voltage-monitor

Overview

The voltage-monitor node reads voltage levels through an ADC with configurable voltage divider support and alert thresholds. It translates raw ADC values into calibrated voltage readings, accounting for external resistor divider networks. Ideal for battery monitoring, solar panel voltage tracking, and power supply supervision.

Properties

Output

{
  "voltage": 12.45,
  "rawAdc": 24315,
  "dividerRatio": 0.25,
  "thresholdExceeded": false,
  "channel": 0,
  "timestamp": 1640000000000
}

Wiring

  V_in (e.g. 12V)
    |
   [R1]  30kΩ
    |
    +-------→ AIN0 (to ADC)
    |
   [R2]  10kΩ
    |
   GND

  Ratio = R2/(R1+R2) = 10k/40k = 0.25
  V_adc = 12V * 0.25 = 3.0V

Example: Battery Voltage Monitor

Monitor a 12V lead-acid battery and alert when voltage drops below safe level.

// Function node: Battery health analysis
var voltage = msg.voltage;
var history = flow.get('batteryHistory') || [];

history.push({ v: voltage, t: Date.now() });

// Keep last hour of readings
var oneHourAgo = Date.now() - (60 * 60 * 1000);
history = history.filter(r => r.t > oneHourAgo);
flow.set('batteryHistory', history);

var status = "healthy";
if (voltage < 11.8) status = "critical";
else if (voltage < 12.2) status = "low";
else if (voltage > 14.4) status = "overcharge";

// Calculate discharge rate
var rate = 0;
if (history.length > 1) {
    var oldest = history[0];
    var hours = (Date.now() - oldest.t) / 3600000;
    rate = (oldest.v - voltage) / hours;
}

msg.payload = {
    voltage: voltage.toFixed(2),
    status: status,
    dischargeRate: rate.toFixed(3),
    hoursRemaining: rate > 0 ? ((voltage - 10.5) / rate).toFixed(1) : "N/A"
};

return msg;

Example: Solar Panel Voltage Logger

Track solar panel output voltage over time and log to database.

// Function node: Solar voltage classification
var voltage = msg.voltage;
var hour = new Date().getHours();

var panel = {
    voltage: voltage.toFixed(2),
    timestamp: msg.timestamp,
    hour: hour,
    generating: voltage > 1.0,
    peakHours: (hour >= 10 && hour <= 15)
};

// Efficiency estimate based on expected peak
var expectedPeak = 18.5; // Voc of panel
panel.efficiency = ((voltage / expectedPeak) * 100).toFixed(1);

if (msg.thresholdExceeded) {
    panel.alert = "Voltage threshold exceeded";
}

msg.payload = panel;
return msg;

Common Use Cases