Power Usage Sensor


  • Standard MySensors Pulse Meter
  • 3DU5 phototransistor detects meter pulses


WARNING: This build works around high voltage.

My Company and I accept no liability whatsoever for your own well being or that of your electrical gear.



 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 * Version 1.0 - Henrik EKblad
 * This sketch provides an example how to implement a distance sensor using HC-SR04 
 * Use this sensor to measure KWH and Watt of your house meeter
 * You need to set the correct pulsefactor of your meeter (blinks per KWH).
 * The sensor starts by fetching current KWH value from gateway.
 * Reports both KWH and Watt back to gateway.
 * Unfortunately millis() won't increment when the Arduino is in 
 * sleepmode. So we cannot make this sensor sleep if we also want 
 * to calculate/report watt-number.
 * http://www.mysensors.org/build/pulse_power

// Enable debug prints
#define MY_DEBUG

// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

#define MY_NODE_ID 51

#include <SPI.h>
#include <MySensor.h>  

#define DIGITAL_INPUT_SENSOR 3  // The digital input you attached your light sensor.  (Only 2 and 3 generates interrupt!)
#define PULSE_FACTOR 1000       // Nummber of blinks per KWH of your meeter
#define SLEEP_MODE false        // Watt-value can only be reported when sleep mode is false.
#define MAX_WATT 10000          // Max watt value to report. This filetrs outliers.
#define INTERRUPT DIGITAL_INPUT_SENSOR-2 // Usually the interrupt = pin -2 (on uno/nano anyway)
#define CHILD_ID 1              // Id of the sensor child

unsigned long SEND_FREQUENCY = 10000; // Minimum time between send (in milliseconds). We don't wnat to spam the gateway.
double ppwh = ((double)PULSE_FACTOR)/1000; // Pulses per watt hour
boolean pcReceived = true;
volatile unsigned long pulseCount = 0;   
volatile unsigned long lastBlink = 0;
volatile unsigned long watt = 0;
unsigned long oldPulseCount = 0;   
unsigned long oldWatt = 0;
double oldKwh;
unsigned long lastSend;
MyMessage wattMsg(CHILD_ID,V_WATT);
MyMessage kwhMsg(CHILD_ID,V_KWH);
MyMessage pcMsg(CHILD_ID,V_VAR1);

void setup()  
  // Fetch last known pulse count value from gw
  request(CHILD_ID, V_VAR1);

  // Use the internal pullup to be able to hook up this sketch directly to an energy meter with S0 output
  // If no pullup is used, the reported usage will be too high because of the floating pin
  attachInterrupt(INTERRUPT, onPulse, RISING);

void presentation() {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Energy Meter", "1.0");

  // Register this device as power sensor
  present(CHILD_ID, S_POWER);

void loop()     
  unsigned long now = millis();
  // Only send values at a maximum frequency or woken up from sleep
  bool sendTime = now - lastSend > SEND_FREQUENCY;
  if (pcReceived && (SLEEP_MODE || sendTime)) {
    // New watt value has been calculated  
    if (!SLEEP_MODE && watt != oldWatt) {
      // Check that we dont get unresonable large watt value. 
      // could hapen when long wraps or false interrupt triggered
      if (watt<((unsigned long)MAX_WATT)) {
        send(wattMsg.set(watt));  // Send watt value to gw 
      oldWatt = watt;
    // Pulse cout has changed
    if (pulseCount != oldPulseCount) {
      send(pcMsg.set(pulseCount));  // Send pulse count value to gw 
      double kwh = ((double)pulseCount/((double)PULSE_FACTOR));     
      oldPulseCount = pulseCount;
      if (kwh != oldKwh) {
        send(kwhMsg.set(kwh, 4));  // Send kwh value to gw 
        oldKwh = kwh;
    lastSend = now;
  } else if (sendTime && !pcReceived) {
    // No count received. Try requesting it again
    request(CHILD_ID, V_VAR1);
  if (SLEEP_MODE) {

void receive(const MyMessage &message) {
  if (message.type==V_VAR1) {  
    pulseCount = oldPulseCount = message.getLong();
    Serial.print("Received last pulse count from gw:");
    pcReceived = true;

void onPulse()     
  if (!SLEEP_MODE) {
    Serial.print("  pulse\n");
    unsigned long newBlink = micros();  
    unsigned long interval = newBlink-lastBlink;
    if (interval<10000L) { // Sometimes we get interrupt on RISING
    watt = (3600000000.0 /interval) / ppwh;
    lastBlink = newBlink;



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