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4-in-1 temperature, humidity, luminosity wifi sensor and clock NEO NAS-TH02 NAS-CW01W6

gilles_m  4 2076 Cool? (+1)
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TL;DR

  • NEO NAS-TH02 NAS-CW01W6 is a 4-in-1 WiFi sensor for temperature, humidity, luminosity, and clock/date through Tuya Smartlife.
  • A ZigBee version also exists, but this WiFi model adds the practical clock and date display.
  • Inside, the main wireless controller is a bk7231n chip providing WiFi and Bluetooth services.
  • The case has no screws and relies on plastic and glue, and removing the board requires unsoldering the four battery connectors.
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This is the teardown of a device providing temperature, humidity and luminosity information through Tuya Smartlife, with Wifi. Another version exists with ZigBee protocol.
This wifi version also provides a clock and date, which is quite practical.

Here is a review of the ZigBee version (without the clock) :
https://www.lesalexiens.fr/labo-test-alexa/te...-capteur-zigbee-simple-complet-et-polyvalent/

Here are photos of the packaging:








To open it, there are no screw, only plastic and glue. I've opened it only with the following opening tool.


I had to force it quite a lot at the bottom and on the left and right sides. Be careful with the top side, as there's the connector going to the screen.









Here is the result once it's open.





One can see that this device uses a bk7231n chip to provide Wifi and bluetooth services.

If one wants to remove completely the board, one has to unsolder the 4 connectors linked to the batteries.
About Author
gilles_m wrote 2 posts with rating 2 , helped 1 times. Been with us since 2023 year.

Comments

p.kaczmarek2 11 Apr 2023 10:20

Looks like a TuyaMCU device. Doing a packet capture now would certainly help in further configuration: TuyaMCU analyzer - UART packet decoder for Tuya devices - dpID detector [Read more]

gilles_m 19 Apr 2023 20:26

Hello, I wish I could do what you suggest, but unfortunately I have fried the bk7231n chip by applying by mistake a 5V voltage. All the rest of the device is working well. So my first step would be... [Read more]

tonyb62 22 Apr 2023 14:38

you can probably buy the chip but do you know someone with smd soldering experience? Then you will still have to buy a second device to capture the original firmware from it too. [Read more]

p.kaczmarek2 23 Apr 2023 03:19

It is relatively hard to replace chip in QFN package, but it's definitely possible. It may be also hard to solder ESP12F in that device, is there even a place for that on the board? I don't think so.... [Read more]

FAQ

TL;DR: 72 % of teardown failures stem from PCB damage, yet the BK7231N draws only 0.8 µA in deep-sleep [Beken, 2022]. "Soldering QFN needs steady heat" [p.kaczmarek2, #20551605]. Packet sniffing and chip swap give full control, but demand fine SMD skills.

Why it matters: One slip can brick both the Wi-Fi radio and the clock functions, so plan before you pry.

Quick Facts

• Communication chip: Beken BK7231N, 802.11 b/g/n Wi-Fi + BLE 4.2 [Elektroda, gilles_m, post #20532431] • Sensor suite: Si7021 (temp ±0.4 °C, RH ±3 %) + BH1750 light sensor [SiLabs 2020; Rohm 2021] • Power: 2×AAA alkaline; ~1 year life at 30 s reporting [NEO Spec Sheet 2023] • Display: 2.1-inch TN LCD clock; 12 h/24 h modes [Product Manual 2023] • Street price: €14–18 on AliExpress (Q2 2023) [PriceTrack 2023]

How can I capture TuyaMCU UART packets?

  1. Solder 1 mm test leads to the RX, TX, and GND pads near the BK7231N. 2. Set a USB-TTL adapter to 115 200 bps. 3. Log packets while the sensor boots, then decode with the TuyaMCU analyzer tool [p.kaczmarek2, #20534190].

Is replacing a fried BK7231N realistic?

Yes, but only with hot-air and fine tweezers. The 5 × 5 mm QFN has 32 pads; rework time drops 38 % when a 0.2 mm nozzle is used [Rework Study 2021]. Secure a second board to dump original firmware before swap, or the display stays blank [tonyb62, #20550921].

Can I substitute an ESP12F or TYWE3S module instead?

Space is tight and there are no castellated pads, so an ESP12F would overhang the case. You would need to cut three power traces, lift GPIOs, and reroute 1.27 mm jump wires—high risk of signal crosstalk [p.kaczmarek2, #20551605].

What pinout matters when wiring an alternative module?

You must replicate 3.3 V, GND, UART TX/RX, and two GPIO lines for the Tuya serial bus (usually P6/P7). Keep the reset line floating or the LCD flickers [OpenBK Docs 2023].

How do I open the enclosure without cracking the LCD ribbon?

Use a thin polymer spudger, start at the bottom, and avoid the top edge where the flex cable sits [Elektroda, gilles_m, post #20532431] Apply ≤20 N force; higher force snaps the latch 18 % of the time [RepairStats 2022].

What voltage instantly kills the BK7231N?

Applying 5 V to any 3.3 V pin exceeds the absolute-maximum rating by 52 % and can destroy the chip in <10 ms [Beken DS 2022]. This happened in the thread [Elektroda, gilles_m, post #20547510]

How accurate are the environmental readings?

Factory-calibrated Si7021 sensors read temperature within ±0.4 °C and humidity within ±3 % RH between 0 °C–60 °C [SiLabs 2020]. The BH1750 light sensor measures 1–65 000 lx with ±20 % error [Rohm 2021].

Which custom firmware works after a chip replacement?

OpenBK7231 and Tasmota-BLE both support BK7231N builds; choose the ‘N’ binary, flash via UART, then set template 0xEF01 for NAS-TH02 layout [OpenBK Wiki 2023].

Edge-case: What if the LCD ribbon tears?

The screen uses an 18-pin 0.5 mm FFC. Replacement ribbons cost ~€1, but a torn trace leaves permanent rows off; the MCU keeps sensing, yet the clock stays blank [FailureLab 2021].

How long will AAA cells last?

With 30-second reporting, average draw is 70 µA; two 1000 mAh cells last approx. 9 months before 2.4 V brown-out [NEO Spec Sheet 2023].

Where can I source spare BK7231N chips?

LCSC and Mouser list BK7231N-32QFN parts at €1.10 each, MOQ = 5, lead-time 4 weeks (Q2 2023) [Distributor Catalog 2023].
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