Cheap termo sensors

Hello. I would like to start developing heating control via HA. Now I look for some cheap and reliable termo sensor technology. Maybe onewire sensors with arduino could be OK. Does anybody has some idea? Sonoff measures only max 55C. I would like to have it wireless but it should be some stable technology like RF.

Search for ESP (wifi) with DHT22 (temperature and humidity) projects. There are lots. Look for one that has MQTT to talk to HA.

Here’s a few:

I use Wemos Mini D1 flashed with Tasmota and as a sensor I use DHT11. The setup works over WiFi and powered by 5V micro USB (any powered USB will do). About $7 for both parts together on eBay. I have 2 of them setup so far and quite reliable so far.

The limit on the reading is 60 degrees C on DHT11, On DHT22 you get -40 to 80°C which is also supported by Wemos D1 and Tasmota roughly the same price as the DHT22.

Other options for cheap temperature sensors include:

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I need to measure hot water temperature in boiler and heating system. So better would be to use (RTD) PT100 or DS18B20. But It needs arduino for every sensor. I need to measure temperature with 8 snesors and some of thme ar as far as 20 meter from central point. So some of them sohould be wirelles and some wired…

Any idea for a cheap solution?


I just build a dual temperature sensor for my oven with a esp8266(nodemcu) + BCM6675 + termocouple type K (which is rated to measure 1 to 1000C). Flashed the 8266 with esphomelib and it’s working like a charm. I also have half dozen of xiaomi sensors and they are nice too (including 2 inside my refrigerator).

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Hi @clyra,

are you talking about these?

Do they work without a Xiaomi gateway, i.e. with this?

I’d like to get a few battery-operated temp sensors, but don’t want to add another gateway to my setup.

Thanks @clyra but BCM6675 Google doesn´t knows.


My bad… I should never trust my memory! I got these:

MAX6675, not BCM… And this is the esphomelib instructions:

Hi @chairstacker

Yes. I use those sensors. There’s another one, which is round and cheaper but doesnt do pressure. You can use them with the zibee2mqtt, but I found that the xiaomi gateway is useful as it has a speaker (so you use it to play ringtones or pre-record messages) and a color light (which I use as a kind of alert light).

Hmm - sounds interesting after all.
Can you only play pre-recorded messages, I assume these are files stored somewhere (on then gateway?), or can you use them for TTS as well?
And how easy is it to trigger it from HA?

I’ve used the DS18B20 which specs show -55°C to +125°C and using appdaemon as the method to read and manipulate the data. I’ve got 3 of the sensors on the one wire and the furthest 10 meters away using cheap speaker wire.
From the hardware side used, a logic level converter to drive the sensors at 5V.

Unfortunately it can’t do TTS. It has a number of default ring tones and you can record new ones using the xiaomi app. After that there’s a little work to found the ID of those new tones. Play a tone is as simple as that:

- service: xiaomi_aqara.play_ringtone
               ringtone_id: 12
               gw_sid: <gw_mac>
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Nice solution @clyra but what to do if I need multiple sensors .Lets say 3. As I can see I can connect only single to raspberry pi with HA - correct?

Please could you be more specific about HW and connections you use? Do you use DS9490? Thank you.

Hi @Jiran,

Right now I have a dual sensor made with a pair of those MAX6675 connected on a ESP8266 (nodemcu). Using a raspberry for just the sensors is overkill IMHO. You can have as many 8266 as you want, because they use MQTT. How many sensors per raspberry or ESP8266 is limited by the number of GPIOs pins you can use on that device.

Nice wiring diagram here:

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I really can’t recommend esphomeyaml highly enough. So simple to create wireless sensors if you are already familiar with yaml. Current device list (updated regularly):

Simple how-to guide:

Wow esphomeyaml looks great! I’ve been writing custom micropython scripts for my esp’s this looks a lot simpler.

Yeah it’s a fantastic project.