Motion sensors with PCF8575 [solved]

I have this project where I need to monitor like 50 sensors or so, most of them are motion sensors, but there are also some other types of sensors (temperature, light,...)
Is it possible to read multiple sensors using an Arduino UNO with an PCF8575 bus expander?

Thank you!

Are they all I2C sensors?
Then most likely yes.
If not, then no.

No, they are not I2C
Something like

Should I look for something like PCF8591?

What other options do I have?

I've been doing some research and it looks like you can extend your arduino ADC ports using chips like PCF8591 (which is a 8 bit A/D D/A converter) through I2C interface or MCP3008 (10 bit ADC) with SPI interface.

I have found a great tutorial here

Thank you guys and good luck with your projects!