# 12vdc regulated power?



## Ray Dunakin (Jan 6, 2008)

Can someone recommend a good power unit to supply 12vdc for structural lighting?


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## Torby (Jan 2, 2008)

Malibu transformer?


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## Totalwrecker (Feb 26, 2009)

http://www.mpja.com/products.asp?dept=465&main=1 

Depending on the Watts you need there should be one here that meets your needs.


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## Ray Dunakin (Jan 6, 2008)

Torby -- I originally planned to use a Malibu, but they're AC. Wouldn't matter for the lights but I would also like to have the option of running small motors for animating things. 

Totalwrecker -- Thanks for the link. I really don't know what kind of wattage I will need in the long run. Right now there's only a couple dozen 16v grain of rice bulbs, but eventually there will be many more, and possibly some small motors too. 

Is it possible to have too much watts? What about the amps? I have no idea what either of those are or how they might factor into my needs.


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## armorsmith (Jun 1, 2008)

Ray, 

As for a source, try looking at www.newark.com (Newark Electronics) and search for power supply. 

Amps and watts are directly related by voltage. ie. 12V X 0.1 amp = 1.2 watts. As long as the amps (watts) of the power supply exceeds the draw being placed on the power supply by your devices (lights, animations, etc.) it is OK. 

Bob C.


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## Dan Pierce (Jan 2, 2008)

Why not use the Malibu for lights and a DC pack for the DC motors. 

You will alays outgrow the power rating of a DC power pack, so keep your lights separate from the start.


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## Greg Elmassian (Jan 3, 2008)

One thing about malibu transformers (other than they are cheap) is that they are cheap... ha ha... 

Yep, the output voltage varies a lot according to the load. So, not only do you need to pick your lights carefully, but you need to test the voltage output based on the load, and if the load changes, then the voltage can, i.e. have a few bulbs burn out, and then the voltage goes up and then more lights go out. 

So a regulated power supply is a good idea, besides the need for DC motor support. 

There's lots of options out there, but Ray, you need to estimate the current required. 

Regards, Greg


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## Torby (Jan 2, 2008)

Go someplace like allelectronics.com and see what they have listed under power supplies. I'm sure they'll have something that will do nicely. 

In the shop, I powered lights with a malibu transformer. I wanted DC for something so I just put a diode bridge.

I started out with an old computer power supply to run accessories. I had used it for years to run whatnot. But just after I mounted it, the silly thing quit working.


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## bvdrr (Jan 3, 2008)

I got mine at Radio Shack,12v 10 amp. It powers all the lights in my layout very well and there are quite a few.
Fred


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## Ray Dunakin (Jan 6, 2008)

Ok, I think I've narrowed it down to this one: 

http://www.mpja.com/prodinfo.asp?number=16001+PS 

Can anyone tell me if there's some reason that this would not be a good choice -- something I might be overlooking?


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## Greg Elmassian (Jan 3, 2008)

looks ok Ray, is 3.5 amps enough for what you are doing? 

Also, I'm assuming you are using 12v bulbs? you will get some voltage drop on long wire runs, so take that into consideration, but I'm guessing you do not want blindingly bright lights, so a lesser glow is probably better, i.e. loss of a couple of volts will be fine. 

Regards, Greg


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## Ray Dunakin (Jan 6, 2008)

Thanks. I'm not sure about the amps. The bulbs I'm using are rated at 30mA.


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## Greg Elmassian (Jan 3, 2008)

well, at 30 ma each (ma = milliamps) you can run 100 of them from this power supply... I think you will be fine!!! 

Regards, Greg


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## Ray Dunakin (Jan 6, 2008)

Thanks Greg!


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## Ray Dunakin (Jan 6, 2008)

Well, the power supply arrived today, and to my dismay there is no power cord included with the unit, nor any instructions. It has a terminal strip marked L, N, Ground, and V- V+ . 

The L, N and Ground are for AC, but I have no idea what L and N stand for or which parts of a power cord should be connected to which terminals. 

I'm not real comfortable with the idea of having these AC terminals exposed, especially so close to the DC output terminals. Is there any way to safely cover the AC terminals after the cord is connected? 

There is also a tiny pot switch marked "V adj". Does this mean I'll have to adjust the output? 

Lastly, the unit's case is metal with lots of holes, presumably for ventilation. I want to put this thing in a weatherproof plastic container. Will that be a problem?


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## barnmichael (Jan 2, 2008)

Sorry I didn't see this thread sooner. You bought a precision supply designed to be mounted inside a piece of equipment. You'll have to get an enclosure for it, wiring will be a pain, etc. 

Go to The Shack (formerly known as Radio Shack) and buy a 12 volt supply. They have some with cigar lighter sockets on them. Tell the sales droid (you want batteries with that?) that you want something to run your CB radio in the house. That is language he might understand. Don't let him sell you a big wall-wart or line-lump. You want something in a box with a power cord and terminals on the back. They typically come in 3amp, 5amp or 10 amp sizes. I suggest getting the largest you can afford. Normally the terminals are similar to the ones on the back of many track supplies. Should run you


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## barnmichael (Jan 2, 2008)

Posted By Ray Dunakin on 07 Jan 2010 08:39 PM 
Well, the power supply arrived today, and to my dismay there is no power cord included with the unit, nor any instructions. It has a terminal strip marked L, N, Ground, and V- V+ . 

The L, N and Ground are for AC, but I have no idea what L and N stand for or which parts of a power cord should be connected to which terminals. 


L= line (normally black wire)
N= neutral (normally white wire)
Ground= ground (normally green wire) 
I'm not real comfortable with the idea of having these AC terminals exposed, especially so close to the DC output terminals. Is there any way to safely cover the AC terminals after the cord is connected? 

Not normally. Some supplies have a plastic strip to cover the terminal strip.
There is also a tiny pot switch marked "V adj". Does this mean I'll have to adjust the output? 


Rule of thumb in electronics. If you do not know the answer to that question, don't touch it!

Lastly, the unit's case is metal with lots of holes, presumably for ventilation. I want to put this thing in a weatherproof plastic container. Will that be a problem? 



IMHO, not a good plan. These supplies need good air circulation. They are meant to be an internal component of another piece of equipment.


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## Dan Pierce (Jan 2, 2008)

For the easiest/safe way: 
Get a Malibu transformer and add a 10 amp diode bridge to the output. (some are 44 watts and some are 88 watts, 10 amp diode bridge will handle either. 
Run your lights and motors. 
No dangerous wiring or vent holes. 
Made for outdoor use and UV protected. 
Power cord included. If you buy the inexpensive lighting kit, you get 4 watt lamps and 50 feet of outdoor UV protected wire and water resistant at that.


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## Greg Elmassian (Jan 3, 2008)

Dan, while your idea is inexpensive, the Malibu systems are NOT regulated, and indeed, the output voltage varies A LOT with the load. 

Also, they are way over 12 volts.... 

I really do not think it's a great solution, the 12v lamps like grain of wheat/rice, etc, do NOT handle over voltage well. 

Anyway, he already bought the regulated supply... 

Regards, greg


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## Ray Dunakin (Jan 6, 2008)

I bought a 3-prong, three-wire power cord from Home Depot and connected it according to the instructions provided here: 

"L= line (normally black wire) 
N= neutral (normally white wire) 
Ground= ground (normally green wire)" 

Finally got around to plugging it in, and it promptly shocked me. The only thing I was touching was the rubber "handle" part of the plug, so I don't know how it could shock me, but it did. So I'm throwing the whole thing out and starting over. 

I need to find a REGULATED, 12v power supply that already has a cord, and is not intended to be installed inside some piece of equipment. 

Any suggestions?


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## TonyWalsham (Jan 2, 2008)

If you don't need more than about 1 amp, mains supply plug in wall warts are available in 12 volt switchmode version for very low cost.


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## Ray Dunakin (Jan 6, 2008)

Update: 

I eventually ended up getting this -- 

http://www.amazon.com/Pyramid-PS26KX-Amp-Power-Supply/dp/B000Y8GFIE 

It's 25 amps and has all the "bells and whistles". It cost more than I had hoped to spend but cheaper options just weren't working out for me. I've been using it for over four months now and am very pleased with it. One nice thing is the adjustable voltage. Most of the time I set it to 12v (my grain of rice bulbs are 16v), but I can reduce the power to dim the lights if needed for photographic effects. On the other hand, I have to watch that the knob doesn't get accidentally bumped up to the full 15v output.


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## NavyTech (Aug 2, 2008)

You can save yourself a lot of money if you pick up a used computer power supply that people toss in the garbage. You can remove the wires you do not need and you can use more than one for no cost.


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## krs (Feb 29, 2008)

Posted By NavyTech on 27 Sep 2010 03:15 PM 
You can save yourself a lot of money if you pick up a used computer power supply that people toss in the garbage. You can remove the wires you do not need and you can use more than one for no cost.



True - but read the last few posts on page 1.
The OP had trouble hooking up a standard, well labeled switching supply - wiring up a computer supply would be a bit more complex.


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## Greg Elmassian (Jan 3, 2008)

Umm... Ray uses the variable voltage feature... pretty difficult to modify an old PC supply to become a variable voltage supply. 

Greg


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## Tom Bray (Jan 20, 2009)

If you can live with 13.8V you can use a standard supply from Radio Shack, or a amateur radio power supply. I think Radio Shack have one that puts out 10A, it has binding posts on for the DC side, a power plug on the other. MFJ has a couple of supplies that are variable down to about 5V and go as high as 15V, they also put out lots of current, again, these have binding posts for the DC, a power plug for the AC. 

I use a lawn light transformer and put in 14V bulbs into all the buildings. You could also use 16V bulbs and they will last longer. The transformers pretty much put out 12VAC, plus they have sensors on them to turn them on in the evening for a set amount of time. 

One thing is that if you use a high current supply, make sure you use fuses to protect those thin 28AWG wires - they will smoke and catch on fire if there is a short ... pretty spectacular. 

Tom


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## Tom Bray (Jan 20, 2009)

One comment about PC power supplies ... They need a minimal load on the 5VDC line for them to regulate properly. The newer ones probably have different requirements since I think they have a 3.5V output. 

Multiple output switching power supplies often are designed with the assumption that one of the outputs has a minimum load on it for them to work correctly. 

Tom


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## Madstang (Jan 4, 2008)

I have used Malibu lighting in my buildings since I started and have never had a problem with lights, but I also use the 4 watt bulbs. In some instances I increase the wattage. 
Marty uses solar, but I have found that the brightness is not to my liking. 
Malibu is only good with their bulbs, they do not give off enough light with the 12-16 volt bulbs, they only give a warm glow with those. 
But usede inside buildings they are perfect.


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## RimfireJim (Mar 25, 2009)

Posted By Tom Bray on 27 Sep 2010 09:53 PM 
One comment about PC power supplies ... They need a minimal load on the 5VDC line for them to regulate properly. The newer ones probably have different requirements since I think they have a 3.5V output. 

Multiple output switching power supplies often are designed with the assumption that one of the outputs has a minimum load on it for them to work correctly. 

Tom 
Very true, and the consequences of insufficient load can be more serious than improper regulation. About 10 years ago at work, I was associated with a project where this requirement wasn't met, and we had power supplies dying on us while we were bench-testing the electronics assembly. We had to add a load resistor during testing that simulated the load in the product. That was an expensive lesson, as the damage wasn't covered under warranty due to failure to adhere to mfr's requirements. IIRC, the minimum load was something like 10% of the continuous rated output of the PS.


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