How To Modify Model Train Controller?

[dr pepper]

Its been so long since you started the post I've forgotten what the aim was, but your right there will be a V drop across the const current source, and that will affect the minimum o/p voltagem dont forget though if your using a darlington it will drop 1.2V itself, so your 2V becomes 0.8v, and you could always bodge this a little putting a diode in series with the o/p dropping it another 0.6V and protecting the transistor.

The ad654 looks like an interesting device, never used one of those.
Heres a link to a calc for the 4046 vco if you need another option, one benefit is it has a programmable minimum frequency:
https://www.changpuak.ch/electronics/calc_03.php

 

[muso52]

Hi dr,
I'm pretty ok with the dc voltage controller aspect of this project thanks to the like's of yourself and others so can I invite you to look at a new thread I hope to write later today with respect to very low frequency voltage to freq. convertor?
The plot thickens but I hope you will consider it of interest as it unfolds!
Willy

 

[dr pepper]

Yup certainly will, progress is interesting.