My hat goes off to Stan2004 for his clever solution to the automated siding request. The 555 IC timer is a great device and as a EE, I am blown away by how many applications that chip can handle. Again, my congrats to Stan. Now, for a 2nd offering.
I devised a circuit (attached) which accomplishes essentially the same task. It uses eight components (Stan used 15). The track setup is the same, an isolated center rail siding and an isolated center rail section between two switches. Two magnetic sensors are alongside each track section and are triggered by a magnet mounted on the train loco or one of the cars. The isolated track sections can be any length depending on available layout size. The benefit to my approach is that it is simpler and perhaps easier to implement for a model railroader. I calculated the total cost of the parts to be around $42.00 (the latching relay cost $5.20). Also, the DPDT relay provides two sets of double throw contacts which might be necessary with some switches and can be useful for other signalling capabilities.
