Although having separate 24vdc supplies for inputs and outputs may be considered ideal, I have never experienced a problem in using a common supply, Either use a common regulated 24vdc supply or if unregulated, make sure there is sufficient capacitance to keep ripple to a minimum.
If you set up a common ground plate and take the power supply common's and all shields to this common point, then this should take care of noise sensitive devices.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.