Quick links to major topics on this page:

• Why use air power?
  
• Pictures of the original / standard air motors
• Pictures of the new "parallel" air motor with microswitch
• How to control with DCC
• Make an inexpensive air accumulator
• Enclosing / protecting the electronics
• EA-ZE Air common part numbers

Why use air power to power turnouts?

This is another part of my quest for low maintainence and reliability:

So, I thought, why not use a simple air powered mechanism, a small air hose for supply, and no electrics.

The air motor is a stainless and brass piston assembly with an internal return spring, so a single air line controls it.

There is only one current manufacturer I am aware of: E-Z Air. (There was another, DelAire, now out of business.)

I went with EA-ZE Air for 3 reasons:

• I like the distributor, California and Oregon Coast Railway, very nice people, helpful, friendly, etc (Talk to Stretch). http://www.cocry.com/
• They understand the pneumatic side of the product very well, and have many options, the product quality is top notch.
• They had solenoid controlled air valves, so I can control the turnouts remotely.
• They now have air motors with an internal, truly waterproof switch to route power to live frogs.

Standard / original type air motor:

Here's a picture of the motor installed on an Aristo-Craft wide radius switch. It took 5 minutes to put it on, and this was my first one!

Remove the screws to the throwbar, then the 2 screws holding the original turnout motor.

Now place the motor in position by hand, and put a bend in the brass wire such that the plunger is pulled out by about 1/8". Don't worry about being precise, the motor has about 1" of travel, and the spring and air pressure make it self adjusting.

Now I put a second bend in the wire, and then bent the very end so I could thread the wire in without disturbing the turnout.

I should clip the excess wire off some time! Works great!

New style parallel air motor with micro switch:

Here is a a second style of  air motor that is parallel to the track and can be ordered with a (real) waterproof microswitch inside.

I have them on all of my Aristo-Craft #6 switches since the electrics in the Aristo-Craft switches rot out quickly or the Aristo-Craft microswitch jams or both!

The EZ580 & EZ581 are for the normal LGB/Aristo-Craft/U.S.A. Trains (except #6) turnouts. The EZ582 & EZ583 are for the U.S.A. Trains #6 only. The EZ584 & EZ585 are for the PECO 45mm turnouts.

Here's the insides of the original design:

The picture above shows the original brass operating rod, which did not work too well for me.

Since then the operating rod has been changed to this:

This new design solves three previous issues:

• The wider and thicker "rod" puts less localized stress on the fragile Aristo-Craft throwbar, so they last longer.
• The reduction in slop (because the new design is thicker than the previous wire) makes full use of the somewhat limited travel of the air motor.
• The soldered joint between the plate and the wire could be a bit fragile and break.

You still need to remember that the microswitch is triggered at full travel. So, when installing:

1. apply air pressure to the switch motor
2. Then bend the throw rod so at full travel, it just throws the switch all the way.
3. When you release pressure, you will have enough travel for the other extreme, and you have guaranteed that the microswitch will trip when you want it.  

(show installed picture here)

DCC operation

EA-ZE Air has solenoids available in 3 DC voltage ranges.

I picked the 24 volt (nominal) ones, in anticipation that my 20v RMS DCC power supply would probably be a good match. The solenoid needs constant voltage to keep the solenoid open. Turns out the solenoid takes about 125 millamps when on, and they will pull in at about 15 volts.

Most DCC accessory decoders for turnouts are for momentary operation. Well, that won't work. The ones that work with the "Tortise" motors DO provide constant voltage output, but usually no more than 40 millamps.

The new Digitrax quad accessory decoder, DS64, has a higher current rating and can be programmed to run "stall type" switch motors, i.e. sending constant voltage forever to the switch motor.

Wiring the decoder

First, you must be careful in how you power the the solenoids, ANY time you use a device that can produce Back EMF you must be careful that the controlling device can handle this. (Back EMF from a solenoid can short out the output transistors in a controller).

Virtually all the DCC decoder manufacturers told me that their accessory decoders would NOT work with a solenoid.

A simple explanation: When you turn "off" a device that makes a magnetic field, as the magnetic field collapses, it induces a voltage and current spike that can be a lot higher than the current originally used to power the device. Most of you have seen a spark when disconnecting a circuit. That's the Back EMF.

This spike is great at destroying solid state electronics because it is so much greater in power than what you were switching in the first place... it's of shorter duration, but that's immaterial to a transistor.

So, rather than having an accessory decoder that can handle 8 amps per output, we find an inexpensive way to not let this spike into the electronics.

The solution is a diode.

Since these decoders are designed for "stall type" motors, they provide positive voltage for "thrown", and negative for "straight through".

Well, a DC solenoid will operate no matter what the polarity, so (forgetting BEMF for the moment), if we connected the solenoid to the outputs, it would always be energized.

So we use another diode such that voltage only flows to the solenoid when the voltage is positive, and the diode blocks current flow when the decoder switches polarity to negative.

I use two inexpensive 3 amp diodes from Radio Shack. Don't go lower on the amps, it's not worth it. (higher is ok)

Each set of 3 terminals (from the left) are the outputs to the turnout motor (the two with the blue and red wires are power from the track).

We only use the first 2 terminals in each group. The first screw terminal is the positive, and the second common.

You can see the 2 black wires to the solenoid. The diode on the left makes it so that current flows only when the left terminal is positive. The second diode is basically across the solenoid's leads in "reverse" fashion. This diode absorbes the Back EMF when the solenoid power is switched off.

If you did not use the first diode, the solenoid would always be getting power, since it engages no matter what the polarity.

More importantly, the second diode protects the decoder from being destroyed by the Back EMF.

Do NOT eliminate either diode, the unit will not work, and you will destroy the decoder output.

An inexpensive air accumulator:

Since my air supply is about 150 feet away, I made an inexpensive air tank to supply air pressure. I fed the system with the thin tubing since it was easier to run the thin tubing all that distance.

3" ABS tubing and caps from Home Despot and there you are, simple and inexpensive.

If you don't want to run a long line back to a compressor, consider an inexpensive air tank, that you can take and fill yourself, and leave out by the layout. Here's a 5 gallon one I got from Pep Boys:

Outdoor / weather proof enclosures:

Here's the box that holds the decoders and the solenoids:

My switchyard has a lot of switches, and unlike the box above, which is under shelter, I need 16 solenoids, 4 DCC controllers, and to be weatherproof. 

So, I bought another outdoor drainage cistern. This one is about 9 inches wide by 1 foot tall, a smaller version of the one I used to put my DCC electronics in.

I had to close up the 2 holes in the sides, using the stock adapters, cut down with a rubber "plug" in the center hole where the pipe would go. Here is one of the 2 completed covers to seal up the unit:

The next thing I needed was to put some "feet" on the unit, and cover the large slots that would be the drainage grate with screen to keep out critters.

I used window screen and some pvc fittings to make the feet, PVC elbows with caps glued inside as plugs as you can see in the picture below:

The picture below shows the base as it will sit on the ground and be covered with the drainage housing. I used some grey PVC nipples to screw into the "feet" and then glued a fitting on top, so I could tighten the feet in place. I trimmed the white PVC fitting for clearance inside.

Now on to the housing itself. I needed to house 16 solenoids, 4 Digitrax DCC decoders, and a mainifold for the air distribution. I bought 4 sheets of lexan that were very close to the right size and trimmed them to fit in the housing:

Each piece has the corners notched to clear the PVC foot hardware on the base:

These 4 "backplanes" will be used to hold a decoder and 4 solenoids:

Now all it takes is two wires from the track for the decoder, and to hook up the air lines.

EA-ZE Air part numbers:

EZ663 - 24v solenoid (they have other voltages)

EZ570 - "original" air motor for Aristo-Craft & LGB
EZ580 - "parallel" air motor with microswitch for LGB/Aristo/USAT
EZ581 - "parallel" air motor without microswitch for LGB/Aristo/USAT
EZ582 - air motor with microswitch for USAT #6 only