One of my hopes for the garden railroad is to be able to build some of my own electronics for it. Whether some off-track movement or lights, or a piece of automation that helps manage the trains. It would be very useful to be able to control the automation from the DCC throttle. So there is my starting point: build an Arduino system that listens to DCC and does something with the signal.  After some searching on line I found several options and settled on the basic design from  Dave Bodnar at Train Electronics . One of the components needed is an optocoupler. I wasn't familiar with this so did some reading and turns out, this is a pretty ingenious little device. It provides a way to have signals pass from a high voltage part of a circuit (for me DCC running at about 15-18V) to a low voltage part (the Arduino at 3.3 or 5V) while having them electrically isolated. The incoming signal get converted to light (hence to opto-) which is picked up by a photodetector and sent ba...