Servo motor for switching turnouts


R

Rocky Lines

Member
Hi, I have a couple of turnouts that are in hard to get to places. I have thought that using a micro servo motor might work in these locations. I am not using a DCC system to control any of my switches. As a matter of fact, most of my switches are the old style side mount Atlas Model power types. I just happened to need a couple of curved turnouts so I got a couple of Peco turnouts. They fit nicely, but now I have to "switch" them. What is the minimum needed to operate a servo? I was hoping it could be as simple as running power leads from an old style transformer to a momentary (on)-off-(on) switch (either a slider or toggle), and from this switch to the servo. Does this work, or is there a little I am missing? Most of the servos I have seen have three wires going into them, much like the side mount table top switch motors I am currently useing. Do they work the same way (sort of at least)? I have seen several You Tube videos that so servos being used to switch the turnouts, but none showing anything I would consider "simple" activation. Any help would be wonderful please.
 
You can't control a Servo by just applying power to it.
It's a pulse control circuit, and you will need something like the equipment that Tam-Valley has.
I have some servo controlled turnouts myself, and I use ESU's Switchpilot servo. It can control the servos either by push-buttons (like Tam-Valley's), or by DCC.
 
Servo wiring

I can't believe how many "hits" I got when I tried to perform a couple of searches. Way too many to dig through. I tried. Can you or anyone out there help me out by providing me with a couple of links to conversations or You Tube videos or anything that can spell out the basics for using and wiring servos with manual activation (push bottons or momentary switches) please?
 
One thing you have to get used to is that servos can't be controlled directly with pushbuttons or momentary switches at all. They need (at minimum) a circuit that produces the right electronic signal, and maintains it continuously. It's possible to do that with an oscillator circuit like this:

http://sarconastic.tripod.com/servodriver.html

Although that one is set up with a control knob for sending the servo to any position, it would be easy to use a toggle switch instead, and just have two positions.

If you want pushbuttons or DCC for input, then you have to use a microprocessor circuit like Tam Valley makes.
 
Thank you. I looked at this page and it has some information that I can understand. Mostly it is above my head and there are no pictures of the finished product or of the control knob. I am very definately a novice or lower at understanding electronic schematics like this one. I need even more "basic" help. This is a good starting point though.
 
An alternative if you like DIY tiinkering...

Most servos can be quickly dis-assembled to replace gears for example. Inside are 2 wires (neither in common with the 3 input wires) going to the motor. With a momentary On-Off-On DPDT switch (e.g., from Norvac ;)), one On can apply CW voltage and the other On can apply CCW voltage. There are built-in mechanical stops that limit motion to about 3/4 of a rotation. When applying DC voltage directly to the motor, the speed and torque will be proportional to voltage and the direction reverses with polarity. The motor will start spinning at maybe 1-2V and up to 6V DC with proportional speed and torque. You can experiment with your DC controller to find a suitable operating voltage and then just use a recycled cellphone charger and a few 10 cent diodes to tweak the charger output voltage in 0.6V steps.
 
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