All About Resistors
LED Color Red Yellow Green White (Lunar)
Volts Typical Minimum Typical Minimum Typical Minimum Typical Minimum
5 205 180 205 180 130 105 130 105
9 475 390 475 390 390 330 390 330
12 680 560 680 560 590 510
590 510
Resistors are necessary part of an LED circuit.  Their job is to limit the amount of current that is made available to the LED.  So, what resistor do you select?  The below lists will guide you depending upon what supply voltage you are using and what color you are lighting up. You may also want to visit our ďhow to read a resistorĒ page as well.

The coulomb labeled Minimum Values is the lowest resistor value you should ever use.  Using a lower value may severely shorten the life or destroy the LED. 

The coulomb labeled Typical Values is the resistor value recommended by the manufacturer that produces the maximum amount of light safely.
All About Resistors

Resistor values in ohms

BeNscale Models has found that when these Typical Values are used, the light output produced by the LEDís is too bright and unbalanced for our taste.  What we mean by unbalanced is that one led is brighter than another color when the signal changes.  This will be very apparent when changing to or from green.

The best way to find the resistor that will produce your desired color temperature is to simply experiment.  Start with a 1K resistor and increase value from there. An inexpensive way to find this value is to use a potentiometer (a variable resistor).  You can simply turn the knob and watch the brightness change.  MAKE SURE TO PUT A REGULAR RESITOR IN SERIES WITH THE POTENTIOMETER TO PREVENT LED DAMAGE.  When the potentiometer is in the minimum value position, the value is 0 ohms, meaning there is no resistor in the led circuit.  By using a regular resistor in series with the potentiometer, the led always has a resistor protecting it. Once you have found your desired brightness, measure the value of the potentiometer and the regular resistor.  You can now purchase regular resistors with the value you have found. 

Donít worry so much if you cannot find the exact value.  A value that is plus or minus 100 ohms is not really going to affect the brightness provided it does not bring the value down below the minimum values listed in the table above.      

BeNscale Models uses 5 volts to power the signals on our layout.  We have found that using the following resistor values seems to satisfy both the brightness and color balancing issues.

Red 2K ohms
Yellow 1K ohms
Green 10K ohms
White (Lunar) 4.7K ohms