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I have used the AHT10 before, I liked it, it worked well. After that I bought new a AHT10 but it is not working with my Arduino. I am using this library.

I checked closly, and there is only one small difference. The old board (the working one) has a 702 N (datasheet.) The new one has a K27 and not working (datasheet).

I am using these pins with an Arduino Nano:

VIN ----> 5v

GND ----> GND

SDA ----> A4

SCL ----> A5

When I use the new AHT10, the Arduino stops working. There is no printing on the serial monitor. If I remove the AHT10 from the board it starts repeatedly printing this error:

AHT10 not connected or fail to load calibration coefficient

If I plug-in again the new AHT10, it stops to printing to the serial monitor and the Arduino does not work. If I remove the new AHT10 from board and plugin the old AHT10 it starts to work again. The old AHT10 starts to meausuring temperature and humidity.

What I sould I do? How can use this new AHT10?

enter image description here

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    \$\begingroup\$ I wonder if it has nothing to do with the 2N7002 FET. I don't know if it is simply a visual effect or something else, but is the top-left pad of the 10k resistor net missing solder? \$\endgroup\$
    – Justme
    Dec 16 '20 at 20:14
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Looks 4x10k resistor soldered bad. try to clean all the board and re-solder pins

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A part marked K27 can also be a dual NPN BJT with a similar pinout.

I doubt that's the issue. If the MOSFET is used as a level shifter it's connected directly to the I/O lines and may be subject to damage from ESD. Also check out that top left pin on the resistor network for proper soldering. It's possible it's not soldered or that there is a hairline crack in the thin solder that allows it to pass final test but not work after it is corroded a bit.

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I had an almost identical problem with an AHT10 sensor bought on Aliexpress.I solved it by powering the sensor in 3V and using a 3 / 5V converter on the SDA and SCL ports

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  • \$\begingroup\$ may be you are right but seller bought back this sensor and they said sorry about that. I guess everyone had this problem \$\endgroup\$
    – mehmet
    Jan 18 at 8:45
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If you check the datasheet you will see that the AHT10 has a maximum input voltage of 3.8V with 3.3V being recommended. Other versions of this sensor (e.g., AHT20) allows for a higher input voltage. Thus, the question is not why the newer version doesn't work, but why the older version does.

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