💬 Power Meter Pulse Sensor

[gohan]

Are you getting instant power measurements correct?

[xydix]

Yes. I guess.
I don't have anything to compare with but i think it is accurate.
I have a 1000blink/kwh
Example:
Node send state every 20 sec.
pulsecount: 8 pulses every 20 sec.
Instant power in W is about 1400W

8 pulses x 3 = pulses /minute =24
24 pulses x 60 min = pulses /hour = 1440.

Edit.
Now I get a new value every 20 sec, before I didn't get any value (W) from the node at all because it was too high. I only received pulse count and kWh earlier.

[gohan]

Besides the cap, what exactly did you do?

[xydix]

Nothing more.
I use the same arduino, haven't uploaded anything new to it since i tried it last time.

What I had to do was lower the sensitivity on the LM393 because at first the signal-LED glowed a bit but when i adjusted it to lower sensitivity and closed the door to get it totaly dark the led blinked exactly as the meeter.

I have it on a bredboard and connected the cap between GND and to pin 3 so it is connected close to the arduino but i guess it shouldn't matter.

Have you tried it?

[gohan]

I can't believe it, IT WORKS!!!!! I added the cap directly under the pins of the LM939 board. Thanks man!

[xydix]

I am glad to hear it works for you too.

[gohan]

There is probably a sw way to correct this problem, I'll think about it

[xydix]

It waswhat I thought too.
As I said earlier, when I tested this my conclusion was, short blink, almost a flash will counted as a pulse (kWh) but it does something wrong with the calculation of instant power usage.
A slower blink will correct this.
My meeter gives a very short blink.

[gohan]

Yes, could be that a simple debounce could do the trick but I'll have to look deeper into it. @Yveaux what do you think?

[gohan]

@xydix Could you try to increase the 10000L to 100000L interval in the OnPulse function and see if it works without the capacitor?

[user2684]

I tried to build something similar and it is working nicely, thanks for sharing the idea! However, I've noticed the light sensor (alone) consumes 1mA constantly which is quite a lot when used for a battery powered project. Even if I report to the controller once per hour (summing up the power consumption along the way), still the light sensor needs to be always on, meaning I'd probably need to replace batteries after a month or so. Is there any workaround or alternative sensor which I can use or am I doing something completely wrong? Thanks

[cstewy]

@user2684 I had the same issue when I built this with a standalone atmega328p running on 2x AA's. I set it up with wake on interrupt from the It was constantly drawing 1.6mA to power the tsl257 to detect the flashes. My target was 1+ years on 2 x AA's. My solution to achieve this was to sleep for 125ms, wake up, send power to tsl257 to check light state (on/off), if it changed from previous reading then there was a pulse (well half pulse). By measuring every 125ms I can guarantee to capture fast pulses up to 14.4kW. (3600000/125)/2. It is 20kW max draw for residential in my country. Now:
Average mA Consumption Sleep 0.1
Average mA Consumption Wake 0.064516129
Average mA Consumption Transmit 0.002916667
Battery Life (2xAAs) = 1.7 years

[user2684]

@cstewy many thanks and very interesting. You basically saying it consumes less by waking up every 125ms rather than being asleep but with the sensor eating up current continuously. Definitely worth trying thanks! Meanwhile I've reduced the number of radio transmission and the batteries lasted for a couple of months but still is not ideal. Thanks! I'll try and report back

[artipi]

Hello, i'm stuck with this sensor, because no Interrupt is really working. I've cut down the code to this:

/**
 * 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.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - Henrik Ekblad
 *
 * DESCRIPTION
 * This sketch provides an example how to implement a LM393 PCB
 * Use this sensor to measure kWh and Watt of your house meter
 * You need to set the correct pulsefactor of your meter (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 value.
 * 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_NRF5_ESB
//#define MY_RADIO_RFM69
//#define MY_RADIO_RFM95

//#include <MySensors.h>

#define DIGITAL_INPUT_SENSOR 2  // The digital input you attached your light sensor.  (Only 2 and 3 generates interrupt!)
#define PULSE_FACTOR 500       // Number of blinks per of your meter
#define SLEEP_MODE false        // Watt value can only be reported when sleep mode is false.
#define MAX_WATT 1000000          // Max watt value to report. This filters outliers.
#define CHILD_ID 10             // Id of the sensor child

uint32_t SEND_FREQUENCY =
    15000; // Minimum time between send (in milliseconds). We don't want to spam the gateway.
double ppwh = ((double)PULSE_FACTOR)/1000; // Pulses per watt hour
bool pcReceived = true;
volatile uint32_t pulseCount = 0;
volatile uint32_t lastBlink = 0;
volatile uint32_t watt = 0;
uint32_t oldPulseCount = 0;
uint32_t oldWatt = 0;
double oldkWh;
uint32_t lastSend;
//MyMessage wattMsg(CHILD_ID,V_WATT);
//MyMessage kWhMsg(CHILD_ID,V_KWH);
//MyMessage pcMsg(CHILD_ID,V_VAR1);


void setup()
{
  Serial.begin(9600);
  Serial.println("Start 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
  pinMode(DIGITAL_INPUT_SENSOR,INPUT_PULLUP);

  attachInterrupt(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), onPulse, RISING);
  lastSend=millis();
  Serial.println("Start setup: last sent: ");
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);
}

void presentation()
{
  // Send the sketch version information to the gateway and Controller
  //sendSketchInfo("Energy Meter", "1.3");

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

void loop()
{
  
}



void onPulse()
{
  Serial.println("onPulse:");
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);      
  pulseCount++;
  Serial.println("pulseCount:");
}

The Problem ist, that only on Start the interrupt ist working once, but no LED blinks.

Can someone help?

Thanks.

[mfalkvidd]

@artipi using Serial.print and delay from within an interrupt service routine will mess things up. Interrupt service routines must be executed quickly.

From https://www.arduino.cc/reference/en/language/functions/external-interrupts/attachinterrupt/:

Since delay() requires interrupts to work, it will not work if called inside an ISR.

You need to do the blinking inside loop().

[artipi]

Ah, this explains many things. Thank you, now its working:)!

[alowhum]

@artipi can you share your code?

[artipi]

@alowhum: Its the original code. Nothing changed. I've only made some tests with my version...

[patrikr76]

Hey guys

So i am trying to use this sketch with the sleep mode set to true 'cause i need to run it on battery.
It works fine running with usb power on it and sleep mode on false.
But with sleep mode true i am getting nothing in myscontroller after the initial startup.
All i changed is the sleep mode from false to true.
Running it on a clone nano with some chinese "flame detector" sensor.
Been trying to figure out if it has something to do with how it reports when in sleep mode but it should still report whatever the send frequency is set to right?
I was using a tv remote to fake impulses, with seems to work on usb power, but not on battery.
Any suggestions?

Best regards
Patrik

[mfalkvidd]

@patrikr76 just to make sure we are on the same page, could you clarify which sketch you are using? This thread has discussed lots of sketches and it would be a pity if we’re looking at different code

In any case, the debug log from the node will give the best information on what is happening.

It could also be useful to only change one thing. Right now you change sleep mode and switch to battery, right? How does the node behave with sleep mode on, but still running on usb power? How does the node behave with sleep mode off, but running on battery?

[patrikr76]

@mfalkvidd , you are absolutely right. Let me clarify.
I am using the example code that is under build and power meter pulse sensor, updated may 1st, 2018.
Running it with "sleep mode = false" it works fine with both usb and battery power, just drains the battery quite fast.
Setting it to "sleep mode = true" it doesn't work either on usb or battery power.

Here's how the serial monitor looks for the startup phase with sleep mode as true.

23:21:24.219 ->  __  __       ____
23:21:24.219 -> |  \/  |_   _/ ___|  ___ _ __  ___  ___  _ __ ___
23:21:24.219 -> | |\/| | | | \___ \ / _ \ `_ \/ __|/ _ \| `__/ __|
23:21:24.219 -> | |  | | |_| |___| |  __/ | | \__ \  _  | |  \__ \
23:21:24.219 -> |_|  |_|\__, |____/ \___|_| |_|___/\___/|_|  |___/
23:21:24.219 ->         |___/                      2.3.0
23:21:24.219 -> 
23:21:24.219 -> 16 MCO:BGN:INIT NODE,CP=RNNNA---,VER=2.3.0
23:21:24.254 -> 25 TSM:INIT
23:21:24.254 -> 26 TSF:WUR:MS=0
23:21:24.254 -> 33 TSM:INIT:TSP OK
23:21:24.254 -> 35 TSF:SID:OK,ID=2
23:21:24.254 -> 37 TSM:FPAR
73 TSF:MSG:SEND,2-2-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
201 TSF:MSG:READ,0-0-2,s=255,c=3,t=8,pt=1,l=1,sg=0:0
23:21:24.428 -> 205 TSF:MSG:FPAR OK,ID=0,D=1
2080 TSM:FPAR:OK
23:21:26.306 -> 2081 TSM:ID
23:21:26.306 -> 2082 TSM:ID:OK
23:21:26.306 -> 2084 TSM:UPL
23:21:26.306 -> 2087 TSF:MSG:SEND,2-2-0-0,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=0,st=OK:1
23:21:26.306 -> 2095 TSF:MSG:READ,0-0-2,s=255,c=3,t=25,pt=1,l=1,sg=0:1
23:21:26.306 -> 2100 TSF:MSG:PONG RECV,HP=1
23:21:26.306 -> 2103 TSM:UPL:OK
23:21:26.306 -> 2104 TSM:READY:ID=2,PAR=0,DIS=1
23:21:26.306 -> 2109 TSF:MSG:SEND,2-2-0-0,s=255,c=3,t=15,pt=6,l=2,sg=0,ft=0,st=OK:0100
23:21:26.341 -> 2118 TSF:MSG:READ,0-0-2,s=255,c=3,t=15,pt=6,l=2,sg=0:0100
23:21:26.341 -> 2125 TSF:MSG:SEND,2-2-0-0,s=255,c=0,t=17,pt=0,l=5,sg=0,ft=0,st=OK:2.3.0
23:21:26.341 -> 2134 TSF:MSG:SEND,2-2-0-0,s=255,c=3,t=6,pt=1,l=1,sg=0,ft=0,st=OK:0
2203 TSF:MSG:READ,0-0-2,s=255,c=3,t=6,pt=0,l=1,sg=0:M
23:21:26.410 -> 2210 TSF:MSG:SEND,2-2-0-0,s=255,c=3,t=11,pt=0,l=12,sg=0,ft=0,st=OK:Energy Meter
23:21:26.445 -> 2220 TSF:MSG:SEND,2-2-0-0,s=255,c=3,t=12,pt=0,l=3,sg=0,ft=0,st=OK:1.0
23:21:26.445 -> 2228 TSF:MSG:SEND,2-2-0-0,s=1,c=0,t=13,pt=0,l=0,sg=0,ft=0,st=OK:
23:21:26.445 -> 2234 MCO:REG:REQ
23:21:26.445 -> 2237 TSF:MSG:SEND,2-2-0-0,s=255,c=3,t=26,pt=1,l=1,sg=0,ft=0,st=OK:2
2252 TSF:MSG:READ,0-0-2,s=255,c=3,t=27,pt=1,l=1,sg=0:1
23:21:26.480 -> 2257 MCO:PIM:NODE REG=1
23:21:26.480 -> 2259 MCO:BGN:STP
23:21:26.480 -> 2263 TSF:MSG:SEND,2-2-0-0,s=1,c=2,t=24,pt=0,l=0,sg=0,ft=0,st=OK:
23:21:26.480 -> 2269 MCO:BGN:INIT OK,TSP=1
23:21:26.480 -> 2272 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:21:26.480 -> 2277 TSF:TDI:TSL

As far as i can see it seems fine and also shows up in myscontroller.

And here is an example how it looks after 20 seconds sleep.

2414 MCO:SLP:WUP=-1
23:26:36.346 -> 2416 TSF:TRI:TSB
23:26:36.346 -> 2418 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:26:36.346 -> 2423 TSF:TDI:TSL

I don't see any connection attempts with my gateway, or shouldn't there by any if the sensor is not triggered?

Here i can show how it looks when tricking the sensor with the ir on the mouse.

2456 MCO:SLP:WUP=-1
23:27:48.785 -> 2458 TSF:TRI:TSB
23:27:48.785 -> 2460 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:27:48.785 -> 2465 TSF:TDI:TSL
2467 MCO:SLP:WUP=-1
23:27:48.924 -> 2468 TSF:TRI:TSB
23:27:48.959 -> 2470 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:27:48.959 -> 2476 TSF:TDI:TSL
2478 MCO:SLP:WUP=-1
23:27:49.098 -> 2480 TSF:TRI:TSB
23:27:49.098 -> 2481 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:27:49.098 -> 2486 TSF:TDI:TSL
2488 MCO:SLP:WUP=-1
23:27:49.235 -> 2490 TSF:TRI:TSB
23:27:49.235 -> 2492 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:27:49.270 -> 2497 TSF:TDI:TSL
2498 MCO:SLP:WUP=-1
23:27:49.408 -> 2500 TSF:TRI:TSB
23:27:49.408 -> 2502 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:27:49.408 -> 2507 TSF:TDI:TSL
2509 MCO:SLP:WUP=-1
23:27:49.546 -> 2510 TSF:TRI:TSB
23:27:49.546 -> 2512 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
23:27:49.546 -> 2518 TSF:TDI:TSL

Interrupt is triggered and it wakes up, but nothing is sent to the gateway.

Have i missed something?

[mfalkvidd]

@patrikr76 great info, thanks!

The -1 in Wup=-1 indicates that the node was waken up by timer and not by interrupt. That’s very strange, since the time stamps clearly show that 20 seconds has not passed.

Could you add

Serial.println(pulseCount);

after

sleep(SEND_FREQUENCY);

to see if pulseCount is increased?

[patrikr76]

@mfalkvidd , Here's the serial monitor after adding the serial print.

2269 MCO:SLP:WUP=-1
14:15:15.125 -> 2270 TSF:TRI:TSB
14:15:15.125 -> 0
14:15:15.125 -> 2272 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
14:15:15.125 -> 2277 TSF:TDI:TSL
2279 MCO:SLP:WUP=-1
14:15:37.264 -> 2281 TSF:TRI:TSB
14:15:37.264 -> 0
14:15:37.264 -> 2282 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
14:15:37.264 -> 2287 TSF:TDI:TSL
2289 MCO:SLP:WUP=-1
14:15:59.354 -> 2291 TSF:TRI:TSB
14:15:59.354 -> 0
14:15:59.354 -> 2293 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
14:15:59.389 -> 2298 TSF:TDI:TSL

As you see, it sleeps about 22 secs with no pulse on it.

Moving the mouse over it gives this.

2353 MCO:SLP:WUP=-1
14:18:09.982 -> 2355 TSF:TRI:TSB
14:18:09.982 -> 4
14:18:09.982 -> 2357 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
14:18:09.982 -> 2362 TSF:TDI:TSL
2363 MCO:SLP:WUP=-1
14:18:23.059 -> 2365 TSF:TRI:TSB
14:18:23.059 -> 5
14:18:23.059 -> 2367 MCO:SLP:MS=20000,SMS=0,I1=255,M1=255,I2=255,M2=255
14:18:23.059 -> 2372 TSF:TDI:TSL

Looking through the code, this one raises a flag.

if (pcReceived && (SLEEP_MODE || sendTime))

The pulseCount send is within that if statement which is not fullfilled because it doesn't receive pcReceived.
Or am i wrong?

[patrikr76]

Found a solution, which is not ideal.
I was having similar problem with a motion sensor not being able to send, adding a delay after sleep helped on that one, but it was just a 5ms delay needed.

On this one i had to add a 1 sec delay in the begining of the loop. I tried smaller but then it didn't work.
I am starting to think it is the nano clone that has crappy components.

[mfalkvidd]

@patrikr76 nice work.
Sounds very similar to https://forum.mysensors.org/topic/9655/delay-after-tsf-tri-tsb/14

[StKilda]

I have two meters I would like to measure: One that the LED is off most of the time and briefly pulses on per increment (at 3200 pulses per Kwh - so I adjusted the pulse factor accordingly). This works fine. The second meter, the LED pulses off (meaning the led it lit most of the time, and pulses off briefly). Do I need to adjust the code in any way to deal with this meter? Thanks. Really impressed it works virtually out of the box.

[mfalkvidd]

Great work @stkilda
I think the sketch will work without modification. The easiest way to find out is probably to try it.

[gohan]

you may need to change the interrupt behavior, but try it first

[bjornhallberg]

Is there a suggested replacement for the TSL250? While it can still be found, it seems to be discontinued for the most part.

I've had no luck with the LM393 solution for my new power meter. Just can't tune it to pick up the led impulses. What sort of diode solution is everyone else using? I'm aware of the possibility of IR communication (https://wiki.hal9k.dk/projects/kamstrup) but it seems a little over the top.

[gohan]

I used these https://www.aliexpress.com/item/5-pcs-LM393-Light-Sensor-Photosensitive-Sensitivity-light-Sensor-Module-For-Arduino-Smart-Car/1729424221.html

[FullMetal]

Hello
my skectch works very well, only I have a double pricing, I manage to recover the information. but I have to modify the code in order to have my exact consumption.
but my code sends me information always on the same IDs.
thank you

[mfalkvidd]

Hi @fullmetal, welcome to the forum

Could you explain what double pricing means?

[FullMetal]

Thank you for your welcome @mfalkvidd

Our electricity provider offers several rates.

HP: Full time
HC: off-peak time

usually the HP/HC rate is programmed at night by the provider.

As the consumption is saved by the arduino, I need two different IDs to trace the information to domotics

[FullMetal]

Here is the modified code:

#define MY_PARENT_NODE_ID 0                   // define if fixed parent
#define MY_PARENT_NODE_IS_STATIC
#undef MY_REGISTRATION_FEATURE                  // sketch moves on if no registration
#define MY_NODE_ID 2                     // fixed node number

// Enable debug prints
#define MY_DEBUG

// Enable RS485 transport layer
#define MY_RS485

// Define this to enables DE-pin management on defined pin
#define MY_RS485_DE_PIN 2

// Set RS485 baud rate to use
#define MY_RS485_BAUD_RATE 9600

// Set blinking period
#define MY_DEFAULT_LED_BLINK_PERIOD 300

// Flash leds on rx/tx/err
#define MY_DEFAULT_ERR_LED_PIN 13  // Error led pin
#define MY_DEFAULT_RX_LED_PIN  7  // Receive led pin
#define MY_DEFAULT_TX_LED_PIN  6  // the PCB, on board LED

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

#include <MySensors.h>
#include <SPI.h>
#include <Bounce2.h>

#define DIGITAL_INPUT_SENSOR 3  // The digital input you attached your light sensor.  (Only 2 and 3 generates interrupt!)
#define DIGITAL_INPUT_HCHP 5
#define PULSE_FACTOR 250       // 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 2              // 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 pulseHpCount = 0;
volatile unsigned long pulseHcCount = 0;
volatile unsigned long lastBlink = 0;
unsigned long oldPulseHpCount = 0;
volatile unsigned long watt = 0;
unsigned long oldWatt = 0;
double oldKwhHp;
unsigned long oldPulseHcCount = 0;
double oldKwhHc;
unsigned long lastSend;

Bounce debouncer = Bounce(); 
int oldValue=-1;


MyMessage wattMsg(1,V_WATT);
MyMessage kwhHpMsg(3,V_KWH);
MyMessage pcHpMsg(2,V_VAR1);
MyMessage kwhHcMsg(5,V_KWH);
MyMessage pcHcMsg(6,V_VAR1);
MyMessage hchpMsg(7,V_VAR2);
const int ledPin =  13;      // sortie digitale

void setup()
{
   // Fetch last known pulse count value from gw
   request(2, V_VAR1);
   request(6, 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
   pinMode(DIGITAL_INPUT_SENSOR,INPUT_PULLUP);
   pinMode(DIGITAL_INPUT_HCHP,INPUT_PULLUP);
   pinMode(ledPin, OUTPUT);

   attachInterrupt(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), onPulse, RISING);
   lastSend=millis();

    // After setting up the button, setup debouncer
   debouncer.attach(DIGITAL_INPUT_HCHP);
   debouncer.interval(5);
  
}

void presentation()
{
   // Send the sketch version information to the gateway and Controller
   sendSketchInfo("Energy Meter", "2.0");

   // Register this device as power sensor
   present(1, S_POWER);
   
    // Register this device as power sensor
   present(2, S_POWER);
   
   // Register this device as power sensor
   present(3, S_POWER);

   // Register this device as power sensor
   present(5, S_POWER);

   // Register this device as power sensor
   present(6, S_POWER);

   // Register this device as power sensor
   present(7, S_POWER);
}

void loop()
{
   unsigned long now = millis();
   if (digitalRead(DIGITAL_INPUT_SENSOR) == LOW ) {
   // LED Power On
   digitalWrite(ledPin, HIGH);
   // LED Power Off
   digitalWrite(ledPin, LOW);
   }


{
 debouncer.update();
 // Get the update value
 int value = debouncer.read();
 Serial.println("");

 if (value != oldValue) {
    // Send in the new value
    send(hchpMsg.set(value==HIGH ? 1 : 0));
    oldValue = value;
 }
} 


   // 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
           }
           Serial.print("Watt:");
           Serial.println(watt);
           oldWatt = watt;
       }
       
           
   /////HP
         if (digitalRead(DIGITAL_INPUT_SENSOR) == HIGH ) {
       // Pulse cout has changed
          if (pulseHpCount != oldPulseHpCount) {
           send(pcHpMsg.set(pulseHpCount));  // Send pulse count value to gw
           double kwhHp = ((double)pulseHpCount/((double)PULSE_FACTOR));
           oldPulseHpCount = pulseHpCount;
           digitalWrite(ledPin, LOW);
           if (kwhHp != oldKwhHp) {
               send(kwhHpMsg.set(kwhHp, 4));  // Send kwh value to gw
               oldKwhHp = kwhHp;
           }
           digitalWrite(ledPin, HIGH);
       }
       lastSend = now;
       
      }else if (digitalRead(DIGITAL_INPUT_SENSOR) == LOW ){
      if (pulseHcCount != oldPulseHcCount) {
           send(pcHcMsg.set(pulseHcCount));  // Send pulse count value to gw
           double kwhHc = ((double)pulseHcCount/((double)PULSE_FACTOR));
           oldPulseHcCount = pulseHcCount;
           digitalWrite(ledPin, LOW);
           if (kwhHc != oldKwhHc) {
               send(kwhHcMsg.set(kwhHc, 4));  // Send kwh value to gw
               oldKwhHc = kwhHc;
           }
           digitalWrite(ledPin, HIGH);
       }
       lastSend = now;
      }
      
   }else if (sendTime && !pcReceived) {
       // No count received. Try requesting it again
       request(2, V_VAR1);
       request(6, V_VAR1);
       lastSend=now;
   }   

   if (SLEEP_MODE) {
       sleep(SEND_FREQUENCY);
   }
}

void receive(const MyMessage &message)
{
  /////HP
   if (digitalRead(DIGITAL_INPUT_SENSOR) == HIGH ) {
   if (message.type==V_VAR1) {
       pulseHpCount = oldPulseHpCount = message.getLong();
       Serial.print("Received last pulse count from gw:");
       Serial.println(pulseHpCount);
       pcReceived = true;
   }
   }
   /////HC
   if (digitalRead(DIGITAL_INPUT_SENSOR) == LOW ) {
    if (message.type==V_VAR1) {
       pulseHcCount = oldPulseHcCount = message.getLong();
       Serial.print("Received last pulse count from gw:");
       Serial.println(pulseHcCount);
       pcReceived = true;
   }
   }
}

void onPulse()
{
   /////HP
   if (digitalRead(DIGITAL_INPUT_SENSOR) == HIGH ) {
   if (!SLEEP_MODE) {
       unsigned long newBlink = micros();
       unsigned long interval = newBlink-lastBlink;
       if (interval<10000L) { // Sometimes we get interrupt on RISING
           return;
       }
       watt = (3600000000.0 /interval) / ppwh;
       lastBlink = newBlink;
   }
   pulseHpCount++;
   }

   /////HC
   else if (digitalRead(DIGITAL_INPUT_SENSOR) == LOW ) {
     if (!SLEEP_MODE) {
       unsigned long newBlink = micros();
       unsigned long interval = newBlink-lastBlink;
       if (interval<10000L) { // Sometimes we get interrupt on RISING
           return;
       }
       watt = (3600000000.0 /interval) / ppwh;
       lastBlink = newBlink;
   }
   pulseHcCount++;
   }
}

[mfalkvidd]

@fullmetal cool. Thanks for explaining, and for sharing your sketch.

[FullMetal]

In fact, my code does not work as I would like, HC information systematically go back to the HP ID.

Can you help me

[cstewy]

Update: Running for over 12 months on 2 regular AA batteries using the method I described above. Basically rather than powering the tsl257 constantly, I wake up every 125ms then send power to the tsl257, check if there has been a state change in the power meter light then go back to sleep.

[it-slav]

Hi

My heat exchanger does only give one pulse / kWh which results in that there can be hours between the pulses. When doing the watt calculation micros are used and that counter overflow after 70minutes. See: https://www.arduino.cc/reference/en/language/functions/time/micros/

I have modified the sketch to use millis instead of micros when the time between the pulses are above one hour and micros if it is less than an hour.

I hope I did it correct

Best regards
Peter Andersson

/*
 * 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) 2013-2019 Sensnology AB
 * Full contributor list: https://github.com/mysensors/MySensors/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.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - Henrik Ekblad
 * Version 1.1 - Peter Andersson added millis watt calculation if time between pulses > 1h 
 *
 * DESCRIPTION
 * This sketch provides an example how to implement a LM393 PCB
 * Use this sensor to measure kWh and Watt of your house meter
 * You need to set the correct pulsefactor of your meter (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 value.
 * http://www.mysensors.org/build/pulse_power
 */
#define MY_REPEATER_FEATURE    //Added

// Enable debug prints
#define MY_DEBUG

// Enable and select radio type attached
#define MY_RADIO_RF24
//#define MY_RADIO_NRF5_ESB
//#define MY_RADIO_RFM69
//#define MY_RADIO_RFM95

#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 1       // Number of blinks per of your meter. Normally 1000
#define SLEEP_MODE false        // Watt value can only be reported when sleep mode is false.
#define MAX_WATT 100000          // Max watt value to report. This filters outliers. Normally 10000
#define CHILD_ID 1              // Id of the sensor child

uint32_t SEND_FREQUENCY =
    20000; // Minimum time between send (in milliseconds). We don't want to spam the gateway.
double ppwh = ((double)PULSE_FACTOR)/1000; // Pulses per watt hour
bool pcReceived = false;
volatile uint32_t pulseCount = 0;
volatile uint32_t lastBlinkmicros = 0;
volatile uint32_t lastBlinkmillis = 0;
volatile uint32_t watt = 0;
uint32_t oldPulseCount = 0;
uint32_t oldWatt = 0;
double oldkWh;
uint32_t 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
    pinMode(DIGITAL_INPUT_SENSOR,INPUT_PULLUP);

    attachInterrupt(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), onPulse, RISING);
    lastSend=millis();
}

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()
{
    uint32_t 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 don't get unreasonable large watt value.
            // could happen when long wraps or false interrupt triggered
            if (watt<((uint32_t)MAX_WATT)) {
                send(wattMsg.set(watt));  // Send watt value to gw
            }
            Serial.print("Watt:");
            Serial.println(watt);
            oldWatt = watt;
        }

        // Pulse count value 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 pulse count value received. Try requesting it again
        request(CHILD_ID, V_VAR1);
        lastSend=now;
    }

    if (SLEEP_MODE) {
        sleep(SEND_FREQUENCY);
    }
}

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

void onPulse()
{
    if (!SLEEP_MODE) {
        uint32_t newBlinkmicros = micros();
        uint32_t newBlinkmillis = millis();
        uint32_t intervalmicros = newBlinkmicros-lastBlinkmicros;
        uint32_t intervalmillis = newBlinkmillis-lastBlinkmillis;

        if (intervalmicros<10000L && intervalmillis<10L) { // Sometimes we get interrupt on RISING
            return;
        }
        if (intervalmillis<360000) { //Less then an hour since last pulse, use microseconds
           watt = (3600000000.0 /intervalmicros) / ppwh;
        } else {
           watt = (3600000.0 /intervalmillis) / ppwh; //more then an hour since last pulse, use milliseconds as micros will overflow after 70min 
        }
        
        lastBlinkmicros = newBlinkmicros;
        lastBlinkmillis = newBlinkmillis;
    }
    pulseCount++;
}

[mfalkvidd]

Thanks @it-slav

I have created a pull request based on your sketch.

https://github.com/mysensors/MySensors/pull/1306

There were some merge problems, but I think I got them all ironed out.

[butaluk]

Hello everyone.
Is it possible to evaluate two electricity meter signals with one sensor?
Thank you!

[mfalkvidd]

@butaluk yes, as long as they are not too far apart to run the cables

[butaluk]

@mfalkvidd Thank you. no, the counters are in one place. Do you have an example code for me?

[sundberg84]

Hi! I have just revised my pulse sensor and have a few suggestions to the code. I have mentioned this before but there can be issues when requesting V_VAR1.

In current code we request V_VAR1 one time and then goes to sleep, and if you like me have a 10 minute sleep period it can take along time to get V_VAR1 if you have a radio on the outside of your GW range.

I would suggest adding:

} else if (now - lastSend > 5000 && !pcReceived) {
    // No pulse count value received from controller. Try requesting it again.
    request(CHILD_ID, V_VAR1);
    recrequestcount = recrequestcount + 1;
#ifdef MY_DEBUG
    Serial.println("Req p-cnt");
#endif
    lastSend = now;
    return;
  }

and before sleep:

else if (!pcReceived) {
    //We dont want to sleep if !pcRecieved. Return and wait 5 sec to request a new value.
    return;
  }

In HomeAssisant you also have the specific problem that if V_VAR1 isnt stored, the controller will not answer - so you can keep asking for a pulsecount forever without an reply. To avoid this the first time I have added:

else if (recrequestcount == 5 && !pcReceived) {
    //For some controllers, if you dont have any V_VAR1 stored node will not get an answer.
    //Try 5 times, then set V_VAR1 to 0 and update controller
#ifdef MY_DEBUG
    Serial.println("Set p-cnt and update controller");
#endif
    pcReceived = true;
    recrequestcount = 0;
    send(pcMsg.set(pulseCount));  // Send pulse count 0 value to gw
    double kWh = ((double)pulseCount / ((double)PULSE_FACTOR));
    send(kWhMsg.set(kWh, 4));  // Send kWh value 0 to gw
    lastSend = now;
  }

This setup works great for me, but I dont have the bigger picture - might break something else.
I can add a pull request if you think this should fit.

Here is my full code (but It includes battery measurments)
https://github.com/sundberg84/HomeAutomation/blob/master/Ver 2.X/2.3/EnergyMeterPulseSensor_Feb2020/EnergyMeterPulseSensor_Feb2020.ino

Also there is a strange error with SEND_FREQUENCY / timer when you have this interrupt. Works great if you dont have any interrupts but as soon as you get pulses the timer gets about 4 times as fast as it should be - I have added a correction to this, but I dont know whats causing this.

uint32_t SEND_FREQUENCY = 4*60000*15; // Minimum time between send (in milliseconds). We don't want to spam the gateway. (Corr * 60sek * minutes)

[snady]

Hi
I have done search of this thread and no one seems to have mentioned latency.
I have a test setup using a LM393 running on a particle photon with a sketch that also runs a flashing led. I have tested this with various led flash lengths and intervals, the highest rate being a 10ms flash with 10ms interval . I have a consistent precise reading of pulse interval and number but have identified that there is a 1ms delay between the flash and the start of the interrupt function. This latency is consistent, whatever the interval between and I can only assume it is a result of latency caused by LM393 and interrupt, though I find it strange that the latency is exactly 1millisecond even when measured in micros. Under low meter loads this discrepancy would most likely go unnoticed but with high loads of 72kWs it results in a significant error when calculating the instant power.
Has anyone else noticed this or can give another reason for this that I am missing?
A subtraction of the identified latency from the pulse interval reading, calibrates the setup and produces exact readings

[frydrik]

Hello, this sensor can be adapted for 2-4 meters ?

[keithellis]

I've been building one of these pulse meters up, it seems to be working on the bench very nice. Just got to build a case and get a power supply of the Arduino. But I have designed a case to hold the LM393 sensor onto the meter. I removed the light sensor and re-soldered it flush to the board making it easier to mount on the meter. Its a simple box but works quite well.

The files are on thingiverse here

Hope this is useful.

[keithellis]

@sundberg84 Thanks very much for this post. I was struggling to get the sensor appear in Home-Assistant. Your note on the fact that HA never returns V_VAR1 on first use was very useful and pointed me in the right direction.

My modifications looked like this:

} else if (sendTime && !pcReceived) {
		// No pulse count value received from controller. Try requesting it again.
		request(CHILD_ID, V_VAR1);
    retryCount++;
		lastSend = now;
	} else if (retryCount >= 5 && !pcReceived) {
      //For some controllers, if you dont have any V_VAR1 stored node will not get an answer.
      //Try 5 times, then set V_VAR1 to 0 and update controller
    pcReceived = true;
    retryCount = 0;
    send(pcMsg.set(pulseCount));  // Send pulse count 0 value to gw
    double kWh = ((double)pulseCount / ((double)PULSE_FACTOR));
    send(kWhMsg.set(kWh, 4));  // Send kWh value 0 to gw
    lastSend = now;
  }

The whole sketch is here:

/*
   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) 2013-2019 Sensnology AB
   Full contributor list: https://github.com/mysensors/MySensors/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.

 *******************************

   REVISION HISTORY
   Version 1.0 - Henrik Ekblad
   Version 1.1 - Peter Andersson added millis watt calculation if time between pulses > 1h

   DESCRIPTION
   This sketch provides an example how to implement a LM393 PCB
   Use this sensor to measure kWh and Watt of your house meter
   You need to set the correct pulsefactor of your meter (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 value.
   http://www.mysensors.org/build/pulse_power
*/

// Enable debug prints
#define MY_DEBUG

// Enable and select radio type attached
#define MY_RADIO_RF24
//#define MY_RADIO_NRF5_ESB
//#define MY_RADIO_RFM69
//#define MY_RADIO_RFM95

#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       // Number of blinks per kWh of your meter. Normally 1000.
#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 filters outliers.
#define CHILD_ID 1              // Id of the sensor child

uint32_t SEND_FREQUENCY =
    20000; // Minimum time between send (in milliseconds). We don't want to spam the gateway.
double ppwh = ((double)PULSE_FACTOR) / 1000; // Pulses per watt hour
bool pcReceived = false;
volatile uint32_t pulseCount = 0;
volatile uint32_t lastBlinkmicros = 0;
volatile uint32_t lastBlinkmillis = 0;
volatile uint32_t watt = 0;
uint32_t retryCount = 0;  //If value not being returned from controller, increment this counter
uint32_t oldPulseCount = 0;
uint32_t oldWatt = 0;
double oldkWh;
uint32_t lastSend;
MyMessage wattMsg(CHILD_ID, V_WATT);
MyMessage kWhMsg(CHILD_ID, V_KWH);
MyMessage pcMsg(CHILD_ID, V_VAR1);

#if defined(ARDUINO_ARCH_ESP8266) || defined(ARDUINO_ARCH_ESP32)
#define IRQ_HANDLER_ATTR ICACHE_RAM_ATTR
#else
#define IRQ_HANDLER_ATTR
#endif

void IRQ_HANDLER_ATTR onPulse()
{
	if (!SLEEP_MODE) {
		uint32_t newBlinkmicros = micros();
		uint32_t newBlinkmillis = millis();
		uint32_t intervalmicros = newBlinkmicros - lastBlinkmicros;
		uint32_t intervalmillis = newBlinkmillis - lastBlinkmillis;
		if (intervalmicros < 10000L && intervalmillis < 10L) { // Sometimes we get interrupt on RISING
			return;
		}
		if (intervalmillis < 360000) { // Less than an hour since last pulse, use microseconds
			watt = (3600000000.0 / intervalmicros) / ppwh;
		} else {
			watt = (3600000.0 / intervalmillis) /
			       ppwh; // more thAn an hour since last pulse, use milliseconds as micros will overflow after 70min
		}
		lastBlinkmicros = newBlinkmicros;
		lastBlinkmillis = newBlinkmillis;
	}
	pulseCount++;
}

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
	pinMode(DIGITAL_INPUT_SENSOR, INPUT_PULLUP);

	attachInterrupt(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), onPulse, RISING);
	lastSend = millis();
}

void presentation()
{
	// Send the sketch version information to the gateway and Controller
	sendSketchInfo(F("Energy Meter"), F("1.1"));

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

void loop()
{
	uint32_t 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 don't get unreasonable large watt value, which
			// could happen when long wraps or false interrupt triggered
			if (watt < ((uint32_t)MAX_WATT)) {
				send(wattMsg.set(watt));  // Send watt value to gw
			}
			Serial.print("Watt:");
			Serial.println(watt);
			oldWatt = watt;
		}

		// Pulse count value 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 pulse count value received from controller. Try requesting it again.
		request(CHILD_ID, V_VAR1);
    retryCount++;
		lastSend = now;
	} else if (retryCount >= 5 && !pcReceived) {
      //For some controllers, if you dont have any V_VAR1 stored node will not get an answer.
      //Try 5 times, then set V_VAR1 to 0 and update controller
    pcReceived = true;
    retryCount = 0;
    send(pcMsg.set(pulseCount));  // Send pulse count 0 value to gw
    double kWh = ((double)pulseCount / ((double)PULSE_FACTOR));
    send(kWhMsg.set(kWh, 4));  // Send kWh value 0 to gw
    lastSend = now;
  }


	if (SLEEP_MODE) {
		sleep(SEND_FREQUENCY, false);
	}
}

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

[keithellis]

Got this sensor up and running now. Comparing it to my old clamp meter the kWh reading was reading 2-3 times higher, the Watts was about right. I added a 0.1uF capacity across the ground and data pins of the sensor and it is working well now.
The graph below shows the comparison of my two sensors. the old clamp meter is Energy previous hour, the new pulse sensor is Temp energy previous hour
You can see they are not aligned, until about 20:00 when I added the capacitor and they drop in line.

[Olmo]

Hi everyone, I just implemented this energy meter and it's working quite good. Thanks for all the help.

I have 1 question, however. Since my sensors runs on batteries, it sometimes dies. I then need to replace the batteries and "restart" the counting. It's not ideal, but I have no way of plugin the sensor to power next to the meter.

When the sensor dies, I read the kWh reading of the meter manually and store it in an input variable. How can I use this to set the kWh value of the mysensor variable at initialization?

I see this line: request(PC_CHILD_ID, V_VAR1);, however it's never running for me. Somehow it does not work properly with home assistant.

Would request(KWH_CHILD_ID, V_KWH); do the trick? (provided that I store the kWh value from the meter in the same state created by the mysensor S0 pulse counter)

thanks a lot

[voxeg hult]

@asgardro Thanks for your nice prompt feedback.

[ramisthand76]

Pulse Power Measurement: Measuring Instantaneous Power of a Short Pulse. ... Thermopile sensors are often used to measure single shot pulse energy;

[FredC]

@keithellis Lovely idea.
I've followed suit and knocked up one but with the sensor facing the other way, so that it faces the meter, and the preset pot is and LEDs are facing away from the meter.

That way the sensor side of the case can be stuck to the face of the meter, and the pot adjusted without removing it from the meter. The flashing light on DO flashes in sync with the LED on the meter. Theres a little ring that holds the sensor flush with the face of the case so it can lie flat on the front of the meter.

Also, its a good idea to use black / dark coloured PLA so as to block out the any stray light that may illuminate the sensor (such as when the meter man comes to read it and shines a bright torch to see the dials).