From Meh to WOW – With 1 “Tiny” Hack! – YouTube – where the comments mention better ways than this convoluted solution
Posted by jpluimers on 2026/02/03
[Wayback/Archive] From Meh to WOW – With 1 “Tiny” Hack! – YouTube shows an interesting but convoluted solution to solve temperature drift on a cheap Tuya WT410-BH-3A-W thermostat (there are similar models, see below) based on the replacement sensor [Wayback/Archive] WSEN-TIDS Temperature Sensor IC & EV-Kits | Sensors | Würth Elektronik Product Catalog.
Luckily the commenters stepped in and suggest better and easier ways.
On the other hand, the solution is nice to know as it allows plugging in a remote thermostat that sits in a better place to read the temperature while the control bits stay in a place where it is easier to manually adjust.
Chapters:
- 0:00 Thermostat Problem!
- 1:17 Intro
- 1:38 Teardown!
- 2:26 How it Measures Temp?
- 4:00 Possible Problems
- 4:27 My Solution!
- 7:04 Creating a “Hack” PCB
- 8:00 Testing my PCB
- 9:19 Final Test & Verdict
Other parts used:
- DAC: [Wayback/Archive] MCP4725 | Microchip Technology
- Microcontroller: [Wayback/Archive] ATTINY402 | Microchip Technology
The thermostat modified is a Tuya WT410-BH-3A-W, but there are similar models as per these queries – not sure if they all suffer from the same problem and can be solved in the same way (but my guess yes and yes):
- [Wayback/Archive] Tuya WT100-BH-3A-W at DuckDuckGo
- [Wayback/Archive] Tuya WT200-BH-3A-W at DuckDuckGo
- [Wayback/Archive] Tuya WT410-BH-3A-W at DuckDuckGo
- [Wayback/Archive] Tuya WT100-BH-16A-W at DuckDuckGo
First some comments about usefulness of a solution like this:
- This helps me understand how I can use a remote thermometer and feed the temperature data into the thermostat. Thank you!
- This has SOOOO much more potential.
You often see on weather forecasts something like a “Realfeel” temperature which is supposed to be the temperature it feels because of the temperature + humidity effect.
You could program your little microcontroller to input both temperature and humidity and output a “Realfeel” equivalent temperature.
This might fix the problem I have had with ACs that under a specific set of environmental conditions it’s too hot, but lower the set point 1 degree and it becomes too cold. I think this might be from the AC not just cooling but also dehumidifying so under some circumstances it is overdoing the “RealFeel” cooling and always too hot or cold.
Then comments expressing alternatives:
- I might have been tempted to simply substitute a trimmer pot for the fixed 10k divider. But this was way more fun
- Looks like it is WT410 thermostat. I found some manual, where it says that the default temperature compensation temperature is set to -2 degrees and you can change that parameter in a range from -10 to +10 degrees. Also you have NTC contacts for external temperature sensor in the rear unit housing on pins 7-8. But cool project and idea anyways!
…
maybe they are self-heating or get heated from the electrionics in the box, and that’s why they defaulted the setting to -2deg. In this case your project makes a perfect sense, but it’s crazy that they crapped the most important part of the thermostat…- The trick is to install it and let it acclimatise. The power supply does warm up the enclosure a little, and is probably the reason for -2C offset.Also, the underfloor heating might be creating an updraft within the wall cavity /speculation
- I worked for a smart thermostat company and temperature correction was a big problem. The main products were line voltage baseboard thermostats and we had to consider self-heating from the relay across different amperages and the brightness of the LED. The microcontroller didn’t have a temperature feature but I’m sure heat from that also contributed.
- Even though this is kind of crazy and impractical (still love it), it’s smart to use an DAC. Learnt something new for my future projects.
- I would have used the OpenBK firmware (Tasmota like firmware for the Realtek Tuya chips) and install it on the device. After that, you need to add the device configuration for your device and there you can also calibrate your temperature value. An advantage: no need for the cloud service anymore and it integrates directly into Home Assistant.
Btw, I have a similar problem to solve with an old Buderus heating system. The temperature sensor is always off, since it is sitting in direct sunlight, so I would like to use the output of our weather station. Maybe this would be the way to go there, too 🙂- …
In my case, I swap the WBR3 chip with a ESP12F and then run ESPHOME (where it is easy to calibrate the T°C sensor).- I like that engineering has these small details like temperature IC reacting to copper on PCB, it won’t show in any schematics and it’s easy to miss something obvious like that
- I would have swapped that Tuya module for a espressif module, reverse engineered the display pin out/protocol, and grabbed something from my drawer of temp sensors.
- You could put your thermal imaging camera to good use to find which component is producing the most heat (my bet is on the voltage regulator) and add a thick copper wire to its ground pin to “pull” as much heat away from it, maybe dumping it somewhere cooler into the white PCB. At first I thought about the ground pad of U2 but if it runs hotter it would add heat instead of absorb it.
- That’s why my smart home thermostatic valves operate based on data from external smart temperature sensors. The valve in each room operates according to the external smart thermostat value in that room. If a valve in a room activates, the boiler starts operating. Regardless of the temperature on the boiler or valve, they apply the rules based on the data from the external sensor. This way, I achieve more stable room temperatures and optimal gas consumption.
- I would just replace R12 with a poti and simply calibrate the sensor. The slightly none linear NTC does not matter for the small indoor temp differences.
- I managed to get very accurate temperature reading with a TMP117 sensor. We measured it’s accuracy with laboratory grade thermometer and it achieved +- 0.25 deg C accuracy in our tests, close to +- 0.1 deg C as advertised. We employed this to measure/control temperature of a heatbed to perform thermal cycling for PCR (polymerase chain reaction) with very high accuracy.
- did something similar for the heater and outside temp sensor… I have used the DS18B20 and a digital potentiometer with the ESPHome. Works like a charm…
- All my life in HVAC. I noticed that the gap inside the wall was not both isolated and insulated from the inside of your thermostat.
It looks like you had a very big hole in the wall as well.
Even if there is only a tiny little hole big enough to bring the wire up into the back of the thermostat it’s still a smart play to seal that little hole (at the least with a piece of adhesive tape) to keep the unconditioned air out of the wall from travelling out of the wall cavity via the inside of the thermostat and then over your thermostat sensor bulb, stopping your thermostat registering the room temperature. In some cases that internal wall space can be slightly pressurised due to the wall cavity opening above or below the conditioned space or even outside the building, making the problem worse. At the very least I would seal the gap around the sensor bulb and the housing so that inside the wall Air is not able to exfil the wall via any path related to the sensor bulb.- The WiFi chip used on this board (WBR3) is supported by ESPHome as far as I’m aware.So you could’ve also just flashed ESPHome onto it & added the I2C temperature sensor directly.You’d also be able to make it fully local that way.
Pretty sure that with your current config, it’ll just drop out from Home Assistant if you lose your internet connection…
--jeroen
[Wayback/Archive] From Meh to WOW – With 1 “Tiny” Hack! – YouTube
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