There's no positive or negative. Does it matter?

[Anonymous]

I made an observation that I never knew existed until I got into wiring my accessories. Many books that I have read and even you guys here talk about connecting accessories to a positive and negative. That makes sense one would think. Except for one thing. The transformers I own do not have marked posts as to positive or negative and the accessories are not marked either.

I noticed it makes little difference which wire goes to which post, as long as you have one going to each. So, is this correct? Or are my accessories/transformers unusual?

Wanted to ask this before I started hooking up a bunch of things---BTW, thanks for the suggestions as to how to hook up multiple accessories!

[spankybird]

HI Jack,

You have a good point. Most accessories do not have a positive or negative post and it does not mater which is which.

Most and not all, transformers have an common terminal witch is consider the negative. The ‘A’, ‘B’ etc. post is consider the positive. And I believe that there is one or two Lionel’s out there that is just the opposite.

Hard to tell which is which.

[Anonymous]

Since we use AC, there really is no "positve" or "negative". But there still may be concerns about the phase of the AC if you are applying more than one transformer the same circuit. Since the whistle and bell buttons apply DC to the rails, it does matter which way you wire to the rails. But it's easy to tell if that's reversed, and then you just switch the wires.... no harm done.

[Anonymous]

Jack:

A/C current doesn't work the same as D/C, but, from a safety perspective, it does matter which wire goes where. This matters more when you're working on household wiring than layout wiring, but you should still follow the same wiring practices.

Instead of positive & negative, A/C has Hot & Common. "Common" is not to be confused with what is usually called "ground," which is actually a connection to earth ground.

Essentially, think of the hot wire as being a water pipe under pressure, and the common as being a return pipe where the water isn't under pressure, but just flows back to where it came.

Generally, you want your switches to interrupt the hot wire in the circuit, not the common. This has to do with the possibility of a person touching something that inadvertently contacts the common while the power is off.

If the receptacle's hot lead is connected to the common in the appliance, and something contacts the common that a person can touch, you've got an electroution risk present. If the hot lead from the receptacle is connected to the hot side of the appliance, on the other hand, even if something a person can touch comes in contact with the common, there's no electrocution risk.

Every accessory has a hot & a common connection. What you do on a layout is connect all of the commons together. Generally, you'll need a larger wire on the common because all of the current flowing back to the transformers goes through the one wire.

So, while everything will work no matter how you connect things, keep the commons with the commons & the hots with the hots.

Tony

[Anonymous]

Thanks guys! But Tony, which is which? My Lionel transformer has two posts on it. Nothing is marked as anything. So is hot the left or right post?

Also, another question: Do you really NEED to have the jumpers on the back of the ZW in the spots not being used? If so, I'm short a jumper.

Thanks again!

[Anonymous]

heres the back of a ZW...

[eZAK]

Amtrak Jack,
No jumpers on the ZW needed!

What transformers do you own or will you be using?

With a volt meter and some knowledge you could determine which post are which.

Tony is correct about wiring, But if you are only using One transformer for just acc. then it would not make a difference in our low voltage world.
The problem arises when using more than one trans.
You would have to correctly phase each trans

[Anonymous]

Hi guys!

Jerry: I have no problem knowing the back of the ZW, you use B-U and C-U, but thanks!
eZak: The transformer I started all this about is Lionel's 6-03-2934-000. I think it came with a set. If you email me I can send you a picture of the back, but believe me, it is just two posts with thumb screws marked "AC" at the bottom of course.

Good news about the new ZW! I lost a jumper and according to the manual, you need them. I didn't really think so.

[Anonymous]

I was meaning you to use this to descibe things to us.

[lionelsoni]

Jack, if you've only got two terminals, it doesn't matter which is which.

Tony, unfortunately there is a very "common" exception to your general rule of returning all accessory circuits to ground and switching the other side. That is the widespread use of an isolated running rail to control a crossing gate, signal, switch motor, or what-have-you. In these cases, the train's wheels act as an electrical switch between the accessory and the common side of the transformer, which is usually connected to the running rails.

The philosophy of switching ground or common is (was?) widely used in automatic telephony, where all the relay logic was done on the ground side, with relay coils returned (-48 volt) battery. The reasoning was that any ground faults in the extensive wiring of the relay contacts would do no more harm than to energize the relay coils, avoiding any fire hazard and allowing the undamaged remainder of the exchange to continue to operate.

[Anonymous]

Thanks Bob!

[Anonymous]

Jack:

The general rule with Lionel transformers that are maked is that the U post is the common. The 1044 (which I have) is one known exception. On a ZW, the U post is definitely common.

What Bob says about isolated rails is true. I have an MTH grade crossing set with sound that I have wired up that way. I also have a SPST on-off switch wired in between the transformer & the rail, which allows me to turn off the sounds & flashing lights. The reason I did this is because my layout is so small that the dinging sound would play almost constantly with out it, and there are times I just want a little peace & quiet.

Tony

[Anonymous]

QUOTE: Originally posted by vitabile

Jack:

The general rule with Lionel transformers that are maked is that the U post is the common. The 1044 (which I have) is one known exception. On a ZW, the U post is definitely common.

What Bob says about isolated rails is true. I have an MTH grade crossing set with sound that I have wired up that way. I also have a SPST on-off switch wired in between the transformer & the rail, which allows me to turn off the sounds & flashing lights. The reason I did this is because my layout is so small that the dinging sound would play almost constantly with out it, and there are times I just want a little peace & quiet.

Tony

Thanks Tony. That is something I do need to do!

[daan]

Just something simple to make the difference between AC and DC clear. DC is a continuous positive and continuous negative power source, like a battery of a car. AC is in fact DC, only it switches polarity at a rate of 50 to 60 times per second (depends on the turning speed of the generator used in the power plant). That's a fact you can't change with electricity when you make it from movement.
Chemically made electricity is always DC and mechanically made electricity is always AC.
Since we like to talk about electricity in an easy way, we also talk about + and - when talking AC. In fact you take 1/60th part of a second, and when you look at it then, you have the same thing as with DC, a + and -.
Since they change 50/60 times per second, both plugs are "live". The life part switches between the two plugs all the time.

[eZAK]

Jack try this,
Phase your trans with the ZW.
Mark the post accordingly.
Also mark the plug or replace with a polerized one.

The ZW's 'U' terminal should be jumpered internaly.
This can be tested using a volt meter.

[lionelsoni]

Daan, sorry, but you can very well generate DC mechanically, as with an automobile generator, for example.

Also, if you look at 1/60 second of (American) AC, you will not see constant voltage but a complete cycle of a sine wave, through both polarities. You have to take a much shorter snapshot before it looks like DC.

I would take the term "live" to mean ungrounded, which would mean that the grounded side of an AC circuit is never "live". The other side however always is (except for the instants 120 times each second when the voltage between the wires is zero).

[daan]

@ lionelsoni, an automobile generator has an electronic device in it, which is called a rectifier.. The only way to convert movement into electricity is make a magnet move along a coil, which always gives a + when moving forth and a - when moving back. Or when using a rotary magnet, a + when the negative pole moves by and a - when the positive moves by.
A rectifier will convert ac into dc. A car generator makes 3 sinuswave's (3 phase) AC which is rectified in a 3 step rectifier, which also acts as a power cut-off to avoid battery overload.
But that's something we don't use on modeltrains, so besides the point anyway...

[lionelsoni]

Daan, you're thinking of modern cars, which have what are usually called, in English, alternators. They are indeed AC generators feeding 3-phase bridge rectifiers. Older cars (like the 1962 Volvo in my garage) have DC generators.

Edison famously insisted on DC generation in the beginnings of electrical power distribution, but lost out to Westinghouse's AC, which could be transformed. Early Lionel catalogs listed DC controllers for those whose houses were supplied with DC. I have one of these.

Diesel-electric locomotives until recently have used DC generators to produce the electrical power for their traction motors. They are now moving to AC generators, similar to (but much larger than) those in automobiles.

The point that you are missing is that the commutator continuously rewires the generator as the shaft turns, so that the polarity of the voltage induced by moving the armature coils through the magnetic field is always the same as seen at the output terminals.

Nevertheless, it is even possible to construct a DC generator, although not a very practical one, without a commutator: Get a toroidal field magnet with two large circular faces separated by a small gap. Mount a copper disc on an axle within that gap. Connect one wire to the center of the disc, another to a brush or brushes running along the rim of the disc. When you rotate the disc, a DC voltage will appear between the wires.

[daan]

Bob, this is sounding interesting. You mean that a DC generator actually works like a sort of can motor? Instead of the brushes applying the power it is used to take of the power? In that way you can have DC coming out, because you change polarity while rotating the anchor automaticly. In fact you still make AC, but by changing connections all the time the result at the connections is DC. Never thought of it that way.. Normally I work with 380V AC and 24 V DC at my job, so about higher voltages in DC I don't know much. My DC is the result of a rectifier, but your explanation makes a lot of sense. Thanx.

[spankybird]

Bob brings back many old memories of working on cars when I was a teenager. Most US cars before the mid 60’s had DC generators (with commutator). The real problem with these was that it required a higher RPM than idle to charge the battery. Many cars ended up with a dead battery if left idling to long. When AC alternators enter the scene around 1963 or 1964, they would produce a charge at 800 rpm. They also outlasted a DC generator life. Some cars I remembering replacing the generator once a year.

[lionelsoni]

Yes, Daan, there is very little difference between a DC motor and a generator. In fact, regenerative braking in locomotives works by reconnecting the traction motors as generators and feeding the resulting electrical power back to the wire or third rail or, in the case of Diesel-electrics, to a resistor bank.

The Lionel reducers were produced in 110 and 220-volt versions. Depending on which way you plugged them in (plugs were not polarized until much later), you had an even chance that the toy-train track rails were connected to that voltage. Can you imagine getting away with selling toys like that nowadays? Safety aside, my 110-volt model 107 does work very smoothly, however. I run it on AC, which works just as well as DC for these contraptions, which are essentially high-powered potentiometers.

I once had the pleasure of repairing the generator on a 1968 Volvo 144S while it was parked at the curb. The field winding had come open; and I was incredibly lucky to be able to see the break through a ventilating slot from under the car. I was able to solder it back together without even removing the generator!