What are relays for?

In general, relays are usually used when a low power "trigger' signal (i.e.-a insulated track section) is used to control higher amperage circuits.

An example would be a starter relay in your car where a 12 volt "battery" signal is used to close a set of contacts that may carry up to 200 amps of current to operate your starter motor.

In our railroading applications, we use 12 volts of power to close a relay that may trigger several accessories at the same time (which likely draw more amps).

I use relays on my reversing loops to change the polarity of the loop itself as the turnouts are thrown.

Ray

If your using DCS and have an AIU or Accessory Interface Unit your are in effect utilizing relays. The AUI takes a command signal from your TIU and closes an associated contact. Those contacts can be used to control a switch the same way the control button works that came with the switch, or you can operate accessories.

As for your reversing ground that's used as an anti derail safety signal you still wont to keep them in place between you sensing rail and the return signal port on the switch motor that throws the switch.

You see unless you are running a script via the DCS system there is no way to avoid a derail other then pushing the switch button yourself when an engine MTH or otherwise enters the turnout and I can guarantee that you will be running many applications and products other then what you plan for your script.

Have Fun.  

What is a script dcs?  So i dont need relays or any insulated track. I can run full power to the whole layout all the time and just not start the ngines that i dont want to run.

A script is a program you can set up in your DCS that tells trains and accessories to do what ever you tell them to do in a preprogramed event sequence, that you setup

.  You can operate a number of engines, switches and accessories in sequence from a simple command from your Hand Held unit and repeat that sequence time and time again.

Check your DCS manual, or better yet get your hands on a copy of the new DCS companion. It will go much deeper into the subject then I can here.

Your above statement is true, but I would still install the switch safety jumpers we spoke of above. You may and probably will wont to run a conventional engine in the future, so I would also have a throttle control from your transformer, not just a brick. Just remember that your TIU wont's about 18VAC on it's input ports so make sure you have Volt / Amp meters on the transformer, such as the MTH Z4K, or Lionel ZW.

Have Fun!

I can run full power to the whole layout all the time and just not start the ngines that i dont want to run.

That's not so good an idea for several reasons:

• DCS engines (PS2 and PS3) log time on their odometers whenever they are getting power, whether started up in DCS mode or not. Leaving them on powered tracks will run up their chronometers and heat their electronics, as well.
• Having lighted passenger cars or engines on when not in use sucks power off that won't be available for trains that are actually running, i.e., engines, lighted passenger cars, etc.
• If there's a short circuit on the tracks or some other issue, it's much easier to troubleshoot the problem if one can selectively turn off track power.

What is a script dcs? 

It's what GG1Man states in his post above. However, it's actually called a "Record/Playback session" in DCS terminology.

This and a whole lot more is all in “The DCS Companion 3rd Edition!" This book is available from many fine OGR advertisers and forum sponsors, or as an eBook or a printed book at OGR’s web store!

I have no clue what this means. I thought all realtrax switches have the auto switch built in them. I dont have any reverseing loops and why would the polarity need to be changed on 3 rail track?

"As for your reversing ground that's used as an anti derail safety signal you still wont to keep them in place between you sensing rail and the return signal port on the switch motor that throws the switch."

Even if you don't start a DCS engine it still draws power.  The DCS engine chronometer runs whenever the engine is powered - not just when it has started up.   Additionally lighted passenger cars and caboose, powered/animated rolling stock, etc. can draw a few Watts each.  It all adds up.  So if just sitting idle on your yard, these will reduce whatever transformer power you have to run the active trains.  As mentioned earlier, this would be a good use of a AIU/relay to control on/off power to a siding, spur, yard section, etc. from the convenience of your DCS remote.

Actually, Stan, I don't believe an AIU relay has the capacity to control a track circuit, except using it to drive another relay.

HRSPLA:  There is no need to reverse polarity on loops when using 3-rail track.  Also, one does not turn lff a track using DCS (other than wiring it through a relay controlled by an AIU, or by placing it non a separate TIU channel.  But Barry and STan are correct.  I would add that a derailment short on a layout can cause shut down locos to start up.

I would add that for expert advice on DCS, post your questions on the DCS forum, not here.

What gauge wire should I use for my track power of the power distribution block and the transformer?

RJR posted:

Actually, Stan, I don't believe an AIU relay has the capacity to control a track circuit, except using it to drive another relay.

Stan, I was referring to the internal aiu relays.

On my layout, entire layout is toggled blocks.  Power with dcs signal goes a foot from TIU to control panel, which has toggles on a layout map, and then 14 gauge wire from toggle to block.  Great for teducing voltage loss and I get solid dvs signal strength.

RJR posted:

Stan, I was referring to the internal aiu relays.

Not sure I understand your comment?  The photo I showed is indeed of the internal AIU relays showing 10 Amp capacity which (in my opinion) is suitable for controlling a siding or yard spur.  That is, I hope the OP is not running engines or consists in a yard at more than, say, 10-20 sMPH max sMPH before hitting the mainline!  At such slow speeds a DCS engine (even pulling cars) should be drawing no more than a few Amps...definitely nowhere near 10 Amps.

Out of curiosity, how do you deal with the issue of manually flipping a toggle switch to turn on a block with a DCS engine?  Of the various methods, which have you chosen to get the DCS engine to stay silent in command mode when you flip the toggle switch to apply power to the block? 

stan2004 posted:

RJR posted:

Actually, Stan, I don't believe an AIU relay has the capacity to control a track circuit, except using it to drive another relay.

 

The AIU relays that I use are rated 10 Amps (@277V AC). Of course there are limitations on printed-wire and connector capacity.   But comment is definitely to the point.  That is, relay's have limitations.

Stan, many AIU models have 5A relays, and would certainly not be suitable for track power.  Also, the AIU specifications say 4A, and the connectors don't accept a very large wire, about #22 is their limit.  Here's one of my AIU's.

HRSPLA(?),

If you do a search to will find posts from GRJ, Barry, and others that the actual relays in the AIU are rated at 5 amps, and MTH states 4 amps for it's AIU rating.  GRJ also mentioned that older AIUs may have had higher rated relays, which is what Stan above may have.  4 amps is probably good enough to run an engine by itself as well as freights, but may not be enough for a lighted passenger train.

All command engines are on all the time if they are on powered track, so I want the ability to turn off track power to sidings where they are parked so the engines last longer.  I was going to use 30 amp relays triggered by Lionel's ASCs (or AIU) for my track power because these relays were easy to find, but now I'm going direct through Lionel's BPC2 which has relays rated at 20 amps.  My tracks are powered by two PH180s through a TPC400 and a 15 amp electronic CB, so I want the higher amp rated relays.  I do not run my track power though the TIU because it will not handle over 10 amps, so my TIUs are connected in passive mode.

See, its pretty simple.  However, if you don't want to use relays get a good SPDT or SPST switch, they are a lot cheaper.  Whatever you do, I recommend parking your engines on track that has switched power.

Because of my power requirements, I run 12 gauge wire from the TPC to the distribution block, 14 gauge almost to the track, and short 16 gauge feeder wires to the track (for easier soldering).

ADDED:  Looks like GRJ beat me to it (again).

You typed too much stuff, I was able to slip in.

I'm not using a AIU so i dont need relays for my switches?  I will have a z4000 for power.  I will be running no more than 2 engines and maybe a switcher in the yard at one time no lights or accessories that need power. Will the z4000 be enough for that? 

It's full circle back to the topic name.

In your initial post, you said you're building a "full MTH DCS layout".  I (apparently mistakenly) equated that to meaning everything is under command control so you can sit back with your handheld remote and be master of your universe.  In this interpretation of full DCS  you would use relays (via an AIU) to activate the switches via remote control.  But if you are OK with manual control (that is, the control box that come with the switches) then you don't need relays.

Separately, if you choose to remotely control block power you would use relays (via an AIU; or an AIU with help from external higher Amp relays).  But if you are OK with manual control using toggle switches to turn on/off block power then you don't need relays.

If the "relay" question can be settled it might allow better focus on your latter question about whether a Z4000 is enough.  That is, I think this issue is independent of whether you use choose to use relays for controlling turnouts or for block on/off power control.  In my opinion of course...

HRSPLA:  I run as many as 7 locos on a single Z4000 simultaneously with no problems.  Only reason I don't run more is because the track gets too crowded.

Stan: when I power on a track, it's because it want to run the loco(s) on it.  There'd be no point in powering up otherwise--all my locos have supercaps so I don't have to poweron the track to charge batteries.  So, after I throw the toggle, I hit startup on the remote or smartphone, just as I'd do if the loco started silent in command.  As an aside, even without the watchdog, locos often start in command; don't know why.

It's interesting that MTH has apparently made a major change in AIU relay capacity.  I've never opened any of my 3 so I don't know what's inside.  Now for clarification:  I assumed we are talking about the accessory relays; does MTH use different relays for switches and for accessories.

I would note that my system of wiring blocks means that only the short lengths of wire from transformer to TIU to control panel, under 2 feet, are carrying the full load of all locos running on a TIU channel.  Rarely would the 14-gauge lead from toggle to block (which can run up to 40 feet) be feeding more than one loco, unless I were double-heading.

Sorry I didnt know that you could control switches from the dcs remote. Now I have more to think about.

HSPLA:  Yes.  This is done by use of an AIU, which can control 10 switches plus 10 accessories.  My recommendation would be to go and build your layout first, and get everything working.  Use the standard controllers or equivalent momentary contact toggles to control the switches.  An AIU can be added easily.  Trust me, you will want the redundancy you get from having manual controllers in addition to AIU control over switches.

If you will only be running DCS locos, no conventional, with 2 main lines, a yard, and some sidings, I'd have each handle of the Z4000 feeding 2 TIU channels, with the TIU itself being powered by a wall wart via its AUX port.  I'd set the variable channels to function as fixed.  I'd use one channel each for each mainline, the yard, and the siding(s).

Stan,

Out of curiosity, how do you deal with the issue of manually flipping a toggle switch to turn on a block with a DCS engine?  Of the various methods, which have you chosen to get the DCS engine to stay silent in command mode when you flip the toggle switch to apply power to the block? 

Either one of the following:

• Turn on the siding's toggle switch, engine comes up in conventional and press Startup. This does not work for lashups.
• Highlight engine in the Engine List (Active or Inactive), turn on the siding's toggle switch and press the thumbwheel. Engine comes up in DCS mode, dark and silent. Press Startup. This works for both individual engines, as well as lashups.

This and a whole lot more is all in “The DCS Companion 3rd Edition!" This book is available from many fine OGR advertisers and forum sponsors, or as an eBook or a printed book at OGR’s web store!

Robert,

I run as many as 7 locos on a single Z4000 simultaneously with no problems.  Only reason I don't run more is because the track gets too crowded.

That's because you don't ever have smoke turned on. With smoke turned on, I expect that you could operate about 4 engines without issues.

No question using smoke would reduce number of locos I could run, as well as ruining my lungs.  But let's get specific about "issues."  A Z4000 breaker opens at approximately 10 amps on either handle.  At 10 amps, the Z4000 is perfectly capable of supplying sufficient amperage to run trains.  So the only issue I can see is either (1) the breaker will open if you exceed 10 amps or (2) actual voltage on the track will be insufficient, which (since the transformer can furnish the amperage) can only be caused by inadequate gauge wire or poor wire or track connections.   I avoid the latter because the center rail of each of the many blocks is fed by 14-gauge wire direct from the control panel and my blocks are fairly short.

Robert,

so the only issue I can see is ... (1) the breaker will open if you exceed 10 amps

That's the issue to which I was referring.

OK, it either opens or it doesn't.  If it doesn't, you're ok.  Can we agree that a modern transformer is adequate power supply until you reach a point where the breaker opens regularly?

It's not like years ago with postwar (and prewar) Lionel transformers, where you could overload them drastically without the inadequate breaker opening, and get inadequate voltage situations.  In the middle of the last century, I ran 2 steam locos, a #97 coal elevator, and 4 022 switches (each bulb being 5 watts) on a 100-watt Type R.  A modern 100-watt transformers (like a Z1000) would have blown a breaker.

Robert,

Can we agree that a modern transformer is adequate power supply until you reach a point where the breaker opens regularly?

Absolutely! I didn't think we were in any disagreement, at all.

I use the AIU to control my switches but I use external relays controlled by the AIU. It is much easier to replace an external relay than one in the AIU.

RJR posted:

...

If you will only be running DCS locos, no conventional, with 2 main lines, a yard, and some sidings, I'd have each handle of the Z4000 feeding 2 TIU channels, with the TIU itself being powered by a wall wart via its AUX port.  I'd set the variable channels to function as fixed.  I'd use one channel each for each mainline, the yard, and the siding(s).

HRSPLA, irrespective of whether a Z4000 can handle your entire layout, the configuration as proposed by RJR can address the issue of on/off power of the sidings/yard so unused/idle engines are unpowered.  In other words with 4 TIU outputs you can choose to turn off one or more of them.  So you effectively have "relay" control of block power; of course you do have to insulate the siding or yard from the mainlines such that power only comes from the respective TIU output. 

If later you add more sidings, spurs, blocks, whatever that you want to independently or selectively power under DCS control you can consider relays (via an AIU).  Or add additional TIU(s) each providing controlled power to 4 blocks ... albeit a high cost per "relay" if that's the sole purpose of the additional TIU!

Barry, we agree.  But often the question appears on the forum, is my transformer powerful enough to run....?  The answer to me is that if you are using a modern transformer (i.e., with an intyernal electronic breaker, like Z4000 or PH-180) in good condition, it's good until/unless the breakers open during ordinary use.  If the transformer is running within its amp rating and the track voltage is insufficient, then your wiring is probably deficient.

Also, with a modern transformer, if you're drawing with amp ratings and transformer output voltage drops substantially with that load, you probably have an internal; transformer problem.  Also, since components do fail, even with a  modern transformer, I recommend for redundancy an external breaker.