This project is a mashup of different experimentations. I wanted to try the SHT21 sensors and I was looking for a CO2 sensor at the same time accurate and not too expensive.
CO2 Sensor
Until recently, gaz sensors were either analogue (and totally uncalibrated) or relatively expensive (when not both at the same time). Then came the MH-Z14 which is a affordable "Non-Dispersive InfraRed" sensor, in theory quite selective.
The MH-Z19 from the same company can be found for ~ $25. The main issue is the partial documentation. Some commands are still a bit obscure.
A great source of information is the wiki https://revspace.nl/MHZ19 and there a quite a few examples on github to get started.
At first experimentations were a bit frustrating but after a while things started to stabilise a bit and sensor's readings from the past few month seem to make sense. The solution was to reject sub-standard readings and to average valid ones over a period of 5 minutes.
One quite annoying thing a bit this module when using breadboard or prototype PCB is that it has weird dimensions (not a multiple of 2.54mm) and won't fit nicely.
Calibration
Calibration can also be an issue, specially because of the ABC calibration every 24h. The system would be great if it spanned over let's say a week which would give you several chances to open the window but as it is (i.e. using the minimum value of previous day as base), reading were becoming strange day after day. It turns out that it works a lot better without ABC and a manual calibration from time to time.
Then manual calibration can be triggered by software or using the hardware pin. To avoid trying to fit a switch on the enclosure, the solution retained was to use a reed switch inside and to press a neodymium magnet on the cover once the air of the room has been well recycled.
Wemos D1 mini
Although I initially planned to use nodemcu modules, I decided to try Wemos D1 mini which are smaller, cheaper and able to cope with higher speed communication via USB so firmware upload is twice as fast.
Besides this, there really behave like any other ESP8266 solution. Wemos offers a good selection of shields (power, relay, LED, sensor, ...) which I haven't tried as well as modules based on the more powerful ESP32.
It is probably best to use their official online shop as there seems to be quite a lot of fake modules around, and not necessarily cheaper.
I2C Oled
Having used a 0.96" Oled screen for the time bomb, I really thought that using a 0.91" 128x32 I2C SSD1306 screen would be trivial. As it turns out, library for the former is not compatible with the latter because they lack of a proper framebuffer. After digging around, I found that the Adafruit library was working (one parameter is of a different value) even if the hardware looks quite different (more pins).
To be perfectly honest, if I was to make another sensor, I would give up the screen and use coloured Led shinning through (the plastic is slightly translucent) as the physical fitting was probably the most challenging part of this project (even if simple by DIY standard).
A sprinkle of MQTT
Communication with base is, of course, via MQTT, nothing new or complicated here. There is a sampling every minute for the CO2. The average value as well as the current values of temperature and relative humidity are sent every 5 minutes.
Wifi off (really?)
Since this new sensor is installed in our bedroom, I wanted to switch the Wifi on only when needed MQTT communication to send the values. I basically used the dedicated function for this. Is is really switching off "radiations"? Who knows... as I discovered with the electricity meter project, electric consumption is not lowered by it.
Powering the sensor
I knew from the start that using battery would be a challenge and I didn't even bother. Between the screen, MH-Z19 and the Wifi, it is probably around 200mA anyway. The USB port of the Wemos D1 mini is plugged directly on a small power adapter. The usb cable can also be used to upgrade the firmware as no OTA was implemented on this project.
All in a "sensor box"
Like almost everything else, directly from China, I found an enclosure designed for sensors (or thermostat?) which was the right size to fit everything. The USB power adapter is external, the ESP8266 at the top and the thermometer at the bottom, by the vents in order to stay as accurate as possible. Despite this, the temperature appears 1.5°C higher than without cover. The offset can be corrected in software.
Code
As usual the code and schematics are available (AS IS) on github.
It includes a SHT library and MH-Z19 library.
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!
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.
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.
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.
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.
Tick, tock, tick, tock... When time is up, lie-ins and good nights become a thing of the past!
Counter using a ESP8266 (nodemcu) and OLED Colour display and accessing NTP. The code can be found at the following address: https://github.com/guillier/Time_Bomb.
Lors d'un récent voyage sur les lieux de la guerre 14-18, nous en avons profité pour faire quelques recherche sur un arrière-grand-oncle de ma femme que nous savions décédé lors du conflit. Nous avons trouvé sa tombe au cimetière de Lijssenthoek (Poperinge, BE).
La mise à disposition de bornes d'accès à des documents numérisés dans les différents musées et cimetières et la présence d'un François Guillier sur l'anneau de la mémoire de Notre-Dame-de-Lorette, m'ont amené à rechercher des informations sur des soldats portant mon nom.
Après quelques recherches sur différentes bases de documents en ligne, et de fil en aiguille, j'ai réussi à retrouver la trace de plusieurs homonymes.
Recensement
François
Après vérification, il se trouve qu'il s'agit de mon arrière-grand-oncle !
Né le 10 mai 1892 à Villaines-sous-Malicorne (Sarthe)
A épousé Marguerite Marie Garnier le 6 février 1916
Mort pour la France le 30 juillet 1916 à Fleury-sur-aire (Meuse) de blessures de guerre
