Pulse meters - part 1

Here is some evolution about the Gas Meter 'Gazpar' for which I developped a generic battery backed-up solution.

Gazpar

As mentionned before, the "official" cable is for sale at a hefty price (for what it is) of ~20€. I would have gone for this cable, had the meter been outdoors or in a humid room, but since it is located in my kitchen, I simply used the trick found on some forums: Female dupont wires. And it works very well indeed.

Dupont Female

Counting

One of the main differences between the electricity and gas smart meters, is that the former will deliver all the information (including current reading) in a continuous way. In case of power cut, upgrade or crash of the microcomputer/microcontroller, nothing is really lost and things will restart as soon as possible.

The gas meter, smart or not, will only give pulses... if nobody is listening, the information is lost and the status of the reading not longer accurate.

Keeping the value

The basic idea is to decouple the counting process from the processing unit. The counting unit should not need any update or needs to restart often.

One idea was to write the current value on a flash memory but these are notoriously bad as time goes by. Wear and tear could soon be an issue.

Apprently, there is a kind of memory called Ferroelectric RAM/FRAM for which the number of write cycle is not a problem. But these are not wildly sold (but can be found as breakout board) and certainly overkill for just keeping a counter.

So in the end, the easiest solution seemed to use a basic ATTiny85 powered and keeping the value in RAM. This solution will be described in the next post.

    Gazpar's socket

    As mentioned 9 months ago, the new French smart gas meter is called Gazpar and has a socket. So far I couldn't find any info about it but slowly, details are starting to emerge:

    In this thread (in French), there is a link to a adaptation cable reference EER31130 sold by Schneider Electric for their own product but it looks like it could by used for any solution.

    It also gives an indication of the type of socket (made by JAE but unfortunately I can't find the exact reference).

    JAE connector

    Schneider Electric's "pulse emitter" has the following characteristics which give other info about what the Gazpar might be (open collector (most likely) or reed switch):

    • Compatibility with meters with pulse output of types: Open collector (electronic) / dry contact (mechanical contact), REED switch (magnetic) with the following characteristics:
    • Voltage on the contact: 2.7 V (delivered by the Pulse Emitter)
    • Closed contact impedance: <1 kΩ
    • Open contact impedance: > 1 MΩ
    • Pulse duration: > 66ms
    • Delay between pulses: > 33ms

    A suivre...

    Teleinfo with Wifi on the Linky

    Following the upgrade of my electricity meter (from rotating disk to latest generation of smart meter), I am now able to use the Teleinformation output (hurrah!)

    Linky

    The Linky smart meter has a slot for a "LRT" module and a 3-pin header for teleinfo (the traditionals "I1" & "I2" as well as a power source named "A").

    There are also two communication modes available: Historical (the only one available so far) & Standard (i.e. the new one starting with Linky).

    LRT

    The "Linky Radio Transmitter" (Emetteur Radio Linky) is a module developed to transmit the value to a household display. Specifications show they can be using either Zigbee or KNX. It was supposed to be totally open but I am yet to see a schematics of it.

    ERL/LRT

    At least the Interface Specification is available. I reused the name of Zigbee attributes for the MQTT publication.

    Teleinfo

    Official docs are available (in french) on Enedis's website, in particular NOI-CPT_02E for Teleinfo in general and NOI-CPT_54E for Linky in particular.

    The electronics part is mainly based on work done a long time ago by others, specially Charles Hallard (Démystifier le décodage Téléinformation et l’optocoupleur SFH620 and PiTInfo V1.2, en finir avec la téléinfo capricieuse).

    Board

    My board is vague cousin of Charles Hallard's Wifinfo but where most of the components are already embedded on the nodemcu module.

    CH340G (USB to UART)

    Something worth noting is that CH340G seems to be struggling with 7N1 (7 bits instead of the usual 8). Although it doesn't matter for day to day usage of the ESP8266, it makes tests (emulation of the Teleinfo frames) more difficult.

    It could be the driver though I am using Linux. Using boards (Amica) based on CP2102 or FT232 didn't show any problem.

    Power

    From the meter

    In theory, the pins "A" and "I1" are maint to be used as the power source. That said, the characteristics are 6 Vrms (50 kHz) and 130mW. This is far from the ESP8266 requirements (~ 150mA) and if it would be easy to rectify and smooth the current, a storage system (super cap or battery) would be needed to deliver peaks of currents every time the data is published (re-charging being one while module is in deepsleep).

    External 5V source

    To keep things simple and since I already had a 5V source at my disposal, I used the embeded regulator on the nodemcu board (through the Vcc pin but it could have been through the micro-USB socket).

    OTA

    Having the circuit permanently plugged to the meter means that the option of remote updates is a big bonus. The module is off/asleep most of the time so the best method was the HTTP Server one. But in order to make things easier and more secure, there is a physical jumper to allow OTA or not. When jumper is on open position, no OTA is possible. In the other position (closed), every time the program starts (i.e. every minute), it checks if an upgrade is available.

    This is were the additional python script comes handy. By running a webserver and comparing the MD5 checksum of the firmware on the module to the one on the server, it is possible to launch the upgrade sequence only when necessary.

    MQTT

    Selected data is transferred using the MQTT protocol. As mentioned above, the names/topics used are based of the ones in the ERL/LRT documentation.

    ADCO  --> Serial Number used in topics (ssssssssssss)
    
    BASE  ---->  cm/teleinfo-ssssssssssss/data/index {"value": "000073370"}
    PAPP  ---->  cm/teleinfo-ssssssssssss/data/apparent_power {"value": "00320"}
    IINST ---->  cm/teleinfo-ssssssssssss/data/rms_current {"value": "001"}
    

    Since the tariff is a constant one and not a differential one, there is only one reading to report and there is no need to advertise which tariff is active. People dealing with Heures Pleines / Heures Creuses would have to change the code.

    Deep sleep

    In order to reduce the amount of power drained, reduce the heat production and because there was no need to keep the module on for nothing, I decided to turn the wifi off. But it turned out that it isn't as straightforward as it initially sounded. Just calling the corresponding fonctions doesn't really make any difference in term of power consumption and forums are full of examples looking really like black art.

    On second thought, I decided to go to the deep sleep route which turned out to be easier to implement and perfectly adapted to this kind of usage. The teleinfo is continuous with values coming all the time but having a refresh every second or so has very limited interest. Even everything minute is kind of luxury.

    The only downsides of deep sleep are the need of a physical wiring for reset purpose and that the programme really resets every time. In this case where the bridging is stateless (state/info is held by the smart meter and given every single time) it doesn't matter the least.

    Next version

    This version has been running for a while without any issue. Once the meter is properly registered by the supplier (they seem to have technical issues actually), they should be able to change the mode to "Standard".

    This new mode is only in Linkys, uses a different serial speed (9600N7 instead of 1200N7) and provides more information. The "codes" are slightly different too.

    There is no physical modification needed and everything is documented so making the software changes should not be too complicated.

    Will see....

    Module in its box

    Code

    As usual the code and schematics are available (AS IS) on github.

    New meters

    Back after a hiatus of a few months. The main reason can easily be guessed from the previous post! :-)

    This time I will be talking about so-called "Smart meters" since both my antiquated electricity meter and gas meter were recently replaced.

    Linky

    Linky is the name for the French electricity smart meter. They are manufactured by different companies but all have exactly the same flashy green colour!

    Smart Meter - Linky

    Linky is highly controversial but not for the right reasons IMHO. Opponents seem to concentrate on false and bizarre statements about radiations when they don't assert the meter embarks a camera! Long term loss of job (meter reading people) and above all the risk of privacy breach (it is technically possible to know how much electricity is used in real time hence to know what are people's daily routine and/or if they are on holiday, etc...) could have been causes worth a battle. But honestly opponents only managed to discredit themselves and look like a bunch of lunatics!

    Let's not forget that the original reason behind the arrival of smart meters is (by extension with smart grids) to be able to better handle the production of electricity by "green" means (wind, solar, ...) which are highly unpredictable and require to collect real time usage to try to balance production and consumption.

    The fact you can now be charged with real amount rather than estimates and you don't have to be home any more to open the door is a real bonus too. Note that in France, contrary to some countries like the UK, you don't have a "smart energy monitor" in standard. This kind of display with the current consumption in currency seems to be given only to the poorest families. AFAIK there isn't any similar solution sold yet.

    There is a slot for the emitter module ("ERL") and "Teleinfo" is available! Hurrah!

    So my first task was to create a MQTT/Wifi module to transmit the real time data. I'll give all the information about it soon.

    Gazpar

    The smart gas meter is called Gazpar and is controversial too (obviously!). The transmission of information is slightly different. First it is only one-way and for reading: Nothing can be done remotely. Reading are transmitted by FM then mobile network twice a day.

    It is like a old "dumb" meter clad in an bright orange cuirass.

    Smart Meter - Gazpar

    For me the main issue is the loss of the magnetic pulse reading. I actually suspect that is is used internally by the Gazpar electronics but it is no longer available for personal use.

    There is a "socket" but I can't find much information about how to use it (dry contact? Not so sure specially that the battery should last 20 years and in theory the fact that something is plugged in is sent to gas provider) and I am rather shy to try anything. If someone has any information about it... Please contact me.

    The good news is that there is a shiny "6" on the litre digit so, reusing the old electricity light sensor, I am able to count the "pulses".

    TCRT5000

    Le compteur gazpar est équipé d'une prise. Cependant quasiment aucune information à ce sujet n'est disponible. Cela pourrait être un contact sec mais j'ai du mal à croire qu'il s'agisse d'un relais (avec une pile qui doit durer 20 ans et du fait que l'utilisation/occupation de la prise semble faire partie des informations remontées). Je suis preneur de toute information à ce sujet... Merci d'avance.

    EDIT (16/12/2018):

    The cable is for sale on (at least) two online shops. By the time you add VAT and postage, it's almost 20€ or 24€ (horrendous for what it is) but let's hope the price will go down with time.

    Regarding how it is connected internally, I still haven't been able to find any documents but my best guess is that there are 2 reed switches bundled together, one used for the internal counter, the other one directly connected to the socket.

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