currently track occupation on model railways tend to use either IR sensors/reed switches at entry/exit points or current sensors on the traction current.
anyone else tried multiplexing AC & DC down the tracks and using analoge filters to seperate them DC for the motor and AC for the track circuits.
drop a filter on a coach and the AC can be dragged out to power vehicle lights (always on no matter if vehicle has traction power) or just a 'load'.
AC flows then there is 'something' in the section.
possibly complex but can detect stationary objects
wondering if anyone else has tried this before i fry something.
all comes from something i was asked to look at a while back (being sort of technically adept, well i've not killed myself or destroyed more than 50k worth of stuff in one go yet).. how to detect the state (occupied or otherwise) of a hidden loop, and stop a train once its clear of the points.
from small things... i tend to adopt an 'engineering solution' i.e. go overboard, don't care its fun.
just need some circuit layout software for the mac...
Another trick is to split the loop into two sections. The end section is very short. Energise the main section but cut the power to the end section. The engine will then stop automatically!
Detection could be optical, but you could also feed a small voltage to the end section? Not enough to power the motor, but enough to detect the current drain when it is occupied.
low current, not enough to actually move stuff has been considered, my problem is a recent carrer working for the rail industry... i'm playing with track circuits, well because i can i guess. though i dare say i'll blow something up.
optical works, but requires things to be in a 'known' state, or the sensors to be carefully located. i guess it depends exactly what your after.
i'm trying to get more than one unit looping on the same oval at once without hitting each other... some sort of block detection is a requirement for that.
the other thing i'm trying to do is piggy back vehicle lighting etc, with the AC will drive since its always live.
That would solve your lighting!
Or you could use normal DC and a "supercapacitor" (ie. a high farad low voltage capacitor).
I run my Union Pacific train (N scale) with a FRED (Flashing Red Emergency Device). Off the shelf circuit with a SM LED and "supercapacitor" (only about 5mm dia). This will keep flashing for a few minutes after power has been removed. DCC in my case, but the concept works with DC as well.
I think I read somewhere that the next generation DCC would include 2-way DCC communication.
Another idea: Use induction loops. These would pick up the engines but not the coaches/wagons.
