# Wiring LED for control board (train yard control)



## PeterH

Hi,

I have a DC HO layout.

I just build a board with a map of my train yard on it.

I have a black board with white electrical tape to show the tracks.

I want to wire in LED lights that show which direction the track is running (forward or reverse).

My power supply is putting out 14.8 volts(VAC).

So can I have two circuits tapped into each track, with a resistor on each side of the LED to protect it from the change in polarity (when I switch directions).

Current>>>>>Resistor>>>>Red LED>>>>>>Resistor>>>>

then switch directions and have another set up like this

<<<<Resistor<<<<<<Green LED<<<<<<Resistor<<<<Current

Thanks,

Peter


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## T-Man

Peter, one resistor for two LEDs wired back to back.
I have one in my Reverse Thead post #8, I used a 470 ohm resistor I may have gone to 330 ohm to get more brightness. The 470 is for 12vDC protection. Remember you get a voltage drop on the track anyway. Radio Shack has an inexpensive LED assortment for you to test out..

I like the signal on the table. than on a board.
The back to back works well with switching DC and AC operation(AC both are always on)


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## PeterH

T-Man,

Thanks for the reply!

I saw this post of yours,

"The electronic switch circuit is easier to troubleshoot when it is attached to a directional light. I set up a two sided light. The LEDs are standard Radio Shack from their assortment package 5mm. I placed a red and green in series and the second set opposite in polarity so only one set lights at a time. and the feed had a 470 ohm resistor."

I don't really understand it though.

I want red for forward and green for reverse. 

Do I solder in this order,

Power from track>>>resistor>>Red>>Green>>back to track

When I reverse track direction and the flow of electricity, won't the Green bulb be unprotected and blow?

I can't get my mind around this uni-directional LED stuff.

Peter


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## T-Man

You never solde,r you always test first, and after soldering. I'd do the LEDs first then the resistor then the wires then test to the track. Can't get much simpler than that

Direction: forward is relevant to you, If it goes the wrong color switch wiresto the track.

They do not blow, Electricity follows the least resistance they protect each other. They do have a minumum back voltage.
The resistor guards all weither forward or reverse.

I blew enough LEDs to prove it.


Multidirectional: LED D is for diode, one direction , a neat lliitle device.











The dark lines are the pos feed/long lead.
A shown if the left rail is pos red will light. Now how your engine runs is your problem. Test it.


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## PeterH

T-Man,

That is just what I needed!

Thanks for your excellent help and diagrams.

Peter


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## tankist

one thing to add. while LED is a diode of course, it doesn't like reverse voltage and doesn't handle it as a switching diode does. 
but you could just use bipolar LED.


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## PeterH

*Finished Yard control board with lights*

So I finished the map of the yard with lights and switches.

I ended up using LEDs that had resistors incorporated into them (in the colored lens there is an LED and a small resistor. It is a Radio Shack product. The red shows forward and the green shows reverse. The toggles operate turnouts in the Yard. My son loves the light show.

Thanks for the suggestions and help guys


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