I bought Miniatronics 3 mm. Yeloglo LEDs to change the regular bulbs on my locos. They come with 470 ohm resistors. Is that enough or should I go for higher rated resistors? I read that some modelers recommend up to 1000 ohm. Almost all my locos have been converted to DCC now.
LEDs with 470 ohm resistors are BRIGHT. If you go with 1k - 2k you will dim the Led to a more realistic level and also double the life if said led David B
470 ohms runs them right at their rated maximum current for DCC on typical HO track voltage. They will be very bright, and if you ever accidnetly change the track voltage, you could fry them. With 1K, they are plenty bright, and running at less than half their rated current, so even bumping the voltage up won’t cause them to go over the limit. Sometimes even 1K is still too bright, so you can go higher if necessary.
–Randy
Can you use two resistors in series to increase the resistance? Just curious as I have a bunch of lower rated ones and wanted to reduce the brightness on a couple of locos?
-Bob
Sure, but you can get 50 1/4 watt 1k ohm resistors for .99$ shipped on ebay. Space is a premium in our locos. David B
I also use 1K resistors for my LEDs. The larger resistor will limit the current. Besides dimming the LED, it also reduces the power used by the circuit. This is important, both to limit what your precious DCC system needs for the locomotive, and to reduce the heat generated by the resistor inside the shell.
Disregarding the negligible resistance of the LED itself, a 1K resistor driven at 14 volts will use, from Ohms Law (I=V/R), will use 0.014 amps. The power IxV will be 0.196 watts. If you use only a 470 ohm resistor, you will use 0.030 amps, and use 0.417 watts. In many cases, you’ve probably got a 1/4 watt or even 1/8 watt resistor, which is too small to handle that kind of current and may overheat or even melt down, damaging your engine.
Thanks everyone.