Swimming pool Temperature - WiFi

After looking at the thread about the 433 MHz pool solution i wanted to make one with WiFi instead with an Fibaro sensor.

Sonoff was a good option to make one myself using the following parts.

Sonoff TH10

Sonoff DS18B20 Waterdichte Temperatuursensor

USB Serial adapter for flashing with Tasmota and powering the device (only usb power. You can also use the mains)

I’m not the smartest when it comes to flashing devices or soldering parts together but even for me it was very easy to make this happen. I will explain the steps i took later.

Because i am using the TH10 it would be possible to even connect a pool light or something to the device and control this through Homey.

I will update this with a few photo’s later this week.

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This is the temporary solution.
The powerbank supplies the serial adapter wich is connected to the TH10 by 3,3 v.

Later today this will be put in a closed box that will hang outside the pool.

Here is the end result.

If anyone has tips how to improve it or make it better against moisture. Let me know!
Now I have an moisture pad inside it and drilled a little hole in the bottom.

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Hello Maurits,

your setup looks great to me.
I like to build it too.

Can you please explain how to build the hardware and how to programme it ?

Also how to activate it in the Homey I like to know.

Can you please share some more information ?


The hardware I used is mentioned above.

The steps are from the Tasmota wiki.

1) Connect the wires from the USB Serial adapter to the TH10

Placement of pins may vary. Important to swap the RX and TX cables.

2) Check your serial-to-USB adapter so it supplies 3.3V power instead of 5V
There is a black clip that you can lift and place over 1 pin where it says 3v

3) Flash the chip with NodeMCU PyFlasher
I downloaded the latest version from here

4) Configure the wifi settings

5) Install MQTT on Homey and set it up

6) Configure MQTT on the Sonoff device

7) Configure the module that it is an TH device and assign the sensor

8) Add to homey as an new device

This is a short explanation you can find a lot on the Wiki and in this Topic

What about the power? How long will it last on that powerbank? (And how many mAh is it?)

The serial adapter is powered with a powerbank with 10.000 mAh.
It was at 50% on 25th of june when i started. This morning it was still at 50%.

I am now waiting it to drain so i can estimate how far 10.000 mAh will get me.

You can always choose to disconnect the serial adapter and use the 220 v option. And even connect a lamp to the other connector.

hi there, i just ordered a xiaomi flora 4in1 sensor for 7 euros and will put it into the swimmer in the pool or did i missed something?

looks nice

Looking at the device, the temperature sensor is located in the part that stays above the soil (the white part in the image below), which would mean that you’d be measuring air temperature and not water temperature.

Upgraded the pool temperature sensor. No I can use the Sonoff functionality to also turn on and off the pool lights.


A more or less ready-to-use alternative could be the temperature sensor from BleBox, of course without controlling lights.


is t connected with homey?

A different setup with similar Sonoff (Th16) connected to Homey through @robertklep App with Tasmota (here using standard Sonoff waterproof case); Great to automate filtration and prevent from icing)

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For those interested, it is easy to perform the shown modification on the case not using initial holes but 1- sealing them and 2- drilling, placing new holes where it best fits.
Especially to get the sensor connector centered with the hole and easier access for the electricity connection. Without doing this, I would admit, the case is difficult to use …