ITAD and Multiple Devices

Yes I have done this before.  Just hook each up as instructed and you will be good to go. I had two PW block signals hooked up to the same device and there was no problem.

The ITAD can trigger both...but I don't think it will reliably detect a passing human a few feet away.   I suppose if you mount the ITAD at the edge of the layout aiming outward at your guests, some percentage will trigger the ITAD particularly if wearing light-colored clothing.

If you have time/interest in the DIY approach, I was thinking about Lego-like approach with, say, 3 low-cost (a few bucks each) modules from eBay.  For example,

(1) motion detector module

(2) power supply module to convert 14V (or whatever) Accessory AC to a suitable DC voltage

(3) timer-relay module to operate the accessories with the same time-delay function that an ITAD provides

The latter two modules come up over and over on OGR.  It's the occupancy/motion sensor that is the trick in this case.

You may remember from a few years back Travis the Trout singing/flapping fish

It used a 5 cent photocell to detect changes in brightness to trigger the action when someone passed by.  It did not work in the dark though.  The point being if you narrow the requirements to guarantee ambient lighting, then you can use additional sensing methods.  For example, there are low-cost eBay light sensor modules - essentially a nite-lite - to activate something when the sun goes down.  So a guest who walks up to the layout would likely block ambient room light from hitting the sensor which could then trigger the time-delay relay module.

Thanks guys for the input.  Always appreciate the responses

Stan, on the motion detectors, is the 'Radar' detector superior to the infrared one? Also, I didn't see any connections for other device control on the radar detector? Just curious and trying to learn a bit here.  And, Travis Trout must be cousin to Billy Bass.  

I think there was Larry the Lobster too - and maybe others?

Anyway I haven't messed with the microwave detector and I guess calling one better than the other depends on what's important for the application.   Here's a more bare version for less than $1 shipped. 

If you search on the model number there are youtube videos and other hacker/DIY write-ups.  It appears you power it with 3.3V DC.  Of course there would be homework to draw up exactly how power this from a typical O-gauge power sources (14V Accessory AC) and then to drive a relay module to control multi-amp Accessories.

This module's lot in life seems to be as an implant in a wall light switch. 

The so-called PIR motion detectors sense the heat from the human body against the background/ambient temperature.  So, for example, this technology might not be so good for train occupancy detection of a caboose or unpowered room-temperature rolling stock. 

Some technologies depend on motion as opposed to simple occupancy.  In electronics, it is generally easier to detect changes or variations in an electrical parameter vs. detecting the absolute level being above/below some calibrated threshold.  I'm thinking a microwave system might be better easier to hide/disguise behind an optically opaque barrier like a thin piece of wood.

Thanks Stan, I will check out the youtube videos. I might just order a couple of each to add to the 'stuff to lay with' pile I already have. This stuff is so cheap, much less than buying more trains and just as fun...I just can't resist! There are so many of these things I can't keep up!   If you would like to have me check anything on these things, I would be happy to.

A little different maybe (not a fish), but there is also a Squakers McCaw. My daughter has an African Gray parrot (live one) and we got her a 'Squakers McCaw' as sort of a gag gift a few years ago. The real parrot threw a fit when he saw Squakers. The real parrot growls when he gets mad! She had to move Squakers out of his room.