# NCE Switch-Kat, using Multiple LEDs possible?



## Project Galileo (Oct 28, 2015)

I am new to DCC and N scale. I have some experience with electronics, however, not enough to figure out my current idea. The table I am building can be seen in the Layout sub forum. Look for the Distillery thread. The user will have the ability to control turnouts through the NCE Power Cab or through a planned manual control panel. To do this I will be using NCE Switch-kats for the Kato turnouts and crossovers being used. The Switch-Kats allow for wiring in manual switches easily. The Switch-Kats also have a feature that lets you to attach LEDs to signal turnout position. That will make the control box very blingy. I likey.

The circuit they recommend looks like this. I would use red and green LEDs. Lighting outputs for the Switch-Kats are rated at 100mA.









While pondering this circuit I wondered about adding LEDs. Beside the red/green pair on the control box could I add a red/green signaling pair by the switch on the layout? For the double cross overs could I add two red/green signal pairs for trains coming each way? 

*My first question for the forum is could I wire in multiple LEDs to this circuit if I don't exceed the 100mA lighting output of the switch contoller?*

On my bench I already have 3mm Red T1 200-300 MCD 1.8-2V, and 3mm Green 100-200 MCD 1.9-2.1V LEDs in stock. That leads me to my next question.

*The second question is what resistor would I use to wire two or three of the LEDs I already have?*

I have tried using online resistor calculators but they don't tell me how bright the LEDs will be with the different resistors. I am hoping somebody here has experience with making the LED just the right brightness for the model/train table etc.


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## Project Galileo (Oct 28, 2015)

Inspiration for the lights came from a picture of the Grand Junction Colorado D&RGW yard. My hope is to model the LEDs into these bumps I marked on the picture. Being able to view the switch status from anywhere on the table may prevent driving against turnouts that are the wrong way too.

If anyone with knowledge of such things knows what these bumps are...


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## DonR (Oct 18, 2012)

Yes, you can parallel LEDs to the ma limit of the device.

You can use one resistor in the common if you know the
total LED current draw for the circuit and use an
on line calculator to determine the ohms.

Or you can use one resistor in the common to each
pair as in your posted circuit. The plus side would
simply be parallel, while the common would be a buss
to each pair where the resistor would be used before
the LEDs.

How many parallel LEDs do you propose per device?
Remember, only one of each pair will be lighted
at any given time.

Don


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## Project Galileo (Oct 28, 2015)

Like this where the reds or greens are only lit up at one time?


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