Automatic Switch Project

Posted on Feb 6, 2014

Model railroad turnouts, often called switches, can be controlled in a number of ways. The most basic is a manual control that is thrown by hand. Remote activation is usually accomplished by either pneumatic (air) or electrical means. The project that is the focus of these articles has several turnouts that must be remotely activated by a microcontroller. As mentioned in the last

Automatic Switch Project
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article the output power available on a PICAXE is quite limited, certainly nowhere near what is required to throw a turnout. I have seen many turnout motors drawing nearly 2 amps when activated so some sort of intermediate device, like the transistor that was used with the relays, is needed. Before we can choose the appropriate device to operate the turnout we need to examine how turnout motors operate. The two most common electrically operated turnout motors utilized in garden railways are those made by LGB (item number 12010). We will also examine a slightly less common unit from Circuitron called the slow motion Tortoise. Although not designed specifically for garden railway use it can easily be attached to most turnouts. In the photo below the five screws that hold the sides of its case together have been partially removed. Oops - guess I voided the warranty! All three of the turnout motors operate in much the same way. Power goes to each turnout motor through two wires. When power is applied in one direction, that is the positive connection goes to one terminal while the negative goes to the other, the turnout is turned one way. When the polarity is reversed the turnout is activated in the other direction. The design of the AristoCraft 11299 utilizes a small DC motor to throw the turnout. The small motor`s power is multiplied by a set of gears. The most unique characteristic of the AristoCraft units is the inclusion...

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