The standard yellow LED's have been used as N-scale locomotive headlights for quite some time now. They'll do, but they are not very prototypical. In 2000 the new "bright white" LED's came out. These are indeed very bright, but they weren't exactly white. They have a distinct blue tint to them. All sorts of tricks have been documented in magazines and on the Web trying to camouflage this blue tint. In early 2003, Jim Hinds of Richmond Controls made available to us new "golden-white" LED's that have a more prototypical look to them. They maintain their brightness, but they drift more toward the prototype yellow. I have converted one of my E8's to the golden-white LED's and lined-up the three models in this photo shoot. Taking photos of lights using a flash on the camera is very difficult. The first photo was taken with the flash on, the second one with the flash off. I prefer the second one. In both photos you will see the bright white LED (left), the new "golden-white" LED (center), and the original Kato "standard" LED (right).

My original collection of "bright white" LED's came from Digi-Key. I bought the T-1 size (part # CMD204UWC-ND) and T-1¾ (part # CMD333UWC-ND). However, I am now going back and converting all of my locomotives to using the "golden-white" LED's (which I order from Richmond Controls).

When you buy a new LED, it has two leads. One should be longer than the other. The longer one is the anode, the other is the cathode. The anode should be connected to the positive lead of the power supply and the cathode should be connected to the negative or ground lead. If both of the LED's leads are the same length, then look for a flat side at the bottom of the LED's housing. Look at the LED straight on from the top and you'll see one edge is not round but flat. The lead nearest the flat edge is the cathode, or negative lead. Please note: never connect an LED directly to a power supply - it will self-destruct. Always have at least a resistor in the path so that the current through the LED can be controlled. This resistor is called a "current-limiting" resistor.

The new bright LED's are great, but they can be a bit too bright. When you run locomotives with these LED's in the dark, they actually light up quite a bit of the surrounding scenery. The LED's brightness comes from the amount of current that runs through it. The less current, the less bright, and vice-versa. Using Ohm's Law, we can calculate the desired value of the resistor needed, given a certain power supply's output. Tweaking the resistance allows us to tweak the LED's current. Ohm's Law states that voltage is equal to current times resistance (V = I * R), where V is voltage, I is current, and R is resistance. Most LED's have a maximum comfort level of 20mA (0.02A). So, if I want to turn down the brightness a bit, I might want to shoot for 10mA (0.01A). My example uses a 12V power supply. The LED has a voltage drop of 3.4V (supplied by manufacturer's documentation), so the required resistance can be calculated. Please note that typically white LEDs have a drop of around 3.5V and red LEDs have a drop of around 1.8V, but always go by the manufacturer's documentation, if it is available.

where Vps is the voltage of the power supply (in my sample that's 12 volts), and Vdrop is the LED's rated voltage drop. So, connecting a 860ohm resistor between the positive lead of the power supply and the positive (anode) lead of the LED will allow 10mA of current to run through the LED.

It is pretty straight-forward to switch out the yellow LED's in most locomotives for the T-1 size bright LED's. It is a matter of careful soldering. You may want to make some notes so that you remember where on the locomotive's circuit board the anode and cathode leads of the LED go. If your locomotive originally had an incandescent lamp in it, you will most likely need to supply a new resistor for the new LED as the locomotive's internal wiring probably didn't have one already. Note that a DCC decoder will protect the LED from inductive voltage spikes generated by the motor.

I have never been a fan of the micro lightbulbs. They burn out and generate some amount of heat. I thought that since the white LED can be pretty bright, they might function as a good source for interior lights. This is why I bought the T-1¾ sized LED's mentioned above. I was thinking about connecting a number of lit structures to a DS54 stationary decoder so that I can turn lights on and off using the handheld control. Although a front fascia panel mounted on/off switch would do the trick too. This drawing on the right and the table below show a simple circuit for lighting a structure. ID Description Value P1 Power Supply 12V 500mA R1 Resistor 1000 ohm ½ Watt D1 T-1¾ White LED 15mA

Doing the math, I concluded that there is a theoretical maximum of 33 LED's that can be fed with this power supply. I used an old telephone answering machine's wallwart power supply. Any supply will do, just do the math stated at the top of the page. Unloaded, my power supply generated a high 19.75 volts. When I measured the current through the completed system, it showed a drain of 15.7 mA. Using a four-story N-scale building with paper behind the windows (representing curtains) it produced likable results in a darkened room. In a brightly lit room it didn't do much. Given the large number of LED's that can be driven with this system, I could place a couple of LED's in a single building.