Charlie Ferrara's List: RC Information

If you want to add a power on indicator light, now's the time to do it. LEDs are quite inexpensive, have incredibly long lifetimes if run at 20 ma or less, produce essentially no heat and can be wired to the +5v rail. However, LEDs are current driven devices and will require a dropping resistor to ensure that it does not burn out immediately. A 1/4 watt carbon film resistor rated at 180 to 220 ohms wired between either of the leads and the PSU will work nicely. LEDs, being a diode, are also polarized and must be wired with the positive lead (anode) attached to +5v rail and the negative lead (cathode) attached to DC ground. LEDs have a flat molded into one side of the base --- this flat will be on the same side as the cathode. If your LED is new and has not had the leads shortened, the longest leg will be the positive lead or anode, but locating the flat is the safest means of determining polarity. Although commercial mounting clips are available, a 3/16" ID rubber grommet works out just as well. Drill your case to accept the grommet, pop it into place and push the LED in until the base bottoms out against the grommet. It will protrude about 1/8" for good visibility. I prefer diffuse lens to clear since they show up better when viewed from the side, but either lens style will add a little DIY pizzazz.