@stan2004 Stan, please accept my apologies for the confusion my attempts at a circuit design and subsequent retraction of those preliminary ideas may have caused. I think your suggestion does accomplish the goal of emulating "the Real McCoy" using 18V track power. Jim also mentioned in his original post the possible option for:
@LIRR-Jim posted:Thank you again .. The question is how does one create a circuit that delivers -4.5v (from either 18v track voltage or a dedicated ~5v power supply) ..
Your suggestion delivers on the 18V power option and your recommendation for the Latching Dual Coil DPDT 5V relay started me thinking that maybe I could combine that relay with my earlier DPDT switch diagram as the foundation for a 5v sourced solution. The further I got into it, the more I realized it wouldn't be as simple (for me) as I'd hoped.
Since John was online this morning (5/6), I reached out to him for his advice on my concept. During the course of that conversation, he suggested using a Boost Converter that would provide +/- 5VDC from a 4.5V source.
@stan2004 posted:I'm not sure where you guys are going?
...and was about to comment on some theoretical issues therein; the circuit has/had a so-called race condition that might lead to its demise but I see the diagrams have vanished.
I'm a bit embarrassed to have overlooked the race condition in my preliminary design in the first place. There might be a way to make that circuit design functional by relocating one small RC circuit each, across the coils, but the point seems moot now...
Since your track power option provides one requested solution and John's fulfills the other ~ 5V option more elegantly than mine would have, even with corrections, I decided to withdraw my suggestion. If you'd like for me to send the revisions on that design to you via email, please contact me via the email address in my profile.
Again, please accept my apologies for my mistake and confusion I may have caused.
Steve
