Power Meter Pulse Sensor

created by hek , updated

This sensor counts LED pulses from your house meter and converts it into Watts and accumulated KWh.

Locate the little LED on your meeter and mount the light sensor over it to register the power-consumption rate blinks.

There are a few parameters that need to be tuned for each power meter's pulses/KWh (usually says XXX imp/KWh somewhere on your meter). Set the PULSE_FACTOR in the example sketch to pulses/KWh rating on your meter.

You can also set frequency that your sensor will report the power consumption by updating SEND_FREQUENCY. The default is 3 times per minute (every 20 seconds).

The sensor has two modes of operation:


Use this mode if you power the sensor with a battery. In this mode the sensor will sleep most of the time and only report KWh. Unfortunately the sensor cannot report the current consumption in Watts because the sensor can not track time while sleeping; the elapsed time between two blinks is required to calculate the current consumption in Watts.

SLEEP_MODE = false

In this mode the sensor will not sleep and will report the current consumption in Watts and cumulative KWh to the gateway. This mode requires constant power so you will need to connect the sensor to an electrical outlet.

Wiring Things Up

Start by connecting the radio module.

Sensor Arduino Comment
VCC VCC (3.3 - 5V) Red
DO (digital out) Digital pin 3 (D3) Green

Tune the sensitivity/trigger level by adjusting the trim potentiometer on the sensor board. If you plan to use a TSL250R instead of an LM393, refer to the data sheet below for the pin connections.


 * 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 <[email protected]>
 * 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

#include <MySensors.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 CHILD_ID 1              // Id of the sensor child

unsigned long SEND_FREQUENCY = 20000; // Minimum time between send (in milliseconds). We don't wnat to spam the gateway.
double ppwh = ((double)PULSE_FACTOR)/1000; // Pulses per watt hour
bool pcReceived = false;
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(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), 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) {
    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;


NameSize# Downloads
lm2903-n.pdf1.56 MB130

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