USING L.E.D.'S AND AA BATTERIES
This is an inexpensive way to have nice bright headlights. It's especially good for battery powered
locomotives because it doesn't drain the main batteries. And it doesn't cost much, about 5 dollars for a
At the core of this system is an L.E.D. (light-emitting diode) that is plenty bright, has a wide beam angle,
and costs only $1.00 each, found at www.allelectronics.com.
(1/31/04) Another source of bright LED's is www.richmondcontrols.com They have LED's of very nice
colors - not too blue and not too yellow - for $1.50 each. The colors are called Golden White and Sunny
White. The major difference is that when off, the Golden White is yellow and the Sunny White is clear. The
5 mm size will fit for all the applications in this article. These are brightest at about 3.4 volts, a bit higher than
two AA batteries.
BATTERY TYPES AND VOLTAGES
AA size alkaline batteries are 1.5 volts each, whereas Nickel-metal-hydrides are 1.2 volts. If a headlight
is nice and bright at 3 volts, it might not be so bright at 2.4 volts. If you are contemplating a change in battery
types, keep this in mind when experimenting with resistor values.
2 bright yellow LED's @ 1.00 ...2.00 All Electonics #LED-72
10 ohm resistor .10
Battery holder for 2 AA's 1.00 FSH-10
Mini toggle switch 1.00 MTS-4
Two AA batteries 1.00
This particular LED is listed as 3000 mcd (3 candlepower) and has a relatively wide viewing angle. As far as
the resistor goes, all you need is a little 1/4 watt size, and you may want to experiment with a couple different
resistances. For a typical 20 milliamp LED, 50 ohms will drop the voltage by one volt. Most LED's work in
the 2.5 to 3.5 volt range, and draw between 20 and 40 milliamps. Sometimes (but not always) this is
specified on the package. The formula is:
Voltage = Current (Amps) times Resistance (Ohms).
Positive and Negative: on LED's, look for a flat spot on the side of the base. The lead next to the flat side is
negative. Here's a hookup diagram:
All Electronics www.allelectronics.com or 1-800-862-5432
Hosfelt Electronics 1-800-524-6464
Richmond Controls (LED's) www.richmondcontrols.com
In an RS-3, I managed to fit the battery holder in the smoke generator compartment and the switch under the
radiator fan (after removing the fan and motor and adding a piece of styrene).
In an RDC, I placed the battery holder in the motorman's compartment and the switch under the right front
door. But since the LED's fit very loosely in the pockets, I had to fabricate a bracket with a piece of styrene
with holes drilled to fit the LED's.
To install this circuit on an RS-3, I mounted
the on/off switch on a styrene plate, and the
battery case in the smoke unit area, easily
accessible to charge or replace the batteries.
To install this circuit in an FA-1, remove the pilot
with 4 screws, install the switch and battery holder
on the pilot as shown above, replace the headlight
bulb with an LED, and solder the red and black
wires to the LED leads. (Flat spot on LED =
Negative side). Many thanks go to Paul Norton
for this idea. He presented it in the Aristocraft
Forum in December 2003.
In a later FA1 application, I mounted the on/off
switch on the pilot, to the right of the coupler, and
painted the toggle flat black. It's nearly invisible
but extremely convenient.
The Budd Car's bright headlight shines brightly
against the snowbanks in the wee hours of Dec. 5,
This doodlebug headlight is a Richmond
Controls Golden White LED. Notice the
realistic color, not too yellow, not too blue.
The LED would be a little brighter at a higher
voltage, but it's already bright enough at 3
volts from two alkaline AA batteries.