Make your own railroad switch points

John’s been in touch with how to make your own railroad switch points:

“Al,

I have been working on designing a switch machine that can be mounted under the table, and has power, flexibility and can be used to light signal LED’s to both show on the layout control panel, and on the layout itself.

There are good switch machines out there for sure, like the Tortoise® but I wanted my own.

All of the components of the switch machines were ordered from eBay from various vendors, and the plastic sheet from a local home store. One “storm door” ¼” thick (6mm or so) plastic should make several dozen machine frames.

The diodes are – 1N4001 Rectifier Diode 50V 1A

Micro Switches are – Mini Micro Limit Switch Long Roller Lever Arm SPDT Snap Action

The Motors are – 9G SG90 Mini Micro Servo For RC Robot – Helicopter

The Double Throw panel switches are – 6 Pin 2 Position ON-ON DPDT Mini Latching Toggle Switch

The description in BOLD is what you would enter in the eBay search for the components. Now for the details.

The best price for the motors is, about $0.65 each if you order 20 or so. The rest of the components come up to about $1.20 so the machine costs < $2.50 when completed. I found the cheapest prices for all of the stuff above from China eBay vendors. The schematic for the railroad switch machines is: switch schematic

Please note the current arrows for the diodes are drawn by U.S.A. theory, Europe uses “common” theory which has electron flow in the opposite direction – pay no mind, the schematic works either way so don’t reverse the diodes.

If, when you build the machine, it does not throw, reverse the motor leads.

Note that when the motor goes to the right as the little arrows are indicating, the arm on the shaft will open the micro-switch on the right and stop it there. A “piano” wire on the arm goes through the board and operates the track switch.

The motors as delivered need to be modified, as they come with a tiny circuit board that operates them by servo pulses. I wanted straight DC operation, so the PC board had to go.

The pictures below show how the motors come, and how they are modified.

Note: these will operate 180° but can be made to operate full rotation if the little potentiometer inside is removed too, but that requires taking the gearbox apart.

Use for the track switch machine is not required since the throw is only about 20° from center.

Also note these little motors are really powerful, with the gearing they can easily operate most anything on a HO layout, like bridges, turntables, or carnival rides. They are not full continuous duty, however so for accessories which would run more time reduce the voltage to about 3 volts.

switch electronics

switch electronics

(All images are clickable)

The pictures above show how the motors arrive, removal of the back cover and what’s inside – be careful here, the gearbox can come apart, but only if you mess with it.

Holding the motor body, remove the circuit board and re-solder the lead wires back to the motor – use minimum heat to connect the wires, and fine rosin core solder. Put the cover back and secure the 4 screws.

The next section is the preparation of the acrylic plastic sheet, I used ¼” Lucite® and have a little X-Y vise on a small drill press that I use. I lay out a strip with the motor openings for the sheet, then mill each out, cutting them off as they are milled.

Make your own railroad switch points

When the plastic opening is milled, the corners need to be squared off, I clamp them in a vise and file out the remaining radius so the motors will fit.

I made a go gauge to assure the openings will fit the little motors. Because there is some play in the micro-switches, the tolerances can be pretty loose on the motor position, and where the actual switches are mounted.

The motors come with a number of actuators, like in the pictures of the accessory bags that come with the motor. I use the one with 7 holes because it’s the longest and hits the rollers of the micro-switches well.

Make your own railroad switch points

Once the diodes are soldered in, I drill a few holes for the motor wiring, on the early ones I put on heat shrink tubing like above center, but later found that I could route the wires on the diodes so a short circuit was not possible, like on the switches above right viewed from the back-the micro-switches are on the other side of the plastic, and those below. I’m not worried about bare wires, only 5 volts.

Make your own railroad switch points

After about 6 machines done and the several small mods I made, I now have the entire process from cutting the plastic blanks to testing the machines down to about 30 minutes per machine.

As a side note, some of the track railroad switch on my layout, especially in the yards, are Atlas Snap Switches®, and these will be used with the stock switch solenoids.

I will be using DPDT center-off spring loaded switches instead of the slide switches the Atlas products come with. This is for no other reason than the consistent appearance of my control panel. For the 5 volt supply, I am using a rewired little train set power-pack with the speed potentiometer removed and a few other added parts to get solid 5 volts.

I know for many this will seem like a lot of work, but at $11.00 each and I need 29 machines, the savings are substantial, also I have constant 5 volts available at the switches which I can add a dropping resistor and use for the LED signals.

The final wiring for the railroad switch, LED signals and control panel will be another article.

John”

A huge thanks to John – anybody else made something similar to his railroad switch machine? I’d love to hear from you if you have.

That’s all for today folks, but don’t forget the Beginner’s Guide if you want all the shortcuts to make your dream model railroad, without the heartache, blisters and toil.

Please do keep ’em coming – and don’t forget today is the last day to grab the launch price on the latest print out scenery (the office block).

Best

Al

PS Latest ebay cheat sheet is here.

21 Responses to Make your own railroad switch points

  1. Gary O'Connor says:

    Thank you John. I had written off getting electronic switches because the amount I need would have set me back a fortune, but with you solution it has become a desirable proposition once more.

    I look forward to your next article on the wiring and control panel with bated breath.

    Gary O’Connor – Australia.

  2. Norm Dotti says:

    When I started reading this I wondered “Where do the pulses for the servo come from?” Your solution is very clever; it doesn’t need them! Thanks for the idea.

  3. Roland Aldridge says:

    Very nice work. A couple of suggestions – you can drill little holes and mount the diodes with their through the holes, soldering on the other side from the diode bodies. This will keep them neat rather as though you had made a circuit board for them.
    The other thing is that acrylic sheet tends to crack slowly, starting at the inside corners. It can take months but if that happens it will be a pain to have to redo them. At the least run superglue all round the inside corners to fill in the tiny stress cracks you can’t even see so as to at least delay this problem, or else use a less brittle plastic like grey PVC or polycarbonate.

  4. John Bury says:

    Great “how to” article. Just goes to show what can be done with some knowledge and imagination. I look forward to the next installment.
    Jack in PA

  5. John Bigglestone says:

    Hi John. Brilliant solution

    Please could you clarify if you are using latching or non latching DPDT switches? Or does it really matter.?

  6. Kevin McArdle says:

    Seems like a lot of work. Maybe if I only had to make one. This is one instance where I will spend money to preserve my sanity, and preserve time, since I’m seventy.

  7. Thomas Murphy says:

    Wonderful idea ~ shall give this a go-about.

  8. Rob McCrain says:

    John what a brilliant solution. You’ve managed to get the price point for motoried points/turnouts to a place that just about anyone can afford. Thank you for that. Rob McCrain, Farland Howe

  9. Jim Logue says:

    Great ideal! Thanks

  10. Dr. Bob says:

    Simple, practical, and genius. I’ve seen many of these same concepts work very well on large model railroads. And when you look at the bottom line being proposed, maybe some of the commercial market “switch machines” will get the hint. Well done John!

  11. Bill Roberts says:

    Thank you, thank you, thank you. I have a box full of burned out switches and a stomach full of frustration over switches. I am a Chemical Engineer (retired at 84) and am barely knowledgeable in electronics and I am doing back flips when I read your article. I am so appreciative of your contribution to our hobby I find it hard to express.

  12. pretty kool build….
    I’m not really an electronic ‘tech genius’ but it looks like a real $$$ saver
    if one IS …
    keep em runnin’ fellas

  13. Great piece and I am quite looking forward to the second installment. This makes the concept both practcal and affordable for even the most electronics-challenged among us. I plan to jump on this as soon as the follow-up piece appears.

  14. John N Frye says:

    Thank you for the comments, I appreciate everyone’s thoughts and input. To the question about the DPDT switch, that stands for Double Pole (2 separate circuits) Double Throw (2 positions that connect wires). For my little machines, there is always 5 volts applied to the wires on the bottom of the machine, so these DPDT switches stay in position once moved. I plan to use this voltage for signals on the layout and on the control panel. The notes about the Atlas Switches indicate that they will have momentary DPDT center off switches which return by springs to center off position when released, no voltage out to any wires leaving them, because the solenoids on the Atlas switches only need a pulse, and if left on will burn out.
    John

  15. Graeme Coleman says:

    Thanks John, looks great, only one question, with tortoise type switches we remove the spring from the switch and the motor ‘holds’the switch over at stall. You mention your motors have a limited ‘run time’ do they still hold the switch/point over indefinately – as in under load – or do I need the springs to stay in the switches? Thanks in advance, Graeme.

  16. John N Frye says:

    To Graeme’s question – Do the switch motors stay over once thrown? Yes, because of the gear train, moving the motors by hand takes some effort, this is like “internal” friction so when they get to the end of their travel, they stop and stay.

    john

  17. Skip L. says:

    Beyond me.., -Way beyond me! -Whew!! -Some of you clever blokes must be really electronically talented!!
    I find it much easier (and more fun) just to use recycled 3-rail Marx turnouts; the manual ones for those closest to the table’s edge and the neat electric ones with their button controllers for further away, for across the board.
    Realism you say?
    It’s all in the mind of the beholder I say…
    Nevertheless, ENJOY! ;>})

  18. Graeme Coleman says:

    Thanks for the reply John, and for the info in the first place. I have a few Tortoise in, but cost, especially here in Australia has had me hold off buying more. Your help will get me back ” on track’. Thanks again, Graeme

  19. Rolland says:

    The end switches are n/c correct. Really nice tutorial.

  20. John N Frye says:

    The micro-switches are DPST one contact normally open N/O, one normally closed N/C. When the motor activates the switch at the end of the travel, the micro-switch changes state and the N/C opens and stops the travel.

    John

  21. Jon Aplin says:

    Thank you John for this great How-to. I have all the parts needed to make my own. About 17 of them. Love the fact that it didn’t cost a years wages to do this.
    I’m about to start putting them together. I will be adding a light near the DPDT switch to show which track the points are lined up for. I wanted to use Red and Green for go/nogo but haven’t figured out the Red side yet. I do have the Green figured out. As the Leaf switch activates to stop the motor from turning it completes the circuit for the Green to come on. Also, I have to use a resistor to drop voltage for the LED.
    Happy modeling.
    Jon

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