LED Sources

Sources for white and bright yellow Light Emitting Diodes.

Ditch Lights

Ditch Lights Programming decoders for ditch lights and dimming headlights.

ATSF Tender Marker Light

I started with some small red LED's, bend the leads down both with them coming out the sides of the light and top & bottom.  I think out the side looks better.  Painted all but the lens black.  One some I need to add a filler piece of strip styrene between the leads to fill the existing hole in the tender shell.

Voltage Regulator

For 1.5 Volt bulbs I use a voltage regulator so I do not have to worry about differing track voltages at different layouts I may operate.

This is the standard circuit.  You must go find a connection on the decoder for the ground connection as it is normally not brought out to a wire.  You can continue on with green and purple wires etc.

If you cannot find a ground on the decoder (say the decoder is shrink wrapped), then you can use some fast recovery diodes to the track pickup.  The 1N4148 are good for about 200 mA at 4 ns recovery.  Digikey MUR110RLGOSCT-ND is 1A at 35 ns recovery. You can continue on with green and purple wires etc.  Check you voltage output, I've gotten a report that when using the diodes to the track the output voltage is higher then it should be.  I suspect it's due to a difference in the voltage drop of the 1N4148 and whatever diodes used on the decoder.

This circuit is for if only one function needs a regulator or you what a regulator for each function output.  You can substitute yellow, green, purple, etc wires for the white for other functions.

I now add capacitors to the circuit of the regulator, especially if I'm going to use non-linear effects (Mars, gyra...).  The Cap comes from the National spec sheet.  They are not absolutely needed.

Another version of the circuit from Don Crano.

Here's a version using a TO220 package for the LM317.  With a 270 ohm surface mount resistor and 47 ohm 1/4 watt resistor.  The blue lead goes to the decoders blue lead (or plus voltage common on PnP decoders).  The other lead of the through hole resistor is connected to the minus side of the decoders bridge rectifiers or if a sealed decoders then to the unbanded ends of the two diodes that are connoted to the track pickups.  The middle lead in the common for the 1.5V lights, the other end of the lights go to the decoder function outputs.

R2 & R1  = Output Voltage
47 & 270 = 1.47V
40 & 220 = 1.48V
47 & 220 = 1.52V

Here the blue wire is the 1.5V supply, connected to one lead of each 1.5V bulb, black wire goes to decoder negative (soldered to bridge rectifier).  The right most lead of the LM317 is the positive power input, in this case it was soldered to the plus tab of the rear light of a Digitrax DH163A0 decoder.  The lead was bend into a hook.  I used Kapton tape to insulate the tab of the LM317, the tab is internally connected to the output terminal.

SMT

I've started to use SMT (surface mount technology) parts to make my voltage regulators.

The blue wire is +V_raw from the decoder (blue wire on wired decoders), yellow wire is the negative from the decoder (this is not normally provided by wire in decoders, you have to go find it), the black and green wires are the +1.5V output (the green was just an extension of the front bulb wires, which were not long enough to reach the regulator.  The regulator is the LM317MDT, the TO-252 package.

To read the value on a SMT resistor, take the first two digits and multiply
by 10 to the third digit.
470 = 47 x 10^0 = 47 x 1 = 47
221 = 22 x 10^1 = 22 x 10 = 220
Note some SMT resistors may have four numbers, then it's the first three
times 10 to the fourth digit.
1234 = 123 x 10^4 = 123 x 1000 = 123,000 ohm = 123 k-ohm.
Four digit are not too common.  They are more precise value and therefore more expensive.

Here's the bare PCB, cut with a motor tool with cut off disk from blank PCB stock.

White LEDs

Kato N scale C44-9Ws showing off white LEDs.

Left is factory Kato yellow LEDs (which are much brighter than factory yellow LEDs on Digitrax and Lenz PnP decoders and Atlas N scale locomotives)

Middle is white LED without any filter.

Right is white LED with Lee Filter #204 filter.

I got the filter at a local theatrical lighting store.  I have not tried it, but a Kodak Wratten #85 filter is said to work as well.   Lee's description for #204 "Full C.T. Orange converts daylight to Tungsten 3200 K, Mired shift +159".

Note:  white LEDs I've bought recently have less blue content then earlier ones, but still enough to need a filter but not the same filter.  Lee #205 is "½ C.T. Orange converts daylight to Tungsten 3800 K, Mired shift +109" works good for newer white LEDs.  Should it ever be needed, they have #206 ¼,4600,+64.

From the Left:
Richmond Controls Golden White LED (now used by Kato, Digitrax, and soon Atlas and others)
White LED with Lee Filter #204 filter.
White LED with Plaid Gallery Glass Window Color - Amber #16020.
White LED with Lee Filter #205 filter.
White LED without any filter.

All the white LEDs (except for the Richmond Controls) were from eLED.COM, part number E7104QWC-D.   All the LEDs were powered by the same source and used the same value of resistor.   The picture is of the light produced from the LEDs reflected off a piece of white styrene in a darkened room with a Olympus C-700 digital camera.

Turned Down LEDs

Too fit white LEDs into Kato SD90MAC ditch lights, I chucked one into my cordless drill and turned them down with a file.  First sticking the light end into the drill to remove the collar from the LED, then putting the LED lead side into drill to turn down the end.  Be careful not to do too deep and expose the metal.

Doodlebug

This Bachmann HO doodlebug had three axial bulbs for even interior lighting.   Later 'bugs I've done have four bulbs.  The bulbs are from All Electronics, part number LPFS-12.