Signal Systems

It depends on what you consider a "signal system".  I've done signals with a relay or two, very common.  If you're talking something more exotic than that, I'd probably consider some sort of microprocessor control.

 

trainman129,

How deep do you want to get into this? A few relays to throw signals between red (yellow) and green, or, somewhat prototypical tumble-down, two or more blocks behind and ahead of the train(s)?

Remember though, if it's the latter you need a layout with several blocks that are long enough to make it believable, and worthwhile.

 

Dave

Like Dtrainmaster said, the complexity depends on how far down into the weeds you want to get. As a practical matter, as Dale H posted above, using insulated rail and DC relays is probably the most reliable way of triggering signals. Where things get more involved is "aspects" and interconnecting blocks.

 

First, you need long enough blocks for this to be practical. A block should be long enough to hold the longest train you generally plan to run.

 

Next, looking at aspects, your typical MTH and Z-Stuff signal is actually only "two-aspect" -- i.e., a red and a green. The yellow is actually part of the green aspect as it sits yellow for a few seconds before going green. Prototypes use a four-aspect variant -- off, clear (green), approach slow (yellow), and stop (red). There's are two additional variations with flashing yellow (I've seen it but am not sure what it means) and flashing red (stop before proceeding slow). In a model context, three and four aspect can be done with the Atlas/Custom Signal system package, but can also be done with the judicious interconnection of SPDT relays triggering true 3-aspect signals (no internal electronics.) There's an eBay seller that has cheap 3-LED signals that have an internal resistor for use with 12VDC which would work for this purpose.

 

The big thing is planning. Aesthetically, for a 3-aspect setup to work, you want at least one more block than the aspects you want to display. Plan your signal placement where it makes sense. You don't want them behind blind curves or other things that would block the engineer's (model and operator) view. The physical block (where the insulated rail begins) should realistically be about 12-24" past the signal for better appearance, but isn't necessary.

 

I have some schematics lying around for three-aspect wiring. I'll see if I can dig them up. 

Do you know the user on ebay who sells them ?

seller name: wehonest_us

 

here's a signaling board discussed in various OGR threads:

 

http://www.ebay.com/itm/Logic-...;hash=item3a706beaad

 

If the OP would clarify if by "solid-state" he specifically means to exclude electromechanical relay methods then there have been OGR threads about simple circuits using, say, the 555 timer IC.  What's interesting is the price of relay modules on eBay is down to about $1 per relay with 10 Ampere contacts!  So even if switching low-level milli-ampere currents for LED signals (as most layouts now use) going solid-state doesn't save much money. 

 

OTOH for complex timing or logic such as blinking yellow or red as Matt describes, going solid-state is the only practical way with the obvious advantage of smaller size.  Of course the off-the-shelf signaling suppliers use programmed microcontroller chips to do more complex signal timing.  So, again, to answer the OP's question there have been OGR threads about using Arduino or other methods to implement arbitrarily complex signaling systems but taking the leap into software and programming is not for everyone.

I'm wondering if he isn't subscribed to threads he starts or posts in, that would explain why he doesn't get back to the thread.

 

The vendor is "WeHonest_CN". They have a bunch of model railroad/slot car related items in various scales. The stuff isn't fancy, but it's inexpensive and with a little paint can be made more presentable. The link to the 3-aspect signals is here and the signals look like this:

 

 

I filled in the back of those signals with JB-Weld and painted it black, hides all the wires coming out and really helps the appearance.

 

I'm thinking about trying something that would have a signal green as a train approaches, turn red as it passes, with the signal behind that one red and the one behind that yellow. Two way operation would be nice but not a requirement. The commercially available systems are quite nice but way beyond my means financially.

Are you still pursuing the solid-state approach for this? 

 

If so, how many Red-Yellow-Green signal heads do you want to start with?

 

And is you layout set-up for isolated-rail block detection?  Or perhaps you are 2-rail and need to use another detection scheme like an Infrared beam?

I'm in 3 rail. Layout is divided into train length blocks of isolated outside rails. Blocks are connected to terminal strips on a panel under my layout. Prefer solid state switching again due to costs.

Another question: how do you handle insulated outside rails where you have track switches branching off both sides of the right of way?

You just have to insulate the switch as it leaves, our modular club modules have that situation, and we reserve one rail for signaling.

Dale:

I assume if I use a 24VAC relay the rectifier goes away but is the cap still a good idea?

Joe

If you're going to use a cap, you have to have DC, hence the regulator.  A cap won't do anything powering the relay with AC, and a polarized cap will likely turn into a firecracker.

 

Thanks John

I fully realize this is a a case of re-inventing the wheel but I sketched out the example of 3 signal heads for single direction travel.  As previously discussed you need multiple isolated blocks beyond each signal head to implement the logic you specified.  It becomes obvious that each signal head needs to see the occupancy status of its own block and the next 2 blocks. 

 

 

 

So each signal head as 3 input signals which are either 1 (occupied) or 0 (clear).   This can be translated to the 3 outputs (Red, Yellow, and Green) in many ways, from transistors, to digital logic, to programmed microcontrollers, etc.

 

For about $2 or $3, here's a digital circuit which implements the logic table from the diagram.  It handles the case of a train straddling adjacent blocks.  But if a train straddles 3 blocks, all the lights go out; this can be solved with a 5 cent diode but is meant to illustrate how all circuits have restrictions. 

 

And here's a short video showing the circuit in action.  For proof-of-concept I simply taped up some sections of rail and used aluminum foil to create short blocks.

 

The idea here is to illustrate what I believe is involved for a solid-state, no-relay, single-direction block circuit that drives a 3-aspect LED signal head. In my opinion this is about as complicated as one ought to go for DIY signaling circuitry.  So if considering bi-directional signaling, 3-over-2 signals, flashing indicators, etc., I think one must give in to a purchased signaling system or joining the Arduino/microcontroller community.  OTOH I'm willing to kick around DIY signaling circuit design if that's what makes the hobby enjoyable to you!

I would like to use the two head dwarf signals. How are they hooked up to work with Ross switch Machines? 

 

They are from the people in china, "we-honest"

I think this is where I break out my "C" coding pencil.

 

Perhaps you didn't get the memo, but a pencil is not solid-state.

 

Anyway, if relays are allowed to play, here's a proof-of-concept using the eBay relay module approach.  I only had an 8-channel relay module lying around of which I used 2 channels (2 SPDT relays with 10 Amp contacts).  At just over $1 per channel this would be, say, a $3-4 solution.

 

One nice thing about these modules is they have a transistor buffer on input side so the control current is quite small (a few mA).  This means it's easier (smaller capacitor) to implement some kind of anti-chatter protection which is required for isolated-rail from potential intermittent wheel-to-track contact loss.  That is, if directly driving a relay coil through the isolated-rail the control current is much higher and can require a relatively bulky capacitor which adds to cost and size.

 

And here's a short video.  Note these relay boards generally come with an LED per channel which turns on when the respective relay is active.  You can see (and hear) the 2 relays turning on and off.

 

My coding pencil seems pretty solid state...

 

 

Stan, that works well and those relay modules are very cheap!  You could have four signals on an 8-position relay module.  A handful of parts and you have four signals covered.