spst switch

[rookie]

Help! I am trying to isolate 2 short sections of track. One is to park my switcher while train is in operation and one is to park my loco while my switcher is making up trains. I have a single outer loop track with an inner turnout with sidings for cars. I have wired up a test track and connected the spst switch in between track and power pack but i can't get it to change direction. How do i wire this up correctly? Will i need to use separate switches for each section? thanks in advance for responding, david

[OldTimer]

A single pole single throw (SPST) switch is like a light switch.  To control a siding, do the following. 
1:  Gap one rail of the siding where you want the on-off section to start.  It doesn't matter which rail you gap,  but if you do more than one siding, you should be consistent.
2:  Run a wire from the the layout side of the gapped rail to one contact on the switch.
3:  Run a wire from the siding side of the gapped rail to the other contact on the switch.
When the switch is on, the siding will have power and your loco will run.  Flip the switch off and the loco will not receive power.  Hope this helps.
OldTimer

[rookie]

thanks very much

[jward]

you commented about not getting it to change direction. by "it" i assume you mean the locomotive.

you will not get your locomotive to change direction using a spst switch. all it will do is turn something on or off, in this case a section of your track. to reverse your locomotive you must use the reversing switch on your power pack.

i am also assuming that you run dc and not dcc (easy command, dynamis, etc....)

you will probably want to do more than just control one siding to park your switcher. having only that siding controlled by the spst switch. without having other switches controlling sections of your mainline track you will have no way to isolate your mainline train so the switcher can independently run. you'll need to divide your mainline into at least 2 "blocks" and ideally 3 or more. you'd hook up each section according to the excellent directions oldtimer gave. block wiring isn't that complicated, it's the same basic circuit repeated over and over.

you can take this a step further by using spdt switches instead of spst. make sure you use the kind with a "center off" position. using spdt switches, you can now connect two power packs to your track, and two trains can run indepoendently of each other anywhere on the layout.

the switches themselves would be wired this ay: the center terminal on each is connected to the track it controls. the outer two terminals would go to your two power packs. be sure to be consistent in your wiring, so that flipping each switch one way connects it to power pack "a", and flipping it the other way connects it to power pack "b."  the center position completely disconnects power from the track, allowing you to park a locomotive and leave it there.

[CNE Runner]

Jeff - I think you meant to write DPDT instead of SPDT for block wiring. In the event Rookie is attempting to run two power packs (Cab A + Cab B); the common is 'flipped' for reversing. In other words, the common wire needs to run to each DPDT selector switch (as well as the load wire) to properly run an insulated section of track (block) via two power packs. I would recommend the ON-OFF-ON type of DPDT switch so the operator can completely shut off the power to that block...allowing one to store a 'dead' locomotive on a siding without having to worry about it starting up expectantly. Reversing the current flow is still accomplished through the power pack (or at least that is the easiest method). If one is going to wire a layout for block control, it just makes sense to wire for two controllers.

DC requires a lot of wiring (as opposed to DCC - which theoretically only requires two wires); so color coding and terminal strips are essential. If you decided to stick with [I assume] DC, I would definitely suggest you wire your layout for two cab operation. Should you ever decide to go to DCC, you just leave all the DPDT switches in the Cab A position and replace your DC power packs with a DCC unit.

To make this long story - shorter - I would recommend DCC over DC any day. Yes, DCC is more expensive to purchase (and DCC-equipped locomotives cost significantly more), but that is the way the hobby is going - and you will be happier in the long run.

Ray

[jward]

no,
spdt is what i meant. dpdt allows you to add another circuit for lights on your control panel if you have one. otherwise, the extra set of contacts is unused. the only time you'd nneed to use a dpdt is for reversing loops or sections, as your auxiliary reverse. even that can be eliminated with the use of a bridge rectifier between the block switch and the track, or by wiring the reversing section through the contacts of a switch motor.

to prove my point, the atlas selector is a bank of four spdt switches intended to be used as block control. you only need to break the circuit to one rail. the other rail is a common return to both power packs. it is irrelevant which direction each pack is set for. as long as they aren't both connected to the same block, they are electrically seperate circuits with a common return.

think along the lines of a dual power supply as used in many electronic applications. one power supply has it's negative  connected to ground, the other its positive.

[rookie]

You know, things on a model rr track would be a lot simpler for me if i could just make everything out of wood........but there is no such thing as a wood electrician now, is there? thanks guys

[jward]

rookie,
it can be a bit overwhelming at first, but  there are some good books out there that show how it all works.

i would recommend picking up a copy of :
The Atlas Beginner's Guide to HO Model Railroading.

chapter 3 details block wiring, using the atlas components, and also explains their equivalent electrical switches. it shows how to wire them, with diagrams, to make the railroad do what you want it to. the rest of the book applies this to various track plans.

the book is only about $5 or 6 but it is a valuable reference that you'll probably wear out.....any hobby shop should carry it.

good luck and tell us how it works out.....

[rookie]

I'm not doing something right. My track is wired to a pp and powered up. Old timer said to run a wire from each side of the gapped rail to the switch. Didn't work. Do i run the wires from the same side of the track or one from each side? Do i need to hook the switch up to the pp? Does the switch get it's power from the track without being connected to the pp? If the track already has power how does running only one wire on each end work? I'm not an electrician but i' not a complete idiot either. Well, okay, maybe mostly! I have already wired up my other switches. Sorry, didn't mean to write a letter. Just need clarification, at least i can spell correctelly.....hee hee

[OldTimer]

If you did exactly what I suggested, then your switch is bad.
Do not connect the switch to the PP.
The switch, when it is on, closes the circuit that was opened by gapping the rail.

Do this to help you visualize the problem.
1.  Draw a straight line on a piece of paper.  That line represents your rail.
2.  Erase a piece of the line near the middle.  That represents the gap in the rail.
3.  Draw a second line attached to the first line at the gap.  Draw this line at an angle.  Pretend that this line is pivoted where it connects to the first line.  That line represents the switch.
4.  Imagine moving the line representing the switch around it's pivot so it touches the other line at the gap.  You have just closed the switch.

Or, try this.
You used to be able to buy SPST knife switches so we're going to make an imaginary knife switch. 
1.  Hold a table knife in your left hand.
2.  Hold a fork in your right hand.
Your left arm is the wire coming from the main line
Your right arm is the wire going to the siding.
3.  Move your hands so that the knife blade goes between two fork tines.  You have just closed the switch and powered your siding.
Hope this helps.
OldTimer

[jward]

the coonventional way to hook up block switches is, in fact, to hook them up to the power pack.

the one side goes to the power pack, and the other side goes to the gapped rail on the siding.

whatever you do, DON"T connect the switch to both rails of the track. this will short out your power pack the first time you turn the switch on, and might even burn up your pack.

the method oldtimer uses, to connect your switch to the rails on wither side of the gap, will work. but it is not a system you can use or modify to run multiple trains in the future.

[rookie]

Thanks again, old timer! I finally found my problem, at least the one on my train. I had a bad connection with a switch on my track at another location which was killing my power where i was placing my spst switch. After correcting that my switch works just like you said it would. I had it wired up right before, just wasn't aware of the short. See, i can follow good directions! I appreciate all of you guys sharing your expertise, which is why i asked in the first place. Thanks,a very happy rookie

[NarrowMinded]

May I suggest heading to the auto parts store and picking up an auxiliary fuse block strip, all my power sources pass through one of these before they connect to anything. Using an appropriate fuse will prevent costly mistakes for both new and old modelers/builders.

NM

[OldTimer]

You're very welcome, Rookie.  Glad I could help.

[Jim Banner]

May I suggest heading to the auto parts store and picking up an auxiliary fuse block strip, all my power sources pass through one of these before they connect to anything. Using an appropriate fuse will prevent costly mistakes for both new and old modelers/builders.

NM

Do you find you are blowing a lot of fuses?  Like every time a derailment causes a short?  While a fuse offers much quicker protection than the circuit breaker in a power pack, the circuit breaker automatically resets itself.  A fuse is rather like a bee protecting its hive - one shot and it is dead.

I am all for using fuses on every output of every auxiliary power source, and on the power inputs of things like DCC boosters, but on the track outputs of power packs, like rookie is using, no.

Jim