Hi everyone,
I wanna build a little data logger for Humidity and Temperature using DHT22/AM2302 sensor and SD Card module.
I have seen some schemas connecting directly ground, 5v and data (digital port 2) to Arduino and other schemas using a pull-up resistor between data and vcc.
What's the difference?
Many thanks
It requires a pull-up resistor.
You can use the internal pull-up (that's why you sometimes see circuits without external pull-up resistor) but it's pretty weak, better to use a stronger pull-up (10k is a good value for this).
I just put an ohm-meter to five AOSONG AMS2302 DHT22 devices, between VCC and DATA and am reading a surprisingly consistent 4.7K-ohms. And I stickem on an Arduino Uno R3 and an ESP-12E (MakerFocus) and works great, so far! No more monkeying around with pullup resistors!
I suspect AOSONG must've got enough complaints from people to add the bugger internally??
You probably have one of the versions with small PCB attached (so three pins instead of the four the sensor itself comes with), which will then also have this pull-up resistor in place.