The circuits on this page are basic designs for "Diode Matrix" switch machine control systems that can be used to operate "Stall Motor" switch machines in 'Ladder' type storage yards or other multiple turnout areas.
The driver circuits themselves use LM556 dual timer chips to reverse the polarity of the voltage to the switch machine motors.
The principle for these diode matrix circuits on this page is very much the same as for those used to control twin coil type switch machines except that the diodes handle much lower currents.
The switch machine used to develop these circuits was a Circuitron Tortoise slow motion type switch machine (Model number 800-6000).
The following diagram is for the circuitry of the 556 - Switch Machine Drivers. On the Diode Matrix system schematics these circuits are represented by a logic block diagram in order to simplify the diagrams.
More information on this ciruit can be found at this link - 556 Timer Stall-Motor Switch Machine Drivers.
The next diagram shows the above schematic in a block form that is used in the following circuits on this page.
The next diagram is for a basic diode matrix system that will operate the switch machines for one end of a four track ladder yard.
Tracks 1 through 4 are selected with the appropriate push buttons. This in turn SET's or RESET's, through the diode matrix, the appropriate switch machine motor controller to its "N" or "R" condition and operates the turnouts.
Included in the diagram is a "Truth Table" that shows the position of each turnout for the particular track that is selected. The "X" or "DON'T CARE" symbol means that it does not matter where that turnout is lined to if track 1 or 2 is selected.
In the following diagram; extra diodes, as indicated by the dashed lines on the schematic, have been added so that the turnouts above a selected track are moved to their "N" positions when the lower track's button is activated.
For example: If track 2 is selected, the track 3 turnout will go to its "N" of straight through position.
The "Truth Table" in the Homing diagram shows that there are no "X" or Don't Care positions for this version of the circuit.
The Homing circuit can not be used if trains are left sitting on the turnouts as the switch would throw under the parked car.
The following diagram shows how diode matrix systems using the LM556 Flip-Flop block could be "Cross Coupled".
This means that if a double ended yard had separate matrix circuits at each end - these could be connected together so that both ends of the yard could be operated from the matrix selector at either end if desired.
When the tie switches are open the turnouts at the each end of the yard are operated by their respective matrix systems. When the tie switches are closed the turnouts in the yard can be operated from either end.
Two options for connecting the separate matrix systems are shown. For Track 1 the connection is at one location only. For TRACK 2 the connection can be made from either end of the yard.
The only limitation to cross coupling is that both ends of the yard should be symmetrical as would be the case in the diagram shown at the bottom of the schematic.
The next circuit shows how a multiple position rotary type switch could be used to select the desired track.
The "Master Throw Button" is an optional device but it does prevent the turnouts from moving as the rotary switch is moved from one selection to the next. The button also allows route to be pre-selected.
Interlocking train detection circuits could be tied into Master Throw Button to automatically operate the turnouts or prevent them from throwing if they are blocked by a train or signal system.
If desired, one motor control block could simultaneously drive the switch machine motors at both ends of tracks in a ladder yard.
In fact, due to the nature of the stall motors used in these switch machines the entire switch control system draws less current when the motors are in motion than when they are stalled at the ends of their travel.
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.