Previously Karl had posted a neat little PCB for electrocouplers with the Blunami. I made a shrink version of that, but I was still somewhat concerned about the common ground from the track power and the Blunami DC common.
Concern got the better of me and I created a version that eliminates any possibility of a grounding issue and also increased the power handling capability. This version handles up to 5 amps of power, so it can be used for smoke, electrocouplers, or most anything you might want to drive from a function output of the Blunami board. It requires a DC input from around 10V to 18V to trigger the relay. That can be reduced to around 8V DC if you simply jumper out the 470 ohm resistor, that component is there to allow 18V function inputs without over-driving the 12V relay coil.
The electrocoupler output also has a TVS protection diode to clamp any power spikes from the EC being de-energized that could cause issues with sensitive electronics. A reverse polarity diode is provided across the relay coil to prevent any voltage spikes from that coil feeding back into the Blunami board.
---EDIT---
Given the expanded functions possible with this board, I've renamed it as a more universal solution. It can actually switch any power source based on the function output, so I am calling it a Function Buffer. I also had a small error in the footprint of a component, so I needed new boards anyway.
