12VDC Accessory Power Supply for Turnouts ?

[Traintraveler]

When I read "Easy Model Railroad Wiring",  it mentioned the  use of  a  accessory power

supply to run your turnouts and lights instead of hooking them up to the AC terminals of

the powerpack. One suggestion was a Radio Shack item #22-127 (regulated) 12VDC.

This was suggested so the power pack's full potential could be used to run the trains.

Has anyone done this ? I'm trying to understand this and it's a bit confusing when you

think 'AC' for turnouts and lights and then use a 'DC' power source to run your turnouts. 

Is the key "regulated" where you are OK to do this ?  Help ! 

[loathar]

Another good power source is an old computer power supply. You get 12v/5v and 3.3v all in one supply. You can also find used power packs on E-bay cheap. I don't know the specs on the Radio Shack product. You just have to make sure it can put out enough Ma or amps for what you want to run.

[Texas Zepher]

I always use separate power supplies for everything.   Trains get one (several actually), lights get another, and turnouts yet another, etc.  If you use the same supply for lights and turnouts the lamps will dim everytime a turnout is thrown.

The twin-coil type turnouts do not care what power is supplied to them.  The are just electro-magnets and will pull the iron on AC or DC.    It is the slow motion stall motors used for turnouts (like the Tortoise) that require DC. 

[mobilman44]

Hi,

I'm a DCC holdout, and run my layout with two MRC Controlmaster 20s.  They have more power than I'll ever use, but I still have all turnout solenoids and other accessories wired to a third MRC powerpack (forgot the number).  You can get a huge choice on Ebay, and if you take care of them, they will certainly last and serve you well.

ENJOY,

Mobilman44

[tomikawaTT]

My dedicated turnout power supply is a 12.6 volt (unregulated) AC filament transformer rated 3 amps.  By using diodes in the connections to the hot probe studs and the coils I get away with a single wire to power my twin-coil switch machines.  The common coil wire is connected to a return bus that is wired to the opposite end of the 12.6v output.  Resulting coil power is 1/2 wave DC, 16VPP, 5.6V RMS (after allowing for approximately 1.4V diode loss.)  The transformer is plugged into a dedicated 120VAC (house power) circuit which is switched off when the layout is not being operated.

The same arrangement could be used to power Tortoise stall motors, substituting SPDT switches for the pair of studs.  No diodes would be necessary at the machine end.  VPP and V RMS would be slightly higher.

I have standardized my system to have +DC throw the points to the 'normal' route, and -DC throw the points to the 'reverse' route.  My rail power is analog DC, using common rail and an individual power supply for each moving locomotive.  There is no connection between the rail and turnout power circuits except at the house power sockets.

Chuck (modeling Central Japan in September, 1964)

[claymore1977]

Another good power source is an old computer power supply. You get 12v/5v and 3.3v all in one supply. You can also find used power packs on E-bay cheap. I don't know the specs on the Radio Shack product. You just have to make sure it can put out enough Ma or amps for what you want to run.

I am gonna bump what Lothar suggested and provide a link:

 http://www.tc.umn.edu/~beck0778/powersupply.html

Its very VERY powerful and provides regulated voltage at +12.0Vdc, -12.0Vdc, +5.0Vdc, -5.0Vdc and +3.3Vdc. 

Good Volt/Wattage/Amp breakdown chart:

http://www.abcd.com.au/cases/power_supply_review.htm

You can combine these + and - voltages to get just about whatever you need.  Aka, take a small motor and wire it from the +5 to the +3.3 and get 2.2 Volts provided to the motor.  -5 and +3.3 will provide 8.3Volts to the motor.  +5 to Ground, is 5.0 to the motor... etc.

You can also tke +12 to -12 if you have any 24V loads!

 

A inexpensive, new 400W ATX power supply can only run $25 (with s&h) if you shop a bit.

http://computers.pricegrabber.com/power-supplies/m/12074049/search=400W%20power%20supply 

[Traintraveler]

It certainly appears than it is very common to have more than one power source so

you can operate various items independently.

I'm embarrassed to ask, but I have an old MRC 'Throttlepack' (model 501) than indicates

it to be a "HO Hobby Transformer". Can I use this for accessory items for my N scale

items ?  It lists 16V DC, 18V AC, 25VA output.

Thank you. 

[claymore1977]

It would... although the 16Vdc is a bit high for most 12V accessories...

[MisterBeasley]

If you are running twin-coils turnout machines, such as Atlas or Peco, then you should use a Capacitive Discharge circuit.  You can go out and buy one, under commercial names like Snapper, and that will work just fine.  I think a Snapper comes with a power supply, and plugs into the wall.  Or, you can build your own for a few dollars in parts.  That's what I did.  I used a diode bridge so I could run it from the AC terminals of an archaic toy train transformer.  The rest of the circuit is a couple of resistors and a couple of capacitors.  Putting it together is a great first electronic assembly project for people just getting into (or back into, in my case) the hobby.

A CD circuit has a couple of advantages.  First, it is a "storage" circuit.  You give it a small amount of power from your transformer, and it stores it up, only releasing it as a much bigger jolt when you need to flip a turnout.  That gives you a better, more solid throw, particularly with Peco which is more power-hungry than Atlas, or when you wire together multiple turnouts, as you might on a crossover track.

Second, the device protects your turnouts.  Twin-coils like momentary-contact control buttons or switches.  Sometimes, these things stick and apply continuous power to the coil.  If this happens, the coil usually overheats and often burns out.  With a CD circuit, the power applied is a big jolt, but then it tails off to a much lower level.  The coils can tolerate this leve for a lot longer than they can take straight power from the transformer, so they will more likely survive a stuck control button without damage.

The Atlas slide-buttons, the black things with the blue sliders that come with Atlas remote turnouts, are particularly prone to this sticking problem.  The best thing you can do to preserve your switch machines is not to use these in the first place.  The next best is to replace them all right now.

[NeO6874]

It would... although the 16Vdc is a bit high for most 12V accessories...

 

true, but if the DC is controlled by a potentiometer or rheostat, you could have anything from 0 - 16VDC going trough the wires.  Then you can get the lights "just right" as far as brightness and stuff goes.... 

[claymore1977]

 

true, but if the DC is controlled by a potentiometer or rheostat, you could have anything from 0 - 16VDC going trough the wires.  Then you can get the lights "just right" as far as brightness and stuff goes.... 

 

LOL just don't accidentally nudge the pot or rheo or one might let all the magic smoke out of all the accessories attached :)

To much of a risk for me.  12Vdc power supply for 14V bulbs is much safer than a 16Vdc power supply (throttled to 12Vdc) for 14Vdc bulbs.  I would build/buy a power supply that doesn't have the 'potential' to fry LEDs and bulbs.  (Sorry about the bad pun, but I couldn't resist) 

[dad1218]

  I use a Radio Shack 12V .5A power supply. I used some Atlas selector switches and a momentary push button. Works good for Kato twin coil machines, I even wired the 2 turnouts in my crossover together to act as one.

          Gary

[claymore1977]

When I read "Easy Model Railroad Wiring",  it mentioned the  use of  a  accessory power

supply to run your turnouts and lights instead of hooking them up to the AC terminals of

the powerpack. One suggestion was a Radio Shack item #22-127 (regulated) 12VDC.

This was suggested so the power pack's full potential could be used to run the trains.

Has anyone done this ? I'm trying to understand this and it's a bit confusing when you

think 'AC' for turnouts and lights and then use a 'DC' power source to run your turnouts. 

Is the key "regulated" where you are OK to do this ?  Help ! 

I just realized that your actual question hasn't been fielded yet!  As has been mentioned above several times, it is good to get the Accessory load off of the power pack that is being used for Locomotive power.

An unregulated 12V power supply will have its output voltage drop significantly as loads are added to it.  Additionally, the output voltage is subject to any variation in input voltage.  For light bulbs and LEDs, this usually isn't much of an issue.  Its the solid state components that can fry easily you have to worry about.

A regulated 12V power supply will take care of 99% of the above mentioned problems and maintain output voltage right at 12Vdc (or atleast very close).

Voltage regulators are cheap so there is no point in not getting a regulated power supply! 

[Phoebe Vet]

I use Radio Shack  12VDC 1500mA AC Adapter

Model: 273-1775  |  Catalog #: 273-1775

This 12VDC 1500mA AC Adapter powers devices requiring 12VDC.

For lights and turnouts.