Variable voltage output

Projects General Guidance
1

An output pin can be high or low, but can it be proportianate? i.e. output 1v, 2.5v or 5v depending upon other inputs?
I am wanting to drive a Crydom proportional controller such as http://www.crydom.com/en/Products/Catalog/l_pcv.pdf which has a 0 - 5v input.

2

but can it be proportianate?

Not directly but with PWM and a filter you can get it to be the same, you use analogWrite();
See this page:-
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

3

Thanks Mike, I can follow that.