Quiescent Current Analog Input ESP8266

Question

I'm planning an ESP8266 project, where I connect a soil moisture sensor to an ESP8266 chip (only the chip, not a board like the NodeMCU) (Analog Input). Since the whole setup will be battery-powered, I'm trying to minimize the quiescent current as much as possible. Now my question is: is there a quiescent current through the analog input pin of the ESP8266? and if yes, how large is this current approximately?

Thanks in advance

• Seamus: If your moisture sensor uses dc, consider watching this video: youtube.com/watch?v=udmJyncDvw0

Answer 1

That depends on if you're using a NodeMCU or a "naked" ESP8266.

The NodeMCU has a fixed voltage divider with 220K/100K resistors to ground, contributing about 10 µA to quiescent current (plus the much smaller current caused by the ADC input impedance).

If you're using a NodeMCU you also have to worry about the USB-to-Serial chip and the on-board voltage stabilizer.

The input impedance of the ADC input of a "naked" ESP8266 is (probably) a lot higher, 1 or more MΩ, although it is almost impossible to find definitive numbers.

• MarayJay: Thanks for your answer. I was also looking for definitive numbers, but couldn't find any. I'm currently switching from the NodeMCU to the naked ESP8266, so your answer fits perfectly :) However if anyone finds out the definitive numbers, please post them here :)