Aquaguard Motherboard — Arduino Based

Built this Arduino-based controller to replace a faulty Aquaguard motherboard. It uses pressure and water level sensors to control the UV light and solenoid with simple timing logic. If your RO system has a similar configuration and you’re comfortable working with hardware, this project is for you.

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📸 Project Overview

Complete Setup

UV Ballast (Choke)

🔗Link: Philips UV Ballast (11W–14W)

Original Wiring Reference

Original Controller Specs

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Features

• Water pressure detection (input switch)
• Tank water level detection (float switch)
• UV light control via relay
• Solenoid valve control via relay
• UV warm-up delay (~5 seconds)
• Non-blocking logic using millis()
• Serial debugging support
• LED indicators (same behavior as original controller)

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⚙️ How It Works

Logic:

• If pressure is present AND tank is low:

  • Turn ON UV
  • Wait ~5 seconds
  • Turn ON solenoid (start filling)

• If:

  • Tank becomes full OR
  • Pressure is lost

👉 System turns OFF UV + solenoid

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🔄 State Machine

         ┌─────────────────────────────────┐
         │                                 │
         ▼                                 │
      [IDLE]                               │
   UV OFF, Solenoid CLOSED                 │
         │                                 │
   Pressure OK + Level Low?                │
         │ YES (after 5s stabilize)        │
         ▼                                 │
   [UV_WARMUP] — 5 seconds                 │
   UV ON, Solenoid CLOSED                  │
         │                                 │
   5 sec elapsed?                          │
         │ YES                             │
         ▼                                 │
     [RUNNING]                             │
   UV ON, Solenoid OPEN                    │
         │                                 │
   Tank full OR pressure lost?             │
         │ YES                             │
         ▼                                 │
      [FAULT]  ── 2s cooldown ─────────────┘
   UV OFF, Solenoid CLOSED

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Pin Map

Pin	Component
D2	Pressure switch
D3	Level switch
D4	UV relay
D5	Solenoid relay
D6	Blue LED
D7	Green LED

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⚡ Wiring Notes

• Switches use INPUT_PULLUP
• Short to GND = ACTIVE
• Relays handle AC and DC load R1 for AC for UV Choke and R2 to the 12 v to the solenoid
• Arduino only controls relays (low voltage)

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⚠️ Safety

• UV ballast runs on 220V AC
• Never connect AC directly to Arduino
• Use proper insulation and enclosure
• Double-check relay wiring

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🛠️ Hardware Required

Component	Qty	Notes
Arduino Uno	1	Or nano
5V Relay module	2	One (UV), one (solenoid)
Water pressure switch	1	Normally open, closes when pressure present
Float level switch	1	Closes when tank Empty, opens when Full
Blue LED	1	3mm or 5mm
Green LED	1	3mm or 5mm
220Ω resistor	2	Additional
Jumper wires	—	—
12V DC supply	1	For solenoid coil
UV ballast/choke	1	Ready-made, controlled via relay

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🚀 Getting Started

1. Clone this repo

   git clone https://github.com/yourusername/aquaguard-arduino.git

2. Open in Arduino IDE

   • File → Open → aquaguard.ino

3. Select correct board

   • Tools → Board → Arduino Uno
   • Tools → Port → your COM port
   • Tools → Programmer → AVRISP mkII

4. Upload

   • Click Upload (→)
   • Open Serial Monitor at 9600 baud

5. Wire up per the pin map above

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💡 Notes

• LED behavior matches Exactly with the original Aquaguard controller
• RED LED (UV fault indicator) is not implemented (optional)

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🔍 Troubleshooting

Symptom	Cause	Fix
Upload fails with openocd error	Wrong board selected	Tools → Board → Arduino Uno
Low memory warning	Too many strings in RAM	Wrap all Serial.println strings in F()
Relay clicks on for 1-2 sec then off	Wrong relay polarity	Swap LOW/HIGH in setSolenoid() or setUV()
LED blinks when it should be static	Inverted switch logic	Flip == LOW to == HIGH in switch read function
Solenoid opens immediately, no UV delay	State machine skipping warmup	Check uvStartTime and UV_WARMUP_MS
False triggers on level switch	Switch bouncing	Increase stabilizing delay from 5000 to 8000ms

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🤝 Contributing

Pull requests welcome! If you've adapted this for a different purifier brand or added features like:

• LCD display support
• WiFi/IoT monitoring
• Filter life tracking
• Flow rate sensor

...feel free to open a PR.

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📄 License

Aapache License — free to use, modify, and distribute. See LICENSE for details.

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