Smart HVAC Monitoring: Beyond the Switch

For homeowners using coal or wood boilers, knowing when to add fuel is often a matter of "Listening" to the system or manually checking a thermostat. The Grundfos Pump Status Indicator provides a far more elegant solution. By interfacing with the digital diagnostics of a Grundfos Alpha 1L water pump, this project gives you a visual "At-a-glance" dashboard of your entire home heating status, even from a distance.

The Power of PWM Communication

The Grundfos Alpha 1L isn't just a motor; it's a smart device with a built-in signal output. While most people simply toggle the power, this pump provides a PWM (Pulse Width Modulation) signal that transmits rich telemetry data:

1. Flow Rate & Power: The duty cycle of the signal indicates how hard the pump is working ($0\text{-}100%$ load).
2. Error Detection: If the pump detects a low input voltage, a dry-running condition, or a mechanical blockage, it changes the PWM profile to a specific "Error Frequency."
3. Connectivity: By using a tiny DigiSpark (Attiny85), the project decodes these pulses to understand the pump's health without interfering with its operation.

Visual Dashboard: The RGB Mapping

To translate complex signal data into something intuitive, the author utilizes a single RGB LED mounted in a visible area (like a bedroom balcony). The mapping is simple and effective:

• Green: Pump is RUNNING and healthy.
• Off: Pump is idle (thermostat threshold reached).
• Red/Blue Flash: ERROR detected (low voltage, pump blockage, or dry run).

Implementation Efficiency

What makes this project "Easy" and efficient is the use of the DigiSpark. It's incredibly cheap, small enough to be hidden inside a standard electrical junction box, and can be powered directly from the pump's auxiliary supply or a small $5\text{V}$ transformer. This marks a significant upgrade over "Passive" indicators (like a simple lightbulb in parallel), which only tell you if the pump has power—not if it is actually moving water.

I am heating my house with coal, and the water pump is switched on and off by a thermostat. By knowing when the pump is turned off, I can easily tell when to add more coal. This project goes deeper than a simple 'on/off' light, using the pump's own PWM datasheet to provide a comprehensive, color-coded status monitor.