I need 40 analog pins in one Arduino.

Now I have an project about Control 40 photoresistances at the same time in one Arduino.
And then send the serial message to a PC.
And then PC do something with the recived data.

But one arduino only have 6 analog pins.

please tell me how can do with it.

thanks for your time.

Three options that come to mind:

  1. Analog multiplexer (which is basically the same as what's in the Uno because it only has 1 ADC)

  2. External ADC's

  3. Combination of both