SparkFun Forums

[hsadeghilam]

Which pins on ESP8266 can be used as analogPin to do analogRead? I connected wires with 20 mA current to pins 4 and 0 and my board became very hot!

[paulvha]

You do NOT provide current, you provide voltage. On an ESP8266 thing that should be max 1V on the A0/ADC. The current is based on the voltage divided by the internal + external resistance.

[hsadeghilam]

So one wire goes to ADC and the other one to GND? How I can find the value of internal+external resistance? When I measure the voltage of my wires its about 25 V. How can I reduced it to 1 V?

[paulvha]

Indeed input to the ADC and the other to GND. If we you have max 25V make a voltage divider: take 2 resistors serial: 1K (connect to GND, ADC and resistor 2), the other resistor2 :24K connected the 1K, ADC and the power source (25V). That way the maximum voltage is 1V to the ADC.

[hsadeghilam]

I just tried it and surprisingly I figured out my sensor spits out a variable current (at a constant voltage), so reading voltage does not work for me. Any suggestion on how I can read current?

[n1ist]

Pass the current through a resistor and measure the voltage across it
/mike

[hsadeghilam]

Thanks! It worked fine