@gunrunnerjohn and other electronics gurus, I need your help!
I would like to build a circuit that "conditions" track power to feed a wireless receiver / decoder that was originally designed for battery RC operation.
Let's assume that I'm putting the typical 18 or 19 volts, 60 Hz unregulated AC into the track, with a current capacity of ~8 amps. For various reasons, there may be places on the layout where the voltage at the rail head drops as low as 16 volts. Also, the voltage on the rails may drop slightly due to load when multiple locomotives, lighted cars, etc., are in operation. My locomotives are powered by DC can motors not drawing more than a few amps (and probably closer to 1 amp most of the time.)
The decoder / receiver i want to use was originally designed for G-scale locomotives, to be fed from a 14.8V Li-ion battery.
I can imagine that I would need a high-current bridge rectifier to change the track AC to DC of the correct polarity. Also, a filter capacitor to smooth out the "ripple" from the sine wave or modified sine wave.
I was warned that this decoder is very fussy. To maintain consistent speeds, it supposedly needs to be fed a tightly regulated DC voltage of perhaps 15V or more. I proposed using a zener diode to limit the excess voltage to this value, but the developer stated that a zener wouldn't work. He didn't offer details as to why it wouldn't work. I don't have any experience with zener diodes, except I've heard that they can be used to "clamp" voltage to a max value.
The developer also stated that a high-current voltage regulator circuit such as I'm proposing might be too large, and that it would get hot. He re-emphasized the point that voltage must not vary with load.
I've never built a circuit like this. I know it would be a good practice to heat-sink the rectifier to a metal surface. But beyond that, I'm not sure what's so complicated. I mean, firstly, how would the decoder "know" whether the DC is coming from a battery, or rectified DC from the track? Also, can you think of any reason why operation would be compromised if the DC voltage fluctuates slightly in the range of 15 to 17 volts?
Thanks in advance for sharing your opinions about this project!