Small 1.5v LED's?

[tehachapifan]

I purchased my first TCS decoder and noticed it says it already has a resistor for the function output. Cool! But I see it says the LED (or bulb) needs to be 1.5v. Thinking the LED's I typically use are pretty standard, I attempted to hood up a warm white 3014 SMD but couldn't get it to light up. Then I noticed these call for 2.8V~3.4V. Will 1.5v not cause these to light up at all? Also, it seems 1.5v LED's in these sizes don't seem as available....unless I'm not looking in the right place.

[peteski]

There are no 1.5V LEDs.  LEDs aren't made for specific voltages (like incandescent bulbs).  LEDs are semiconductor diodes which use various types of chemistry which requires certain minimum voltage to start conducting (glowing).  The lowest voltage LEDs are red (1.7V) and most blue and white LEDs need around 2.6-3.2V to start conducting (glowing).

It sounds like the TCS decoder you bought has a 1.5V voltage regulator built-in to produce 1.5V positive voltage for subminiature 1.5V incandescent bulbs).  You can't use that with LEDs. But that decoder shoudl ale have the standard full voltage positive output (the blue wire). If that is the case then you can use LEDs (with added resistors). Just hook them up between the function output (negative) and the common positive blue wire.

[tehachapifan]

Thanks, Peteski. This decoder is a drop-in for the Kato NW2 and has no wires. The function outputs I mentioned appear to be all there is. Interesting they chose an output voltage that only works with a bulb.

[peteski]

Ah, now that I know which decoder you are using I looked it up at http://www.tcsdcc.com/Customer_Content/Installation_Pictures/N_Scale/Kato/NNW2/Kato_N-Scale_NW2.php

The headlight LEDs are already on the decoder. But these decoders do not have a 1.5V regulator.  The pad circled in blue is a standard "blue wire" common positive. But there is a built-in resistor on the F1 output. ( I see the resistor on the photo next to the F1 soldering pad circled in red).  Plus the instructions mention that it will work with a bulb or LED.  You should be able to hook up any LED without additional resistor and it should illuminate.

If you properly hooked up the LED (negative lead to the pad circled in red) and positive lead to the pad circled in blue then if F1 is turned on the LED should illuminate.  If it doesn't then something is wrong.  Either the F1 is not really turned on, or the decoder or LED are defective.  I'm assuming that the extra output is F1 (it is not mentioned in the installation instructions).

[tehachapifan]

Thanks, Peteski. I'll have to wait 'till later to mess around with this more. I managed to let the smoke out of the decoder when I was attempting to touch the pads with another LED with the leads reversed, thinking I may have soldered the leads backwards. Thank goodness for goof-proof warranties!

[Kisatchie]

...Thank goodness for goof-proof warranties!

Hmm... Kiz put a company
out of business with their
goof proof warranty...