DCC Wiring Inquiry

If you are using Tortoise turnout motors, there is a new product call the Hare (

does what you want, but it is not cheap.

Another way would be not to throw the switch, but to stop the train. Many of us wire turnouts so that only the selected has power, the other route is dead. If you extend that dead section for a foot or so, if a train approached from the wrong direction, it will suddenly receive no current and stop rather quickly.

Ed

in article akSaf.64$SV1.54@trndny01, Matt Brennan at snipped-for-privacy@verizon.net wrote on 11/4/05 3:40 PM:

Try this URL:

My "paste" inadvertently wound up including the ") which" in the URL below. Sorry.

Ed

in article BF913C25.11382% snipped-for-privacy@unearthlylink.net, Edward A. Oates at snipped-for-privacy@unearthlylink.net wrote on 11/4/05 4:26 PM:

Check out the "Hare" at Tony's Train Exchange - Hare, cause it goes with the Tortoise - which does what you want. Dunno about any other switch machines.

Steve Newcastle NSW Aust

First, let's establish what direction you are going. Common terminology regarding direction of approach to a turnout (switch) is: A: Facing point B: Trailing point

At least in North America.

"Facing point" means that you are approaching from a track that may take one of two or more diverging routes selected by the turnout position. E.g. FROM single track TO double track

"Trailing point" means that you are approaching from one of two or more diverging routes that consolidate into a single route by passing through the turnout. E.g. FROM double track TO single track.

OK? I'm not trying to be an azzole here, just trying to establish the importance of using commonly accepted terminology, and let you know what it is.

On a full-size railway, if the turnout is not properly aligned for a trailing point movement, it will most probably be damaged as the train passes through it*. On a model railway, it will most probably derail the train.

It sounds like this is the situation you are trying to avoid. Trailing point approach. I do not know of any DCC plug&play device that will detect from which track the train is approaching and align the points appropriately. However, this does not mean that it cannot be done. It has been done uncountable times, and Lionel even had tinplate turnouts that did it automatically. The only way I can think of to do it in HO scale is to construct your own detector that works by either sensing current in an isolated segment of track, or by an optical detector. When a train is detected the detector output operates the turnout motor in a specific direction, such that if the turnout is already properly aligned, it will remain so; but if it is not, it will be thrown to the proper position before the train can short circuit or derail.

IT ~may~ be possible to use a Digitrax PM4 to accomplish this task by sensing a short circuit and switching polarity on the turnout motor instead of the track. But I'm just thinking in print here and have not throughly examined that possibility.

Here's another thought. If a train is using the turnout at the same time that a second trian is detected, it will throw the turnout under the first one unless you engineer some form of lockout protection. In that case, you will also have to protect against the second train creating a short circuit when it enters the turnout's area of control. Causing the turnout to remove power from the track not selected will not work. You will have to sense current demand or lack of it in the other track. You can then use that to remove power from the other approach route until such time as no current is sensed.

The whole thing sounds like it might be interesting and I bet somebody like Greg Procter or Terry Flynn (both of whom enjoy the electronic aspects of the hobby) has already got a system/method developed. Not being an electronically oriented fellow myself, I don't know if I want to get into the nitty-gritty, down-and-dirty of it.

*NOTE: For other readers, this does not apply to spring switches.

Froggy,

Thanks Froggy! You were correct with your assumption. Choice "B" is the scenario I am looking to safe guard. I was scrounging around in my pile of train materials, but I could not find the terminology fast enough. I am pleased that you have provided it in your reply.

Edward and Steve - the "Hare" is the answer. Many Thanks to you both!

Steve, the Tony's Train Exchange link, with the added imagery, perfectly described the situation I was hoping to resolve with the use of a "Hare". It's perfect. I don't anticipate two trains arriving at the same time. I just want to be able to automatically throw certain switches on the layout when an engine is approaching against the points. The "Hare" will allow me to include portions of track that can accomodate an unattended train in a continuous loop while other parts of the layout are being actively operated. I am very pleased by this finding.

My sincere thanks for introducing me to the "Hare".

Matt

in article snipped-for-privacy@news.east.earthlink.net, Froggy @ thepond..com at Froggy @ thepond..com wrote on 11/4/05 4:53 PM:

I think the PM4 could use it's autoreverse stuff to change the turnout as you suggest (maybe, as you say, thinking as I write), but your other caution is most valid: trains approaching the same turnout from opposite directions, so you through turnout that one train is running against and set up a head on collision. Whoops.

If it were me trying to prevent the derailment AND the collision, I might use the PM4 and extend the divergent track section a foot or so (maybe longer, depends on how much room you have), then wire the Tortoise to "power" the frog (which is now quite long). A train running against the turnout will short, and if you are using multiple blocks for circuit protection (like with a PM4) only one block will stop.

My layout (see my webpage for a diagram) does this by accident (I didn't design it with that in mind, but it works that way). If I'm running fast against the turnout, the train can coast into the turnout and derail anyway. If I'm just doing low speed stuff, it stops right away, and the PM4 beeps, I slap myself in the forehead and say, "What a moron" (meaning me), fix the turnout direction and continue on.

And me too. I never had a need for this particular type of device or function, but it is good to know. A hare could be used to construct a working "spring switch" such that the switch would allow the passage of a train or engine approaching against the points and then subsequently restore the turnout to its normal position after the movement was in the clear. Perfect for operating on a non-CTC railroad where sidings are equipped with spring switches.

Froggy,

If you have no need to run in the opposite direction,( ie facing) then you can eliminate all these expensive gadgets, no tortoise, no hare, spend the 30 dollars on something else. Just use a turnout with isolated frog and leave the switch blades loose so the trains can trail through. Keith

I think the neatest application of the Hare is to have an automatic reversing loop: the Tortoise and Hare combination would allow trains to go into the loop either way and exit properly with the current polarity of the loop and the switch properly set without intervention.

Ed

in article snipped-for-privacy@4ax.com, Keith at snipped-for-privacy@dsl.pipex.com wrote on 11/5/05 1:55 AM:

Have a look at the following link

I was introduced to this site by Marcus Amman, & it seems to answer all things, & I am still going through it

Froggy: As other pointed out, the new "Hare" DCC turnout control ($29.95 retail) will work with Tortoise switch machines.

A more generic solution -- and naturally, more expensive -- which works with DCC and conventional DC is to use a Circuitron TC-4 ($19.95) and a TC-3 for Tortoise machines ($18.95) or TC-1 for dual coil machines ($29.95 retail) in combination. Circuitron's catalog & application book describes how to wire it.

I don't know the specifics of how the "Hare" works to determine when to throw the turnout points (I only saw the review in Model Railroader).. can someone explain the principle of how it determines that a train is approaching and decides to throw the points?

I used the Circuitron circuits to control the reversing loop at the end of my out-and-back layout; it sure sounds like the new "Hare" can do the same function for DCC layouts at less cost and less hassle.

____ Mark

Got that bit, but is that property connected with DCC, or does it act independently of the control system.

I quit responding to this thread when I decided that I didn't understand exactly what the user was trying to do. I don't understand how the turnout is only ever used in a single direction. If that's the case, why is there a turnout there? How does a train get to the "other" track?

Froggy,

It's not really that the turnout is used only in a single direction, but rather when it is used by trains approaching from the trailing point end of the turnout. In that case, Matt (and I, and others I'm sure) want to make sure that the points are properly (and automatically) aligned for the approaching train.

A couple of cases where this could occur:

1. At the end of a passing siding or a two track staging yard. When a train leaves the siding or yard, it would be nice to have a circuit to make sure that the turnout points are aligned for the train, in order to avoid a derailment or short. In this case, when a train approaches the turnout from the facing point the operator would manually throw the turnout to whatever direction is needed.

1. At the turnout for a reversing loop. If a layout has an out-and-back configuration with a simple reversing loop at the end of the line, once again it would be nice to have a circuit that aligns the turnout properly when the train approaches it. In this case, it really doesn't matter which leg of the turnout a train takes when it approaches the facing point side of the turnout, since the loop is just there to turn the trains around. The turnout points can just be left aligned to whatever direction the last trailing-point train set the turnout, and the next train that uses the reversing loop will take the same route that the last train used (but when it gets through the entire loop and is now approaching the same turnout from the opposite track on the trailing point end of the turnout the circuit is used to throw the points to the proper track).

____ Mark

Marklin switches have had this feature forever, the swiches are electromagentic spring loaded... No matter which way the switch is thrown if you approach it from the trailing side - all goesa OK.

Just for info. Thomas

Froggy @ thepond..com wrote: > And me too. I never had a need for this particular type of device or function, but

Let me explain. I have two parallel tracks exiting the hidden staging area. They meet at one switch [a "trailing point" approach] inside a tunnel before entering the on-line layout on a single track. My need for the "Hare" is to safeguard against a derailment in this scenario. This switch is out of sight. A train approaching from the on-line direction [a "facing point appraoch"] is not a concern. The train can take either route w/o concern. It will end up in hidden staging as desired.

Matt

This would be handy for aligning turnouts to allow passage from a siding onto the main track the same way a prototype spring switch does. As soon as the last car is through the turnout it realigns itself to the main track. You would have to ensure that the train in the siding did not trigger the device until it was ready to resume movement on the main track. you would also need to have a way to detect that the train was completely outside the limits of the turnout before allowing it to return to the normal position.

This is what I thought was being done when I first read the original message, but subsequent postings caused me to think otherwise.

Froggy,

How does the Hare determine that a train is approaching the trailing point of the turnout? I read that gaps are required to have isolated track sections about two feet from the frog. Does the Hare measure power load on the rails to determine if a loco is approaching?

If so, it sounds like a little different approach to detereming the length of the gapped sections at the frog might be needed if the engine is pushing cuts of cars or if it is backing a cut of cars out through the turnout.

_________ Mark Mathu Whitefish Bay, Wis.

It's easy with a locomotive because you can sense the current demanded by the motor. With the troublesome trucks it is a different matter. You need to put resistor wheels on them, or devise some other method of detection. Optical perhaps?

The section dedicated to the Hare must be long enough to allow the approaching train to be detected and for the switch motor to fully operate while the train is running at the maximul allowable speed. There is no set value. You will have to determine it for yourself based on your application. The longer the trigger section, the higher the train speed can be.

Froggy,

primary U.S steam railroad turning facility or "Y", or "Triangle" instead of having a turntable. Or, maybe he wanted a reversing triangle/loop for operation of coal loading/unloading balloon loops, either way the thread that I posted earlier with the direct link at the following site

would give the answer.