I’m wiring my first DCC layout and using Caboose Industries ground throws with the switch built in to power the frog in my hand laid turnouts. I want to wire to the control panel a green LED and a red LED with resistors to show the direction in which a turnout is positioned. I know how to do this in DC. But since in DCC, the ground throw is powered to the frog under DCC (modified AC current)… can the wires to the panel still run off of the ground throw switch tabs? Will the LEDs work with the AC current? Or will the LEDs be damaged (assuming the resistor is proper size)? My questions it seems to me are also relative if I used a dwarf signal running off of the ground throw tabs as well.
If the above Jason reply is true, how does one get light indicators wired to the control panel in DCC off of ground throws? Must be some alternative thing to do. (I know how to do it with a Tortoise because it can be powered by DC, and not AC.) But can’t yet afford Tortoises on all my turnouts.
That site has the answer but essentially you have to convert your AC current to DC, resistor it down so you don’t blow the LED.
I’m not sure how to fully respond becuase I don’t use manual turnouts. I’ve seen all sorts of things through this forum though and I’d look to the long timers here to respond with something more.
The Caboose throws only have one set of contacts (SPDT). You can use them either for powering the frog or for controlling signals, but not both. TO do both you’ll have to add a small relay and get two sets of contacts (DPDT), one for the frog and one for the signals.
Randy has it right. Even if you use a rectifier, you are only going to have one color of LED lit. While it is true that LEDs are DC devices you can light them on AC as long as you limit the currents and voltages properly, but they’ll only be lit for half the cycle. (Doesn’t help, in this case).
For jktrains: I’m pretty committed since I’ve already installed the Cabooses with the switch. I’m counting on it to handle the frog… but I know there is a way to jimmy a regular ground throw up to a slide DPDT switch to control the frog. But, still doesn’t take care of the panel light. Maybe I should just let the Caboose do the frog, and then put a switch stand gismo on the throw bar and show the signal that way. Just seems the control panel is a nice way to go. I could pull the Caboose back out. Nothing has to be in stone, so I’d like to hear about your alternate solution please, and thanks.
For ereimer: I found the ground throws not to be difficult to install once I had the first one done. They do have small parts and the magnifier headset helps.
For Everyone: I’m coming to the conclusion from the reponses, that everyone on DCC uses the Tortise on all turnouts, or on less active turnouts doesn’t bother to wire to control panel. Am I right? Is there any alternative not using a LED, but some other bulb in the control panel circuit?
In an earlier thread I asked about using a dwarf signal with the DCC, and Zepher replied as follows, which made me feel that the dwarf would light OK. Do you agree, and would the same thing work for the panel LED? Hoping this copy of his reply works:
Joined on 10-12-2004
Colorful Colorado
Posts 3,351
Re: Wiring Dwarf Signal to Ground Throw — need electrical help!
It might be possible. The frog polarity will be identical to one rail and opposite the other even though it is alternating. It should be possible to design a circuit that uses a diode to rectify the DCC wave and charge a capacitor which drives an LED. Two copies of the circuit would provide an indication for each leg of the turnout. It’s a little beyond my capability, but keep searching.
I think that solution you found does it. I wasn’t thinking too well. If you use the frog as the common, and the two rails (obviously with appropriate resistors) as the power one LED will light (half the time) and the other will be off, since there won’t ever be voltage across it. Not so hard after all.
The easy solution is to use a dpst slide switch mounted in place of the ground throw. Measure the throw distance of the turnout and use a slide switch with a similar throw, usually a mini-slide switch. Cut a recess into your roadbed/subroadbed just like you would for the ground throw with switch contacts. Use one set of contacts to power route the frog and the other set to control your control panel indicator LEDs. You could either use 2 LEDs, 1 red and 1 green or a bi-color LED with 3 leads. Using a bi-color LED would free up some space on your control by cutting in 1/2 the number of LEDs to be installed.
To connect the slide switch to the turnout use a piece of piano wire. Drill a hole in the lever of the slide switch equal to the size of the piano wire. You can either mount the piano wire to the throw bar of the turnout by drilling a hole, like you would with a ground throw or by cutting a slot in the roadbed using the hole in the throw between the points.
The advantages of using a slide switch are: 1) much cheaper - 2 at RS for $2 or so vs. $3 for one ground throw; 2) 2 sets of contacts to be used; 3) the slide switch provides constant pressure on the points and lock the points in place much like a Peco turnout and 4) no assembly required.
You can paint the throw handle of the switch yellow if you want so it stands out. Otherwise the mini-slide switches are a lot less conspicuous than a ground throw, especially after scenery is done.
A simple solution that’s cost effective and practical. I’ve used this to control a turnout to a siding on a module that power routed the frog and controled a single target searchlight signal on a module. Turnout thrown for the main line the approaching train sees a green signal; thrown for the siding the signal shows red. Very effective.
I dont think that will work since the DCC signal is not polarity sensitve. Using a bridge recitfier will convert the essentially AC power to DC, but one output of of the rectifier will always be positive and the other will always be negative. Remember that changing the direction of travel of a locomotive in DCC does not involve changing the polarity of the power on the rails, its handled by the deocder. Each rail is neither positive or negative, but is alternating. Thats why a non-decoder equiped loco doesn’t move and just buzzes away. The AC type current causes the motor to continously change direction.
To test you solution you should be able to take a bi-color LED and connect on lead to one rail and the other lead to the opposite rail, using the appropriate resistor (approx a 1k ohm resistor). According to your solution, when you do this it should light and either red or green for example. If you then swap the LED connection you’d get the opposite color. I don;t believe this will happen, I think you get yellow/orange either way as the AC alternates the LED color from red to green so quickly that the eye sees yellow.
A good thought, but one that I don’t think will work.
With a two lead bi-color LED you are exactly right, with a three lead bi-color LED, using the frog as the common and one lead to each of the other rails I think the result should be a different color depending on the polarity of the frog.
Two-lead bi-color LEDs won’t work (well, not well) in this case. Only 1 of the two would light up, but they’d be orangish-red when lit.
The single LED idea should work, but some LEDs do not like relatively high reverse voltages. But you can;t protect each individual LED with a second LED or diode reverse biased, as this would allow a dead short across the track. This is where bi-color LEDs can be handy. It won’t allow for a nice red/green indication, you’d have orange and orange, but there’s be no reverse voltage issues.
A three-lead bi-color LED would be electrically the same as using an individual red and green LED.
You could always use light bulbs with 1N4001-type diodes. Regular silicon diodes don’t have the same issues with reverse voltage that LEDs do - a 1N4001 can withstand up to 400 volts in reverse. Hmm, might be able to use a regular diode plus LED plus resistor as well.
I really thank everyone for taking time to help me and I’m learning a lot from this discussion.
jktrains: thanks for the slide switch solution which I see would work. I’ll probably use this as my fall back option since my ground throws are already installed.
rrinker: at the end you said using single LEDs (red and green) each connected to the common frog and their other ends to outside rails through a regular diode, plus LED, plus resistor might be best solution. Not being knowlegeable, how would I ask for a “regular” diode at say Radio Shack. Is there a size to get? Is that a bulb or just a part?
It seems there is a consensus from quite a few now, that the two LED (similar to dwarf signal) solution should work. I think I should try and test it (with and without the regular diode). Has anyone out there by chance, ever tested (or used) this solution?
I’m skeptical that the two LED solution will work. It sounds like a like of extra pieces, with other diodes and resistors needed for something that an $0.89 part will accomplish. I’ll try the 2 LED solution this evening on my module with the LED signal and see what the results are. I’ll keep it basic - 2 LEDs and a current limiting resistor.