I'm looking for Guidance to design a system operated from a touch screen to operate let's say an air conditioner with buttons foe temp, fan speed and mode. Can an Ardunio board do this by itself or is a special module needed from the appliance to send info to the Ardunio board. Also has anyone done this and what components did they use. If you are familiar with this type of project I am willing to pay for your expertise.
Quite certainly an Arduino can do this, and quite likely you need some extra hardware to communicate with your AC.
If the screen has to look pretty with slider controls and similar widgets, look at a Nextion display. If not, an SPI screen should do (and would leave some Arduino pins free for other purposes ).
An air conditioner usually has a IR interface/controller which can generally be emulated by an Arduino.
This sounds like a standard domestic thermostat, albeit with a touch screen. You could certainly do it with an Arduino but I wouldn't be surprised if such a thing already exists. Is there more to it?