ESP8266 Community Forum

- Thu May 12, 2016 7:47 am #47352 I'd like to run 2 photocells on my NodeMCU 1.0.
Would it be possible to run them both into AO, and then use NPN resistors on each photocell to select which sensor is active?

Please forgive my abysmal diagram.

- Thu May 12, 2016 7:59 am #47353 The photocells are always in parallel in your circuit so no.

David

- Thu May 12, 2016 8:08 am #47354 I thought that I'd be able to shut down a photocell using a NPN resistor, so only one would be read by AO.
I'm a complete noob at electronics. (Can you tell)
Is it possible to do it with NPN resistors? Or am I thinking about this the wrong way?

- Thu May 12, 2016 8:24 am #47355 You need to select the voltage at the junction of the photocell and resistor. As you have it the photocells are in parallel and you are switching the resistor to ground. Have a look at Analogue Multiplexers. this might help http://playground.arduino.cc/Learning/4051.

David