I am pretty sure this has probably been asked before bit I cnat find anything, and the search feature (old and new) isnt working well for me.
I have numerous GE Dash 9 and AC440s, and I am putting individual lighting in them, so I bought soem 1.3mm and 1.5mm Minatronics bulbs and put them in, and after being on for just a couple minutes I noticed that the 1.5mm bulbs had heated up so much that they started to melt the plastic! I am looking for some LEDs the same size (preferably ones I don’t have to install resistors with). I have checked Miniatroics adn all they do in that size is red, green, and yellow. Anyone have any suggestions?
LEDs always need resistors. A VERY few, and these are rather large size ones, come with resistors as part of the package. Do not fear the resistor, it has no polarity and simply can not be hooked up wrong. Bulbs can be used with resistors as well. Minatronics has the smaller bulbs in 1.5V versions too - with a resistor these will work on 12-14V and not get as hot as the same size bulb in a 12V version.
Yep definitely sounds like you need a resistor to limit the current flowing through the LED. Althoug I am surprised that the LED put off enough heat to melt the plastic without first burning itself out. Jamie
He was using miniatronics light bulbs, not LEDs. Even hooking an LED up with an improper resistor so that it ends up burning out, it won’t get hot enough to melt a plastic shell.
12v LEDs are usually very large. 8mm or bigger and not cheap. Some decoders put out 3 volts for head/tail lights if your using DCC so you won’t have to use resistors.
Resistors will get hot so watch where you mount them. They can melt your shell.
If you are using the right resistors they shouldn’t even get warm, with LEDs. Assuming 14.5 volts to the track, most white LEDs are 3.1 volts. Using a 1K resistor you get (14.5V - 3.1V)/1000ohms = 11.4ma. 11.4ma through a 1K resistor (I^2R, 0.0114A * 0.0114A * 1000ohms) is .130 watts, a bit over 1/8 watt. No way is that going to melt a shell.
And with a decoder that puts out 3 volts on the headlights - these decoders have a resistor to support the 3V bulbs used in some P2K locos. They cannot drive an LED directly. Even the TCS A6X which has a regulator on board to support the 1.5V bulbs in Athearn Genesis and others cannot be conencted directly to an LED. LEDs need a resistor, period, unless it’s one of those 12V types - and those just have a resistor built in to the base of the LED. For the P2K decoders, if you want to use LEDs the instructions show you how to bypass the on-board resistor. For the TCS A6X, the directions show three wiring options, with the function common connecting to two different places. For 1.5V bulbs the common goes to the regulator source, for 12v bulbs or LEDs (with resistors), it connects to the ‘traditional’ location for the ‘blue’ function on Atlas form-factor decoders.
Those are exactly what I was looking for. This one at Litchfield is probably the one I will go with unless I find one at that google link. All I have to do now is figure out what resisters I need to use with my NCE decoders.
The same 1K ohm/ 1/8 watt resistors. NCE decoders put out about13 -14.5 volts for the lights. I prefer the Sunny White LEDs from Lichtfield Station…
The LEDs are not going to fit in the headlight holes, so you’re going to have add some lenses and light them from behind. I use Microscales’ Krystal Kleer, (it has many other uses as well).
1K. Exactly like it says. Always check, but most white LEDs are about 3.1 volts. With 12-15 volts to the track, a 1K resistor is just about perfect (see above). I mean, you can do the calculation. Function output voltage - LED voltages divided by desired current, from Ohm’s Law: E=IR or R = E/I whenre E is the voltage, I is the current in amps and and R is the resistence in ohms. The mistake with this most peopel make is take the current from the LED rating. The current rating for an LED is the MAXIMUM it can handle. If you base the calculation on 12 volts to the track run the LED at its maximum current, and then run on track where the voltage is 15 volts, you’re not exceeding the LED’s rating. White LEDs tend to be VERY bright anyway, runnign them at 10-11ma leaves them MORE than bright enough AND the less current flowing through the resistor the cooler it stays.
On those particular decoders, with current regulation, no. Resistors would not be needed. Reading the documentation, it doesn’t seem all the 165 decoders are the same - the Atlas board makes no mention of the regulator but based on some information posted on the product page it does have the regulator but might be set to the 30ma that you get from the Kato board if you cut the link mentioned in the instructions.
Here is a comparison of a 1.2mm, 1.5 volt lamp with a SMT LED. The lamp voltage is 1.55 volts and 9.4ma. Very little heat. The lamps come from www.led-switch.com.
The LED is a SMT LED from Litchfield Station. 12.4 volts DC, 1 k resistor, 12.24ma.
