Seegrid Aging Room Environmental Monitoring System

An Arduino Mega-based multi-room temperature and humidity monitoring system for industrial aging room environments. Reads four DHT22 sensors on the Aging Room, receives wireless RS485 sensor data from Skit Room and Camera Room Nano nodes, logs all data to an SD card, and serves interactive web dashboards per room with real-time alerts.

How It Works
System Architecture
RS485 Network
Requirements
File Overview
Installation
Setting Your Authentication Password
Memory Architecture and Data Persistence
Web Interface URL Reference
Usage
Adjusting the Temperature Threshold
Security Features
Data Logging
Configuration Constants
Troubleshooting
Version History

How It Works

Once running, the system enters a continuous monitoring loop that:

Reads all four DHT22 sensors every 2 seconds and updates the LCD display. The display rotates through sensor zones automatically.
Receives RS485 serial data from Skit Room and Camera Room Arduino Nano nodes every 6 minutes. Each Nano reads a DHT22 sensor and transmits a packet (SKIT:21.5,45.2\n or CAM:21.5,45.2\n) over RS485. The Mega parses and stores the values.
Controls the LED indicators based on sensor status — solid green when all sensors are within the threshold margin, slow red blink when one or more sensors are out of range, and fast red blink on a sensor read failure.
Logs sensor data to SD card every 5 minutes on strict 5-minute clock boundaries, writing timestamped rows to daily files. A midnight janitor automatically deletes files older than 180 days. Data survives power outages and can be downloaded directly from the web interface.
Serves a web dashboard per room — Aging Room at /, Skit Room at /skit, Camera Room at /camera — each with interactive Chart.js charts, live sensor status bars, system status panels, and threshold adjustment controls.
Provides a hidden admin page at /admin for SD card file management — listing all files with sizes, downloading individual files, and deleting files with safety guards on active data files.
Syncs time via NTP at startup and twice daily (midnight and noon). The system first contacts the internal NTP server 192.168.80.8 and falls back to the public NTP pool pool.ntp.org if unavailable. DST transitions occur correctly at 2:00 AM on the 2nd Sunday of March (EDT) and 1st Sunday of November (EST).
Runs a hardware watchdog armed at 8 seconds. If the system stalls for any reason — network hang, SD deadlock, infinite loop — the Arduino reboots automatically. Each reboot is timestamped and logged to EVENTS.txt on the SD card.
Tracks network connections per IP address. A maximum of 8 simultaneous global connections and 3 per IP are enforced; idle connections are released after 5 minutes.
Persists temperature thresholds to EEPROM — one each for Aging Room, Skit Room temp, Skit Room humidity, Camera Room temp, and Camera Room humidity — so all user-configured values survive power outages.

System Architecture

                    ┌─────────────────────────────┐
                    │     Arduino Mega 2560        │
                    │                              │
                    │  • 4× DHT22 sensors (A–D)   │
                    │  • Ethernet W5100/W5500      │
                    │  • SD Card (logging)         │
                    │  • LCD 20×4 I2C              │
                    │  • Serial1 (pin 19) ←── RS485 bus  │
                    └──────────────┬───────────────┘
                                   │ RS485 Bus (A/B twisted pair)
                    ┌──────────────┴───────────────┐
                    │                              │
          ┌─────────┴──────┐            ┌──────────┴──────┐
          │  Arduino Nano  │            │  Arduino Nano   │
          │  Skit Room     │            │  Camera Room    │
          │  • 1× DHT22    │            │  • 1× DHT22     │
          │  • MAX485 TX   │            │  • MAX485 TX    │
          │  Tx every 6min │            │  Tx every 6min  │
          └────────────────┘            └─────────────────┘

RS485 Network

Overview

The Skit Room and Camera Room each use an Arduino Nano with a MAX485 TTL-to-RS485 module to transmit sensor data to the Mega every 6 minutes. The Mega listens on Serial1 (hardware UART, pin 19 RX) and parses incoming packets.

Packet Format

Room	Packet Format	Example
Skit Room	`SKIT:temp,humid\n`	`SKIT:21.5,45.2\n`
Camera Room	`CAM:temp,humid\n`	`CAM:20.3,48.4\n`

Units are raw floats — no C or % suffix in the packet (formatting is applied by the Mega on display/storage)
On sensor failure the Nano sends SKIT:ERR,ERR\n so the Mega knows the sensor failed vs. a lost packet

RS485 Module Selection

Important: You must use a MAX485 TTL module — NOT an RS232-to-RS485 converter.

Module Type	Correct for Arduino?	Notes
MAX485 TTL breakout	✅ Yes	5V logic, DI/DE/RE/RO pins, ~$1–2 each
RS232 to RS485 converter	❌ No	Uses ±12V RS232 levels — will damage Arduino pins
USB to RS485 adapter	❌ No	For PC use only

Search Amazon for: "MAX485 module Arduino" — look for the small green board with DI, DE, RE, RO, VCC, GND, A, B labeled.

DE/RE Pin Wiring

The MAX485 chip uses two direction control pins:

Pin	Name	Function
DI	Driver Input	Data to transmit — connect to Arduino TX
DE	Driver Enable	HIGH = transmit mode enabled
RE	Receiver Enable	LOW = receive mode enabled
RO	Receiver Output	Received data — connect to Arduino RX

Since DE and RE are always set opposite each other, tie DE and RE together to a single Arduino digital pin:

Pin HIGH → transmit mode
Pin LOW → receive mode

Current Wiring Status (Temporary)

While proper MAX485 modules are on order, the Skit Room sensor is wired directly to pin 19 (Serial1 RX) on the Mega as a temporary bypass. Data is coming through correctly. The Camera Room is not yet connected.

Once MAX485 modules arrive:

Wire Nano TX → MAX485 DI, Nano DE/RE pin → MAX485 DE+RE tied together, MAX485 A/B → bus
Wire Mega Serial1 RX (pin 19) → MAX485 RO, Mega DE/RE pin → MAX485 DE+RE, same A/B bus
No firmware changes required — the code already handles DE/RE switching

Transmit-Only Nodes (Skit/Camera Nanos)

Because the Skit and Camera Nanos only ever transmit and never need to receive, the DE/RE direction control is less critical on the transmitter side. A module with DE hardwired HIGH will work fine on the Nano transmit side. The Mega receive side needs RE permanently LOW or proper DE/RE control.

Requirements

Hardware

Arduino Mega 2560 (or compatible)
Ethernet Shield W5100 or W5500
4× DHT22 temperature/humidity sensors (Aging Room)
2× Arduino Nano (Skit Room, Camera Room)
3× MAX485 TTL-to-RS485 modules (1 per Nano TX, 1 on Mega RX)
20×4 I2C LCD display (I2C address 0x27)
SD card module
Red and green LEDs
Push button
MicroSD card formatted FAT32
RS485 twisted pair cable between rooms

Software

Arduino IDE
The following libraries (install via Library Manager):

DHT sensor library by Adafruit
Adafruit Unified Sensor
LiquidCrystal I2C
Ethernet (built-in)
SD (built-in)
Crypto by Rhys Weatherley
arduino-base64 by Densaugeo
SoftwareSerial (built-in, for Nano RS485 sketches)

Pin Configuration — Mega

Component	Pin	Notes
DHT22 Sensor A	40	Digital
DHT22 Sensor B	41	Digital
DHT22 Sensor C	30	Digital
DHT22 Sensor D	31	Digital
Green LED	47	Digital
Red LED	46	Digital
Ethernet CS	10	SPI
Button	50	INPUT_PULLUP
SD Card CS	4	SPI
LCD	I2C	SDA/SCL
RS485 RX (Serial1)	19	Hardware UART
RS485 DE/RE	TBD	Digital

Pin Configuration — Nano (Skit Room / Camera Room)

Component	Pin	Notes
DHT22 Data	4	Digital
MAX485 DI	7	SoftwareSerial TX
MAX485 RO	8	SoftwareSerial RX
MAX485 DE+RE	TBD	Digital (tied together)

File Overview

Mega (Main Controller)

File	Purpose
`Aging_Room.ino`	Main program — `setup()`, `loop()`, HTTP router
`config.h`	All configuration constants and includes
`auth.h`	Authentication function declarations
`auth.cpp`	Salted SHA256 password validation logic
`network.h`	Network and NTP declarations
`network.cpp`	Connection tracking, NTP, DST, and time functions
`sensors.h`	Sensor and LED declarations
`sensors.cpp`	DHT22 reading, RS485 parsing, LED control, button
`display.h`	LCD display declarations
`display.cpp`	LCD initialization and display updates
`storage.h`	SD card and web serving declarations
`storage.cpp`	CSV logging and all HTML/endpoint generation
`README.md`	This file
`CHANGELOG.md`	Version history and change log

Skit Room / Camera Room (Nano Nodes)

File	Purpose
`Skit_Room/Skit_Room.ino`	Nano sketch — reads DHT22, transmits RS485 every 6 min
`Camera_Room/Camera_Room.ino`	Nano sketch — reads DHT22, transmits RS485 every 6 min

Installation

Step 1 — Clone the repository

git clone https://gitlab.com/seegrid/quality/Aging_Room
cd Aging_Room

Step 2 — Install required libraries

Open Arduino IDE, go to Sketch → Include Library → Manage Libraries, and install each library listed in the Requirements section.

Step 3 — Configure the network

Edit Aging_Room.ino if you need to change the static IP fallback used when DHCP is unavailable:

IPAddress ip(192, 168, 48, 20);
IPAddress gateway(192, 168, 48, 1);
IPAddress subnet(255, 255, 255, 0);

Step 4 — Set the authentication password

See Setting Your Authentication Password below. This step is required before deployment.

Step 5 — Upload to Arduino Mega

Open Aging_Room.ino in Arduino IDE.
Select Tools → Board → Arduino Mega 2560.
Select the correct COM port under Tools → Port.
Click Upload.

Step 6 — Upload Nano sketches

Open Skit_Room/Skit_Room.ino.
Select Tools → Board → Arduino Nano.
Upload to the Skit Room Nano.
Repeat with Camera_Room/Camera_Room.ino for the Camera Room Nano.

Setting Your Authentication Password

The system uses salted SHA256 hashing for web authentication. You must generate a hash before deploying — the placeholder in config.h will not work.

Default username: Seegrid
Default password: Not set — you must configure one.

Step 1 — Choose your salt and password

Salt:     SeegridPittsburgh2026    (example — make yours unique)
Password: MySecure!Pass2026        (example — use your own)

Step 2 — Concatenate salt and password

Combine them with no spaces or separators, salt first:

SeegridPittsburgh2026MySecure!Pass2026

Step 3 — Generate the SHA256 hash

Go to https://emn178.github.io/online-tools/sha256.html, paste the combined string from Step 2, and copy the resulting 64-character hash.

Step 4 — Update `config.h`

#define AUTH_SALT            "SeegridPittsburgh2026"
#define AUTH_PASSWORD_SHA256 "your_copied_hash_here"

Step 5 — Save and upload

Save config.h and re-upload the sketch to your Arduino.

Password Security Guidelines

DO:

✓ Change the default salt to something unique per installation
✓ Use a strong password (12+ characters, mixed case, numbers, symbols)
✓ Use a different salt for each deployed unit
✓ Store your salt and password in a secure password manager

DON'T:

✗ Use the default salt in production
✗ Commit your actual password or salt to Git
✗ Add spaces or separators when combining salt and password
✗ Reuse salts across multiple deployments

Memory Architecture and Data Persistence

Flash Memory — Program + Credentials

Property	Value
Size	256 KB
Survives power loss	Yes
Write method	Arduino IDE upload only

EEPROM — Threshold Values

Property	Value
Size	4 KB
Current usage	5 thresholds × 4 bytes = 20 bytes
Survives power loss	Yes

EEPROM stores: Aging Room temp threshold, Skit Room temp threshold, Skit Room humid threshold, Camera Room temp threshold, Camera Room humid threshold.

RAM — Volatile Working Memory

Property	Value
Size	8 KB
Survives power loss	No
Typical free RAM	~2.0 KB at runtime

All HTML strings use F() macro to store in Flash rather than RAM. RAM is monitored live in the System Status panel on each dashboard.

SD Card — Historical Sensor Data

Property	Value
Survives power loss	Yes
Estimated growth	~14 KB/day per room · ~15 MB/year total
Retention	180 days rolling

Memory Persistence Summary

Memory Type	Size	Survives Power Loss	What's Stored
Flash	256 KB	Yes	Program + auth credentials
EEPROM	4 KB	Yes	5 threshold values
RAM	8 KB	No	Runtime variables
SD Card	User	Yes	All historical CSV data

Web Interface URL Reference

All endpoints require HTTP Basic Auth. Replace 192.168.55.151 with your device's actual IP.

Full HTML Pages

URL	Description
`http://192.168.55.151/`	Aging Room main dashboard
`http://192.168.55.151/skit`	Skit Room dashboard
`http://192.168.55.151/camera`	Camera Room dashboard
`http://192.168.55.151/admin`	Hidden admin SD file manager — no nav link

Data / API Endpoints

URL	Returns	Notes
`http://192.168.55.151/status`	`A:21.3\|OK\|45.1,B:20.9\|LOW\|44.8,...`	Aging Room sensor states
`http://192.168.55.151/sysinfo`	`RAM:2048,UPTIME:0d 5h 58m,SD:OK,...`	System info
`http://192.168.55.151/threshold`	`21.0`	Aging Room temp threshold
`http://192.168.55.151/events`	Plain text	Watchdog reboot log
`http://192.168.55.151/temp.csv`	CSV	Aging Room temperature (last 7 days)
`http://192.168.55.151/humid.csv`	CSV	Aging Room humidity (last 7 days)
`http://192.168.55.151/skit/status`	`TEMP:20.7\|OK,HUMID:50.2\|OK`	Skit Room sensor state
`http://192.168.55.151/skit/sysinfo`	`RAM:...,LASTRECEIVE:...`	Skit Room system info
`http://192.168.55.151/skit/threshold/temp`	`22.0`	Skit Room temp threshold
`http://192.168.55.151/skit/threshold/humid`	`50.0`	Skit Room humid threshold
`http://192.168.55.151/skit/temp.csv`	CSV	Skit Room temperature (last 7 days)
`http://192.168.55.151/skit/humid.csv`	CSV	Skit Room humidity (last 7 days)
`http://192.168.55.151/camera/status`	`TEMP:20.3\|OK,HUMID:48.4\|OK`	Camera Room sensor state
`http://192.168.55.151/camera/sysinfo`	`RAM:...,LASTRECEIVE:...`	Camera Room system info
`http://192.168.55.151/camera/threshold/temp`	`22.0`	Camera Room temp threshold
`http://192.168.55.151/camera/threshold/humid`	`50.0`	Camera Room humid threshold
`http://192.168.55.151/camera/temp.csv`	CSV	Camera Room temperature (last 7 days)
`http://192.168.55.151/camera/humid.csv`	CSV	Camera Room humidity (last 7 days)
`http://192.168.55.151/archive?file=FILENAME`	File download	Download any file by name from SD

Action Endpoints

URL	Action	Notes
`http://192.168.55.151/clear-events`	Deletes `EVENTS.txt`	Clears watchdog alert log
`http://192.168.55.151/eject`	Safely unmounts SD, halts system	Must reboot to resume logging
`http://192.168.55.151/admin/delete?file=FILENAME`	Deletes named file from SD	Active data files are blocked

Hostname Access

If DNS is configured on your network:

http://agingroom00.mach.hq.seegrid.lan/
http://agingroom00.mach.hq.seegrid.lan/skit
http://agingroom00.mach.hq.seegrid.lan/camera
http://agingroom00.mach.hq.seegrid.lan/admin

Static IP Fallback

If DHCP fails, the device falls back to:

http://192.168.48.20/

Usage

Finding the Device IP Address

After boot, the device displays its IP address on the LCD for 10 seconds and on the Serial Monitor (115200 baud). The device attempts DHCP first and falls back to the static IP 192.168.48.20 if DHCP fails.

Accessing the Web Interface

Navigate to http://[DEVICE_IP] in your browser.
Enter credentials when prompted:
- Username: Seegrid
- Password: Your configured password

Web Dashboard Features

Navigation Bar
Every page has buttons to switch between Aging Room, Skit Room, and Camera Room dashboards. The Admin page has no nav link — access it directly at /admin.

Sensor Status Bar
Shows live sensor readings with color-coded status. Updates every 29 seconds. Displays temperature on the Temperature tab, humidity on the Humidity tab.

Dot Color	Meaning
Identity color	Sensor within threshold range
Yellow	Sensor outside threshold — shows ↓ LOW or ↑ HIGH
Red (blinking)	Sensor error

Sensor Identity Colors (Aging Room)

Sensor	Color	Hex
A	Blue	`#0072B2`
B	Yellow/Amber	`#E69F00`
C	Pink	`#CC79A7`
D	Light Blue	`#56B4E9`

Chart Tabs

Temperature — sensor readings with threshold lines
Humidity — humidity trends
Archive Data — date range picker to download combined CSV up to 6 months

System Status Panel
Shows RAM, uptime, SD status, last write/receive time, NTP sync time.

Threshold Adjustment (Skit/Camera pages)
Up/Down buttons adjust temp and humid thresholds live. Values are saved to EEPROM immediately.

Admin Page (/admin)
Dark-themed hidden page listing all SD card files with sizes. Each file has a Download button (reuses /archive endpoint) and a Delete button with confirmation dialog. Active data files (temp.csv, humid.csv, SK_T.csv, etc.) are protected from deletion. Auto-refreshes after a delete.

Safe SD Card Removal

Click "Prepare SD for Removal / Halt" in the System Status panel.
Confirm the dialog.
Wait for the LCD to display SD UNMOUNTED / SAFE TO UNPLUG.
Remove the SD card.
You must reboot the Arduino to resume logging.

Adjusting the Temperature Threshold

Aging Room — Physical Button

Press and hold the button for 5 seconds.
Both LEDs alternate at 250 ms to confirm adjustment mode.
Green LED flashes 10 times to confirm entry.
Keep holding — threshold increases by 1°C every 2 seconds, cycling −40°C to 80°C.
Release the button at the desired value to save.
Red LED flashes 10 times, then both flash 20 times to confirm save.
The web dashboard threshold lines update automatically within 37 seconds.

Skit Room / Camera Room — Web Interface

Use the Up/Down arrow buttons in the Threshold Adjustment panel on the /skit or /camera dashboard page. Changes take effect immediately and are saved to EEPROM.

Security Features

Salted SHA256 Authentication

All web endpoints require authentication. Passwords are stored as SHA256(SALT + PASSWORD) in Flash — never in plaintext, never modifiable at runtime.

IP-Based Connection Limiting

Global limit: 8 simultaneous connections
Per-IP limit: 3 simultaneous connections
Idle timeout: 5 minutes
Cleanup interval: Every 30 seconds

Hardware Watchdog

8-second watchdog provides automatic crash recovery. All reboots logged to EVENTS.txt with timestamps.

Data Logging

Property	Value
Interval	Every 5 minutes, time-aligned to clock boundaries
Aging Room files	`YYMMDD_T.csv`, `YYMMDD_H.csv`
Skit Room files	`YYMMDDST.csv`, `YYMMDDSH.csv`
Camera Room files	`YYMMDDCT.csv`, `YYMMDDCH.csv`
Watchdog log	`EVENTS.txt`
Retention	180 days rolling — midnight janitor deletes old files
Time sync	NTP at boot, midnight, and noon
NTP primary	`192.168.80.8`
NTP fallback	`pool.ntp.org`
Timezone	Eastern Time with automatic DST

Configuration Constants

Edit config.h to change these parameters:

#define MIN_THRESHOLD          -40      // Minimum adjustable threshold (°C)
#define MAX_THRESHOLD          80       // Maximum adjustable threshold (°C)
#define DEFAULT_TEMP_THRESHOLD 42       // Default threshold (°C)
#define THRESHOLD_MARGIN       5.0      // Alert margin (±°C)
#define MAX_GLOBAL_CONNECTIONS 8        // Total connection limit
#define MAX_PER_IP_CONNECTIONS 3        // Per-IP connection limit
#define CONNECTION_TIMEOUT     300000   // 5 minutes (ms)
#define SENSOR_READ_INTERVAL   2000     // 2 seconds (ms)
#define CSV_WRITE_INTERVAL     300000   // 5 minutes (ms)
#define NTP_INTERVAL           86400000 // 24 hours (ms)

Troubleshooting

Sensor reading errors / LCD shows "ERR"

Check DHT22 sensor wiring and confirm 5V power is reaching the sensors.
Verify the data wire from each M12 connector is landed on the correct Arduino pin.
For M12 wiring: Pin 2 = Sensor A or C data, Pin 4 = Sensor B or D data, Pin 1 = VCC, Pin 3 = GND.

Skit Room / Camera Room shows no data or dashes

Check the RS485 wiring between the Nano and Mega.
Confirm the Nano sketch is uploaded and running — check its Serial Monitor for Sent: SKIT:XX.X,XX.X.
If using temporary direct wiring (no RS485 modules yet), confirm pin 19 on the Mega is connected to the Nano TX.
The Last Receive timestamp in the Skit/Camera System Status panel shows when data was last received.

RS485 modules not working — direction issues

Confirm you are using a MAX485 TTL module, NOT an RS232-to-RS485 converter.
RS232-to-RS485 converters use ±12V logic levels and will not work with Arduino — they are for PC/PLC use only.
Ensure DE and RE pins are tied together and connected to a digital output pin on the Arduino.
DE/RE HIGH = transmit mode, DE/RE LOW = receive mode.

Dashboard shows "SYSTEM OFFLINE" banner

The Arduino is unreachable. Dashboard retries automatically every 4 seconds.
Check Ethernet cable and power.
If device rebooted, wait ~30 seconds for boot to complete.

Chart not rendering

Confirm browser has internet access to cdn.jsdelivr.net for Chart.js.
Click "Update Now" to force a data refresh.
If device has been running less than 5 minutes, no CSV data exists yet.

DHCP failed / cannot reach web interface

Device falls back to static IP 192.168.48.20.
Try hostname: agingroom00.mach.hq.seegrid.lan

Time is off by one hour

Confirm you are running v1.10 or later which includes the DST month index fix.
Serial Monitor shows DST Active: Yes (EDT) or DST Active: No (EST).

SD card initialization failed

Confirm SD card is formatted FAT32.
Cards larger than 32GB may need reformatting — Windows defaults to exFAT which is not compatible.

Cannot delete a file on the admin page

Active data files (temp.csv, humid.csv, SK_T.csv, SK_H.csv, CA_T.csv, CA_H.csv) are protected from deletion on the admin page.
Use /eject + manual SD removal for full access to delete any file outside the admin page.

Version History

See CHANGELOG.md for full version history.

Acknowledgments

Built for Seegrid aging room environmental monitoring. Uses Chart.js for web visualization, chartjs-plugin-zoom and hammerjs for chart interaction, and chartjs-adapter-date-fns for time axis formatting. NTP implementation based on Arduino examples. Security features implement OWASP best practices for password storage.

Name		Name	Last commit message	Last commit date
Latest commit History 98 Commits
Camera_Room		Camera_Room
Skit_Room		Skit_Room
.gitignore		.gitignore
Aging_Room.ino		Aging_Room.ino
CHANGELOG.md		CHANGELOG.md
README.md		README.md
auth.cpp		auth.cpp
auth.h		auth.h
config.h		config.h
display.cpp		display.cpp
display.h		display.h
network.cpp		network.cpp
network.h		network.h
sensors.cpp		sensors.cpp
sensors.h		sensors.h
storage.cpp		storage.cpp
storage.h		storage.h

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