Abstract:
An apparatus for determining the direction of travel of an electrically driven model train through a model railroad track layout having track segments with rails of opposite polarity is disclosed. A diode and transistor are operatively coupled to at least one rail of a powered track segment, such that passage of an electrically driven model train over the powered track segment in a first direction enables a flow of electrical current through the transistor to a signal or control circuit, while passage of the electrically driven model train over the powered track segment in a second direction does not. The polarity of the rails is determined by a circuit driven by a control circuit attached to an adjacent track segment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/420,270 filed on May 25, 2006, from which priority is claimed and which is herein incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present application is related to the control systems for model railroad systems, and in particular, to a method and apparatus for detecting the presence and direction of any movement of an electrically driven model train along a track system to activate relays, accessories, or directional indicator signals. 
     Model railroad systems are becoming increasingly popular among hobby and train enthusiasts. Typically, in a model railroad system, sections of track are laid out and interconnected with various junctions and switches to provide one or more track pathways for an electrically driven model train to travel along. The electrically driven model train generally receives a supply of electrical power through the conductive portions of the track sections over which it travels. The direction of movement of the model train is regulated by the electrical polarity of the two rails in each track section, and correspondingly, the direction of an electrical current flow from the conductive rails through the electrical motor in the model train. For a first polarity, the model train will be driven in a first direction. By switching the polarity of an electrical potential supplied to the two rails with a reversing switch or relay, such as a double pole double throw switch, the direction of travel of the model train is correspondingly reversed. 
     To sustain movement of a model train around a track layout, sequential segments of track must be supplied with driving electrical power of matching polarity, and down-track junctions must be electrically switched to continue the motion or route the train in the correct direction. Furthermore, it is necessary to provide a means to identify the current track segment on which the model train is presently occupied and the direction of any movement of the train. On basic model train layouts, much of this is done by visual observation of the model train position and direction of motion, allowing an operator to ensure that sequential segments of track onto which the model train will move are provided with the correct polarity. However, on large scale model train layouts, the position and direction of movement of the model train may not be visible to an operator at all times, and multiple model trains may be moving about the tracks simultaneously. 
     Accordingly, there is a need to provide an apparatus which is capable of providing an operator with a signal indicating the presence of a train on a track segment, and the direction of travel of the train across that track segment. It would further be advantageous to provide an apparatus which is capable of utilizing the detected presence and direction of travel of a model train to selectively activate one or more down-track junctions or track segments to maintain automatic movement of the model train in the desired direction. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly stated, the present invention provides a device configured for determining the direction of travel of an electrically driven model train through a model railroad track layout. In a preferred embodiment, the device consists of a diode and transistor which are operatively coupled to one rail of a powered track segment, such that passage of an electrically driven model train over the powered track segment in a first direction enables a flow of electrical current through the transistor to a signal or control circuit, while passage of the electrically driven model train over the powered track segment in a second direction does not. 
     In an alternate embodiment of the model train detection system present invention, the system consists of a set of diodes and transistors operatively coupled to each rail of a powered track segment, such that passage of an electrically driven model train over the powered track segment in a first direction enables a flow of electrical current through a first transistor to a signal or control circuit, while passage of the electrically driven model train over the powered track segment in a second direction enables a flow of electrical current through the second transistor to a second signal or control circuit. 
     In an alternate embodiment of the present invention, the model train detection system is configured with an electrical circuit to detect the presence and direction of travel of an electrically driven model train over a monitored track segment, and to responsively send an electrical signal to the next down-track segment of track to selectively enable the electrical polarity of that track segment for continued travel of the model train in the same direction. 
     The foregoing features and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the accompanying drawings which form part of the specification: 
         FIG. 1  is a schematic representation of a model train detection circuit of the present invention for detecting movement in a single direction along a track segment; 
         FIG. 2  is a schematic representation of a model train detection circuit of the present invention for detecting movement in two directions along a track segment; 
         FIG. 3  is a schematic of a track segment polarity reversing relay circuit; 
         FIG. 4  is a schematic representation of a model train detection circuit utilizing diodes to isolate transistor outputs, which is coupled to an optional track segment polarity reversing relay; 
         FIG. 5A  is a representation of the connections to a two-pole double throw latching relay; 
         FIG. 5B  is a representation of the connections to a four-pole double throw track relay; 
         FIG. 6  is a representation of a “Y” junction model train track segment layout; 
         FIG. 7  is a representation of a reverse loop model train track segment layout; 
         FIG. 8  is a representation of a siding model train track segment layout; 
         FIG. 9  is a representation of a cross-over model train track segment layout; 
         FIG. 10  is a representation of an N-scale model train track layout incorporating train detection circuits of the present invention. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts of the invention and are not to scale. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. 
     Turning to  FIG. 1 , a model train track segment  10 , having first and second conductive rails  12 A and  12 B is shown coupled to a source of electrical power  14  for driving a model train (not shown) over the track segment  10  and a source of sensor electrical power  15 . The sources of electrical power  14  and  15  are operatively coupled to each of the conductive rails  12 A and  12 B through a reversing switch or relay  16 , such as a double-pole, double throw switch. When a model train (not shown) is positioned on the track segment  10 , an electrical circuit is completed between conductive rails  12 A and  12 B by the driving motor (not shown) of the model train (not shown). The selected polarity of the conductive rails  12 A and  12 B determines the direction of movement of the model train (not shown) over the track segment  10  by establishing the direction of rotation of the driving motor (not shown). Switching the polarity, such as with the reversing switch or relay  16 , reverses the direction of movement of the model train (not shown) over the track segment  10 . 
     A train detector  100 , consisting of a diode  102  and a transistor  104  is operatively coupled between the conductive rail  12 B and the source of electrical power  14 . The diode  102  is coupled between the conductive rail  12 B and the source of electrical power  14  to provide a first electrical pathway. A second electrical pathway between the conductive rail  12 B and the source of electrical power  14  is provided by the transistor  104 . Specifically, as shown in  FIG. 1 , a base  104 B of the transistor  104  is operatively coupled to the conductive rail  12 B, while an emitter  104 E of the transistor is operatively coupled to the source of electrical power  14 . A collector  104 C of the transistor is operatively coupled to an external electrical circuit  200 , such as an indicator, relay, or other device. 
     When a model train (not shown) is disposed on the track segment  10 , and the conductive rails  12 A and  12 B are configured with a first polarity configuration, a first electrical pathway is completed from the source of electrical power  14  to rail  12 A, through the driving engine (not shown) of the model train (not shown), into rail  12 B, and back to the source of electrical power through the diode  102 , driving the model train (not shown) in a first direction. The flow of electrical current is blocked from the external electrical circuit  200  by the transistor  104 . 
     When the reversing switch or relay  16  is actuated, the polarity configuration of the conductive rails  12 A and  12 B is reversed. The diode  102  blocks a flow of electrical current along the first electrical pathway, and instead, electrical current flows from source of electrical power  14 , to the emitter  104 E of the transistor  104 . From the emitter  104 E, the electrical current flows to the base  104 B, through the conducive rail  12 B, driving engine (not shown) of the model train (not shown), conductive rail  12 A, and back to the source of electrical power  14 . The model train (not shown) is then driven by the flow of electrical current in a second and opposite direction along the segment of track  10 . Within the transistor  104 , an additional flow of electrical current is directed from the emitter  104 E to the collector  104 C, and provided to the external electrical circuit  200 . 
     In the embodiment of the present invention shown in  FIG. 1 , the train detector  100  is configured to energize the external electrical circuit  200  only when the model train (not shown) is moving over the track segment  10  in one direction. If the external electrical circuit  200  includes an indicator such as a light emitting diode  202 , this indicator will selectively indicate the presence of a model train on the track segment  10  only when the track polarity (and hence train movement) is selected via the switch  16  such that the electrical current flow between the rails  12 A and  12 B passes through the transistor  104 . 
       FIG. 2  illustrates a second embodiment of the present invention, wherein a second train detector  130 , consisting of a diode  132  and a transistor  134  is operatively coupled between the conductive rail  12 A and the sources of electrical power  14  and  15 . The diode  132  is coupled between the conductive rail  12 A and the source of electrical power  14  to provide a third electrical pathway. A fourth electrical pathway between the conductive rail  12 A and the source of electrical power  14  is provided by the transistor  134 . Specifically, as shown in  FIG. 2 , a base  134 B of the transistor  134  is operatively coupled to the conductive rail  12 A, while an emitter  134 E of the transistor is operatively coupled to the source of electrical power  14 . A collector  134 C of the transistor is operatively coupled to an external electrical circuit  230 , such as an indicator, relay, or other device. 
     When a model train (not shown) is disposed on the track segment  10 , and the conductive rails  12 A and  12 B are configured with the first polarity configuration, the diode  132  blocks the flow of electrical current over the third electrical pathway. Instead, the circuit is completed from the source of electrical power  14  to rail  12 A over the fourth electrical pathway through the emitter  134 E of the transistor  134 . From the emitter  134 E, the electrical current flows to the base  134 B, through the conducive rail  12 A, through the driving engine (not shown) of the model train (not shown), into rail  12 B, and back to the source of electrical power through the diode  102 , driving the model train (not shown) in the first direction. The flow of electrical current is blocked from the external electrical circuit  200  by the transistor  104 , while within the transistor  134 , an additional flow of electrical current is directed from the emitter  134 E to the collector  134 C, and provided to the external electrical circuit  230 . 
     When the reversing switch or relay  16  is actuated, the polarity configuration of the conductive rails  12 A and  12 B is reversed as previously described. The diode  102  blocks a flow of electrical current along the first electrical pathway, and instead, electrical current flows from source of electrical power  14 , to the emitter  104 E of the transistor  104 . From the emitter  104 E, the electrical current flows to the base  104 B, through the conducive rail  12 B, driving engine (not shown) of the model train (not shown), conductive rail  12 A, and back to the source of electrical power  14  over the third electrical pathway through diode  132 . The fourth electrical pathway is blocked by the transistor  134 . The model train (not shown) is then driven by the flow of electrical current in a second and opposite direction along the segment of track  10 . As previously described, within the transistor  104 , an additional flow of electrical current is directed from the emitter  104 E to the collector  104 C, and provided to the external electrical circuit  200 . 
     In the embodiment of the present invention shown in  FIG. 2 , the train detectors  100  and  130  are configured to energize the respective external electrical circuits  200  and  230  only when the model train (not shown) is moving over the track segment  10  in the associated directions. If the external electrical circuits  200  or  230  include an indicator such as a light emitting diode  202 , this indicator will selectively indicate the presence of a model train on the track segment  10  only when the track polarity (and hence train movement) is selected via the switch  16  such that the electrical current flow between the rails  12 A and  12 B passes through the transistors  104  or  134  coupled to the respective external electrical circuits  200 ,  230 . 
     Additionally shown in  FIG. 2  is a block switch  140  coupled between the source of electrical power  14  and the relay switch  16 . The block switch  140  is configured to selectively disconnect the source of electrical power  14  from the track segment  10 . To enable the detection circuits  100  and  130  to continue to function, a resistor  142  coupled to the switch  16  provides an alternate pathway to an electrical ground from the detector power supply  15 , through the track segment  10  and each of the detector circuits  100 ,  130  when the block switch  140  is opened. 
     Turning to  FIG. 3 , an optional configuration of an external circuit  200 ,  230  as a polarity reversing relay  300  is shown for use with the detection circuits  100 ,  130 , requiring only a single DPDT relay  166  and including a clamping diode CD to prevent transistor leakage current from accidentally energizing the relay. When a detection circuit  100  or  130  is activated by the presence of a model train (not shown) traveling in the associated direction on an adjacent track segment  10   n , it is necessary to switch the polarity of the track segment  10  to match the polarity of track segment  10   n , ensuring that the model train (not shown) continues to move in the same direction. Polarity reversing relay circuit  300  is operatively coupled to the polarity switch  16  of a track segment  10 . The relay circuit  300  includes an electrically actuated relay element  166 , a transistor  304 , diodes  306  and  314 , and a resistor  308 . The emitter  304 E of the transistor  304  is coupled to the sources of electrical power  14 ,  15  through the reversing switch or relay  16 , which is shown having normally open (NO) and normally closed (NC) contacts. The electrically actuated relay element  166  is coupled between an external circuit associated with a next-adjacent track segment in a first direction, and through diode  314  to the collector  304 C of the transistor  304 . The base of the transistor  304  is operatively coupled through the diode  306  to receive an electrical signal from an external circuit associated with a next-adjacent track segment in a second direction. 
     During operation of the polarity reversing relay circuit  300 , the electrically actuated relay element  166  is energized by a latching pulse received from the external circuit associated with the next-adjacent track segment in the first direction. The relay element  166  remains energized by a flow of current passing from the emitter of transistor  304  to the collector of transistor  304  from the source of electrical power  14 ,  15 . The relay element  166  will remain energized until it is de-energized by an unlatching pulse received from the external circuit associated with the next-adjacent track segment in the second direction. The unlatching pulse is received at the base of the transistor  304 , blocking the current flow between the emitter and the collector of the transistor  304 . 
     When the electrically actuated relay element  166  is energized, the relay element  166  operates the reversing switch or relay  16  to polarize the track segment  10  with the same polarity as the next-adjacent track segment in the first direction. Conversely, when the electrically actuated relay element  166  is de-energized, the reversing switch or relay  16  is operated to polarize the track segment  10  with the opposite polarity, corresponding to the polarity of the next-adjacent track segment in the second direction. Optionally, an LED or other suitable indicators  310  and  312  may be operatively coupled to the reversing switch or relay  16 , to provide an operator with an indication of the polarity (i.e. direction of train travel) of the track segment  10  at any given point in time. 
     The external circuits  200 ,  230  which are operatively coupled to the collectors of the detector circuits  100 ,  130  may include any of a variety of configurations as will be recognized by those of ordinary skill in the art. For example, as shown in  FIG. 4 , selection of a direction of train travel in a first direction on track segment  10  may be configured to provide positive electrical power to a two-pole double throw latch circuit  300 A, shown in  FIG. 5A , associated with a next track segment  10 (+1) in a first direction, while selection of the opposite direction of train travel on track segment  10  provides the positive electrical power to the four-pole double throw track relay  300 B, shown in  FIG. 5B , associated with a next track segment  10 (−1) in the second direction. Activation of either a latch relay  300 A or a track relay  300 B for a given track segment  10   n  will automatically deactivate the other relay  300 A,  300 B associated with that track segment. 
     Optionally, a common external circuit  250  may be operatively coupled between collectors  104 C and  134 C using isolating diodes  252  and  254 . The common external circuit  250  will receive an electrical signal when a model train (not shown) is positioned on track segment  10  independent of the direction of travel of the model train (not shown), i.e. independent of the polarity of rails  12 A and  12 B. The common external circuit  250  may be provided with an indictor circuit to provide an operator with a visual indication of the presence of a model train (not shown) on the track segment  10 . When used in conjunction with external circuits  200  and  230  which are activated in response to the model train presence or movement, the operator may be provided with information identifying the presence of a model train (not shown) on track segment  10  if moving or stationary, and, if moving, the direction of travel, i.e. track segment polarity. The circuits providing the identifying information to the operator may be located remotely from the track segments, such as on an operator control board, enabling an operator to track the model train through tunnels or behind features of a model train layout which obstruct direct visual observation of the train. 
     Optionally a track reversing switch  400 , which is a spring-loaded momentary-on (MON) single pole, double-throw switch, may be coupled between external circuits  200  and  230  to allow for the operator to manually reverse the track direction for the track segment  10 . The track reversing switch  400  will only reverse the train direction of travel for the associated track segment  10 . Train travel direction on the remaining track segments  10   n  is regulated by the train travel direction on the occupied track segment  10 , as previously described. 
     Those of ordinary skill in the art will recognize that track segments  10  configured with the train detector circuits  100 ,  130  and associated external circuits  200 ,  230  may be coupled together in a variety of different configurations in a model train track layout, such as shown in  FIGS. 6-9 . 
     As shown in  FIG. 6 , track segments  10  may be coupled together to form a “Y” junction, wherein a model train (not shown) traveling on track segment  10 -A towards track segments  10 -B and  10 -C will actuate external circuits associated with track segment  10 -A to select matching track polarities on track segments  10 -B and  10 -C, enabling the movement of the model train (not shown) to continue regardless of the setting of the junction switch between the track segments. Correspondingly, a model train (not shown) traveling on either track segment  10 -B or  10 -C towards track segment  10 -A will actuate external circuits to select a matching track polarity on track segment  10 -A, enabling the movement of the model train (not shown) to continue in the same direction. 
     As shown in  FIG. 7 , track segments  10  may be coupled together to form a reverse loop, wherein a model train (not shown) traveling on track segment  10 -D towards track segments  10 -E and  10 -F will actuate external circuits associated with track segment  10 -D to select matching track polarities on track segments  10 -E and  10 -F, enabling the movement of the model train (not shown) to continue around the loop regardless of the setting of the junction switch between the track segments. Correspondingly, a model train (not shown) traveling on either track segment  10 -E or  10 -F towards track segment  10 -D will actuate external circuits to select a matching track polarity on track segment  10 -D, enabling the movement of the model train (not shown) to continue in the same direction. 
     As shown in  FIG. 8 , track segments may be coupled together to form a siding, wherein a model train (not shown) traveling on track segment  10 -G towards siding segment  10 -H will actuate external circuits associated with track segment  10 -G to select matching track polarities on track segment  10 -H, enabling the movement of the model train (not shown) to continue onto the siding regardless of the setting of the junction switch between the track segments. Correspondingly, a model train (not shown) traveling on siding track segment  10 -H towards track segment  10 -G will actuate external circuits to select a matching track polarity on track segment  10 -G, enabling the movement of the model train (not shown) to continue in the same direction off the siding track segment  10 -H. 
     As shown in  FIG. 9 , track segments may be coupled together to form a cross-over between parallel track segments. A model train (not shown) traveling on track segment  10 -J towards segments  10 -K and  10 -L will actuate external circuits associated with track segment  10 -J to select matching track polarities on track segments  10 -K and  10 -L, enabling the movement of the model train (not shown) to continue regardless of the setting of the junction switch between the track segments. Correspondingly, a model train (not shown) traveling on siding track segment  10 -K towards track segment  10 -J or  10 -L will actuate external circuits to select a matching track polarity on track segments  10 -J and  10 -L, enabling the movement of the model train (not shown) to continue in the same direction. 
     By coupling multiple track segments  10  together in various configurations, and by operatively connecting external circuits  200  and  230  for each track segment  10  to polarity switches or relays  16  for adjacent track segments, complex model train track layouts, such as shown in  FIG. 10 , may be assembled. In the complex model train track layout show in  FIG. 10 , the direction of model train travel is defined by the illustrated arrows as either eastbound or westbound over a given track segment. External circuits  200  for track segments  10  which are energized by model train movement in an eastbound direction are operatively coupled to latch relay circuits  300 A in the next eastern-direction track segment, while external circuits  230  for track segments  10  which are energized by model train movement in a westbound direction are operatively coupled to track relay circuits  300 B in the next western-direction track. 
     Movement of a model train east-bound (EB) or west-bound (WB) over the track segments show in the layout of  FIG. 10  results in track segment activations according to the following table: 
     
       
         
               
               
               
             
           
               
                   
               
               
                 Track 
                 Direction of 
                 Sequentially 
               
               
                 Segment 
                 Travel 
                 Activated Segments 
               
               
                   
               
             
             
               
                 1 
                 EB 
                 3-EB 
               
               
                 1 
                 WB 
                 2-WB &amp; 3-WB 
               
               
                 2 
                 EB 
                 1-EB &amp; 3-WB 
               
               
                 2 
                 WB 
                 9-EB 
               
               
                 3 
                 EB 
                 2-WB &amp; 1-EB 
               
               
                 3 
                 WB 
                 1-WB 
               
               
                 4 
                 EB 
                 5-EB 
               
               
                 4 
                 WB 
                 9-EB 
               
               
                 5 
                 EB 
                 6-EB &amp; 8-EB 
               
               
                 5 
                 WB 
                 4-WB 
               
               
                 6 
                 EB 
                 9-WB &amp; 8-WB 
               
               
                 6 
                 WB 
                 7-WB &amp; 5-WB 
               
               
                 7 
                 EB 
                 6-EB 
               
               
                 7 
                 WB 
                 9-WB 
               
               
                 8 
                 EB 
                 6-WB 
               
               
                 8 
                 WB 
                 5-WB 
               
               
                 9 
                 EB 
                 7-EB &amp; 6-WB 
               
               
                 9 
                 WB 
                 2-EB &amp; 4-EB 
               
               
                   
               
             
          
         
       
     
     When a latch relay  300 A is energized for a given track segment, enabling eastbound travel, the track relay  300 B is correspondingly de-energized for that track segment. Conversely, when a track relay  300 B is energized for a given track segment, enabling westbound travel, the latch relay  300 A is correspondingly de-energized for that track segment. 
     Those of ordinary skill in the art will recognize that the specific electrical circuit components illustrated in the figures and described in the specification may be replaced by other electrical components which are intended to accomplish the same functions described herein. For example, PNP transistors may be replaced by NPN transistors provided the associated electrical connections are appropriately modified. Similarly, relay coil components may be replaced by transistorized electronic circuits without altering the scope of the present invention. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.