As my layout grows,  I am contemplating what to use for accessory power.  I define "accessory power" as mostly layout lighting and accessories that do not rely on the main transformer "common" or U terminal as it is referred to on O gauge 3 rail layouts. Typically 12-14 volts, fixed load.  I'm drawing only about 3 amps now, but would like to have 5-10 amp capability.   While the ZW that I use as a main transformer has 4 outputs, I would like to farm out my accessory power to another source.   Here is what I am considering:  1) A separate transformer, using either the fixed or variable outputs.  2) A switching 12 VDC power supply which can now be gotten for about $25 and supplies 20 amps or more.  3)multiple smaller AC or DC supplies.    In addition to 12-14v power, would also contemplate 5VDC power distribution for LED devices.

I would like to get some ideas of what folks are using.  Also looking for a good way to fuse multiple branches off a single high current (AC or DC) supply.

 

Gary Liebisch

Columbus, OH

Super 'O' since 1958!

Original Post

Gary:

I use the 30 amp 12V DC that Ted shows. With the three outputs connected you have 10 amps per output. I have these outputs connected to three banks of Atlas O SPST connector boxes that will go out to various lights. The 12VDC will run LED's and incandescent bulbs.

For powered accessories you will have to set up an accessory transformer. I have three of the old Lionel 1 amp acc transformers (don't think they are made anymore) I use for this purpose.

I use the terminal board Richie shows to distribute power but have started getting into European style terminal strips. I like ferrule crimp connects which work great with the European terminal strips. https://ogrforum.ogaugerr.com/topic/ferrules

Joe

Joe Fauty

Keep in mind that you'll want to add appropriately sized circuit protection to most PW transformers for each circuit.  The Type-Z is rated to provide 14A continuous power, and all of that is available on any single output!  The single circuit breaker is pretty slow, and won't trip until it reaches well above the 14A that the transformer is rated to supply.  If you have a short with light accessory wiring, that's more than enough to generate fire starting heat!

Attachments

Photos (1)
gunrunnerjohn posted:

Keep in mind that you'll want to add appropriately sized circuit protection to most PW transformers for each circuit.  The Type-Z is rated to provide 14A continuous power, and all of that is available on any single output!  The single circuit breaker is pretty slow, and won't trip until it reaches well above the 14A that the transformer is rated to supply.  If you have a short with light accessory wiring, that's more than enough to generate fire starting heat!

John,  

That is very good advice!  Should have mentioned that!

Thanks,

Fred

 

 

Thank you for all the replies!  My main transformer is a ZW with a PSX-1 AC for protection of my DCS TIU.  Ultimately the most flexible solution would be to just add another ZW or smaller transformer with variable voltages.   I think I can protect "lighting only" accessories with fast blow fuses, as long as I branch them at lower values to make troubleshooting easier and to lower the threshold of when they blow.  Ted's idea of a high current 12VDC supply with  regulation down to lower voltages is interesting,  but again would probably branch fuse it thoroughly.

Gary Liebisch

Columbus, OH

Super 'O' since 1958!

Large transformer upper left.  These transformer(s) can have an assortment of uses.   Commonly called buck, or boost transformers , they are used to correct AC voltages where needed.  This one could be wired for either 12 volts or 24 volts with a 120 volt input. 

  

Gary Liebisch posted:

Thank you for all the replies!  My main transformer is a ZW with a PSX-1 AC for protection of my DCS TIU.  Ultimately the most flexible solution would be to just add another ZW or smaller transformer with variable voltages.   I think I can protect "lighting only" accessories with fast blow fuses, as long as I branch them at lower values to make troubleshooting easier and to lower the threshold of when they blow.  Ted's idea of a high current 12VDC supply with  regulation down to lower voltages is interesting,  but again would probably branch fuse it thoroughly.

Yes, I use resettable fuses wherever I’m a little squeamish about a potential short.

 4816CC79-38D7-4E3B-88C4-5F56AF2881F6

 

Attachments

Photos (1)
Gary Liebisch posted:

I would assume by “resettable” you mean they reset themselves after x seconds? Or do they reset by recycling power off and on”?  I like to investigate and clear the short before a reset.

You clear the short, they reset.

Sort of Ted.  They are still passing some current.

A polymeric PTC device is made up of a non-conductive crystalline organic polymer matrix that is loaded with carbon black particles to make it conductive. While cool, the polymer is in a crystalline state, with the carbon forced into the regions between crystals, forming many conductive chains. Since it is conductive (the "initial resistance"), it will pass a current. If too much current is passed through the device the device will begin to heat. As the device heats, the polymer will expand, changing from a crystalline into an amorphous state. The expansion separates the carbon particles and breaks the conductive pathways, causing the device to heat faster and expand more, further raising the resistance. This increase in resistance substantially reduces the current in the circuit. A small (leakage) current still flows through the device and is sufficient to maintain the temperature at a level which will keep it in the high resistance state. Leakage current can range from less than a hundred mA at rated voltage up to a few hundred mA at lower voltages. The device can be said to have latching functionality. The hold current is the maximum current at which the device is guaranteed not to trip. The trip current is the current at which the device is guaranteed to trip.

The 3A ones are a decent choice for this task, it's unlikely that they'll pass enough current to start melting wire larger than around #24.

Add Reply

Post
OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
330-757-3020

www.ogaugerr.com
×
×
×
×
×