ESP8266 Community Forum

- Fri Oct 14, 2016 1:14 pm #56522

Hi,
the analog pin would read ~1/3rd (per voltage divider R2/R3, resulting from the fact that range of analog pin is only 0..1V) of the voltage that results from the voltage divider R6/Rx (R7 or R8 or R9) whichever pushed (sideffects from R1, R1+R2 beeing parallel to Rx) and internal resistance of analog pin neglected).

so expect to read something like (3300*Rx/(1+Rx))*100/320 mV

You should expect if you do the maths and calculations in detail, regardless of high input impedance of the A>D converter the following results are obtained:

Sw1 Pressed: 820 mV A>D input @ 682 uA
Sw2 Pressed: 793 mV A>D input @ 777 uA
Sw3 Pressed: 756 mV A>D input @ 905 uA

Therefore this is a pretty awesome design in that the worst case less than 1 mA of total circuit current is drawn from my circuit provided on a button press.

@schufti please feel free to provide a better circuit solution that meets my specification as iterated above, must have 3 buttons and also control CH_PD at the same time.

Good luck

Dans

- Fri Oct 14, 2016 2:14 pm #56527 It's perfectly fine and serves its purpose if several buttons are needed ... there was no criticism intended from my side, just wanted to show different solution for the OP's setup (if you refer to my post on page 1).

- Fri Oct 21, 2016 10:21 am #56902 Just wanted to follow up here and say that I managed to get everything breadboard up and working properly.

I did have one question: I ended up using a 1k resistor, 2k resistor, and 3.3k resistor for the "button" resistors - I did this MAINLY because I didn't have the other resistor values at home to use. I'm guessing though that Dans used the values he did for a good reason, and I'm wondering if there might be something I'm missing?

Again, thanks for taking the time to help with this, I really appreciate it. Also, for what it's worth, I now understand the voltage divider setup and feel generally much more comfortable with the circuit. Again, thank you!