I got as far as thinking about it

I haven't built one, but I have given the matter considerable thought.  I once purchased a switch machine kit which consisted of a motor which drove a length of threaded rod, an arm driven by a nut on the rod, and a set of contacts to form a DPDT switch actuated by the arm.  Power in one polarity drove the motor until the contact was opened at the end of travel, and reverse polarity did the opposite.

The design is so simple that it should be easy to duplicate.  Micro switches could be used in place of the custom made ones, or all sorts of creative solutions could be devised.

I have wondered how hard it would be to make a small unit out of a pager motor.  It should be small enough that it could be mounted on top of the sub-roadbed (or very slightly recessed into it, I suppose).  I have been collecting old electric toothbrushes, just to scrounge the motors.  When you can buy a toothbrush for a few dollars, and they're made to be disposable, I think of the motors as nearly free!

Cheap jackscrew machine w/contacts

Here's a sketch of a machine I've built in the past, that is along the lines of what Rick mentioned.

It consists of a spare DC motor (3 volt -12 volt) connected via a piece of rubber tubing to a 6-32 treaded rod (long screw with the head cut off. 

The threaded rod is the jackscrew that turns in a 6-32 brass or cad-plated nut soldered to a piece of printed circuit (PC) board.  The PC board slides back and forth in a couple of plastruct channels out of the scrap box.

I make separate traces on the PC board by cutting away the copper-cladding.  I use phosphor-bronze strips (the same stuff I use for wheel wipers) as contacts that ride across the PC board traces.  I grind away portions of each trace where I don't want electrical contact.

To drive switches, crossing gates, etc., drill a hole in the PC board, and hook a piece of piano wire or stiff brass or steel wire in, and away you go.

It's a very cheap, but very useful and effective solution to a lot of mechanical-electrical problems.

edit:  For DCC control, just wire your motor to the cheapest minimum function decoder you can find.  Voila!  Experts in the area of fixed decoders need to chime in here.  It's all do-able, but I can see some wrinkles in the control and direction that fixed decoders should specifically be able to handle.  I don't know; never used 'em.  I rely on pushbuttons on the fascia, 'cause they're the cheaper way.

Hope this helps.

Another way of limiting travel

I've been thinking about this one this morning, and I have an idea...

You could solder a pair of nuts onto either side of a piece of copper-clad board (using the threaded rod to make sure they're lined up).  Each side of the board would be connected via a diode (opposite directions for each side) to a wire connected to one of the motor terminals.  Power would flow through the metal jack screw into both buts, and conduct via one of the diodes.  When the nut runs off the end of the screw, conduction stops, but reversing the polarity lets it start in the opposite direction.  To work properly, of course, the threaded rod needs to be free at both ends.  The simplest way would probably be to turn down a length on each end to run in some type of bearing, or even to turn away a section of the threads a little wider than the thickness of a nut.

Of course, there is no way to adjust the travel.  On the plus side, there is no way for the travel or limit switches to get out of adjustment.

Power routing would require some sort of wiper or contact if you want it in the switch machine.  Personally, I'd use a DPDT to control the machine and frog polarity at the same time.

Question

you have to ask yourself. How much will parts cost for each machine? I have a commercial one that pretty much looks like the one in the sketch.

Rich

Costs

Rich,

Cost is a tough question to answer when the parts are 100% out of the scrap box.  Motors can come from old locos, toys, retail displays.  The PC board material is maybe a buck per unit if you buy a big piece new and cut it up.  Screw and nut = $0.10 + $0.15, or less if you buy by the box.  Plastruct is getting more expensive, but Evergreen Scale Models has styrene shapes in 14 inch lengths @ 4 for $2.99.

Rick,

I didn't go in to detail, but two of the wipers would be for motor control:  you would cut a gap across a trace near the end of the throw, and solder a diode (1N4001) across the cut, so that when the wiper passes the cut trace, current flow stops and the motor automaticaly stops.  With polarity reversed (your DPDT reversing switch), the diode would then conduct current in the other direction to back out of the cut trace area.  You have the same thing at the other end of the trace, with a diode soldered across the gap in the other direction, so your have auto-stop at each end.

Other traces could be used for lights, indicators, sensor feeds to other electronics, etc.

Whew!  This is a lot harder to explain that to throw together.  I hope I made some sense of this.

Home built switch machine

I use Servo Motors to control my turnouts. I only have two right now but they work great. I use an S88 module to control the servo. The module was designed by a friend but he hasnt released it to the public. Others have used servo motors for turnouts and if you search google you may find a cheap controller circuit. Servo motors can be purchased very cheaply. This link will get you to a DIY system that works with Rocrail. Not sure if it will work with JMRI.

http://wiki.rocrail.net/doku.php?id=mgv84-en

Here is a link to Paco's site. I think this is one of the best DIY sites going. Everything you need is posted on this site and he asks for nothing! http://usuaris.tinet.cat/fmco/home_en.htm

Rob teed

Bullfrog switch machine

Right at the top of the page when I log in. $6.00 each. Use your imagination to keep the cost down.

http://www.handlaidtrack.com/BullFrog-Manual-Turnout-Control-Unassembled-p/bf-0002.htm

Yes, a well stocked junk box can work wonders.

Rich

Time is money

Alan, Rich:

Yes, I must concede:  time is money.  I'm just stubborn enough when I'm reaching for my wallet that I just may spend twice what it's worth in time, just to say I built it out of the scrap box.  (But, but;  I am having fun, I'm having fun, I'm having fun...)

Regarding servos, I am reminded of the MRH sponsor in San Diego,  Tam Valley Depot.  He has some great products combining servos and DCC control.  Check him out through the "Advertisers" tab at the top of the page.

5 dollar switch machine

i too have been thinking about this issue for a while and have come up with my own solution. using some styrene and a modified rc servo and a microswitch. the rc microservos can be bought off ebay for as little as 25 dollars for ten. $2.50 each plus a 2 dollar microswitch and some scrap 40 thou styrene. The speed is dependant on the input voltage you use and the microswitch provides frog polarity. takes 5 mins to build. in my opinion excellent value. i knocked up 10 in an hour the other day. as previously stated i do not know how you can "cheaply" control switch motors with dcc. when you factor in the decoders  the idea of budget is really streching its limits.

Dan

Why would anyone want to control switch machines w/dcc?

If you are building a layout to use a walk around throttle to follow your train around the layout, just put a turnout control switch on the fascia in close proximity to each turnout, and flip the switch as needed when you get to the turnout.

The only place where I can see the advantage to using dcc to control turnouts is when you have a large club style layout with a dispatcher who is doing ctc control of mainline turnouts in combination with signals.

5 dollar switch machine

Do you have any photos of your project? I am sure there are some here who would like this solution.

I did a little searching and found the below. Get the issue right from Kalmbach. Some rip out the digital stuff and solder the wires right to the motor terminals and run them on about 6 vdc.

You can also do a Google search for    rc servo turnout control

MR article (Jan 2010) describes ultra-cheap servo turnout motors

Rich

Thanks!

Thanks for the ideas everyone! I like the motor with the screw attached idea.

I currently have assembled a test switch machine but will definitely be trying the copper-clad board idea which looks sturdier than what I am testing now.

The reason I wanted something I could control with DCC is because I am building a portable DCC demonstration layout, plus I like everything related to DCC.  I plan on using a LocoIO circuit for controlling the switch motors.

This is my first experience with the MRH forum, I was surprised to see the amount of people willing to share ideas and will definitely be back if I have more questions.

Any further comments are eagerly anticipated.

More reasons to use DCC

There are times when it would be nice to have complex route control - for example going into a passenger terminal or freight yard - and DCC decoders can do that more easily (sometimes) than a diode matrix.  If you want a switch to throw automatically or in response to some pre-determined signal (like for a reverse loop, or automated meeting of trains) DCC can do that.  If you want to completely eliminate control panels and fascia mounted switches, DCC can do that too.  If you need to line a route ahead of time, while not leaving the train you're working with, DCC can make that easy.

With all that said, I use slide switches as both ground throws and frog power selectors - about as low-tech as you can go.  I like the manual approach, but I know that some people like to be able to do everything from the throttle in their hand.  Different strokes and all.

This thread has given me some things to think about.  I may look into powering some of my harder to reach turnouts, now that I see it can be done so cheaply.

Slide switches

Ken,

Yes, slide switches:  very cheap and very effective.  I just built one, just now.  It took about a minute.  *Of course, this build-it-fast version doesn't win neatness awards, but I just wanted to picture it in case someone wondered what Ken referenced.

easy, low cost switch machine

Hi Andrew;

Here's one I came up with some years ago. For some reason I couldn't get anyone interested in it. The only problem I came up with was the power supply. You need one that will supply 3V regardless of load. 

Here's the basic concept. Start with a 3v can motor, a roll of .023 MIG welding wire, some crazy glue and a 3/64 drill bit. Cut a length of wire 10-12". Clamp the drill bit in a vise and wrap the wire around it in a tight coil of about 5 to 7 turns. leave a leg about 1/4" long on one end of the coil and a leg about 1" long on the other. Gently unwind the coil slightly and push it over the armature shaft of the can motor and let it relax. The coil will grip the shaft like a clutch. Thread the 1" leg of wire through the hole in the center of the throw bar (if there isn't one, drill one) from the bottom of the turnout. Clamp the motor to the bottom of the ties and check for binds and correct travel. When the motor is positioned for the best action, glue the motor can to the bottom of the ties,cut off the excess wire above the throw bar, and you are done.

 I set mine up to act against a light spring which allowed me to cut my wiring in half. It is just on-off instead of power through, power diverge with a center common.  The motors can be found in several places. One of my favorites is The Dollar Tree (everything is $1) They sell toys and small fans with 3v motors in them. The wire is sold at Harbor Freight, same for the drill bit and glue. Your total cost for materials will be less than $2 per switch machine.

A few things to keep in mind, These motors aren't very powerful so your point rails must move very easily. No heavy springs or binding. This can work to your advantage because the pressure between the stock rail and the point rails is very light. If you happen to go through the turnout from trailing point with it thrown against you, the weight of your train will move the points aside and you will not derail. For the same reason, this setup does not work well for conducting track power with the point rails. Most DCC systems don't control track power like this anyway. You will have to carve a well under the switch points big enough to fit the can motor but most of these are quite small so it's no big deal. Usually 1"x1"x5/8" is plenty. Another item I mentioned earlier is the power supply. Wall warts don't work. Their amperage output is severely limited. If you have more than one of these motors connected and you turn them all on, they won't work. Probably the best low-buck,low-tech way would be a 3v bank of rechargeable batteries. I have to do more testing.

I hope this gives you some ideas.

Did you check out the less expensive, new "Mole" switch machine?

To save building your own less expensive machines, you might want check the Mole out first.

You can mount it like a tortoise, or . . . 

in a new, easy to fit way,  way, sunk into the top of your baseboard.

It's very new, so it's fame hasn't spread yet. The Proto:87 Stores FIRST GENERAL ADVERTISEMENT will be in the Feb edition of MRH! Yeah!!!

Motor sources

@alco2nr - perhaps you can share the information on where you can get these $1 DC motors ? I have visited the "dollartree" web site and could not find any motors. Is the "The Dollar Tree" you referred to:

http://www.dollartree.com ?

Cheap Motors

Here's three sources of cheap motors:

http://www.allelectronics.com/make-a-store/category/400/Motors/2.html

http://www.goldmine-elec-products.com/products.asp?dept=1104

http://www.alltronics.com/cgi-bin/category/37

Happy motoring. 

Bernd

Thanks, Bernd

It figures you would know with that Athearn Hustler modification project of yours. I really enjoyed reading you blog on your progress.

Your Welcome Bill

Let's just say google is my friend, plus I used to play around with electronics for model railroading. I also have one of those switch motors that was mentioned earlier on with the nut on a shaft. That didn't work to well so I was working on making up my own. Never finished the project.  I've known about these surplus places for many years now.

Glad I could help out.

Bernd

P.S. I've got another little critter in the works. Just waiting for some parts. It's going to be a test bed for something I want to try.

$5 servo switch machine

 , have you any details , I would like to build a couple

$5 machine thread

Hi Geelong61

Have a look at his new thread which maybe of help to you

https://forum.mrhmag.com/post/sma10-%E2%80%93-build-a-17function-dcc-decoder-for-about-5-12197796

George

Do It Yourself (DIY)

DIY modelers have been building lower cost switch machines for many years. The construction, programming and uses of newer microprocessor controlled devices does include a small investment for development tools (software tools are free) and a moderate to large time investment to learn to use the tools.

The latest designs use low cost servos produced for the Radio Control modeling crowd. Servos can be purchase online for about $3 each ( 5PCS x SG90 Micro 9g Servo For RC Airplane Car Boat Genuine). There are also commercial versions of these products from outfits like Tam Valley Depot (good information on installing and using servos).

Additions references for using, designing and building DCC servo controllers:

Paco's website ( http://usuaris.tinet.cat/fmco/dccfunc_en.html#funcsrv)

Model Railroading with Arduino

Arduino Lesson 14. Servo Motors

Servo (radio control) - Wikipedia

Way back...

When I was a kid, (mid 1950s), I remember my Dad making switch machines for our Lionel pike out of doorbell solenoids.   I'm sure he would have figured out something for the motor style machines if they were in use back then.

Bob Bochenek