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Turnout Power Supply
Tom asks readers:
“I’m new to the hobby and I just set up my first HO layout. I’m ready to wire it. I have ten Atlas Snap Switches that need power. Atlas recommends an AC power supply that puts out 15 -16 VAC @ 2 – 3 amps. Such a supply seems impossible to find. I’ve seen many people recommend an old computer supply, cellphone charger, etc. . . . but these all put out a DC current. Is there any reason I can’t use DC on the Atlas Snap Switches? (I have two old computer supplies, one puts out 32V @ 3.5 amps, the other 20V @ 11 amps.) Will either of these work without burning out the Snap Switches?”
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Atlas Snap switches consist of two coils that operate the switch when a MOMENTARY AC voltage is applied to one of the coils. One coil pulls the switch one way, the other coil pulls the switch the other way. You only energize one coil at a time. Only energize the coli for a split second, do not hold the voltage on. The switches should have come with a control switch. Otherwise use momentary push buttons or a double throw switch with a spring return to OFF.
The coils are essentially inductors with a moving iron core.When an AC voltage is applied to an inductor, the inductor responds with and opposing voltage, reducing the current. If DC is applied, the opposing reaction is not present so too much current could flow. This could burn out the coil.
Atlas does provide replacement coil switch operators separately without buying a whole switch.
Most DC HO train controllers have two terminals marked Accessories. These terminals are AC and are suitable for operating the Snap switches. Otherwise, look for a transformer that plugs into an AC outlet that provides the specified voltage and a current greater than needed. Online hobby electronics stores have them.
Thanks for your reply. I appreciate the explanation of how the coils work. It is very clear. I’m using a Digitrax Zephyr Xtra for train power. It doesn’t have an AC output. Luckily I found an AC transformer to power the switches. It’s actually made by Atlas! Why they don’t advertise this for their own switches is a mystery to me. Anyway, if anyone else is interested it’s part # 1000030.
Tom, I have used Atlas switch motors for a long time but now I am moving into the tortouis slow motion motors now.
To help you out those will all run off the AC side of your transformer 16 volt AC. You can use various switches to control them, BUT, Make sure they are NOT powered continually when not in use which means a momentary switch as Joe Stated. This can be push button momentary switches. Atlas 8 switch units will handle 8 switch motors and you can tie in as many as you want. You will most likely not switch more than one motor at a time anyway. But I caution you to install a on off toggle switch from your power source as someone will surely visit and lay their hand on multiple buttons not knowing and you will see a puff of smoke at each switch that the hand laid on the buttons and held them I know I had a young kid visiting and I was using the slide handle switch controls and she leaned on the handles and all of a sudden I seen poof poof poof on about 8 of my switches.So install a master on and off switch and shut them off when you are not needing to switch them.
Now that said, The tortoise switch motors are DC not sure if they can be AC But the power is continuous to the motor and when the motor goes to the new position, at the end of the travel the switch motor cuts the power within the motor till you throw it the other direction. The motor also has 2 extra circuits where one can power a metal frog and feed the rail power of the rail using the frog. That helps a lot for smaller engines that may not have very many wheel feeds to your engine where they might stop crossing the frog. Atlas switches if they have the metal frog then they can be powered as I said. Other atlas switches have the plastic frog and you would not be able to do that. The second circuit can be used for lighting the direction of the switch by lights on your panel or lights next to the switch or switch toggle switch. On mine I send a green light to the light for the direction the switch is thrown and at the same time send a red light to the other track. and vise versa. Some use them to light a green for the main line and a red for the other. But I like mine better. By using LEDs with resisters you can do a lot with this. You will need a doule pole double throw switch with no center position. That is what I do with mine and will look good and signal correctly for the direction I am going. a 2 light dwarf signal Red and Green will work great for that A tortoise will not drift from it’s set position but an atlas will and you have to make sure the switch is in full travel before the train comes across it Your going to spend 10 to 15 dollars for a atlas switch motor but a tortoise is not that much more considering the 2 extra circuits and a built in fail safe not to hold power to your switch motor and ruin them A tortoise can run 18 to 24 dollars but well worth the extra. You can run an atlas from a momentary switch near the switch itself and feet a buss power to the momentary switch or you can do the same to a stack of switches on your control board and then feed out to each switch Your choice. What ever you decide be sure to install the master power switch when using the atlas switch motors from Newman
Thanks for your help. This information will be very useful. I did actually get a transformer and I hooked up the turnouts. I used the momentary switches that Atlas supplies with them. Unfortunately, the next day I turned on the transformer and two switch motors burned out. I was there alone and I didn’t touch the buttons. All I did was turn on the power. It could only have been due to defective buttons. Today I’ll be buying some SPDT momentary toggles and two new switch motors. I’ll replace all the Atlas buttons.
At least I took the time to drill holes below the throw bars when I laid the track, so I can install under table switch machines without too much extra work. Thanks again.
I have many Atlas Snap Switches. I found that putting a Circuitron Snapper in-line from the power supply makes the switches perform much better and protects against burnout.
For anyone who is interested, consider using a used laptop power supply from a electronic surplus store or on-line electronic surplus web site. They come in various AC & DC voltages and current ratings. Add a couple of momentary switches per turnout, and your set. By using a laptop power supply to power your turnouts, you will not over tax your main train transformer.
Since laptop power supplies are designed for continues on-time, you could use them to power your accessories like layout street lights, accessory sound moduals and action accessories.
You could connect your train transformer and laptop power supplies to a power strip that has a switch on it so you could turn everything on the layout, off at once.