Use 3-wire LED

@ uttrainman

If I understand your question correctly that the turnout points are physically connected to the SPDT switch handle, this diagram should work for you, using a 3-wire bi-color LED.

PS Is that you, Doug?

The above circuit is missing a resistor

Ultrainman-

You need a resistor in series with the common cathode to limit the current flowing through the LED.  The value of the resistor depends on what supply voltage you are using for this circuit and what amount of current (and hence LED brightness) you want.  The forward voltage drop across the red or the green LED is about 2 v, so if you want 10mA to flow through the LEDs, then the resistor value would be:

(Your supply voltage - 2)/ 0.01 = Resistor value in ohms

You said your other turnouts are indicated by "dual" red green LEDs.  You could duplicate that effect by wiring two of these circuits to the same SPDT switch, but exchanging which is red and which is green in one of the pairs.

Dennis

Current wiring of SPDT Switches

I am assuming that the SPDT switches used on your manual throw turnouts are wired to switch the frog polarity. If that is the case the circuit Dave proposed will not work. For a circuit that will work with SPDT switches on a DCC layout check out the circuit on the Wiring For DCC site which can be readily adapted for a control panel indicator.

Confused- what is the switch doing?

I am confused- when I read the original post, I assumed that the spdt switch is not doing anything electrical, and is just being used as a mechanical 2 position assembly to hold the points in place.  If that is the case, then the circuit will work.  If, as Logger01 assumes, the spdt switch is being used to power the frog with appropriate polarity, then the circuit will not work, as Logger01 states.

Dennis

If you

used the switch contacts to power the frog, the easiest thing to have done was to have used a DPDT switch. Then you could use the second set of contacts as drawn above (with resistor, as suggested) for your LED.

Blair

2 LEDs back to back

You don't have to use a single bi-color 3 lead LED, you can use 2 LEDs just connect the two cathodes together and to the negative power supply lead. Then connect the positives through a resistor to the switch terminals.

The advantage of putting a resistor in each LED plus lead is you can adjust the brightness individually to make sure the two LEDs are the same brightness, if that maters to you.

If you are using the switch to electrically power the frog there should be a way to add LEDs to that wiring, but have to think about it more.

Control panel lights

Yes Dave, that would be me. As to your diagram, I'm using dual color Leds that have only two leads.  Can you make that work? I'll check out your blog on the HVT railroad.  FYI, Terry is passing thru on his way back to SG so we will have breakfast together Monday morning.

Doug

Jefferson City, MO

Control panel lights

Dennis, the switches originally provided proper polarity to the frog, the same as the tortoise machines.  Now that they a control panel is being incorporated, it is desirable to have indicator lights on the panel for the turnouts that are manually switched.

Doug

Control panel lights

Jim, switches are used to power frog but want control panel lights to indicate direction of turnouts. Currently using 2 lead leds that are bi color, red/green.

Doug

Control panel lights

Ken, after reviewing your ref wiring for DCC site, I think I can make it work. Thanks.

Doug