...I was kind of thinking about providing the proper 12VDC voltage off a spare post of one of my 4 PW ZW's and running it through a full wave bridge rectifier... If I do this, and I have all my common posts tied together, I should be able to close a block relay anywhere on the layout once the train enters that block's insulated rail ... Does that seem like a wise way to go, or am I dreaming ?
In concept that's a wise way to go but if I understand how you're planning to do it, you will see the dreaded magic smoke and it won't be because you're dreaming!
The bridge rectifier converts the AC voltage from a train transformer to DC. So far so good. But the "-" output from the bridge rectifier is not equivalent to the common post of the AC signal it came from. And connecting the "-" output of the bridge to the outer-rail common (to implement isolated-rail block detection) will not turn out well.
The DC voltage to needs to come from an isolated power source. It could be a 12V DC output wall-wart. It could be 12 V DC from a bridge rectifier fed by a spare AC output train transformer whose common is NOT physically connected to your main AC transformer common(s).
...Seems like I should still install the 220 uF capacitor on the relay power bus to stop chattering, and I can ensure that I am not putting anything over 12 VDC out to the relays on that bus line.....
Just to be clear, the anti-chatter capacitor needs to be on the relay coil side of the block detection circuit...one capacitor per relay. The 22 ohm (or whatever) resistor is also one per capacitor/relay on the relay side of the block detection circuit. In other words, chatter from intermittent/dirty wheel connections causes the relay coil to receive a choppy voltage. By put the capacitor across the relay coil, it smooths out the voltage keeping the relay closed.
I'm interpreting "relay power bus" as the DC voltage (nominally 12V for your application) created one time so to speak. You create this relay DC voltage once...rather than converting AC to DC for each relay.
