Some wiring questions


C

Chemdawg

Member
I was working with my digitrax stuff tonight, and made a small mock layout with my tortoise machines, and my turnouts, etc.... I bought some bi-color LED's in red/green for my faceplate on the front of my layout so I know what direction the turnouts are thrown.

So with this being said..... 1. on my DS64 turnout controllers, what is the voltage going out to the turnout? 2. If it's 12 volts, WHAT watt resistors would I need to bring the voltage down to 2 volt and 2.1 volt. The green lights at 2.1 volts, and the red lights at 2 volts. So I need to reduce the voltage going to the turnout machine from the DS64 voltage to 2.1/2.0 volts.

Is there a formula?
 
To go along with this, how would I wire this to my tortoise machine so that when the turnout is one way, the LED is green, and when it is the other, the LED is red. Anyone have a diagram that makes sense to wire this with the correct resistors?
 
Here is a great link to help you calculate how many ohms your resistor should be.

Your supply voltage is of course 12V. The voltage drop across the LED is the voltage of the LED itself, in this case it's 2V or 2.1V and you'll also need the current of the LED that you're putting in, generally it's 20 or 30 odd mA.
 
It might be a good idea to test the track voltage before making such calculations. DCC can be 14-16 volts across the rails so it's better to know exactly before you make the calculations so that you don't blow any lights.

At the club, there's one block that is 12, one that is 16, and the rest are 14. I always use 16 in my calculations to be safe.

The WATTAGE that you will need depends on how many volts and amps you're trying to drop. The more drastic the drop, the higher wattage you'll need to prevent the resistor from burning up.
 
If your bicolor LEDs are the 2-wire kind, you can wire them in series with a Tortoise machine, no resistor required. The motor in the switch machine sets about the right current. If you have the 3-wire kind, you can wire the two colors (anodes) to the two wires that feed the Tortoise, with a 1K resistor to ground on the middle wire. That assumes that the drive to the Tortoise is +12 on one wire and ground on the other. If you're using negative voltages, it's more complicated.
 
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