Electronics and DCC

Not being much of an electronics expert, please forgive me if my terminology is incorrect or confusing.

OK, so I have this turnback loop at one end of my layout.  I want to control the position of the turnout leading to this loop from two different locations on my layout fascia, with a corresponding panel light (LED) at each location telling me the position of the turnout, so no matter which position the turnout is in, I can change it at either location with the flip of a switch.  I also want to have the position of the turnout control the polarity of the loop, so that any train passing through the turnout will not encounter a short.

On a hunch, I bought a Tortoise switch machine for my turnout, believing that the internal contacts could be used to route the power to the loop.  After reading the data sheet that came with the Tortoise, I see that the internal contacts are only rated for up to 4 amps, and my NCE DCC system is a 5 A system.  So, my first concern is whether I can directly control the polarity of my bus wires under the loop using the Tortoise, or whether I will need to install some sort of relay.  If so, what kind of relay and how do I wire it?

As for controlling the Tortoise from two locations, I can figure out how to wire two DPDT switches in parallel between the power supply and the Tortoise such that changing the polarity at one DPDT changes the polarity at the Tortoise, no matter which way the other DPDT is thrown.  But, I can't see how to wire in a bi-directional LED to indicate the turnout position at each location.

My final problem with the Tortoise is not electrical.  My benchwork is 2" pink foam on 1/2" plywood and when I attempted to mount the Tortoise underneath, with a longer and larger control wire (I used 1/32" dia spring steel wire), there still is too much spring in the wire to move the turnout points.  Do I just go to even larger dia. wire, or is there another way to stiffen the wire I've got, possibly with a brass sleeve, or something else?

Please reply with any suggestions you may have.  If there are sites out there that show wiring diagrams for various Tortoise applications, please direct me to them (I have looked already, but didn't have much luck).

Thanks,

Tom

 This product was made for you.....

It is a PSX-AR from Tony's trains.  It will manage your reversing loop electrical and flip your tortoise for you!

In terms of the throw wire, just go for a thicker piano wire.

David B

and don't worry about a 5 amp system and 4 amp contacts,  unless the loco's in the loop are drawing more than 4 amps it won't be an issue. i would suspect that even 5 amps would be ok as circuitron are bound to understate the capacity to build in a safety zone.   if you are vreally worried, you could use the tortoise contacts to flick a relay rated at 10 amps accross the contacts to switch the power.

First:  The 5 Amp rating of your command station is a limit, not a measure of constant current draw.  The actual current is determined by the load.  If you will only have one train in your reverse loop at a time, you will never draw 5 amps unless you have a direct short.  Such a short should shut down your command station anyway.

I have Digitrax, so I am not familiar with your system, but if it was on my layout I would use a DS-64 to control the Tortoise and a simple push button (or a switch command) to control the DS-64.  You can wire as many push buttons in parallel as your heart desires.

Since the Tortoise uses only two wires and a current flow that reverses directions, you can use LEDs which only allow current flow in one direction and resistors to display which way the current is flowing.

 How many trains will be in the loop at the same time? That determines the current through the contacts.

 My previous layout did not have plywood under the foam, so my Tortoises mounted from the top, using the stock wire. What brand of turnouts are you using? If Peco, try removing the spring. Also, no one says the Tortoise has to be mounted hanging down with the wire goign up, one option is to bend a wire in a J shape so that it goes under the layout a couple of ties away fromt he throwbar, the short leg of the J would go in the throwbar hole. Underneatht he layout, put a 90 degree bend in the wire in any direction that gives you room to mount the tortoise (on its side). Put a loop after the 90 degree bend. Mount the Tortoise on its side with the actuating wire engaging the loop. -----|--(tortoise)  all in a line like that. As the Tortoise wires moved left and right, it will spin the vertical wire which will move the throwbar back and forth. I'm using RC servos this time, cheaper than Tortoises and lots of ways to mount them, with all the clips, clamps, wires, adn bellcranks available in the airplane section of the hobby shop.

 For dual location LEDs, you'll have to run the one Torotise power lead back over to the second DPDT to the second LED and then off to the Tortoise. So if you have power in to one DPDT, then 2 wires over to the second DPDT, then 2 wires to the Tortoise motor, You need to break one of the wires to the Tortoise, put in the LED for that side, run the wire back over to the other side, put the led there (LEDs in series) and run another wire back to the Tortoise

                                --Randy

OK, got the Tortoise installed and working the way I want it.  Decided to go without the DCC gadget and do it with switches and a relay and I'm pretty pleased with the outcome.  The one thing I noticed is the noticeable humming coming from the Tortoise when power is applied.  Is this normal?  Since this is my first (and probably only, for this layout, at least), I don't know what to expect.  It's not that loud, but it's the only one on the layout.  If they're all like this, I wonder how the guys with hundred of tortoises on their layouts can stand it?

Tom

 What sort of power supply are you using, at at what voltage? Cheap DC wall warts aren't filtered very well and let a lot of AC hum through. And a typical 12 volt unregulated wall wart with the light current draw of a Tortoise will probably be putting out 14-15 volts. Try both a lower voltage (9V is plenty) supply and also adding a filter capacitor. This vastly overpriced part from Radio shack will work:

http://www.radioshack.com/product/index.jsp?productId=2102508&filterName=Type&filterValue=Electrolytic+capacitors

Just watch the polarity - the capacitor has a large mark for the NEGATIVE side and must be wired correctly. This will serve to filter out the AC hum from the cheap wall wart and give smooth DC to the TOrtoise. Connect the capacitor close to the power supply.

                                                          --Randy

rrinker:

 What sort of power supply are you using, at at what voltage? Cheap DC wall warts aren't filtered very well and let a lot of AC hum through. And a typical 12 volt unregulated wall wart with the light current draw of a Tortoise will probably be putting out 14-15 volts. Try both a lower voltage (9V is plenty) supply and also adding a filter capacitor. This vastly overpriced part from Radio shack will work:

http://www.radioshack.com/product/index.jsp?productId=2102508&filterName=Type&filterValue=Electrolytic+capacitors

Just watch the polarity - the capacitor has a large mark for the NEGATIVE side and must be wired correctly. This will serve to filter out the AC hum from the cheap wall wart and give smooth DC to the TOrtoise. Connect the capacitor close to the power supply.

                                                          --Randy

That capacitor did the trick.  Thanks!

Tom