You can also check my website:

http://ssandifer.com/Lay/Howard/Const/LEDMarker/Index.htm

I used Jim's flicker free design.

Here is what Jim Hinds (Richmond Controls) has to say in response.

Actually, Richmond Controls targets the MODEL RAILROAD MARKET.    ALL   Richmond Controls circuits are designed to work with ANY form of model railroad power.  DC or DCC, it doesn't matter.  I can't believe that ANYONE would design a circuit of this type that can only work with either DC or DCC --- it's just voltage.

Actually, DC power is much, much more of a problem to Richmond Controls circuits than DCC is.  Older DC power packs have been observed to put out 28 V peaks when lightly loaded.  That quickly kills the 16 V rated capacitor in many Richmond Controls circuits.  On the other hand, most boosters put out 12 V square waves for N Scale or 15 V square waves for HO scale, and these peak voltages are well below the rated input voltage.  I've seen a Digitrax booster with an O Scale setting to make it put out a 20 V square wave.  If you know that you have to survive 20 V, the simple solution is to use a capacitor with a higher voltage rating.  Richmond Controls has two modules (EZ08 and EZ09) designed just for this purpose.  But it would waste too much performance capability to simply use a 25 V capacitor in everything.  And that wouldn't prevent problems when 28 V peaks are coming along.

Some Richmond Controls modules have an input voltage limit of 16 V, which is above the track voltage seen with the more popular boosters.  The reason for this limit is that the input filter capacitor specifications require a compromise between voltage and capacitance.  I typically use a wonderful 150 microfarad capacitor rated at 16 V.  The next available option is 47 microfarads at 25 V.  In my experience, the high capacitance is more useful than another 9 volts of voltage rating that isn't really used.  When a tantalum capacitor is taken a volt or two above its voltage rating, it typically forms an internal short circuit.  This is actually very handy in a Richmond Controls circuit.  The short allows excessive current through the input diode, which then quickly open-circuits internally, acting as a fuse.  This protects the more sensitive and expensive components downstream of the capacitor, and it is really easy for me to replace the capacitor and diode (which I do for free).

But for systems applying more than 16 V on the rails, there are easy solutions if the user is aware what voltage he or she actually has.

One thing that very few people realize is that ALL DC permanent magnet motors have arcing between the motor brushes and the commutator.  When the motor is turning due to applied power, you can look in there and see it.  And you will notice that it becomes much brighter as the voltage is increased.  This arcing causes microscopic burning and pitting of the commutator.

The higher the voltage, the more serious the burning caused by this arcing becomes.  Having a pulse-width modulated input power source, like DCC or Aristocraft DC,  doesn't help much --- the voltage during the pulse is the PEAK voltage.  If anyone asked my advice, I'd strongly encourage them the steer clear of any system, DC or DCC, that puts more than 15 V   PEAK   on the rails.  This is why many well-informed HO Scalers use the N Scale (12 V) setting on their booster when the booster gives them that option.

Any supercap circuit can be used with any load, either LEDs or lamps or something else.  But the design problem is a combination of charging the supercap quickly without tripping out a booster, and then drawing current from the supercap through its appreciable internal resistance while expecting to have much voltage left over at the external terminals.  That internal resistance and lamp currents tend to work against each other, but low LED currents don't cause much in the way of voltage drops in the supercap's internal resistance.

Supercap circuits are ideal for driving LEDs used to create marker lamps.

I use golden glow LEDs, then use "Gallery Glass" for the lenses. Gallery Glass is a liquid used to make "fake" stained glass, you can find it at Michaels and Hobby Lobby. That way I can have one led and different color lenses in the same marker light.