One connector is all you need

[FJ and G]

Some of you forum members provided a tip on connectors to my good toy train buddy. He got hisself one at RS and here's the photographic proof in the pudding.

His layout is fully collapsable. Here's what he wrote in an email:

"Here's what one of my 25-pin quick-disconnect electrical connectors looks like with wiring leads soldered. It seems like a profusion of wires, but alternating with black and red-insulated wiring helps you to sort them out quickly. You'd be surprised how quickly each lead is committed when wiring multiple blocks, three-wire switch machines, accessories, and lights! I have a similar connector for the third section of the modular Port of NY & NJ layout.
 
Once all wiring is completed, metal covers clamp on each of the male and female connectors so that you pull the connector's cover apart to separate the halves--and not the soldered leads!
 
This is a good way to develop soldering proficiency in a hurry ... and a good reason to own a professional-quality wire-stripping tool!

[laz 57]

Looks like SPAGHETTI?
laz57

[lionelsoni]

I would (and have) advised against using what looks like rather small wire for powering trains ("multiple blocks"). The wire should be large enough to stand the fault current that the transformer can deliver, without starting a fire.

That kind of connector is also not designed for high current. They are typically rated at only a few amperes.

[FJ and G]

Thanks for your feedback. I'll let him know that his wiring is hazardous and looks like spaghetti. [:P][;)]

[Anonymous]

Hello Dave: Bob is right, those connectors are meant for communication, not a good idea to use them. Regards Steve

[FJ and G]

Rather than tell my buddy NOT to use them, can I nicely let him know they may not work by reminding him of the amperage that may need to pass thru the device?

If so, pls let me know:

1. What is the max amps (I know it depends on what he's using/running, but can you give me an upper conservative ballpark figure?

2. Does radio shack rate these devices on its packages and if not, how can a novice rate a particular device?

This I feel may be more constructive feedback than just telling him he's making a mistake and they look terrible.

Thanks

[Anonymous]

The current rating varies from 1A to 7.5A depending on the design & quality. The 1A rating was for an IDC connector and is mainly due to the small size of the IDC ribbon cable (28 or 30 gauge). Most wire mount connectors can handle 3A but you will have to look at the manufacturer's data sheet to find the actual current rating.

Also, the wire mount connectors are usually limited to about #22 gauge wire maximum, which is good for about 3.75 amps.

They should be fine for switches & control. For track power, you should use a heavier duty connector or parallel 4 wires together (4 hot & 4 common wires per power block).

Daniel Lang

[Dave Farquhar]

I searched Radio Shack's site and found a category of connector that's suitable for carrying the kinds of power you'd expect to find on a toy train layout.

http://tinyurl.com/47hkn

I suspect the pictures aren't right; the descriptions speak of multiple positions on the connectors but all the pictures only show two positions.

At any rate, these are a much safer way to carry track power, and they're nearly as convenient as those DB-25 connectors.

[andregg1]

you need the "molex" this kind of conector is for high voltage mean 110 v to 230 v
sorry I don't have a picture yet.
Andre.

[FJ and G]

thanks, guys, In a couple hours I'll send him an email like this (pls make corrections where needed). He's a great friend of mine, a retired naval aviator and my former boss.

Gordy,

That is a great wiring job. A couple of comments.

While the connector you wired is great for accessories and other items that require low voltage, I would be a bit concerned about using that particular connector to carry the high amperage used for toy trains, unless that component is specifically rated for such. Toy train current varies from about 2 to 8 amps, depending on a lot of factors.

Most wire mount connectors can handle 3A but you will have to look at the manufacturer's data sheet to find the actual current rating.

Also, the wire mount connectors are usually limited to about #22 gauge wire maximum, which is good for about 3.75 amps.

They should be fine for switches & control. For track power, you should use a heavier duty connector or parallel 4 wires together (4 hot & 4 common wires per power block). Molex is an example of a connector intended for high voltage.

[Dave Farquhar]

Molex sockets are difficult to find. The plugs can be scavenged from dead computer power supplies, so they're plentiful. Sockets can be scavenged from dead computer fans, but those sometimes only have two of the four connections. And a lot of fans use a different plug, especially recent fans.

The Radio Shack connectors I linked are a reasonable alternative.

[lionelsoni]

The Radio Shack connectors are Molex, or direct substitutes. Fry's carries a wide variety of Molex, if you have that store where you live. The Molex connectors come in two pin sizes. I would use the larger for track power.

The Molex pins are designed to be crimped to the wires; but I always solder the crimp. You can crimp and solder a Molex pin onto a stranded 14 AWG wire without much trouble. Solder the crimp to the conductor before wrapping the strain relief around the insulation, so that the heat does not melt the insulation under the strain relief.

The Molex male pins are protected better than some by a skirt around the connector. But it is still a good idea to assign the sex of the connectors so that the male side is dead when the connectors are unplugged.

The connectors and the wire should both be sized for the fault current, not for the typical train current. The fault current is what the transformer can deliver before the circuit breaker trips, not what the train uses in normal running. You want to protect your wiring when a derailment or other short circuit causes that large fault current to flow. Many large transformers can put out as much as 15 amperes, which requires 14 AWG wire to be safe. You can get by with 16 AWG, which is good for 10 amperes, with a small transformer; but I would advise not going below that. Since 14 AWG is used for house wiring, it is cheap and readily available. I highly recommend it.

High voltage is not a concern for toy trains. Virtually any connector or wire can handle the voltages we use.

[FJ and G]

Thanks for your comments and suggestions.

[FJ and G]

I need to enlist your assistance one more time.

He replied:

"hanks for thinking of me, Dave!
 
Here are specs for the 25-pin connector ... rated at 5 amps and upt to 500v AC for up to one minute. Given substantially lower voltage, shouldn't this be okay? (I know its the amperage that is the real concern).
 
Train runs fine on the block powered through the connector I've already wired ... but better safe than sorry!
 
What do you think?"

[FJ and G]

here's the data
-------------------------
 
25-Position Male Solder D-Sub Connector.



PRODUCT FEATURES:

* Contact terminals accommodate up to 20AWG wire

* Steel shell plated with zinc or tin

* The keystone shape of the shell assures proper polarization

* Coupling is accomplished by contact friction, although standard locking accessories may be used

* Rated: 5A, 500VAC for one minute

SPECIFICATIONS:

* Temperature: 40°C to 105°C

* This one is a 25-position HD male connector

[lionelsoni]

Again, the voltage rating doesn't matter. And that the "train runs fine" doesn't mean that it is safe. That connector with 20 AWG wire is okay for a transformer that trips at 5 amperes, if that's what he's using, with an intention never to get something bigger.

[andregg1]

http://www.molex.com/cgi-bin/bv/molex/home_init.jsp?BV_SessionID=@@@@0619716000.1111685464@@@@&BV_EngineID=cccfaddeegghlmdcflgcehedffgdfmk.0&mCnt=/super_family/super_family_saq.jsp&channel=Products&chanName=superFamily&superFamOID=-8810&oid=-8810&pageTitle=Wire-to-Wire
Here you can find information about molex terminals, I use in my layout and is easy to conect and disconect.

[FJ and G]

Thanks again, Bob. I'll pass this along.

[FJ and G]

A Z-4000 puts out 400 watts.

If power supplied is 125 V then amps should be 400 divided by 125, right?

That would equal about 3.3 amps, significantly less than 5 A rating

[andregg1]

may be I wrong, but this kind of transformer are electronic , so when you have a shotcircuit the transformes atomaticly try to increase the voltage and current. so you need some thing little bit strong.

[lionelsoni]

Dave, you are calculating the primary current, whereas it is the secondary current that is going through the connector. At 6 volts, the secondary could be supplying 400/6 or 67 amperes, if it weren't for the circuit breaker or whatever else it might have for protection.

Andre, no matter how the output is regulated, it is certain that there is some form of overcurrent protection that overrides the regulation. In traditional transformers, this was a circuit breaker. In an electronic "transformer", it may take some other form; but it will be present in any case.

[FJ and G]

Gothchya Bob,

I notified him. That electronics and math is daunting to the novice! I respect your knowledge.

[FJ and G]

One last question:

Gordy writes:

"Dave, when you talk of current going through the connector, each of the 25 wires has an individual set of pins ... so, for example, when the loco enters one block it is receiving power through just two wires through the connector ... and when it enters another block it shifts to another set of wires. This block wiring means that no set of wires is drawing a load (i.e., with loco in the block) at one time, right? Other power for switches and lighting also have dedicated wires. In case of lighting, it's a 10v output from the transformer, and I'm wiring two lights in series per connection to keep them dim and prolong life. The accessory terminal, 14V, is only activated when you hit a switch to activate a turnout. I will be running two locos simultaneously, so of course there is a higher load, but each has its own independent circuit. 
 
Is it the total amount of heat generated by this transmission of power that is the problem for the connector?
 
In any case, I'll take your notes with me when I go to Radio Shack tomorrow to pick up another component. I could not locate the other brand of connector you mentioned on the company web site's product listing."

[lionelsoni]

Thanks for the endorsement!

The current rating is on an individual-pin basis; so, unfortunately, you don't get credit for the unused pins.

As for how many locomotives are on a circuit, it doesn't matter. The important thing is still how much current the transformer can supply. If your transformer can put out 15 amperes, you have to assume that it will at some time, like after a derailment, and provide wire and connectors that will not heat up and cause a fire when that happens. Then you can safely draw whatever current you need, up to the transformer's capability, to run as many or as few trains as you like.

Here is another link to the Radio Shack catalog. As was noted, the pictures are wrong; but they are of the correct type of connector.
http://www.radioshack.com/category.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F011%5F003%5F008%5F000&Page=1

[FJ and G]

Thanks again.

I'm pretty certain that I'm not the only person who learned something from this conversation.

[FJ and G]

He's going with the molex!

he's also embarrassed because he took some semesters in electronics in Naval Academy back around 66

[lionelsoni]

Navy electronics is different! They decided long ago that they would consider that current flows the opposite way from the direction that the rest of the world uses, so that it would be easier to teach sailors how vacuum tubes work. Since the navy is responsible for electronics training material for all the services, they all learn it that way. I don't know how many ex-navy technicians I have come across who do it backwards!

[baltimoretrainworks]

I've been using 5 and 15 connector ground bus bars to wire my layout. One 5 connector to each of the a,b,c,d posts of my ZW and one 15 connector to the common. I also use 16 gauge lamp wire for wiring.
Each of the bus bars is mounted underneath the platform with sheetrock screws,
( GREATEST INVENTION FOR LAYOUT BUILDING!!! ) and each connector can hold 2-3 wires.
It also makes it a lot simpler to trace wiring to a particular
section of track.

[lionelsoni]

Drywall screws are of course fine for mounting stuff like that. They can also be okay for layout structure that won't be supporting a person. However, this might be a good place to note that they are very brittle, shear easily, and should not be used for anything that might cause injury if it broke.