LiquidLoopSentinel RevA

LiquidLoopSentinel

LiquidLoopSentinel is a Raspberry Pi Pico-based printed circuit board designed to monitor coolant temperature, flow, leaks, and electrical conditions while providing visual and audible fault alerts.

Overview

LiquidLoopSentinel is a custom monitoring printed circuit board intended for liquid-cooled computing systems and artificial intelligence hardware test benches.

The board integrates multiple sensors with a Raspberry Pi Pico to monitor the condition of a liquid-cooling loop and detect problems such as:

• Abnormal coolant temperature
• Reduced or interrupted coolant flow
• Liquid leakage
• Electrical power abnormalities

When the system detects a fault, it can provide visual status indications through light-emitting diodes and an audible warning through a buzzer.

Features

• Raspberry Pi Pico controller
• Two temperature sensor inputs
• Coolant flow sensor input
• Leak sensor input
• INA219 voltage and current monitoring interface
• Inter-Integrated Circuit communication
• Flow sensor signal conditioning
• Leak sensor pull-up circuitry
• Three status indicators:
  • System operating normally
  • Warning condition
  • Leak detected
• Transistor-driven buzzer
• Dedicated test points
• Separate 5-volt flow sensor power input
• Ground plane
• Through-hole component design for prototyping and manual assembly

System Architecture

                    Liquid-Cooling Loop
                           |
          +----------------+----------------+
          |                |                |
     Temperature          Flow             Leak
       Sensors            Sensor           Sensor
          |                |                |
          +----------------+----------------+
                           |
                           v
                  Raspberry Pi Pico
                           |
                 System Health Analysis
                           |
             +-------------+-------------+
             |             |             |
             v             v             v
          OK LED       Warning LED    Leak LED
                                           |
                                        Buzzer

Hardware

Microcontroller

The system is designed around the Raspberry Pi Pico.

The Pico receives sensor signals, evaluates the condition of the cooling loop, and controls the board's visual and audible warning indicators.

Temperature Monitoring

Two temperature sensor connections are provided:

• TEMP_IN
• TEMP_OUT

Both connections share the TEMP_ONEWIRE data bus and use a 4.7-kilohm pull-up resistor connected to 3.3 volts.

This configuration allows the system to measure coolant temperature at two locations within the cooling loop.

Flow Monitoring

The flow sensor interface provides the following connections:

• +5V_FLOW
• FLOW_SENSOR_RAW
• GND

A resistor-divider network conditions the raw flow sensor signal before it reaches the Raspberry Pi Pico as FLOW_PULSE.

Leak Detection

A dedicated leak sensor connector provides the following connections:

• LEAK_DETECT
• GND

A 100-kilohm pull-up resistor connects the leak detection signal to 3.3 volts.

Electrical Monitoring

An INA219 interface provides the following connections:

• +3V3
• GND
• I2C0_SDA
• I2C0_SCL

This interface supports voltage, current, and power monitoring through a compatible INA219 module.

Status Indicators

The printed circuit board includes three status indicators:

Each light-emitting diode uses a 330-ohm current-limiting resistor.

Audible Alert

A buzzer provides an audible warning when the system detects a fault.

The Raspberry Pi Pico controls the buzzer through an NPN transistor stage, preventing the microcontroller's general-purpose input and output pin from directly driving the buzzer load.

Test Points

The board includes dedicated test points for the following signals:

• +3V3
• GND
• FLOW_PULSE
• LEAK_DETECT

These test points allow important system signals to be measured during testing, validation, and troubleshooting.

Printed Circuit Board

The current hardware revision is:

LiquidLoopSentinel Revision A

The printed circuit board is currently in the prototype and design-validation stage.

Current design characteristics include:

• Two-layer printed circuit board
• Through-hole components
• Front and back copper routing
• Bottom-layer ground plane
• Raspberry Pi Pico socket headers
• Dedicated sensor connectors
• Dedicated test points

Repository Structure

LiquidLoopSentinel/
|
├── README.md
├── LICENSE
|
├── hardware/
│   └── kicad/
│       ├── LiquidLoopSentinel_RevA.kicad_pro
│       ├── LiquidLoopSentinel_RevA.kicad_sch
│       └── LiquidLoopSentinel_RevA.kicad_pcb
|
├── manufacturing/
│   └── RevA/
│       ├── gerbers/
│       ├── drill/
│       └── bom/
|
├── firmware/
│   └── pico/
|
├── docs/
│   └── images/
|
└── mechanical/
    └── 3d/

Development Status

Revision A: In Development

Current progress:

• System architecture
• Schematic design
• Printed circuit board component placement
• Printed circuit board routing
• Ground plane
• Design Rules Check
• Schematic and printed circuit board parity check
• Final component pinout verification
• Connector orientation verification
• Silkscreen cleanup
• Mounting holes
• Final manufacturing review
• Gerber file generation
• Printed circuit board fabrication
• Board assembly
• Hardware validation
• Raspberry Pi Pico firmware

Project Goal

The goal of LiquidLoopSentinel is to create a low-cost, modular hardware monitoring platform that can detect cooling-system failures before they damage sensitive computing equipment.

Development Tools

• KiCad 10
• Raspberry Pi Pico
• C, C++, or MicroPython
• Git
• GitHub

Disclaimer

LiquidLoopSentinel Revision A is an experimental engineering prototype that has not yet completed hardware validation. It should not be used as the sole protection mechanism for safety-critical systems or high-value equipment.

Author

Jose Luis Zaragoza-Calderon Jr.

Computer Engineering