How to wire a Tortoise to Digitrax with relays : LUSENET : Wiring for DCC : One Thread

A while back I saw in Model Railroader an article on using a Digi-Key card edge connector to wire plugable harnesses to Tortoise switch machines. This looked like a good idea to save having to solder these things in place. There was also the idea of a pluggable tester so that you could unplug and test a machine in place. In reading your tips I see that when I start installing DS54 I will be wiring them with 4 conductor phone plugs and that relays are required since the built in contacts will only take 1 amp. It occured to me that I should mass produce an assembly with the card edge connector, the phone plug and a 5-10 amp rated relay to power my Walthers rail switches. What would be the wireing diagram and Digi-Key part numbers for this assembly?

If I left out the relay how many shorts before I have to replace the Tortoise switch machine? If I rework all my rail switches what are the odds of having a short on a rail switch?

What would you charge for 60 circuit board throw ties? There was some other article I recall that had circuit board ties in it. I'll have to look that up.

-- Bob Gamble (, April 28, 1998


Edward McCamey recently sent me this on circuit board throwbars:

I've recently and finally gotten with Russ Clover of Clover House. Although only by mail order - he has excellent, affordable, and responsive service PC Board Tie and Throwbar materials.

They are available in two size thickness (.031 and .062) with widths of scale 8" and 9" in N, HO, S, and O. The N-HO sizes are only $ 2.50 per package of ten pieces of 12" long. This is a real convenient packaging and the consistency is great. Russ responds very quickly. A catalogue of all sorts of craftsman supplies and tools is available for $ 4.50. He has sheets and wires of phosphor bronze as well as sheets of brass and nickel silver. I can really recommend Clover House.

Contact: Clover House, Post Office Box 62, Sebasstopol, CA 95473-0062.

I don't do probabilities! All I can tell you is that people tell me that they have Tortoises failing. I don't want you to take that as imminent catasphrophie. Just that it does happen.

I figured sooner or later someone would want to use the popular Tortoise with a relay and an edge card connector as you have asked. Let's see if any of the other readers of this forum address your question. It's already on my list of things to do, but it will likely be a few months before I get to it.

-- Allan W. Gartner (, April 28, 1998.


Don Crano has a neat little Tortoise modification on his pages. If you modify both sets of contacts, wire them in tandem (doubling the contact space), and wire in a tail light bulb to save grace when a short does occur - then I think you can get by without a relay at all. This is especially true if you DCC Friendly turnouts and are only using the contacts for the issolated frog. The combination of DCC Friendly, doubled and protected contacts for the frog is easy and reliable. Note that the Tortoise people state that the contacts are 1 amp. - but for "breaking" as is common contact rating. You'll usually be making contact changes without any draw on the frog and the "continuious" contact amperage is larger. With a bulb limiting the assembly, you can feel fairly safe. -ed mccamey-

-- Ed McCamey (, March 07, 1999.

Actually have done some testing with the Tortoise and the 1156LL lamps. And found a few interesting things. First as already stated here, I modify all the contacts as per my page. This will cover timing problems just fine. Also when used with positive feeedback on Digitrax system and WinLoc software, I can see the turnout lock in position, and know when it is in travel.

Next is the interesting part, the 1156LL lamps are rated at 35watts, but under testing at 14 volts, they draw 1.6 to 1.8 amps. How this works out to 35 watts, I have no idea, but that is what they draw.

Circuitron states the Tortoise contacts are rated at 4-5amps continous and 1 amp at switching, [make/break]. Do not know what type safety factor they use. But have had a Tortoise with a 1156LL lamp across the contacts, swithcing for one hour. Removed the PCB from it and there was no sign of any heat or pitting. Do not know what the real long term would be like. But does appear, that with the 1.6 - 1.8 limit of the 1156LL lamps, that the contacts can survive.

Figuring, that with the 4-5 amp continous rating, this will cover any time a loco would drive up on a opposing phased frog/point set.

And as long as timing is correct, helped by the modified contacts, or with a true DCC freindly tunrout, read non-switch points.

The only thing left is swtiching contacts under load. This could be a stuck set of points in a non-DCC freindly turnout. Or operator error, switch the turnout under a loco/wheels, etc. But with the current limit of the 1156LL we know we can do this for atleast a hour contious without problems.

Any way, seems like the modifed Tortoise contacts, with a current limting 1156LL lamp are pretty safe, even using only on set of contacts. Double em up if you really want to be safe.

Migh also add, Circuitron, claims they have never received a Tortoise back with burned contacts.



Remember Always Have Fun and Enjoy!, Don Crano Akron, Oh NMRA #096211 Visit Model Railroading with DCC at:

-- Don Crano (, March 07, 1999.

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