Siding Switches and Wiring

Your toggle switch will work fine - it is super heavy duty for a Model RR aplication.    If you think in terms of VA (volt-amp) rating as they rate HO transformers, that toggle would be rated at 20 amps times 125 volts or 2500 VA.     Your train on the track will be in the ball park of 18V and 2-3 amps.    If 3 amps, that is a draw of 54 VA,

If you just consider the amp rating your trains probably draw 3 amps give or take depending on how new and lighted cars etc, and the toggle is rated at 20 amps.   

I think the 14 gauge wire will work just fine and not too much voltage drop.

I don't think you need any fusing or protection on those circuits to the sidings.    If you are still worried, try the "quarter text" after you install the wiring.   Turn on the power and short the track with a piece of metal (the HO guys use a quarter because it fits) and see if the breaker in your power supply or breaker board goes out immediately.    It should.    If the short sits and simmers, your wiring is too light.

Thanks, Jim - just the info I was looking for.

My Z4K trips pretty quickly so that should not be an issue.

I used the 1 3/8" sections of track at the head of each siding to save cutting the center rail, and you have a tab for the connection. You also don't need to make the "round trip" with the wire if you have a transformer closer. Just run the power to the toggle switch from the nearest available track power and then on to the siding. For more than one siding, jumper the power from switch to switch.

Routing the power to the cut, back to a switch, then back to the siding is a lot of lentgh, and that leads to voltage drop and a possible need for fatter wire too. (Wire is chosen for match to max output; X -volts & X amps & X-feet = wire guage needed. It is a standard. "AWG" reference charts for choosing are only a search term away. John's suggestion saves a whole lot of wire; good for the electrical, and good for the wallet .

You will probably want to check the max voltage for the switches before connecting it to the track power.  If it’s operating above the max voltage it will most likely burn out. You will also want to check if it is DC or AC powered as if it is DC, you’ll also have issues since command runs on AC.

I'd also consider a power relay right at the switching point and small gauge wire to the control panel.  The relay probably costs less than the heavy wire run and solves the problem of voltage drop.

gunrunnerjohn posted:

I'd also consider a power relay right at the switching point and small gauge wire to the control panel.  The relay probably costs less than the heavy wire run and solves the problem of voltage drop.

That’s also a good idea.  I’ve surprisingly never experienced voltage drops on my layout anywhere with switches even though I have at least 35ft of telephone wire (24 gauge I believe) going around my whole layout... others could have different experiences.

Evan, he's switching track power, not the switches.  That much 24ga wire handling track power would certainly have a significant voltage drop.  

For a 35 foot run of 24ga wire carrying three amps, the voltage drop is over 5 volts.

gunrunnerjohn posted:

Evan, he's switching track power, not the switches.  That much 24ga wire handling track power would certainly have a significant voltage drop.  

For a 35 foot run of 24ga wire carrying three amps, the voltage drop is over 5 volts.

In that case he’s definetly going to need some sort of a power relay... my mistake.  I thought he was taking power off of the track to power switches lol. (Insert facepalm here)

John H. - Using the 1 3/8" sections and jumper connections is a great idea as well as using track power - thanks.

Adriatic - you're right about the potential voltage loss on the long runs, that's why I was concerned.

Evan - will do.

GRJ - I had considered using a relay to shorten the length of the 14 ga. wire and then use small diameter wire to a switch on the control panel. The problem was the cost of the relays. The relays I saw on the 'net were either rated too high, ie., wouldn't perform at less than 50v input or were rated at too low of an amp draw. I couldn't find anything that fit our model railroad electrical parameters that was less than $35.00 each and, for 10 sidings, that's too much to pay. Do you have a link to a reasonably priced relay ?

Here’s one. The only downside is that it is DC powered, however it is rated at 30 amps.  From my minuscule amount of knowledge on electronics (which is still larger than 99.9% of modern teenagers I believe), you can use a full wave bridge rectifier to convert the voltage from AC to DC and then back from DC to AC.  Those usually go for around $2 or $3... making the total cost of one relay and two rectifiers $8/circuit.

Are you kidding???  You can have relays for peanuts!  Here's some with a contact rating of 10 amps, plenty for this task.

Search eBay: 182525752544, 10Pcs SRD-05VDC-SL-C DC 5V Rating Coil SPDT Miniature Power Relay Blue, $3.53 shipped free.

I think I was looking at solid state AC relays to avoid having to use a rectifier.  

Richie C. posted:

I think I was looking at solid state AC relays to avoid having to use a rectifier.  

Those are definetly more expensive. You just have to decide what is more important... extra wiring time, or extra money. 

Solid state relays are not a panacea, they drop some voltage across the relay, and they are way more expensive.  Adding a very simple 5V module is chicken feed, and hardly any significant wiring issue!  There are literally tons of USB phone chargers that provide 5V for a few bucks, and would power a host of these relays.  I personally think the the solid state relays are a poor choice.

The toggle switch he described could be used for house wiring, nothing on a model RR is going to damage it.

Also that type of solution is what has been used for decades for wiring AC and DC model RRs.    

Actually I am slightly off.    I would think the more direct way is to route from the transformer at the panel to the toggle at the panel, and then only 1 run to the center rail on the track rather from the track back to the panel and out again.

I think that was similar to John H's idea and it's a good one.

My track power goes from each handle of my Z4K to a separate distribution panel - one for each loop of track I have - and then to several drops/blocks on each loop.

I could jumper one side of all the siding switches together at the control panel and then run a wire from the + side of one of the unused terminals on one of the distribution panel to the first switch. Then I would run separate wires from the other side of each switch to the center rail of each siding, after the cut.

That should work to turn each siding on and off as needed; save wire; minimize voltage loss; and save wiring time.

Sounds like a plan and thanks to all.

John H posted:

I used the 1 3/8" sections of track at the head of each siding to save cutting the center rail, and you have a tab for the connection. You also don't need to make the "round trip" with the wire if you have a transformer closer. Just run the power to the toggle switch from the nearest available track power and then on to the siding. For more than one siding, jumper the power from switch to switch.

Quick observation using that method - I know, I may be over analyzing this, but it's an interesting discussion, at least to me.

I believe that the voltage coming from the track before the cut and the voltage coming directly from the transformer (or other track power) through a switch to the far side of the cut will be different (as opposed to wiring both sides of the cut through a switch or using a relay, in which cases the voltage on each side of the cut would be equalized) because you're using two different power sources - one for each side of the cut.

Would that potentially cause any issues, like sparking, when power is on and an engine is moving and a pick-up roller crosses the cut ?

gunrunnerjohn posted:

Are you kidding???  You can have relays for peanuts!  Here's some with a contact rating of 10 amps, plenty for this task.

And if one goes the DC relay approach, you can buy mounted 10 Amp relays with screw-terminal connections for less than $1 per relay.  1, 2, 4, 8, etc. relays per module.  Here's a re-cycled photo from an earlier OGR thread illustrating this technique.  If I recall correctly, one benefit of using 12V DC at the control panel is the availability of handsome, low-cost, illuminated automotive toggle switches.

stan2004 posted:

gunrunnerjohn posted:

Are you kidding???  You can have relays for peanuts!  Here's some with a contact rating of 10 amps, plenty for this task.

And if one goes the DC relay approach, you can buy mounted 10 Amp relays with screw-terminal connections for less than $1 per relay.  1, 2, 4, 8, etc. relays per module.  Here's a re-cycled photo from an earlier OGR thread illustrating this technique.  If I recall correctly, one benefit of using 12V DC at the control panel is the availability of handsome, low-cost, illuminated automotive toggle switches.

 

 

Any links for this?

Richie C. posted:

I believe that the voltage coming from the track before the cut and the voltage coming directly from the transformer (or other track power) through a switch to the far side of the cut will be different (as opposed to wiring both sides of the cut through a switch or using a relay, in which cases the voltage on each side of the cut would be equalized) because you're using two different power sources - one for each side of the cut.

Would that potentially cause any issues, like sparking, when power is on and an engine is moving and a pick-up roller crosses the cut ?

Since you are running with command control at 18 volts, why would you want to use a different power source for the sidings?

But if you do decide to use a separate power source for the sidings, as long as you approximate the difference between the two power sources with some degree of accuracy, there should be no problem.

Stan's diagram illustrates the whole idea nicely. As you have suggested, all that you need to do is jump the cut from the main supply to the center rail of the siding. Then issue commands to the engine in the siding and you're rolling.

Jayhawk500 posted:

...Any links for this? 

If you're asking about the relay method, here are a couple previous OGR threads:

https://ogrforum.com/...60#75340558683775160

https://ogrforum.com/...05#68018408499921205

Consolidated Leo posted:

Richie C. posted:

I believe that the voltage coming from the track before the cut and the voltage coming directly from the transformer (or other track power) through a switch to the far side of the cut will be different (as opposed to wiring both sides of the cut through a switch or using a relay, in which cases the voltage on each side of the cut would be equalized) because you're using two different power sources - one for each side of the cut.

Would that potentially cause any issues, like sparking, when power is on and an engine is moving and a pick-up roller crosses the cut ?

Since you are running with command control at 18 volts, why would you want to use a different power source for the sidings?

But if you do decide to use a separate power source for the sidings, as long as you approximate the difference between the two power sources with some degree of accuracy, there should be no problem.

Stan's diagram illustrates the whole idea nicely. As you have suggested, all that you need to do is jump the cut from the main supply to the center rail of the siding. Then issue commands to the engine in the siding and you're rolling.

Someone else in a prior post suggested pulling power to the switches at the control panel from a source (like a transformer) closer to the control panel and jumpering all the switches together in order to shorten wire length and minimize voltage loss (versus the "traditional" method of pulling wire from both sides of a siding cut to a switch). However, that would mean one power source before the cut from track power (at whatever voltage is present at that point in the track) and one power source after the cut from a different power source (such as a transformer or distribution panel).

I didn't say I wanted to do it - only commented that, although that method would save wire length, wiring and voltage loss, the potential drawback is that the voltages on either side of the cut, since they're coming from two different power sources, might not match and I was asking whether the mis-matched voltages, if significant enough, could cause problems, such as sparking, when the pick-up roller bridges the cut.

It may be that the voltage difference would either be non-existent or minimal enough so that it would not be an issue, but that was my question. Obviously, I could try it out and measure the voltage difference on either side of the cut and see if it was significant or created any issues, but I figured I'd ask the question first and see if anyone knew.   

Richie C:

Understood. You would want a close match for sure.

The relay method, as recommended by GRJ and Stan, is what I would want to do. Because the signals from the toggle switches are low amperage 12 volt DC, you can use thin wires from the control panel out to the modules near the sidings. These could be exceptionally long runs and would minimize the length of the track power to the sidings; no voltage drop.

The 12 volt versions would allow the use of attractive LED lighted auto toggle switches for the panel. You could tell at a glance which sidings are powered and which aren't.

The relay modules are very inexpensive and you can find the toggle switches starting at about a dollar each; search eBay but then come back to the forum. It may take a bit more to wire it up but the idea is rock solid. Good luck!!!

I should have been more specific in my post. Where I said "a transformer", I should have said "a track power transformer" closer to the siding. Sorry I confused the issue.