Zener diode question in simple LED circuit with anti-flicker for model railroad
There are more efficient ways to do this. or there are simpler ways to get a long time constant.



The shared load current is 0.6Vbe/Re=470 = 1.2mA on the emitter. 

Adjust to suit your requirement.

P.S.
There is a risk after ? hundreds hours of use that the LED's go dark using only 100 uA. This is common effect and some MFG's warn against using below ~ 1~2mA currents. It just means the threshold for photoemission has risen above what was used due to an effect caused by such low currents.  Pulsing to 10mA may or may not restore this dim light suitable for N scale realism.  

The other approach is a 0.5% duty cycle pulse @ 200mA (shared) with 20kHz a Schmitt Inverter clock after this current limiter set for same 200mA or R3= approx. 3 Ohms could prevent this with the same low pass filter on supply and same average current.

To cut number of LED's Current must also be reduced with higher Re.

Rev B 12:10 PM