Server room monitoring
July 28th, 2020 by Chief

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Monitoring temperature and humidity in server rooms are usually tasks for dedicated hardware and software. It is just a case of this stupid COVID situation that called for urgent and somewhat desperate measures. Postal services are not functioning normally, delivery time for everything is uncertain and some things are even impossible to buy. Combined with living in a godforsaken place it`s as Chris Rea would say a “Road to Hell”. This is why I went down this road and put Domoticz and ESP to the task and created DIY server room monitoring and alerting system.

Measuring device with ESP and Tasmota

I will try to make this look more like a guide since there is plenty of applications for this kind of device.

DIY server room monitoring system sensors device parts
This was my starting point

I made this as simple as it can be. I combined the ESP8266 development board with a DHT11 temperature and humidity sensor. It`s what I had at my disposal, maybe in a different situation, I would use DHT21 or BME280 sensor. Here is a schematic:

Schematic DIY server room monitoring system schematic
Device schematic

This is as easy as it can be no need for any explanation except power connections. You can supply power like this or simply use a built-in USB connector on the ESP board. I just put a standard USB connector on the other side so it can draw power from any USB port. I chose this method since I did not want any possibility for data communication if the USB is plugged to a port on the server or something like that.

Getting DIY server room monitoring device in the box

DIY server room monitoring system sensors device

It took 30 minutes to put everything together. Measuring part of the DIY server room monitoring system is finished.

DIY server room monitoring system sensors device

I did not use any extra circuit board since there is only few wires and one resistor. ESP board was big enough to host everything.

DIY server room monitoring system sensors device

At the end I found a transparent box that some kind of hdmi adapter came in and used it as a casing. It fitted perfectly.

Flashing Tasmota firmware on ESP8266

I already wrote here about flashing Tasmota on ESP but I will mention it again. First, get your hands on Tasmota Pyflasher and Tasmota firmware. You will want to use the tasmota-sensors.bin file. That is the only one you need in this type of flashing. Second, connect your esp to your computer and press reset while holding the flash button.

Flash tasmota

First point flasher to the location of the .bin file and chose com port number that your ESP uses. Second, hit “Flash Tasmota”.

Flash tasmota

It should soon report that firmware was successfully flashed and that`s all regarding flashing.

Configure Tasmota to use Wi-Fi

Scan for Wi-Fi networks on your mobile phone. You should see a new SSID with a tasmota_something in its name. When connected to that network, you will get a prompt to sign in. Click sign in and you will get a prompt to enter SSID and password of your network. It will look like the picture below, and it is as simple as it can be.

Configure Tasmota to connect to WiFi
Configure Tasmota to connect to WiFi

First, take note that ESP supports only 2.4 GHz networks. Therefore make sure that your network is 2.4 and not only 5 GHz. Second, if you have two Wi-Fi networks you can also configure the other one as a failover.

Configure Tasmota for sensors attached to ESP

Now your device is connected to Wi-Fi. Therefore go to your DHCP server and check what IP address is leased to your Tasmota device.

DHCP console

Afterwards, enter that address to a browser on the device that is on the same network and you should get the Tasmota web interface. Click on configuration and then configure the module. Under Module type, chose Generic(18). Since we connected DHT11 to D1 open the options next to D1 GPIO5 and find and select DHT11(1). Click Save, and go back to configuration.

Now you should see readings from sensor on the main Tasmota page.

Tasmota main menu

Configure Tasmota and Domoticz to work together

From here we go under the assumption that there is Domoticz up and running. If not, here is the full guide for the setup. On the Domoticz go to Setup -> Hardware and Create Virtual Sensors. (If you already do not have a Dummy virtual switch, create one now).

Now back to Tasmota again. We need to configure it to use MQTT and Domoticz. So under configuration, we first go to Configure MQTT and after that to Configure Domoticz.

In the Configure MQTT, under Host() field type the IP address of your mqtt broker. In most cases it will be on the same machine as Domotics. Therefore it will also be the same IP address.

At this time, we go to the Configure Domoticz menu and if you remember the moment when we created the virtual sensor on Domoticz, now we need its idx. In our case it was 2, therefore we will enter number 2 under Sensor idx 2 Temp,Hum field. Certainly, here is just a coincidence that Sensor idx 2 Temp and the number 2 that we got from Domoticz are the same. For instance, if it were the next sensor created on this Domoticz instance it would be Sensor idx 2 Temp,Hum 3.

Presentation in Domoticz

Virtual sensor in Domoticz

Here we can see how it looks like in Domoticz. Not bad ha? πŸ™‚ Besides that, the real power of this is in notifications. Notification settings look like this.

Sensors notifications

So it will send an email and Telegram message if the temperature exceeds 25 degrees Celsius. Not to enter in explanations why this temp as a trigger, let`s just say that it does a great job for me at this moment. And here is how 24-hour log looks like so you will figure out one of the reasons why I made all this in the first place.

24 hour Temp and Humidity log chart.

For instance in this situation it was necessary to log and visualize data to find the problem, and to be able to document it. Therefore, this little project just did that, and in the end, it will stay, as it proved to be quite useful.

DIY server room monitoring system server room installation.

DIY server room monitoring system server room installation.
DIY server room monitoring system installed in rack
DIY server room monitoring system server room installation.
DHT installed on front (cold) side of the rack

Likewise, here are few more pictures of two devices that I made to just be plugged in the AC utility socket and transmit temperature and humidity. For instance, I used adapters of the old cellphones as a power source and put ESP on top of it with DHT21 outside to avoid it being influenced by the heat that adapter and esp produce.

Once more, thank you for reading.  


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March 8th, 2020 by Chief

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This can also be used to verify that Domoticz and Mosquitto MQTT broker are working fine together. Another example is the use of commands like this to update or control virtual sensors or switches on Domoticz from another device like Arduino or ESP. It can be handy if you are making some custom devices that will communicate with Domoticz. Basically, it is a virtual sensor update via MQTT.

Environment that we work on

What we have here is a Domoticz V4.10717 and Mosquitto 1.6.8 x64 installed on the Microsoft Windows server 2016. Why is that important? Well if you have these running on the Linux, commands may be a little different. The principle is the same, but some characters are handled in a different way.

How is this gonna work?

So, we are going to show three examples of Mosquitto commands. One for updating a virtual switch that has only “On” and “Off” options. The second one will be updating a virtual temperature sensor. The third one is an update of the Temperature + Humidity virtual sensor. We will also try to explain what Domoticz expects as input for different sensors, and how to fulfill that with Mosquitto commands.

Updating the virtual switch with MQTT

First, open the command prompt and navigate to a directory where Mosquitto is installed. In my case, it is “C:\Program Files\mosquitto\”. Then go to Domoticz and check the IDX of the virtual switch that you want to update. There are few examples in other Domoticz related articles so if needed you can look there for more info. In this case, IDX of the virtual switch is 3, so here is the command: mosquitto_pub -h localhost -t “domoticz/in” -m “{ \”idx\”:3,\”nvalue\”:1}” .

Take the command apart

The mosquitto_pub is the app. -h is an option that is used to specify the address of MQTT broker, and since it is the same machine we use “localhost”. -t is an option to specify the topic and we use default “domoticz/in”. Finally -m is an option to specify the MQTT message.

Something about MQTT message

Let us peek into what we are sending as a message. “{ \”idx\”:3,\”nvalue\”:1}” For easier understanding here is what Domoticz expects: Topic: domoticz/in, Message: { “idx”:3,”nvalue”:1} . To say it short whatever part is between “” it is a string data type. If something is not between double quotes, it means that it is an int data type. Let`s go back to message that we are sending “{ \”idx\”:3,\”nvalue\”:1}”. there is a backslash before every double quote. In essence, we need to use special character ” as a regular one, so we prepend it with a backslash like this \” That is called escaping a character. I hope it is a little easier to understand this command now. Here are screenshots of sensor status and command execution together. It is obvious that if we send 1 as nvalue virtual switch goes to On status and with 0 it goes to Off.

Virtual switch update with MQTT.
mosquitto_pub -h localhost -t “domoticz/in” -m “{ \”idx\”:3,\”nvalue\”:1}”
Virtual switch update with MQTT.
mosquitto_pub -h localhost -t “domoticz/in” -m “{ \”idx\”:3,\”nvalue\”:0}”

Updating the virtual temperature sensor with MQTT

We will start with the command. mosquitto_pub -h localhost -t “domoticz/in” -m “{ \”idx\”:1,\”nvalue\”:0,\”svalue\”:\”18.4\”} One thing different now is svalue since it is expected to be sent as a string comparing to nvalue that is an integer. What I`m talking about is that 0 is without double quotes and 18.4 is between them. Let us see how the sensor and commands look like.

Virtual sensor update with MQTT.
mosquitto_pub -h localhost -t “domoticz/in” -m “{ \”idx\”:1,\”nvalue\”:0,\”svalue\”:\”18.4\”}

Updating the virtual temperature + humidity sensor with MQTT

The command: mosquitto_pub -h localhost -t “domoticz/in” -m “{ \”idx\”:2,\”nvalue\”:0,\”svalue\”:\”1.2 ; 33 ; 1\”} . Now everything in svlaue is a string that looks like value than space than ; than space than value than space than ; than space and 1 at the end. That is how Domoticz expects iput for this sensor. To be honest, I do not know why is there a third value (1) here, I can only assume that it could be for the battery level or something like that. To summarize important things here 1.2 is the temperature, and 33 is the humidity percentage. Let`s see this one`s screenshot.

Virtual sensor update with MQTT.
mosquitto_pub -h localhost -t “domoticz/in” -m “{ \”idx\”:2,\”nvalue\”:0,\”svalue\”:\”1.2 ; 33 ; 1\”}

That`s all, folks. Now you can manipulate virtual sensors manually or as we said before, perform virtual sensor update via MQTT. Thank you for reading.


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Domoticz and Mosquitto on Windows
March 1st, 2020 by Chief

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This guide is about how to set up a functional Domoticz environment on Windows. Moreover, it is Domoticz and Mosquitto on Windows. As I figured out most of the Domoticz instances are running on Linux-es\Raspberry-es. In contrast, I just want to show how to do it this way. Since I already have a PC running 24/7 and believe it or not I like Windows, it was a logical choice.

Few practical advice’s

Windows Firewall

I know that it is not a best practice, but before you begin I would suggest that you turn off windows firewall for good (just temporary all networks). Finally, when everything is up and running you can turn it back on and configure it to allow ports needed for these apps to work. We will mention that again later.

Microsoft Visual c++ redistributable

Another thing is Microsoft Visual c++ redistributables. If you ask me, download them all from 2013 to the latest version in both x86 and x64 versions and install them from the oldest to the newest one by one. It may sound stupid, but it is not taking much space and many apps rely upon those redistributables. Domoticz is one of them! Finally, if it is hard to find all of them just write a comment for this article, I do have one archive to rule them all and I can send it to you. πŸ™‚

Install Domoticz on Windows

First of all, download the installation from here. Setup is as easy as it can be so there is almost nothing to explain. Just run it and click next. The only thing that I can suggest is that you chose to run Domoticz as a service as it is the right thing to do. Explaining why is not part of this article but let’s just say that due to its nature and purpose Domoticz should be running all the time, 24/7.

Port numbers

In case you are ok with default port numbers (and there are not many reasons not to be) just leave them be and finish the installation. Hence, everything went fine fastest way to check is it working is to open the browser on the same computer where you just installed Domoticz and open this address: http://localhost:8080. You should get something like this.

Service Status

In case nothing opens or page is not available most probably Domoticz service is not running. Consequently, you need to figure out what is happening. Type services in Windows search and open it. Find Domoticz service and check it`s status. The service should be running.

The service status should look like this. If service is not running try to start it. In case service starting ends with failed, or pause or stoped, there is a problem. Most likely you did not turn off a firewall or did not install those Microsoft Visual c++ redistributables that I mentioned before. It is now wise to visit Windows Event viewer and check Windows application logs for errors or warnings regarding Domoticz service. Now, let`s continue with Mosquitto installation.

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433 MHz smoke detector compatible with Domoticz
February 8th, 2020 by Chief

It`s extremely important to have a piece of critical information, right on time. So, it`s great to have an option to be remotely alerted in case of fire or smoke at your house. I`m thinking Telegram… E-mail… and … Domoticz in combination with C50W 433 MHz smoke detector.

So, this article is about choosing and adding a wireless smoke detector to Domoticz. In this example, we used C50W 433 MHz wireless device. No, it does not mean Wi-Fi, but wireless πŸ™‚ There can be a big difference since Wi-Fi is wireless, and wireless does not necessarily mean that it is Wi-Fi.

Wi-Fi vs Wireless

Wi-Fi is a family of wireless networking technologies, based on the IEEE 802.11 standards. In general, it is intended for use in short-range networking of computers, smartphones, and other devices. On the other hand, wireless means that the device can transmit and/or receive something without cables (wires). For example, a walkie talkie is wireless but not Wi-Fi. Then there is a wireless charger. Not to forget our 433 MHz smoke detector that is wireless, and not Wi-Fi. The main reason is the much lower energy consumption. You definitely do not want to change the battery in your smoke detector on a weekly routine.

Back to original theme, adding sensor to Domoticz

First of all, for this to work you need some kind of 433 MHz RF Bridge already setup and working with Domoticz. I Use SONOFF RF Bridge, flashed with Tasmota firmware. RF bridge is both transmitter and receiver on 433 MHz but also has Wi-Fi connectivity, so it talks with Domoticz over Wi-Fi. This Sonoff device is great, and yet under 10 $. After that, you obviously need a 433 MHz smoke detector. I`m using these ones. It is marked as C50W and it costs around 10$. A short piece of advice, there are many devices out there marked as 433 MHz. And manufacturers are not lying about it. The trick is that they use some proprietary or nonstandard protocols, which means they may or may not work with third-party devices. You will need to do some research before buying it.

Configuration of C50W

This pretty little thing comes with a terrible, unusable manual. It also comes without the battery so prepare a quality one. Do not even try to test or use it with a used 9V battery. When the time comes to change the battery it will start beeping at 45 seconds interval and note: it will not give you an audible alarm or send any signal on RF. There are also four jumper places with two jumpers placed in the middle. Their intent is to change electrical resistance and the code it sends over the radio. If you ask me how to place those jumpers I would say that I do not know. Just leave them be for the start. There is a little hole for adjusting sensitivity to smoke, and that also has a great range. You can play with it to adjust it to your needs if you want.

C50W smoke detector

Add C50W to Domoticz

First of all accept “virtual sensor” as a term, since most things you add to Domoticz are represented by VS. If it`s easier observe it as a virtual representation of physical sensor, or its digital twin. Since this kind of device has a normal state, where nothing happens, and an active state where the alarm is triggered, the default state is normal. This means that the state will change only if it detects smoke. So we kind of have a two-state thing, and it may remind us of a ….. switch? True! So let us start with a virtual s… .

Add virtual sensor as digital representation of  C50W

Next chose a Switch as a sensor type, and name it as you wish.

Wirtual switch representing C50W

After that find your switch under switches tab and click on edit.

Edit virtual switch

The whole new world of switches opens up there. We are aiming for the smoke detector.

Virtual switches in Domoticz
And do not forget to save your setting, since I make that mistake almost every time.

Connecting physical and virtual worlds or joining the digital twin to its physical brother

Let`s summarize what we did and what needs to be done. We created a virtual switch that serves as a representation of the real one. What is missing now? A link between them. We mentioned before that C50W sends some kind of code on 433 MHz when activated. What is needed is to intercept that code, and link it to changing state of a virtual switch.

What is going on with RF Bridge

Quick reminder of how RF bridge works. Whenever it detects 433 MHz signal or if you like it more, commands, it reports it to Domoticz via MQTT. It means that you can find that exact code in Domoticz log file, and it looks something like this.

Domoticsz log file capturing command from C50W sensor
Log file in moment of triggering C50W

So this is the code that my C50W will send if activated. Just to mention, you do not need to set fire to discover the code. The big round thing in the middle of the sensor is a test button. When pressed for a few seconds it will simulate triggered alarm and you will get your code transmitted πŸ™‚ .

Time for some blockly work

Now we go to Setup – More options and Events and create a new Blockly script.

Blockly script that will connect  C50W with its digital twin
Blockly script for C50W
Blockly script for C50W

I do not think that this needs much explanation. In short, if the RF bridge detects the value of “x” then set the state of a Smoke detector switch to On. X is a value that you read in your log file. And that is it, ready for testing.

Pressed the test button on C50W and voila…

Digital twin of C50W
Digital twin of C50W

Now the real power comes in. We go to notifications on switch widget and set some alerts.

Configuring alerts on virtual switch

I prefer these two types of alerts. Since this is a critical sensor, Telegram is the first choice as it is delivered instantaneously, and email….. email is just in case. Of course for these to work you must configure them in Domoticz settings, but it is not a big deal. Now if god forbid there is smoke in your house, Domoticz will message you.

If you find this article interesting maybe you should check on this one regarding building a sensors station for Domoticz. Thank you for reading, and if you have any questions, just post a comment.


P.S. I wanted to put the picture of a detector on the ceiling, but it kind of looks stupid. If angle is wide enough to get real impression that it is actually detector on the ceiling than it looks like a little spot, almost undetectable. If it is close enough to have a descent look at the detector than it looks same like on the table πŸ™‚

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Tasmota ESP8266 Sensor station
February 3rd, 2020 by Chief

How does monitoring Temperature, Humidity, Pressure,  Illuminance, and Air quality sounds like? Well, it sounds great especially if we can do it in under 50 US $ budget, and it even has some basic weather prediction functions, when combined with Tasmota and Domoticz.

Why measure air quality?

We had a situation in the city where people started to get sick with respiratory problems at the mass level and it was obvious that a major problem is the quality of the air. I mean it was noticeable with the bare eyes and nouse but authorities kept saying that air is ok, and they were publishing fake results. Moreover, results were in the form of a statement like “Air quality is at a satisfactory level”. Yes, it is ok if you ar an internal combustion engine with a great air intake filter!

How could air become so bad in a city without industry?

This started happening with the beginning of a heating season, and it was just a coincidence that the city got a brand new heating plant. Well, later we find out that it was not exactly in city ownership. Moreover it is a privately owned and operated, with a nice and lucrative contract. In fact, the new plant is so nice that they shut down former plant (with chimneys like two times higher than those at the new plant) that was owned by the city and the only heating option left is this new monster that uses wood as a fuel. I could write a completely new story on this subject, but I will stop here.

Why Nova SDS011 PM sensor?

I came to learn about it from the necessity. I wanted to see what is going on with the air pollution and I found a bunch of sensors there on the market but did not know where to start. In fact, one independent journalist brought few “Purple Air” sensors and installed them around the city, and the results were catastrophic. For example, they measured 300 – 500 (US EPA PM2.5 AQI ) almost all the time for 2 months. On the other hand, 0 – 50 is ok on their scale and that scale ends with 500.

These purple air sensors cost around 250 US $ so they are not so cheap. On the other hand, you just have to put it on a good spot, connect it to Wi-Fi and power. But it is very enjoyable to build something yourself so, DIY again πŸ™‚ . Just one more comment, authorities said that these “so-called” measuring devices like “Purple Air” sensors are not calibrated, and not attested by their accredited agency so the results were wrong. As soon as they started talking things like that, the air became so pure and enjoyable to breathe that everyone was so shocked and happy to have the opportunity to live under so wise rule.

Joost Wesseling (RIVM) – Air quality measurements using cheap sensors

What convinced me even more that I`m on the right track was Mr. Joost Wesseling from The Netherlands National Institute for Public Health and the Environment, keynote at the Things conference in Amsterdam. If you read this article until now, it means you are interested and I warmly suggest you watch this 25-minute video .

Back to technical stuff…

First, we will make a little bom (bill of materials) containing major parts. After all, we are building a quite complex device. Therefore we must know what parts do we need.

PartPrice US $
1. ESP8266 development board2.8
2. Nova PM sensor SDS011 High precision laser pm2.5 air quality detection sensor module 18
3. BME280 temp hum baro sensor 3V3
4. BH1750 light intensity illumination module 3V2.5
5. 5V 2A power supply3
6. Some wires, cables, connectors, screws, cable ties and a box…10

Regarding tools needed for the job, I used: soldering iron, hot glue gun, small drill, angle grinder, few screwdrivers, cutting pliers, multimeter, smartphone and a computer.

Since I had to order some parts from China, there was not much to do until they came. I was killing some time wondering how to assemble everything together. What will I use as housing? I went through some stuff I had and noticed the old HP Inkjet printer power supply. I opened it and after measuring the size, it looked like everything could fit in nicely. And it did, so this power supply casing was a box for my sensors device.

Nova SDS011 PM sensor
Nova SDS011 PM sensor fitted in the box

First I put everything together to see how it works. I had a doubt regarding connecting two i2c sensors in parallel (doubt was about addressing not about can it work or not). BME280 and BH1750 are both connected to scl and sda pins of ESP, and I did not now will Tasmota firmware be able to discover them both without fine tuning. But it worked like the charm from the start.

Wiring diagram of the Tasmota and Domoticz sensor station with SDS011 air quallity sensor.

Wiring diagram

Wiring diagram
Wiring diagram as simple as it can be

Regarding wiring, SDS011 talks on serial, so RX goes to ESP TX and TX goes to ESP RX. +5 Volt from SDS goes to Vin on ESP with the assumption that you will connect that pin later to the power supply of 5V DC. This sensor working voltage is 4.7 – 5.3 V, so do not connect it to 3 V pin, it is to low and it may affect readings. As always ground goes to ground. BME280 and BH1750 use the I2C bus, so their SCL (Serial Clock) together goes to ESP SCL which is on pin D1, and SDA of both sensors goes to D2 on ESP since it is Serial Data pin. Sensors VCC connects to a 3V pin on ESP. We already know about ground :).

Handling SDS011 while working

Just to mention that it is not a bad idea to cover air inlet and outlet of a sensor while you work around it, especially drilling or grinding, to prevent dirt to pollute sensor. When all rough work is done, remove the covers. Better safe than sorry.

Covered air in and outs of a sensor.

How it fitted together

Since the goal was to make it nonexpensive, and yet durable and to finish it fast, this is what I did regarding assembly. I positioned the Nova SDS011 sensor on one side of the box, put a microcontroller next to it and then made some physical barrier to create a compartment for BME280. The reason I wanted it separated was the intention to remove it from any heat dissipation that the ESP8266 board produces no matter how small it is. That way alteration of the temperature reading would be minimized.

Positioning components inside the box

I made a socket for the ESP development board on the prototype PCB, so it can be removed, or replaced easily without any soldering. After all this sensors unit is a prototype. The micro USB connector on the board is accessible when the box is open in case it is needed. There are markings on board so there will not be the accidental wrong insertion of ESP board.

Socket for ESP development board.
Some in image explanations regarding Tasmota  sensor station with SDS011 air quallity sensor.
Some in image explanations

Installation for test measurements

Tasmota and Domoticz sensor station with SDS011 air quallity sensor.
Sensors device installed just near the roof
Tasmota and Domoticz sensor station with SDS011 air quallity sensor.
Place where I installed device on the house

Well, I had the opportunity to dig in some cables since there is still no facade on the house, and I put a few UTP cables in. I used one for PoE camera, other for sensors device power supply, and since this is the IoT time, I left two more cables to wait for it πŸ™‚ . First, I chose this location thinking, that it is high enough from the ground to prevent dust and some other near ground particles to contaminate sensor readings. Second, it is far enough from the roof to have its heat dissipation mess with the temperature readings. Third, it is enough protected from the rain and both air openings are from the bottom so it should be impossible for rain to get into the device or sensors.


Everything built here is a piece of junk without the software.

Tasmota had been flashed on to the ESP. Tasmota will be sending data from sensors to Domoticz. I will not enter into many explanations here, you can find needed information at those two links. I also uploaded flasher and two needed .bin`s here. Firmware is 7.2.0, and it will be obsolete very soon. I put it for those of you that like shortcuts πŸ™‚ . It will do the job, and later you can upgrade.

Flashing ESP with Tasmota firmware

There are literally tons of information regarding the process out there, but I will put it in very short terms again here. 1. Connect ESP to your computer, figure out what com port is it using and configure Tasmota flasher accordingly. 2. Press taster for entering flashing mode and then press the reset taster on the ESP dev. board. 3. Release the reset taster, and then release the first taster on ESP. 4. Select the tasmota-sensors.bin in flasher and then send it to the device. (tasmota-minimal.bin is needed only if you are doing OTA (over the air) upgrade).

Configure module pins with sensors.

We now need to tell Tasmota, what sensor is connected to which pin on the ESP board. I attached the screenshot of the config and when compared with Wiring diagram it is self-explanatory.

Configure Tasmota module
Configure module for connected sensors

Results from Tasmota and Domoticz

When flashed and configured, here is how Tasmota web interface looks like. You just find its IP address on your dhcp server (it will be showed as sonoff-acb or tasmota-xyz or something like that) and enter that IP address in your browser. It is nice to make a reservation (or static assignment) on dhcp so address stays the same. On that interface you can basically read values from the sensors and configure, backup or upgrade Tasmota.

Tasmota ESP8266 Sensor station
Tasmota ESP8266 Sensor station

This is how the results from Domoticz look like.

But it is not just about reading values that came just now, logging gives the real power…

So, from the PM 2.5 monthly shows some real air quality statistics although my sensors unit is still not operational for a full month. One more thing to remember, this shows pollution in PM2.5 ΞΌg/m3 (raw) and the usual standard is US EPA PM2.5 AQI. That means if you are going to compare it to “Purple Air” you need to convert, or at change units displayed on Purple air (it is on the map). Anyway these raw readings converted to AQI are much higher, so you know what to expect.


I wrote this with a simple intention. That is to show how easy to build and inexpensive this kind of sensors unit can be. I hope it serves as a warning and a manual.

If you find this article interesting maybe you should check on this one regarding fixing a “weather unknown” message. Once again, thank you for reading, and if you have any questions or need help, just post a comment. I’ll get in touch with you asap.


Here is a little update on Jully 2020. , a friend send me a few pics of his “do it fast” sensors station. He even added external Wi-Fi antenna for a better connection range.

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Temp + Hum + Baro virtual sensor
January 26th, 2020 by Chief

This is a Temp+Hum+Baro virtual sensor in Domoticz, or to clarify it is its graphical representation. It sure looks nice but there is one very annoying thing going on here and that would be “Prediction: Unknown”. Later we will deal with this problem after we explain our setup and what is going on in the background.


In this case, I have Domoticz running on my Windows 10 PC with (yes it is not on Raspberry Pi, can you imagine πŸ™‚ ) I have PC running all the time anyway so that is the main reason for Domoticz on PC and regarding that subject, we will stop right now. On the other side is ESP8266 with the Tasmota firmware and Bosch BME280 sensor. For easier understanding we will call ESP and BME together “physical sensor”, and another side that represents and logs data on Domoticz will be called “virtual sensor”.

This “Prediction: Unknown” message is not a big deal, but since the rest of the sensor looks so nice it is a shame not to get it in a perfect state. Therefore, I started with the assumption (and we all know that assumption is the mother of all fuckups) that physical sensor is just feeding the virtual sensor and Domoticz with data and that “Weather prediction” is done on Domoticz by applying some kind of algorithm to gathered pressure data. WRONG!

How it really works

I looked into the DeviceStatus table of the Domoticz DB and under sValue for my device, I found data like this: 3.2;66.3;1;1019.5;5. There are five values in sValue: 3.2 was the temperature at the moment, 66.3 was the humidity, 1 was for “Feels like” , 1019.5 was for pressure, and 5 was value for “Weather forecast”. I Googled a little bit and here is what I found regarding Forecast mapping in Domotiz.

0 – Stable
1 – Clear/Sunny
2 – Cloudy/Rain
3 – Not stable
4 – Thunderstorm
5 – Unknown

“Unknown” explained my problem, but beware, this is not correct mapping. On the other hand, this is the correct one:

0 – No Info
1 – Sunny
2 – Partly Cloudy
3 – Cloudy
4 – Rain
5 – Unknown

Therefore, take care as there is lot of semi truth out there….

As a result, it was logical to see what kind of data is Tasmota sending to Domoticsz so I looked into a Domoticz log, and this was coming: MQTT: Topic: domoticz/in, Message: {“idx”:148,”nvalue”:0,”svalue”:”3.2;66.3;1;1019.5;5″,”Battery”:100,”RSSI”:5} So it matched values in DB, that was concluded, weather forecast data should come from the source. And Tasmota was sending 5, and 5 means unknown. But what to do now?


This matter made me stuck for a few days in a discussion with my colleagues. We were trying to figure out possible solutions. A friend sent me the link to a Domoticz forum where guys published Script To Parse WeatherUnderground Multi-Value Sensor, and that was our base. The script can be found at this address along with some other interesting thoughts.

After that we created device lua script with this code:

  -- + lua / device script
local sensorx = 'ESP Outside' --name of the sensor that  has a problem with weather prediction (Temp+Hum+Baro virtual sensor), you put your sensor name
commandArray = {}

if (devicechanged[sensorx]) then
        WeatherTemp, WeatherHumidity, HumFeelsLike, WeatherPressure, WeatherPressureForecast = otherdevices_svalues[sensorx]:match("([^;]+);([^;]+);([^;]+);([^;]+);([^;]+)")
       WeatherTemp = tonumber(WeatherTemp)
      WeatherHumidity = tonumber(WeatherHumidity)
       HumFeelsLike = tonumber(HumFeelsLike)
        WeatherPressure = tonumber(WeatherPressure) -- hPa
       WeatherPressureForecast = tonumber(WeatherPressureForecast)
         if (WeatherPressure == 0) then
             WeatherPressureForecast = 0
                        elseif (WeatherPressure > 1030) then
          WeatherPressureForecast = 1
        elseif ((WeatherPressure > 1010) and (WeatherPressure <= 1030)) then
        WeatherPressureForecast = 2
      elseif ((WeatherPressure > 990) and (WeatherPressure <= 1010)) then
       WeatherPressureForecast = 3
     elseif ((WeatherPressure > 970) and (WeatherPressure <= 990)) then
     WeatherPressureForecast = 4

0 - No Info
1 - Sunny
2 - Partly Cloudy
3 - Cloudy
4 - Rain
5 - Unknown
 commandArray['UpdateDevice'] = '148|0|' .. WeatherTemp ..';'.. WeatherHumidity ..';'.. HumFeelsLike ..';' .. WeatherPressure.. ';'.. WeatherPressureForecast
 -- 148 is the idx of a virtual sensor that is going to be fixed, in this case it is the idx of the "ESP Outside" virtual sensor. You put your idx number

return commandArray

Comments are already in the code, therefore you should not have any problems adjusting it for your sensors and environment. Above all, do not create Lua / All (commented) script, but Lua/Device script. It may work anyway but as a result, you will have an error in Domoticz log file. I hope this will save you some time πŸ™‚ . The script was up and running after this. I peeked in DB to see, what is going on, and there was “3” smiling out on me from the end of the sValue data. πŸ™‚

ESP8266 + BME280 + Tasmota received data in Domoticz DB

What the script does

We dealt with this problem this way. It can be dealt with in many other ways. The script basically reads all the values from the virtual sensor. Then it puts them in variables. After that, it does some math (comparing may be a more modest word) with pressure and as a result updates, four values of the virtual sensor with the same values and the fifth data field is updated with the number that is calculated based on the pressure. I borrowed that calculation from this article: Article is great, therefore if you like this stuff I recommend it for reading. The script runs every time the virtual sensor gets an update from the Tasmota, and in my case, it is every 5 minutes, in other words, it is not putting any heavy load on the hardware.

I`m not gonna enter into weather prediction algorithm, that is not a subject of this article. This is not a commercial weather station or piece of scientific equipment, it is a homemade system and should be treated like that. On the other hand it should work at least like it supposed to. That was the point.


Domoticz virtual sensor

So if you liked this article may be the one about micro-controllers would be also an interesting one, so if you have some time take a look here. And in the end, thank dr_Kosh for the great contribution regarding this problem.

Once again, thank you for reading,


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