For the stall tracks in the roundhouse and for the tracks where I park some diesels, I want to be able to turn the power to the track off and have a red LED to indicate that the power is off for that track. I know how to install a switch to turn off the power to the track, but how do I add a LED to it? I have hunted for a wiring diagram for this, but so far, I have found nothing. Any help would be appreciated.
A Doouble pole Double throw switch would do the honors.
I’ll make a sketch in a few minutes but, in short, one leg would feed the roundhouse track and the other leg the LED. When roundhouse track is off, the opposite contact would turn on the LED.
With the same switch you could have a red and green (or yellow, more appropriate) to show the track is active.
Regards, Ed
The easiest way to accomplish what you want to do without interacting with the track power would be to use a double pole switch, where one pole controls the track power and the other controls the LED power.
Wouldn’t a SPDT work more easily? Power delivered to the track in one position and to the red light in the other. One power wire.
[banghead]
-Kevin
The OP does not mention if his track is powered using DC or DCC supply.
If DC, the voltage to the track would be quite low if moving light engines in/out of a roundhouse or service track. Speed (voltage) down or stopped = no current for LED.
If DCC it would work, the LED across the rails with a resistor but why add extraneous circuitry to the track wiring? Sometimes diagnosing track problems is tough enough without having a bunch of extra LEDs to contend with.
A DPDT doesn’t cost that much, if at all, more than a SPDT. Keep the indicator lights on a separate supply. Easier to wire? Not so much more complicated to make a difference. [2c]
Regards, Ed
Thanks gmpullman for the clear diagram. I understand now that I have to use my DC accessory bus to light the LEDs.
But how would this work with a two-legged bi-color LED?
I found a video done by Tom’s Trains and Things on how to use a bi-color LED, but I am having trouble following it. I am going to watch it again and try better to understand his diagram, but I it is not as clear as the one gmpullman provides for two LEDs.
By the way, I am using DCC. And I did try wiring the LED with a resister to just one side of a DPDT toggle switch, in essence making it a SPDT, but when I do this the LED light only comes on when the power is switched off and there is a locomotive on the isolated track. As soon as I remove the locomotive the light goes out.
If not using track power then you need to add a DC power source just for the LED.
Instead of a resistor you could wire in a button battery of suitable voltage. One button battery could serve several small LED.
For storage of locomotives convert your turnouts to power routing also works, no need for a separate indicator light. Use of a snap relay and rail gap can also convert sidings and roundhouse tracks to power routing. The snap relay has DPDT as do many of the turnout motors. Throwing the turnout kills power and the other side of the snap relay could be used to switch on the red LED. Alternatively, if your control panel indicates turnout lining then you can use that indicator instead of a separate LED.
If no locomotive is parked on the storage track do you need to know if it is powered?
Yes you do, otherwise when you drive your engine off the turntable that track could be dead and the engine will just stop.
That is about as prototypical s you can get to put one in the pit.
My rule is to only use that precious DCC power for trains. In earlier years, people found it convenient to use DCC power for signals, streetlights and even structure lighting. This would reduce available power for the trains.
Yes, a LED only uses a tiny bit of current, but I try to be pretty strict about adhering to this personal rule and generally good practice.
I just look at the position of the power switch: up or down
I agree that the DCC power bus should only be used for DCC. That is why I have two DC busses, one for the Tortoise motors and the other I labelled Accessories and use it for lights and Rapido uncouplers and eventually for signals.
OK, I followed gmpullman’s diagram and it works great, thanks! I would though like to know how to do this with a bi-color LED so I only have to drill one hole in my control panels to indicate the status of a track’s power. My control panels are already pretty crowded with two lights for each turnout.
Easy enough to do with a three-leg LED. The two leg variety requires a reversal of the anode/cathode whereas the three leg is slightly different.
In the modified sketch, essentially the three leg is just like two common LEDs sandwiched together sharing the same (usually) cathode. Note that now the + is the side switched since most 3 leg LEDs have a shared cathode or minus side.
Oh, that never happens, does it?
3734GTW_Pontiac_6-9-55 by Edmund, on Flickr
Regards, Ed
Ed, any chance you could draw a diagram using a 2-leg red/green bi-color LED?
Rich
Do tell —
Runthrough by Edmund, on Flickr
The occasional errant diesel has been observed, too [:-^]
LAUPT_19-L by Edmund, on Flickr
Cheers, Ed
I just learned something from that picture.
I always thought that if the locomotive body was lifted up, the trucks would stay on the rails. I guess that is not true. There is something holding the Blombergs to the frame, quite obviously.
-Kevin
Passenger cars are like that, too. Most will have a plate saying “Locking center pin, remove from inside car”.
The idea of the safety chains was the same, too, keep the trucks aligned with the car as much as possible. With Diesels I’m sure there was consideration for the traction motor cabling, too. I don’t know if the ground fault would trip quick enough to prevent arcing with the possible presence of leaking fuel?
Regards, Ed