 23, 5).

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4. Power Distribution Architecture

Stage	Input	Output	Component	Feeds
Primary DC	12V (Jack)	12V	Connector J1	LM2596 Input
Step-Down	12V	5V	LM2596S-5	MQ-6 Heater, AMS1117 Input
LDO Regulator	5V	3.3V	AMS1117-3.3	ESP32, BME280, ADS1115, SD Card

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5. Pinout Summary

• I2C SDA: Pin 21
• I2C SCL: Pin 22
• SD Card CS: Pin 5
• SPI MOSI: Pin 23
• SPI MISO: Pin 19
• SPI SCK: Pin 18
• Analog Input (Gas): Pin 36 (SENSOR_VP)

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Tech Stack

• EDA Tool: KiCad (Schematic Capture & PCB Design)
• Microcontroller: ESP32 (Espressif Systems)
• Sensors: * MQ-6 (LPG/Gas Detection)
  • BME280 (Temperature, Humidity, Pressure)
• Protocols: I2C (Sensors/ADC), SPI (SD Card)

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Screenshots

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