A Beginner's Power Supply Question

[Anonymous]

First off, the last time i had an HO layout was almost 20 years ago and i was pretty young, so all this neat DCC and complicated wiring either did not exist or was beyond my reach.  now i'm dying to get back in, and from what i've read it sounds like i need some good power sources for all the different little things that eventually might get added. 

Here's my question, what do i use for say, the power supply running accessories such as lighted buildings, or one running only switch machines (unless its easier to run these from the track blocks?)??  i'm assuming that for a larger layout i want seperate power sources for the track, and others for lights and signals, etc.  now the theoretical part, couldn't i just use a 12v transformer like the kind used for low-voltage outdoor lights?  its got a built in timer, can handle a variety of wattage, couldn't this work to power at least lighting inside buildings and whatnot, with the addition of whatever resisters may be needed to keep from blowing out bulbs?  someone help me out, because i am far from an electrical engineer!!  thanks a bunch

Dominic Miele 

[Texas Zepher]

20 years ago and i was pretty young, so all this neat DCC and complicated wiring either did not exist or was beyond my reach.

It definitely existed.  Just wasn't necessarily called DCC.  

Here's my question, what do i use for say, the power supply running accessories such as lighted buildings

The same thing you used 20 years ago.  The Accessory out put of a toy train transformer.

one running only switch machines

Depends on the kind of switch machines you are talking about.  Many modelers have abandon the twin-coil type snap switches and gone to slow motion stall motors.  The twin-coil type would still be powered just like they were 20 years ago.  The stall motors need DC power.

(unless its easier to run these from the track blocks?)??

Do you really mean the track blocks - much harder.  Do you mean from the DCC power block - that is doable just add the cost of stationary decoders.  I personally will never power turnouts from a DCC unit.  Way to hard to operate.

i'm assuming that for a larger layout i want seperate power sources for the track, and others for lights and signals, etc.

Yes, this is true even for smaller layouts.

now the theoretical part, couldn't i just use a 12v transformer like the kind used for low-voltage outdoor lights?  its got a built in timer, can handle a variety of wattage, couldn't this work to power at least lighting inside buildings and whatnot, with the addition of whatever resisters may be needed to keep from blowing out bulbs?

Yup that would work just fine.  That is what our club does.  The only thing would be to make certain the wattage was high enough for what you need.  Our club has two 5 amp 12V supplies for all accessories and turnouts.  Signalling gets it's own power just to prevent any possible cross feeds.

Along this line of thought a wonderful power supply is one out of an old computer.  The computer 12VDC supplies are regulated.  In simple terms that means it is 12V regardless of the load.  On an unregulated supply like a tyco toy transformer (usually indicated with a 12VA output designation) the voltage will drop as the load increases.

[Anonymous]

Here's my question, what do i use for say, the power supply running accessories such as lighted buildings

The same thing you used 20 years ago.  The Accessory out put of a toy train transformer.

what i should have said is power source.  i've seen "boosters" advertised, which i assume are individual power packs used to pump up different sections of track, etc?  what i'm imagining is that for optimal performance i'm going to need individual power packs, or boosters, or whatever, to run the myriad things on a layout.  

one running only switch machines

Depends on the kind of switch machines you are talking about.  Many modelers have abandon the twin-coil type snap switches and gone to slow motion stall motors.  The twin-coil type would still be powered just like they were 20 years ago.  The stall motors need DC power.

ok, now here is where i get mixed up with AC and DC.  you're saying stall motors run on DC, but i thought that everything was running on DC.  what would be running on AC? 

[jeffrey-wimberly]

I have a dozen switch machines on my layout that are all run by one Bachmann trainset power pack. I use an old AT computer power supply to power the lights in my structures. For track power I use a Bachmann EZ-Command DCC system. If I want to run DC only I just flip all my block switches to DC and run them with a MRC Tech4 280 Dual controller power pack.

[Anonymous]

If I want to run DC only I just flip all my block switches to DC and run them with a MRC Tech4 280 Dual controller power pack.

Ok, i'm starting to get the picture.  i'm wishing i hadn't thrown out my old computer without stealing the power supply!  but the last sentence confuses me, when you say "run DC only" do you mean not using Command Control?  i'm still not sure when AC comes in, if it does at all. 

[Texas Zepher]

what i should have said is power source.  i've seen "boosters" advertised, which i assume are individual power packs used to pump up different sections of track, etc?  what i'm imagining is that for optimal performance i'm going to need individual power packs, or boosters, or whatever, to run the myriad things on a layout. 

Ok I understand now.  A DCC booster is for adding additional power to the track.  Usually a booster is added for two reasons.  First is if the total number of locomotives on the track exceeded the power capacity of the primary DCC system.  This of course depends on the DCC system.  Somthing like the Digitrax Zephyr has a power output of 2.5A. or about 10 modern locomotives without sound.   Many DCC systems have a power capacity of 5A or about 20 modern locomotives without sound.   The other reason to add a booster is if you for some reason want to isolate one part of the layout from another.  This way a short circuit in the one area will not cause the whole layout to shut down just that one area.  Regardless of which reason you get the booster they are wired so each one has its own area of the layout and these are generally called power districts.   Most 4x8 type layouts do not need boosters.  Many larger layouts do not need boosters.  Our club has a 193' mainline with a branch and we have seven.  Two of these 7 are used for the locomotive facilities where lots of engines congregate on the track.  We also have on/off switches there so we can turn them off each track and not waste the electricity. 

Now, each DCC booster must have a power supply.  The power supplies must be independent from one another.  Many people use old DC power packs to provide the raw power to the DCC booster.  Once again it depends on the specific DCC booster as to whether the input needs to be AC, DC, and what voltage.   I have one system that will take anything up to 20 volts.   I have another one that will only take AC.

If you want DCC accessories they must be added to one of the boosters and theirr power consumption must be calculated in with the locomotives.

ok, now here is where i get mixed up with AC and DC.  you're saying stall motors run on DC, but i thought that everything was running on DC.  what would be running on AC?

AC is used by some brands of DCC boosters, light bulbs (like street lights, building illumination), smoke units in the scenery,  umm the twin-coil type switch machines.    Of course from there it can get complicated because one can start using diodes and converting the AC to DC at the point of usage.

[Texas Zepher]

when you say "run DC only" do you mean not using Command Control?  i'm still not sure when AC comes in, if it does at all. 

Yes he does.  The switch selects which power straight DC or DCC will go to the rails.   This is for the trains only.  When the switch is thrown one way the DC controller sends power to the track.  When thrown the other way only the DCC controller sends power to the track. 

Don't confuse track power with accessory power or power inputs.

Some DCC units take a standard AC power input, they translate that AC to DCC for the trains to use.  This is just like a traditional DC power pack.  The power from the wall is AC and the power pack translates it to DC for the trains.  The trains (unless you are talking Marklin brand) should never "see" a standard sign wave AC power applied to the track.

Other than that traditional sign wave AC is only for "other" things around the layout.  Mostly light bulbs.

[jeffrey-wimberly]

If I want to run DC only I just flip all my block switches to DC and run them with a MRC Tech4 280 Dual controller power pack.

Ok, i'm starting to get the picture.  i'm wishing i hadn't thrown out my old computer without stealing the power supply!  but the last sentence confuses me, when you say "run DC only" do you mean not using Command Control?  i'm still not sure when AC comes in, if it does at all. 

DC only as in running from the DC power pack only. The role AC plays in DCC is to carry the command codes for the DCC system.