Using landscape transformers on train layouts

It’s fairly common for hobbyists with extremely large train layouts to use outdoor landscape transformers instead of specialized train transformers to power the lights and accessories on their layouts. Landscape transformers are large, rugged, and less expensive. But it can be confusing how to set them up. So here’s a step by step guide to using landscape transformers on train layouts.

I use PC power supplies to power lights and accessories, but that limits me to 12 volts DC for power. I’m OK with that. But if you want 15 volts AC, or you’re uncomfortable modifying a PC power supply, low-voltage landscape transformers are another viable alternative. I don’t think they’re as economical as an old PC power supply, but they cost much less per watt than a train transformer.

What is a landscape transformer?

Using landscape transformers on a train layout
The outputs on a landscape transformer provide 12 volts AC, and some add 15 volts AC. That’s why using landscape transformers on train layouts is so popular. If you buy a used one, you may have to replace one or more terminal screws, but you can use an ordinary machine screw that fits, usually 6-32 or 8-32.

Home improvement centers sell low voltage outdoor lighting, intended to power low-voltage lights to either provide accent or to provide light along a path.

It happens these outdoor low-voltage lights run on 12 or 15 volts AC, like the lights and accessories on train layouts. The transformers they sell to power the lights provide anywhere from 45 watts all the way up to 900 watts or even more. Inside, a landscape transformer works exactly the same way an AC train transformer works. It just lacks the handle for variable output.

Differences from a train transformer

There are some differences between a landscape transformer and a train transformer, but they can all be overcome. First is the case. These are designed to be used outdoors, so they have a rugged, weatherproof case. That makes them overkill for indoor use, but they work fine, even when they say “outdoor use only” on the case. For that matter, they may say they’re only for landscape lighting use. That doesn’t make them unsafe for train layout use. It just means the manufacturer doesn’t want you calling them if you can’t make it work for something they didn’t anticipate. They can’t train their tech support for every possible use for these things. Third, since the transformer is designed for outdoor use, it will have a grounded 3-pin plug on it.

Output-wise, a landscape transformer has screw terminals on its case just like a train transformer would. The number of terminals varies. A transformer that outputs 12 volts will only have two terminals, providing 12 volts AC between them. A transformer that outputs 12 or 15 volts will probably have three terminals. One combination of two of the three terminals gives 12 volts and the other combination gives 15 volts. Using the unsupported third combination would yield 3 volts, which probably isn’t very useful.

Most newer landscape transformers have a photocell on them that turns the transformer off during daylight hours. They may also have a timer on them. You’ll have to defeat the photocell and set the timer to the longest duration you can. The easiest way to defeat the photocell is to put a piece of black electrical tape over it.

How to buy a landscape transformer

You can get a 300-watt landscape transformer that provides 15 volts AC for about half the cost of an American Flyer 19B transformer, and you’ll have to fight a lot fewer people for the deal.
Home centers always have landscape transformers in stock. But if you’re looking for a bargain, you’re probably looking for a big bargain–something under retail. For a bargain, look in the lighting section where damaged, open-box, or closeout merchandise sits. You may be able to find a returned or discontinued model at a steep discount.

An even easier way to get a bargain is to get a landscape transformer on Ebay. Of course you’ll find used transformers there, but you may also find new ones whose packaging was damaged, or discontinued models at a discount.

Either way, you can expect to pay well below the 50-cents-per-watt you would normally expect to pay for a train transformer. If you can live with some cosmetic damage, you may be able to get a monster 900-watt unit for under $200.

The advantage of a landscape transformer over a train transformer

A more modest 200-watt unit, which is still large by train layout standards, should be pretty easy to find for under $50 online. When you can find a Lionel KW for that price, it won’t include shipping. Or you can get a 300-watt unit for around $70, which is about half the cost of an American Flyer 19B, and there will be a lot more of them available.

The disadvantage when trying to get a Lionel ZW or American Flyer 19B for lighting is you’ll be competing with people who want to run trains with them. There’s a finite supply of them and they aren’t being made anymore. Landscape transformers are still being made. If you can’t find a deal this week, try again next week. You’ll find a deal on one much more quickly than you will on something with the Lionel or American Flyer name on it.

Fixing damaged landscape transformers

A used model may very well be missing one or more of its terminal screws but that’s not a big problem. They are ordinary machine screws, usually either 6-32 or 8-32. If you don’t have any laying around, short machine screws cost literally pennies at a hardware store.

The other kind of damage you’re likely to encounter is damaged paint. Just touch it up with some satin-finish black paint if it bothers you. But if the transformer is mounted out of sight under your layout table, a few dings and scuffs may not even matter.

Wiring a landscape transformer for your train layout

An inexpensive low-wattage 12-volt transformer will only have two outputs: a hot post, providing a 12 volt fixed output, and a return post that the power returns to. This is exactly equivalent to the common post in Lionel terminology and the base post in American Flyer terminology. For that matter, you can wire the return post from your landscape transformer to the common or base post on your train transformers so they can all share a common wire under the layout. More on that in a minute.

More expensive transformers will have a 15-volt output in addition to a 12-volt output. These are desirable, as many vintage train accessories were designed for 15 volts. They’ll run on 12, but may run better on 15. High-wattage transformers may have multiple sets of outputs, because a 600 or 900 watt transformer is usually multiple 300 watt transformers inside.

You’ll need to phase the transformer with your train transformer if you want to share a common wire between them. The three-pin plug may make this challenging. But if you have to rotate a plug to phase them correctly, you’ll just have to rotate the train transformer’s plug.

If you buy a high-wattage transformer that’s more than 300 watts, just remember not to put more than 300 watts (100-120 bulbs) on any single output.

Mounting the transformer

Landscape transformers have two keyhole-shaped slots on the back for mounting. They just hook onto the heads of ordinary screws. Set a piece of paper on the back and rub over it to make an indentation in the paper that matches the back of the transformer. Now you have a template.

Set the template up against where you want to mount the transformer on the framing of your layout, make sure it’s level, then drill two pilot holes for screws. I recommend using #8 wood screws about an inch in length. That should be strong enough to support the transformer’s weight. Drive in the screws, then hook the transformer’s keyholes onto them and you’re done. It’s easy and convenient.

Is repurposing transformers safe?

A transformer is just a coil of wires that steps down voltage. What the device on the other end does with that voltage makes no difference.
Probably the most common question is whether repurposing a transformer is safe or if it affects its UL or CE certifications. The answer is yes, it’s safe, and no, it doesn’t affect any certifications. The manufacturer of the transformer isn’t going to help you, but if you can make the accessory work off a train transformer, you can make it work off any other transformer that’s outputting between 12 and 18 volts AC. There’s nothing unsafe at play here.

A transformer is just a coil of wires that steps down 115 volts AC down to a lower voltage. What the thing on the other end of the circuit does with the electricity doesn’t matter, as long as you don’t exceed the ratings of the transformer.

Staying within amperage ratings

To estimate your usage, count the number of bulbs. A train light bulb uses about 2.5 watts of power, to make the math easier. A motor or solenoid may use 5 watts. That means a 300-watt transformer you can pick up for around $75 can power a rather impressive display. You can also measure the amperage if you want to be precise.

Repurposing other household transformers

You can repurpose other transformers too, as long as they supply a useful amount of wattage. An old doorbell transformer will work fine for powering lights, for example. The only problem with them is they only supply about 15 watts, which is less than a starter set transformer. You can power two or three accessories off it, but is it worth the effort?

But if you have a stash of old household transformers and AC adapters laying around, or come across one at a thrift store, garage sale or estate sale, it’s worth looking through it to see if you can find anything useful. If you can find something that supplies 40 watts for nearly nothing, don’t feel bad about using it.

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