Hello. I've got a question about DHT11 sensor. Why should pullup resistor be connected as on the image below:
while as far as I know, pullup resistor should be placed between Arduino 5V pin and Vcc of sensor as shown here:
PS: I know that there is a wrong icon of DHT11, but I couldn't find a correct one.
You require a pullup resistor between the data wire and VCC because the DHT11 uses a bidirectional communication system on a single wire. When neither end is communicating both ends of the link will be in "high impedance" mode - i.e., input mode. In that case the signal will be "floating" and needs the pullup to keep it in a known state.
When actively communicating the outputs switch to "open drain" mode to allow then to pull the signal low against the pull of the pullup resistor.
A resistor in series with the Arduino's 5V and the VCC of the DHT11 is not a pullup resistor. It is not an arrangement that you would ever want, since it would make the voltage to the DHT11 unstable.
