CIRCUIT FOR SUPPLYING TRACTION CURRENT TO A MODEL RAILROAD

Abstract: Circuit for supplying traction current to a block of a model railroad which is divided into blocks. The model railroad comprises means to detect the presence of a train in a block by detecting the traction current supplied from a power supply unit through said circuit to the block of the model railroad, to which said circuit is assigned. Said circuits are used in a train control system for controlling one or more trains onto the model railroad whereby each block has such a circuit assigned thereto, and each circuit comprises a logical unit to which the detection output signals and short circuit allowance signals generated into said circuit are supplied, and which logical units are delivering control signals to the related circuit.

Description: Circuit for supplying traction current to a model railroad. The invention relates to a circuit for supplying traction current to a block of a model railroad, which is divided into blocks and comprises means for detecting the presence of a train in a block. It is known in the world of model railroading to divide a complete model railroad into a number of blocks by dividing at least one of the rails by means of saw cuts or something similar into a number of short mutually insulated sections. The traction current is now supplied to the various blocks in such a way that a train is able to pass from one block into a succeeding block only if no train is present into said succeeding block. For that purpose it is necessary to detect the presence of a train in a block. It is known to attach a little magnet to each locomotive and to install reed -relais underneath each block, which reed relais are operated by said little magnet if the train, to which said magnet is attached is passing. Furthermore it is known to detect the short circuiting of the mutually insulated rail sections caused by the wheels of a train when a train is passing from one block to a succeeding block. Said known detection means have a number of disadvantages. A disadvantage of the first mentioned detection means is that little magnets should by attached to the locomotives or to the wagons belonging to a train and furthermore reed relais should be installed underneath the rails or at least in close proximity of said rails which in many cases is not possible without substantial labour or de¬ facing measures. The above mentioned solution according to which the short circuiting between blocks is detected when a train is passing from one block to another has the disadvantage that said short cir¬ cuiting is appearing a number of times dependent on the number of axles of a train. Said number may vary strongly so that no unam¬ biguous detection is provided. Furthermore, because of filthiness of wheels and/or rails and because a number of wheels of a locomotive is often insulated, not in all cases short circuiting occurs. An'object of the invention is now to eliminate said disad- vantages and to provide a thrustworthy universally functioning circuit by means of which the presence of a train in a block can be determined unambiguously. A further object of the invention is to provide a train control system based on the use of said circuits. Said ob ect is according to the invention, reached with a circuit of the above mentioned type in that said detection means are detect¬ ing the traction current which is from a power supply unit through said circuit supplied to the block of the model railroad to which said circuit is assigned. Underneath the invention will be explained in more detail with reference to the attached drawings. Fig. 1 illustrates an embodiment of a circuit according to the invention. Fig. 2 illustrates schematically a train control system in which the circuit according to claim 1 is used. The circuit illustrated in Fig. 1 contains an input stage com¬ prising the .transistors Tl, T2, T3, T4 and T5, the resistors Rl, R2, R3 and R4 and the gate PI. Said input stage receives through the input 1 a digital signal which is in said input stage converted in such a way that either the transistor T4 or the transistor T5 is con- ducting. The nodal point 2 between the transistors T4 and T5 is through a relatively small resistor R5 connected to the output terminal ' 3 of the circuit. Said output terminal is connected to the one rail of the block, to which said circuit is assigned. The other rail of this block is connected to the zero conductor. As appears from this figure the emitters of the transistors T4 and T5 are res¬ pectively connected to the positive power supply terminal 4 and the negative power supply terminal 5. If a positive signal is delivered * to the input 1 then transistor T4 will come into conduction through the transistor T3 so that the positive power supply voltage is supplied through the resistor R5 to the output terminal 3. If a ne¬ gative input signal is received then through the gate Tl and the transistors Tl and T2 the transistor T5 will brought into conduction so that the negative power supply voltage is supplied through the resistor R5 to the output terminal 3. By means of the digital signal on the input 1, it is therefore possible to supply positive or negative voltages to the output 3, whereby the amplitude of said output voltages equals the positive or negative power supply voltage. A locomotive present into the assigned block will drive in the one direction if a positive voltage is supplied and will drive in the other direction if a negative voltage is- supplied. The longer these pulses are, the faster the locomotive will drive. If a signal alternating between two digital levels is applied to input 1 then it depends on the duty cycle of this alternating signal how fast and in what direction the locomotive will move over the assigned block. If the duty cycle is 50% then the locomotive will not move at all. If the positive pulses are longer then the negative pulses in this alternating signal or vice versa the locomotive will start moving in the one or in the other direction. The longer these pulses are, the fast er the locomotive will drive. If a locomotive is driving in the one or the other direction through said block and also when the locomotive Is at a stand still then with each pulse delivered to the output 3, a current will run through said , relatively small resistor R5. That causes a voltage drop across this little resistor. Said voltage drop is in the first place detected by the transistor T6 of which the emitter is connected to the one terminal of said little resistor R5 and of which the base is through a base resistor R6 connected to the other terminal of said little resistor R5. The collector of To Is through the resistors R7 and R8 connected to the positive power supply terminal 4. If negative pulses are supplied at the output terminal 3 because each time the transistor T5 Is brought into conductance and there is a locomotive present into the corresponding block, then each time a voltage drop will occur across said little resistor R5. Because of said voltage drop the transistor T6 will come into conductance so that the * potential onto the nodal point between the resistors R7 and R8 decreases. Said potential decrease indicates that there is a locomotive present in said block. Said potential decrease can be transmitted straight to the output terminal 6 of the circuit. However, in the illustrated preferred embodiment a monostable flip-flop is inserted between the nodal point of the resistors R7 and R8 and the output terminal 6. Said flip-flop is built around the gates P2 and P3, the resistor R9 and the capacitor Cl and the diodes Dl and,D2. Said monostable flip-flop takes care that, in case the transistor T6 is inhibited for only very short period, then the BU K cA output signal on the output terminal 6 is not changing. Erroneous pulses causing this effect can for instance occur when the rails are locally become filthy so that for a very short period there is no contact between the rails and the wheels of the locomotive. The voltage drop across the resistor R5 is furthermore detected by means of the transisitor T7 and T8, of which the emitters are con¬ nected to the one terminal of R5 and of which the bases are through a voltage divider, made of the resistors RIO and Rll, connected to the other terminal of said resistor R5. The collector of the transistor T7 is through a resistor R12 connected to the positive power supply terminal 4 and the collector of transistor T8 is through the resistors R13 and R14 connected to the negative power supply terminal 5. If because of short circuiting the current through the resistor R5 will increase too larg then, if a negative pulse is supplied because transistor T5 is conducting, also transistor T7 will come into con¬ ductance so that the voltage onto the nodal point between the col¬ lector of T7 and the resistor R12 will decrease. Said voltage decrease is through the ' diode D3 transmitted to the nodal point between the resistor R15 and the collector of transistor T9. If a positive voltage pulse is supplied because transistor T4 Is conduct¬ ing, then also transistor T8 will come into conductance so that in his turn .also transistor T9 will come into conductance with the result that the voltage onto the nodal point between the collector R15 and the collector T9 is decreasing. Said voltage decrease is through the resistor R16 and the diode D4 transmitted to the mono¬ stable flip-flop built around the gates P4 and P5, the capacitor C2 and the resistor R17. Because of said negative pulses, appearing onto, the nodal point between R15 and the collector T9 positive pulses will appear onto the output of P4. This circuit section Is laid out such that the lengths of these positieve pulses are larger than the lengths of the intermediate periods. Therefore the capacitor G3 will slowly become charged through the resistor R18. The voltage across said capacitor C3 is supplied to the Input of a gate P6, of which the other input is through a resistor R9 connected to the power supply terminal 4. If the voltage level across the capacitor C3 crosses the switching threshold value then the output of P6 will become low so that the monostable-flip flop around the gates P4 and P5 is in— -BURE hibited. This low output signal of ?δ is furthermore as short circuit alarm signal supplied to the output terminal 7. The circuit section around the gates P4, P5 and P6 can be reset by means of a signal onto the terminal R. In Fig. 2 the block diagram is illustrated of a train control system in which the circuit of Fig. 1 is used. In the upper part of Fig. 2 a section of a model railroad is indicated schematically com¬ prising the through. going rail 10 and the rail 11, which is divided into sections. Because of the interruptions the track is divided into the blocks A, B and C and D. The rail parts 11a, lib, lie, lid related to each of these blocks are each connected to the output ter¬ minal 3 of a related circuit of the type as is illustrated in Fig. 1. These circuits are indicated by 12a, 12b and 12d in the figure. In the circuit 12a also the connecting terminals 1, 3, 6 and 7 are sche- matically Indicated. A logical unit 13 is combined with each of said circuits 12, from which logical units the units 13a, 13b and 13d are illustrated in the figure. Each of said units comprises a processor and a program memory in which a program is stored carried out by said processor. Said processor supplies on the one hand control signals to the terminal 1 of the circuit 12 and receives messages back from the terminals 6 and 7 of the circuit 12. Oα the other hand each processor is connected to a bus 14 comprising a number of separate conductors. In the figure only four conductors are illustrated, although another number of conductors might be used. Furthermore a control panel 15 Is connected to said bus. Said control panel comprises control elements, one for each of the trains present on the model railroad, by means of which the speed of each train onto the track is determined. Further-" more said control panel comprises logic circuits for initiating the train control system, and for switching on the power supply. Further- more said panel may comprise indicators to visualize various signals. The syste of Fig.2 functions as follows. First the system is initiated in that the position of each locomotive on the track is detected by supplying a 50% duty cycle to each block. Thereafter a control element of the control panel 15 is assigned to each of the detected locomotives. If a locomotive is for instance present in block B then this lo- co-notive will move in the one or the other direction dependent on the traction voltages supplied by output 3 of circuit 12b. The control signal to input 1 of the circuit 12b is delivered by the processor 13b and said processor generates this control signal based on the data received through the bus 14 from the control element assigned to the locomotive present in block B. Assuming that the locomotive is heading left the detection elements in circuit 12b will indicate the fact that the locomotive leaves block B and at the same time the detection elements in circuit 12a will indicate the entering of the locomotive in block A. The processor 13b will now transfer the control of the locomotive to processor 13a. That means that processor 13a receives a signal over the bus 14 from the processor 13b informing processor 13a about the transfer of control and thereafter processor I3b Ignores all further messages from the control element and in stead thereof these messages are now accepted by the processor 13a for further controlling the lo¬ comotive now driving in block A. Above the invention is described on the basis of a preferred em¬ bodiment which is specially destined for pulse control of direct current locomotives. The principle of the invention however can be equally adapted to alternate current locomotives. In. that case one can for instance use an Input stage Into the circuit in which ac phase control is used. Also the detector part of the circuit can be maintained almost without any changes when using ac voltages.

Claims: C L A I M S. 1. Circuit for supplying traction current to a block of a model • railroad divided into blocks, which model railroad comprises means to detect the presence of a train in a block, characterized in that said detection means are detecting the traction current supplied from a power supply unit through said circuit to the block of the model railroad to which said circuit is assigned. 2. Circuit according to claim 1, characterized in that the traction current is supplied by a voltage source through a buffer am¬ plifier of which the output is connected through a relatively small resistance to one of the rails of the assigned block, whereas the other rail is connected to the other terminal of the voltage source, and the detection means are measuring the voltage drop across said resistance. 3. Circuit according to claim 2, characterized in that the voltage across said relatively small resistance is measured by means of a first transistor of which the emitter is connected to the one terminal of said resistance, the base of which is through a base re¬ sistance connected to the other terminal of said resistance and the collector of which is through a collector resistance connected to a fixed potential, which collector delivers the output signal of said detection means. 4. Circuit according to claim 3, characterized in that the col¬ lector resistance is connected to a positive potential and a second transistor of opposite conductivity type is also with his emittor connected to the one terminal of said resistance, with his base through a base resistance connected to the other terminal of said re¬ sistance and with his collector through a collector resistance con¬ nected to a negative potential, which collector delivers another output signal of said detection means. 5. Circuit according to claim 4, characterized in that both output signals are combined by means of a gate circuit. 6. Circuit according to one of the claims 3-5, characterized in that the output signal of said detection means respectively said gate circuit is supplied to a monostable flip-flop of which the output de¬ livers the detection output signal. UKi-rt 7. Circuit according to one of the claims 2-6, characterized in that the voltage across said relatively small resistance is measured also by two third and fourth transistor's of opposite conductivity type, of which the emitters are again connected to the one terminal of said relatively small resistance, the collectors are through col¬ lector resistances connected to a positive respectively negative po¬ tential and the bases are through a voltage divider connected to the other terminal of said relatively small resistance, and furthermore the collector of the fourth transistor is through a voltage divider connected to the base of a fifth transistor of the same conductivity type as the third transistor, whereby the emitter of the fifth transistor is connected to the negative potential and the collector of said transistor is through a resistance connected to the positive potential and also connected to a short circuit alarm output of the circuit, and the collector of said fourth transistor is through a diode connected to the collector of said fifth transistor. 8. Circuit according to claim 6, characterized in that between the collector of the fifth transistor and the short circuit alarm output a delay means is inserted delivering a short circuit alarm signal onto the short circuit alarm output only after a predetermined delay time. . Circuit according to claim 7, characterized in that said delay means comprises a monostable flip-flop of which the output is through a resistance connected to a capacitor, whereby the voltage across said capacitor is detected by a detector delivering an Inhibiting signal for said flip-flop in case the voltage across said capacitor is above a predetermined threshold value. 10. Train control system for controlling one or more trains onto a model railroad which is divided into blocks, whereby each block has a circuit according to one of the preceding claims assigned thereto, characterized in that each circuit comprises a logical unit to which the detection output signals and short circuit alarm signals generated into said circuit are supplied. 11. Train control system according to claim 10, characterized in that all logical units of all circuits, assigned each to a block, are interconnected through a bus. ' UREA 12. Train control system according to one of the claims 10 or 11 characterized in that each logical unit comprises a program memory ' an.d a processor for carrying out the program stored into said memory dependent onto signals received by said logical unit. 13. Train control system according to one of the claims 10 until 12, characterized in that a number of controllers, each asigned to one of the trains riding onto the model railroad, is connected to said bus for delivering signals to the logical units in each of said circuits. 14. Train control system according to one of the claims 10 until 13, characterized in that an indication panel is present for indicat¬ ing a number of preselected signals. 15. Train control system according to one of the claims 10 to 14, characterized in that each logical unit transmits periodically test pulses to each block, of which the length is not sufficient to move a locomotive present into the corresponding block, however long enough to generate an unambiguous detection output signal.

Inventors: BRAAK GERLOF DE
Applicants: BRAAK GERLOF DE
Application year: 1982
Main classification: A63H19
IPC codes: A63H19