0

In the AM2302 datasheet at page 3, table 4, it gives min, typ and max values for Rpu (that the pull-up resistor as it says verbatim) being 30K, 45K and 60K ohm respectively.

Elsewhere in the same table it gives figures for Rp (no u) < 25K ohm.

What is the difference between Rpu and Rp here, and how should the two rows be interpreted?

Tom Hale
  • 431
  • 6
  • 19

1 Answers1

2

The datasheet is as inaccurate as the sensor itself and it is even worse than you think!

In that datasheet is also written: "usually require an external about 5.1kΩ pull-up resistor".

In the datasheet is also mentioned that the output signal can go up to 8 mA for a high output and minimal 10 µA low output. The 10 µA means that the pullup resistor should be 500k or more. That is not correct.

In this datasheet is a picture with 1k.
In this Chinese datasheet is a picture with 5k.
I ran that Chinese datasheet through Google Translate, but that did not help.

Conclusion: The datasheet is not reliable.

You can do as everyone else: use a 10k resistor for short wires, and try 4k7 for longer wires.

That is not the only problem. Some DHT libraries create a shortcut on the data signal.

The AM3202 is not accurate for measuring the humidity. If you want to avoid trouble, then use a better sensor.
A sensor from Bosch is a good choice (for example the BME280 or BME680). Bosch makes datasheets that are reliable. Those sensors from Bosch operate at 3.3V, if you are going to connect that to a 5V Arduino board, then you need level shifters for the signals.

Jot
  • 3,276
  • 1
  • 14
  • 21