wiring an LED turnout switch position indicator

[CraigTloco]

Does anyone know how I would wire a Green and Red Signal Status light (LEDs) to a Bachmann DCC turnout such that I get one light for mainline direction and the other when the DCC switch is thrown to send the train off the mainline?

[jward]

use an atlas snap relay wired in parallel with the bachmann switch motor. the contacts on the snap relay can be easily wired for an indicator light, in fact the instruction sheet that comes with the relay show how to do this.

[blf]

Caboose Industries makes hand thrown switch stands that have built in contacts if you don't want switch machines. Bill

[Jim Banner]

I assume that by "DCC switch" you mean one that is thrown via your DCC throttle.  If so, that lets the Atlas Snap Relay out as there are no external control connections to parallel.  And I don't suppose you spent the extra money for DCC controlled switches just to convert them to manual turnouts.  Answer is:  there is no easy solution.

One possible solution that comes to my mind is to use a second decoder running on the same address as your turnout.  Then wire the LEDs to that decoder.  The exact details would depend on the DCC system used and how it addresses the turnouts.

Another solution would be similar to Jeffery's solution but using small latching relays instead.  I am thinking something like this type
http://search.digikey.com/ca/en/products/V23079B1203B301/PB1085-ND/1633971 sold by Digikey for about $3.50 CAD.  The difference between these and the Snap Relay, which is also a latching relay,  is the current required to operate them.  These small relays require only about 12 milliamps to operate.  This is small enough for the electronics in the turnout to supply in addition to throwing the switch.  A Snap Relay takes about 2000 milliamps which is more than the electronics can handle.  There are two or maybe three complications to this idea.  (1) These small latching relays MUST have dc of the correct polarity to operate.  If you want to connect them to switches that are run by ac, you must add a bridge rectifier to turn it into dc.  (2) The solenoid coils inside the DCC controlled turnouts have no external connections.  This means digging into the turnout to make the three or four necessary connections.  (3) Soldering small connections will be required.  This means having not only the skills but also the equipment - no big old soldering guns for this delicate job.

Once you have the relay operating under DCC control, you can add whatever signals you like.  Separate red and green LEDs or 2 lead red/green LEDs or 3 lead red/green LEDs or incandescent bulbs or semaphore signals operated by Tortoise motors.  I am presently building a working ball signal for my 1880's 0N30 layout which I expect to operate along with a Tortoise motor that throws a turnout.  Both will be operated by one of these small latching relays that in turn will be operated by an automatic reverser as is reverses the DCC on a turn loop.

Jim

[CraigTloco]

Thanks guys. I think I'm going to go the way of the relay using the bridge rectifier. I can use the frog wire to power the relay which is only powered in one switch position and then tap into the continuous track power within the crossover to supply the LED's.

Craig

[jward]

some further thoughts. i don't know how well they'd work in practice.

if you are using dcc, and you have a powered frog, it should be possible to wire an led between the frog and the stock rails. the dcc would supply power to light the led, and the red or green led would light depending on which polarity the frog was.

another idea would be to use two red/green leds in a two head bullseye type signal. typical railroad practice is to give a signal indication of red over green for the turn route, and green over red for the straight route.