Ok, approach I've been using is misguided or going way off track. I'll be looking at your book "Cross Roads", and appreciate your efforts. The intent of the post was not to enter into debate over Learning electronics or having anyone labor because I'm to lazy to do my own research. I feel I learn a lot more doing for myself but just wanted to avoid damages, frustration (delays) in the process.
Attached is a conceptual plan of attack. Each section (LED's, Digital Display, and IR Sensors) has been constructed and bench tested as usable. Additionally, all sections have been in use for a couple years but using a different interface (Phidget). A software program change has prompted the requirement to change the interface to Arduino. Again, I understand the Arduino is a microcontroller, and has capabilities far beyond what I need, one of those properties is it is an interface (required for communication) between the real world and the computer.
Because the examples are BASIC, they use a Uno board, something not suited (but usable) as a single entity. I need to expand on that example because power and quantity of pins dictates it. Thus a Mega (pins) and Sensor Shield (ext. power). Both pieces of hardware have options for using external power sources but cannot find sufficient examples of HOW to combine them or using anything other than the +5 power of the Mega.
I just can't believe a board is designed with 56+ pins but only 3 to 5 are usable at a time because of power limitations, or documented as how to increase that limitation. Furthermore don't understand why this limitation is in place if each section is powered by its own power source for the loadshttps://www.dropbox.com/s/at49i33uhkjnv4z/GantryProject.png?dl=0.