středa 4. března 2015
There is a few things that are still missing - the battery voltage measurement, and I should probably switch off the sensors when Arduino is sleeping to conserve power. The DHT22 draws something like 40uA when idle, which is pretty much a lot of power. Now the question is, how to do that? Using a PNP transistor as a high side switch should work, but I am a bit worried of the voltage drop on it. Of course that would not work at all with CR2032 (that's why I did not add this to the node yet). Another option is to power the sensor from the Arduino digital pin. That should be pretty easy, but again, I am not sure about the voltage. The safest would be to use something like 3.5V for Arduino, which should be fine for all other devices, like the NRF24L01, and still give a plenty of headroom for powering the sensors. Time to do some measurement tomorrow!