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Servos in model railroading
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 Posted: Tue Nov 26th, 2013 12:38 am
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jtrain
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Many of us have probably heard of servos, especially if you have other hobbies like RC airplanes, cars, and boats or if you like robotics.

I was introduced to servos in my electrical engineering class and I feel this could be useful to some of us, especially those who use DCC or use computer programs to control their train movements.

For those who don't know, a servo is essentially a small DC motor that operates on a pulse current, which will lock the motor to a certain position, typically at 0, 90, and 180 degrees. The servos also typically have a lever or an arm attached to the gearbox which can preform mechanical tasks like opening doors, or push/pull over a short distance.

After looking at this video:

http://www.pololu.com/category/12/rc-servo-controllers

saw the potential for servos to control turnouts and the like on model railroads. I don't know how most of you feel about computers (I personally can live with them, and occasionally find a use for them) but it seems that if you had say a large yard to control, or if someone was controlling the main line turnouts on a railroad, plugging a computer into the layout and controlling all the turnouts from one point would save a lot of space and wiring. The video also hints to that if computers aren't your thing, the servo system can also be controlled by buttons and switches.

Controllers, according to the video, come in standard sizes of 6, 8, 12, 18, and 24 channels, each channel capable of controlling one servo.

So on a layout, if you were to have a yard with 20 some turnouts, then the maestro controller would be $50, but I've seen servos sell for less than $5 a piece. So on a yard, were's talking $150 to control 20 turnouts, compare that to about $375 for tortise switch machines or even $240 for atlas remote switch machines.

For simpler operations, like what I want for my 1:20.3 scale layout that I am planning, the first phase will have less than 6 turnouts, meaning a base price of no more than $50 plus whatever it costs for activation switches.

So these things have the potential to be cheaper, even in smaller operations, than what hobbyists generally use. even manual turnout control, which I'm okay with on a large scale layout, are still $20 for a switch stand.

These things are also very reliable, not once in my class did I have something fail that wasn't my fault. And appear to be durable enough to crash into the ground mulitple times in an RC airplane.

What do you guys think? I can see myself using these servos for turnout control. I think they would also be great at a train show, where you can sit in one spot and control all the turnouts digitally, or you could have a control board with activation switches and perform the same task.

--James:java:



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 Posted: Thu Nov 28th, 2013 06:31 pm
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mysterd429
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Tam Valley has a bunch of servo-based products (see here) that look like they'd be useful. I haven't yet tried them, but I plan to!



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 Posted: Fri Nov 29th, 2013 12:03 am
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mdrailbaron
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Good evening James,
 I have been using servos for turnout control for a couple of years and think at least for me, they are the way to go.  They have more pluses then negatives and here are a few ideas that I have used that work.  First I can top mount them  and not need another person to help me line them up. Once set, I use Liquid Nails to "set" the servo in a hole that has been cut into the Homasote.  I use a "C" battery in a battery holder to power the various turnout servos  and the same battery is still powering them after two years and yes I have an ops session twice a month.  I can easily hide them any number of ways, I usually put blue painters tape over the servo except for the slot for the arm, paint it Tie Brown and then glue scenery over top of it.  I don't worry about signaling but if I wanted it, I could use a rotary switch instead of the dpdt, center off toggle switch, that is spring loaded to automatically come back to center and off, so that you don't drain your battery.
  I am at the moment using the points of the turnout to power route but will in the near future place a micro switch to help the points.  Out of appox 75 turnouts that are wired with a servo maybe at the most 5 turnouts will need a little help, the spring steel piano wire in conjunction with the power of the servo has worked quite well.
So that is my story and I am sticking with it.

Steve



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 Posted: Fri Nov 29th, 2013 02:24 pm
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jtrain
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So that is all you need to control one servo? just a center off switch? Somehow I thought it would be more complicated, but if you got it to work, surely that is the way to go.

For power routing, my scale is the very large 1:20.3, meaning that if I wanted to, I could power everything except for about a 2" section of the frog and everything would work just fine.

Thank you for the helpful input. If indeed all I need to power a turnout is a battery, a switch and a servo, I'm looking at only about $5 a turnout.

--James:java:



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 Posted: Fri Nov 29th, 2013 02:48 pm
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mdrailbaron
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Good morning James,
  If you will write me at  traindadders@gmail.com I will forward a small pictorial tutorial on how I set up the servos.  It would not matter what scale or gauge that you model in, all you want to do is throw a turnout, it has nothing to do with track power.
Steve

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 Posted: Fri Nov 29th, 2013 03:00 pm
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W C Greene
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James, since you are modeling 1:20.3, I wonder why you are worried about power routing and all that jazz??? In that scale, there is a much better alternative to power locomotives, etc. than wires and power supplies.

And servos, I have used them for many appications on my layout; conveyors, rotary dump mechanisms, aerial tramway, and more. Many of the servos I have were given to me by r/c flyers and car racers who change them out for the "latest thing" and I keep their junk drawers clean. But you gotta get to know these guys...it also helps when you go totally wireless with your trains.

Woodie



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 Posted: Fri Nov 29th, 2013 04:43 pm
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jtrain
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Woodie,

In short, I'm running indoors and I hope to eventually do DCC when I get around to it. While battery is certainly an option, DCC seems simpler to install and is less of a learning curve for me than battery. Having track power is something I'm familiar with, so it suits me well indoors. Also, I would pay $30 apiece for stationary DCC decoders to power turnouts, but I prefer to run around the layout and flip them via a switch or manually, so DCC for turnout control is something I have no use for. Besides that, you can't beat $5 per turnout for electrical control via a motor.

However I do agree that outdoors, track power is a completely different situation. I've built and operated two garden railroads that use track power, and although it works, battery power outdoors is the way to go, and preferable RC as well. ;)

Regards,

--James:java:

Last edited on Fri Nov 29th, 2013 04:56 pm by jtrain



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