Yes, all my engines are conventional. I included the 22uH thinking about its possible use in the future.
Flat out my ZW produces about 21V, which would deliver about 28VDC max after the bridge. I never run that high or the engines would fly off the tracks on curves. I used the 3300uF as a "flicker eliminator" before adding the super capacitor. That alone carries the LED strip load for about 1/4 second.
But if I build more I would use a 35V capacitor, which is what is now in the schematic. A 2200uF is the same physical size, and the 1000uF 35V that I have a bunch of are smaller.
I thought a bit more about the trade off between the switching regulator versus a simple series pass. One significant advantage of the switching regulator is to reduce current draw. While a series pass would only dissipate about a watt under normal conditions (12VAC and 100mA to the LEDs), its current draw and dissipation when initially charging the super capacitor can be significant. Of course that could be reduced by increasing the series resistance, but that also extends the recovery time after passing through a dead block.
Thermal resistance of a LM317 TO220 is 50C per watt to ambient, so a heat sink would be required to handle the dissipation at higher transformer voltages. Since the emitter follower only drops about a volt, its dissipation is around 100mW.
