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