An easy way to control servos for realistic slow moving turnouts using a low cost SG90 servo and Arduino Nano.
We cover the mounting bracket and the Arduino Program used to control the rate the turnout changes and other accessories dependent on turnout position.
The Mounting Bracket
There are many options here. The most popular include, but are not limited to, aluminum channel, formed acrylic, and commercial laser cut brackets. They all work well.
I am, however, partial to a simple bracket made from scrap plywood or MDF and some small blocks.
These images show the mounting bracket with the servo in place.
The Actuating Lever
I make the actuating lever from a piece of #6 piano wire. It is flexible and, when slightly bent, will return to its original shape. I adjust the angles of rotation on the servo arm to slightly bend the wire to hold the servo firmly in position.
The Actuating Lever Fulcrum
Drill a hole in the bracket base plate through which you will pass the actuating lever. When connected to the servo arm, it will move through an arc dependent on the through and divergent angles set into your servo.
Setting The Turnout Dynamics
The speed of the turnout and the end points of the fulcrum arc depend on the thickness of your layout base. The only way to have your system work the way you want it, is to work through trial and error process on a test stand.
But first, let’s first set our initial servo angles. The procedure for doing that is here.
Drill or cut a hole through the layout base.
With double sided tape attached to the top of the bracket, press it in its temporary position.
Keep the test stand. You will use it to do the initial setup for all your turnouts.
test –
Video https://www.youtube.com/watch?v=u8njP9raP8Q