Help getting started

I studied some electronics at uni 25 years ago so have some theoretical knowledge but almost zero practical. I want to buy/build a micro processor based circuit to monitor input lines and to then control output lines also using micro processor clock.
Essentially based on clock e.g. every 15 minutes set output(1) & wait for inputs(1) & (2) and then set output (2) etc.

Basically clock / event driven to control relays / pneumatic cylinders.

I need to find suitable equipment. Am looking at Modtronix SCB with ethernet, like SBC65EC but this is web based access which is more complex than I want at the start. Nor do I want a computer connected full time to device although I don't mind connecting a cable from computer to device to update micro code. .......Any help appreciated as I really don't know what I am doing. I see lots of books reduced for sale because they are old and I fear the components may no longer be available
Trevv.

This is the 21st century, micro-processors are so last century!

You have a trivial project, a simple and cheap micro-controller is all you need - everything in a single small chip - and performance you wouldn't believe!. Top favourites are PIC and AVR.

I recently made a similar timing circuit which can adjust the timing 1 -15 minutes that is output ON time & also it supports adjustable 0-15 seconds OFF time.

Displays from the three digits & shows remaining time as well. Having only two buttons to control.Internal Timers used.

All the work did with a 18 pin Micro.See how compact is.

you need to familiar with micros.

All the best