Twin Coil Switch Machine Drivers For Single Switch Machines

Circa 2005

  These circuits on this page allow an ON-ON type SPDT or DPDT toggle switches to control twin coil switch machine motors. The handle of switch can be used to indicate the route selected. Some of the circuits are able to control LEDs that indicate the selected route as well.

  The main disadvantage of these circuits is the cost of two large electrolytic capacitors per switch machine.

  The size of the capacitors depends on the power needed to throw the turnout and the supply voltage. The value of the charging resistors depends on how quickly the turnout will be returned to its last position. A resistance of 1000 ohms would be a practical value in most cases. Higher value resistors use less power when idle but take longer to charge the capacitors.

  The resistors should have a 1/2 watt or greater power rating. The capacitors should have a 25 volt or higher rating.

  NOTE: Most of the circuits are shown with DPDT toggle switches but 3 and 4 pole switches could also be used with the extra poles controlling frog polarity or LEDs.

  For more information on other Capacitor Discharge - switch machine power supplies, follow this link. Capacitor Discharge - switch machine power supplies

For Switch Machines With A Fixed - Coil Common Connection

  The first three circuits are for use with switch machines that have an unbreakable connection between the two coils such as those made by Atlas®. These circuits can also be used with twin coil switch machines that have separate coils.

  The next circuit is a variation on the circuit above that can control a relay.

  The next circuit is a variation on the circuits above. This circuit makes use of all the poles on the DPDT toggle switch.

For Switch Machines With Separate Coils

  The following circuits are designed so that the indicator LEDs have "Fast Turn Off". These circuits cannot be used with switch machines that have a Fixed - Coil Common Connection.

Separate Coils With Frog Polarity Control

  The next circuit uses darlington transistors in the high current portion of the circuit. This would allow low currents in the control panel wiring.

Separate Coils With Transistor Control

  This circuit has fast LED turn off. The LEDs could also be supplied from a separate power source.

Separate Coils With Separate LED Control

  The next circuit allows short charging times for the capacitors so that the turnout can be thrown more quickly. Due to the low value of R1 (100 to 220 ohms) the power supply would have to be more robust than if 1000 ohm resistors were used.

Fast Recovery Circuit

Other Circuits

Set Signal / Then Throw

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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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03 March, 2018