Track Routing Control Circuits

For Stall-Motor Switch Machines

  This page shows some methods of track routing control for stall motor type switch machines. The principle method uses a 2 Pole - Multi Position rotary switch while an alternate uses transistors to select the routes.

  The switch machine used to develop this circuit is the Circuitron - Tortoise™ (Model number 800-6000) slow motion type switch machine motor.

  The routers are essentially diode matrix circuits shown in a different format.

  The last circuits on the page are for a method of controlling the matrix electronically. This would, in theory, allow any number of route selections, limited only by the size of the decoder.


Stall-Motor Routing Control Circuits

  The first circuit shows the basic method of route control using a 2 Pole / 3 Position rotary switch.

Basic Route Control schematic

  The circuit uses a split power supply to provide a positive and negative supply in order to drive the motors in either direction. Filtering of this supply is not necessary.

  The rotary switch selects the desired route and the diodes prevent reverse current flows through the switch pole and then to the other motors.

  Also shown is a method of connecting route indicating LED's to the circuit. LED's could also be connected in series with motors for local route indicators near the switch itself.


  The next schematic is simply an expansion of the first and shows route control for a simple 6 track storage yard using a 2 Pole - 6 position rotary switch. The circuit also has optional route indicator LEDs.

Rotary Switch - Route Control For A Six Rack Yard schematic

  The next diagram is a printed circuit board pattern for the route control circuit shown above. The board has provision for mounting the resistors for the route indicator LEDs.

Printed Circuit Board Pattern For 6 Track - Route Control Circuit



Electronic Route Control For Stall-Motor Switch Machines

  The next diagram shows a possible method of selecting the routes electronically through the use of logic devices and transistors.

  As mentioned above this circuit is shown here as a possibility only and has not been tested in practice.

Proposed - Electronic Control Of Track Routing schematic


Electronic Route Control Using The 7445 Decoder

  The next diagram shows an electronic route control method using the SN7445 - BCD to 1 of 10 decoder IC. This device has open collector outputs that can withstand up to 30 volts and are able sink up to 80 milliamps of current.

  As mentioned above this circuit is shown here as a possibility only and has not been tested in practice but should work as designed. Some tailoring of resistor value may be needed if current loads are high.

SN7445 Based - Electronic Control Of Track Routing schematic

  There are a number of other devices that can perform the "1 of X" decoding function, such as the 74138 and 74154, but these do not have the built in open collector outputs of the 7445. Other TTL devices such as the 7407 can perform the open collector output function for these decoders.

  The 74138 decoders can be ganged together in multiples of 8 to easily provide up to 24 decoded outputs. Higher levels of decoding are possible but become more complicated with each increment.

  Adding "Latch" type memory device, such as the 7475, between the thumbwheel and the decoder would allow preselection of a route without having to step through each choice when a change is made.

  The center 2N3906 transistors could be replaced by optoislolator in order to separate the control circuit from the switch machine driver power.


- Circuit Notes -


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Please Read Before Using These Circuit Ideas

  The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.

  If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

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