FR2506965A1 - Logic circuit for model railway turntable control - uses coded disc with LED's and phototransistors feeding comparator to determine position for calculator control of motors - Google Patents

Abstract

A Gray coded disc is fixed to the turntable and the turntable position is read by an assembly of LED's and phototransistors sensitive to infra red radiation. The phototransistors operate relays in their collector circuits to switch a logic 1 or 0 signal to a comparator and calculator circuit comprising severals integrated circuits. The calculator gives the orders for forward or reverse movement of the turntable assembly. The orders are transmitted through a transistor and relay inverter to a power control circuit for the drive motor. A decoder and display circuit enables the coding disc position to be displayed for the operator.

Description

TURNING BRIDGE CONTROL DEVICE
BY LOGIC AUTOMATION WITH INTEGRATED CIRCUITS
APPLICABLE IN PARTICULAR TO RAIL MODELING
The present invention relates to rotary plates and bridges intended to equip the depots of railway model making networks on all scales. It allows positioning automation by simple display of the requested position and by a simple control technique: logic automation by integrated circuits.

 In a treel or miniature railway depot) the rotary bridge allows, from the entry and exit tracks, to position the locomotives on their respective garage tracks, under the rotunda, or to rotate them by 1800 for those which n 'have only one driving cab.

In known devices of this kind, the control of the rotary bridge is obtained by a simple electromechanical inverter allowing the rotary bridge to move in one direction or the other, until reaching the desired position. However, these devices have the following three drawbacks
10) The operator must himself actuate and maintain the reverser, in one direction or the other to send the rotary bridge, in the shortest direction and to reach the desired track.

 20) The operator must constantly monitor the evolution of the swing bridge to stop it in time in front of the requested track.

 30) On the other hand, the electrical circuits of certain existing automatic systems are made up of electromechanical relay logic. This technique has the disadvantage of requiring a large number of relays and a very large number of contacts. This state of affairs leads to very tedious and complicated wiring not within the reach of the non-electrician model maker and to a prohibitive bulk of the assembly accompanied by a consumption of non-negiipeaole electric current.

 The logic automation with integrated circuits according to the invention makes it possible to avoid these drawbacks.

 In fact, the control of the system is obtained not by a simple inverter, but by a comparator computer receiving its information, on the one hand by coding wheels numerically indicating, in plain text, the number of the destination channel, or address, and on the other hand, by an opto-electronic encoder located under the rotary bridge and integral with its axis, which permanently reads the position thereof.

 The comparator computer gives the order to the motor of the rotary bridge to move in one direction or the other to go by the shortest path. When the bridge has arrived at the requested destination, the computer instructs the engine to stop. on the other hand, it displays, in two digital light decades, the indication, in plain text, of the position of the bridge.

The operator therefore only has to display the desired destination and press the start push button. It’s the logic IC that does everything else
- comparison of the destination and the initial position
- choice of the shortest route, start-up, comparison
permanent during the operation of the two data and indication
light of the evolution of the bridge, detection of arrival at
requested point, stop at this position.

 On the other hand, the overall size of the assembly is reduced to its simplest expression by the miniaturization of integrated circuits. The wiring problem is solved by the use of printed circuits, the power consumption is reduced to a few watts. The system plugs in exactly in place of the existing controller without any changes.

 The accompanying drawings describe the various parts of the system.

Figure 1: Encoder disc
Figures 2-3-4: Opto-electronic encoder disc position sensor
Figure 5: Arrangement of the encoder disc and the sensor under the bridge
turning
Figure 6: Electronic diagram of the C1 channel opto-electronic sensor
on the 6 existing and identical)
Figure 7: Electronic diagram of the t1 channel interface circuit board
on the 6 existing and identical)
Figure 6: Electronic diagram of the comparator computer
Figure 9: Electronic diagram of the opto-electronic display of
position
Figure 10: Electronic diagram of power supplies
Figure 11: Electrical diagram of the power circuit
Figure 12: Original electrical diagram
Figure 13: Layout of electronic circuit boards, console
control and swing bridge.

 Figure -1- represents the translucent encoder disc which will be integral with the axis of rotation of the rotary bridge after fixing to it. it is coded in GRAY code in order to eliminate reading errors. Figures -2- -3- -4- represent the opto-electronic position sensor reading electronically the position of the bridge given by the encoder disc passing inside this encoder. This encoder is fixed under the inner face of the turntable according to the general view in Figure -5-.

 Figure -6- shows the electrical diagram of the optoelectronic sensor. The photodiodes are located in the lower branch, the photo-transistors in the upper branch, the resistors -5- and -6- are located respectively on each side of the barrel. Figure -6- represents the diagram of only one channel of the sensor, the latter comprising 6 tracks.

 Figure -7- shows the diagram of the interface card; here too, only the diagram of a track is shown, the other five being identical. The diagram of the computer, the heart of the system, is shown in Figure -8-.

 Figure -9- represents the diagram of the opto-electronic display of the position of the rotary bridge. As for the power supplies and the motor control of the rotary bridge, they are shown in Figures -10- and -11- respectively.

 The figure -12- represents the diagram of origin of a manual control of rotary bridge of model-making railway. It has been shown to clearly show that the electronic automatic control connects directly in place of the original manual control and without any wiring modification. The bridge wiring does not undergo any modification. The non-electronic model maker therefore has no difficulty in going from one system to another.

 As shown, the system includes an encoder disc (1 'integral in rotation with the turntable, see Figures -1- and -5-.

This translucent disc (Plexiglass] is divided into as many sectors as the turntable has directions, in this case 48 directions. It can be adapted to other configurations. The disc is coded in reflected binary code called GRAY code it therefore has six tracks which make it possible to obtain the code for positions 1 to 48, ie the tracks
1 - 2 - 4 - 8 - 16 - 32
States 1 are obtained by transparency, state zero by the masking of transparency by masks.

 The position is read using an optoelectronic sensor (2) provided with 6 t3 diodes) emitting infrared tune per track) and 8 phototransistors (4) sensitive to infrared Each photodiode is supplied through a current limiting resistor t5) t1G05L1 / 4 W1. Each phototransistor is supplied via a resistor t6) (I0OOSL 1/4 W). The sensor is fixed under the turntable to be controlled according to figure -5-so that each track of the encoder disc t1) is opposite each track of the sensor (2).

 Each track coming or not obscuring the radiation coming from the emitting diodes (3) towards the phototransistors t41. The GRAY code giving a state for each position of the turntable via the encoder disc t1) and the sensor (2), the automation system will therefore know at all times the positioning of the turntable.

 When the phototransistor (4) is excited by the infrared radiation emitted by the diode (3), it switches the + 5 volts towards its output. This will be a state 1 for the automation system. When the phototransistor (4) is not excited by infrared radiation from the diode! 3) it no longer switches the + 5 volts and its output is "in the air", ie without electrical potential defined. The automation system reading only potentials + 5 volts or zero volts, will translate this state as a + 5 volts and there will be no difference. It is therefore necessary to remedy this defect by interposing between the output of the phototransistor (4) and the automation system a circuit which will give a 5 volt state for state 1 or lit phototransistor (4), and an O volt state for the unlit phototransistor. This circuit, called interface according to figure -7-, is composed of a 2 N transistor 1711 - (7) - which controls a relay (6). When the phototransistor (4) is lit it sends the + 5 volts to the wearer of the transistor (7), the latter therefore sees its base polarized and unlocks the supply current of the relay (8) which, excited, switches its changeover contact t9) in the + 5 volt position. A state 1, + 5 volts is sent to the computer.

 When the phototransistor (4) is no longer lit, it cuts the power supply to the base of the transistor t7) which blocks the supply current of the relay (8). The latter, no longer excited, drops its changeover contact to the 0 volt position. We have, for the lit and unlit states of the phototransistor t43 respectively the states + 5 volts and 0 volts for the computer. it is understood that as many “interface” systems will be required as there are tracks and phototransistors, ie 6, which will be grouped on the same card. Everything that has been said so far concerns the reading of the position of the turntable.

 The address to which we want to send the turntable will be given by two coding wheels, coded in BCD. A coding wheel for the units, a coding wheel for the tens. The calculator working in pure binary, it will be necessary to convert the code given by the coding wheels which give information in BCD code.

 The BCD code of the coding wheels will be transformed into binary code by a BCD / Binary compound converter (see figure 83 by integrated circuits 74184 - (10) and (11).

 The GRAY code of the system for reading the position of the turntable will be transformed by a GRAY / binary converter composed (see figure -8-) by the integrated circuits 7486 t123 and (13).

 We now have at the input of the computer itself two pieces of information in binary, one, the position of the turntable, the other the position to reach or address.

 The two pieces of information arrive on the integrated circuits 74181, and and (15) which are arithmetic circuits which, using the circuits 7404 (16) and t17], 7411 (18), 7400 (19), 7432 ( 20), 7408 t21), will decode the interval -24 and +24 (for 48 channels). The direction of travel is determined by checking the address relative to the initial position, as a function of its position and as a function of the 48-way half-circle, i.e. 24.

 We name A the position reached and 5 the position to reach.

Circuit 74181 does the operation A - B but not a - A. We will therefore use the output of 74181 (14) and (15) of the diagram to decode the interval -24> A - B dS +24, which will start the bridge on the shortest route.

 The computer gives the “forward-forward” and “reverse-reverse” orders (this being arbitrary) at the output of the integrated circuit (21). These orders are transmitted to the electric power circuit (FIG. -11-) via , for each direction of travel, of a 2 N transistor 1711 (22) or (23) and a change-over relay (24) or (25).

 We must not forget to detect equality, address-position, to stop the bridge in front of the requested address. This function will be fulfilled by the ON 8160 comparator integrated circuit (26) which will stop the movement to the electric power circuit via the relay (271.

 There is a problem with stopping the bridge right in front of the requested stop. It has been resolved by placing the stop contact of the electronic circuit Z 2 in FIG. -11- in parallel with that, mechanical (29) existing on the rotary bridge. This contact Z 2 is given by the relay (26), Figure -11-, itself controlled by the equality relay (27).

 Indeed, the detection sectors of the encoder disc (1) have a length such that the comparator circuit begins to detect as soon as it is in the "zone" of the requested channel, while the bridge is not strictly in the axis of this path. But, as indicated above, the circuit and bridge stop contacts being in parallel, it is the bridge which will self-supply, while the electronics will have given the stop order, as long as it will not be rigorously in front of the track and, it is its mechanical stop system which will control the general stop system of its engine, when it is perfectly in line with the requested track.

BRIDGE CONTROL CIRCUIT:
By examining the original diagram of the plate figure -12- and that of the electronic circuit figure -8-, one realizes that it is not possible to connect them directly since the electronic circuit gives, for both directions of movement, only one impulse.

 A bistable change-over relay with two coils (29) of figure -11- will therefore be required to replace the manual control for reversing the direction of travel and a relay (28) with an opening contact Z 2 for the control of the bridge stop. All this appears on figure -11-.

DISPLAY CIRCUIT
A bridge position indicator, figure -9-, consists of two BCD digital opto-electronic decades. This is useful for the operator located a few distances from the turntable.

 It was produced with two 7-segment display modules, each with an incorporated decoder and BCD input. It must therefore read the position of the bridge, given by the encoder (1) via the position sensor (2). This position is given in GRAY code by the sensor (2) and it is converted into binary to be processed by the computer.

We see that none of these two outputs (GRAY and binary) is compatible with the input of the remote display (BCD). It will therefore be necessary to convert the GRAY code, taken from the interface card output, Figure -7-, into code
BCD. This conversion was carried out on an additional card, figure -9-, in two stages
10) GRAY / Binary conversion using circuits 7486 (31) and (32)
20) Binary / BCD conversion using the transcoder circuit: binai
re to BCD It is a circuit 74185 (33).

 The position indicator is formed by two opto-electronic decades (34) and (35) mounted in BCD. One indicates the units, the other the tens. The inverter (363 serves as a test button to check the good condition of the segments at any time.

ADVANTAGES PROVIDED BY THIS DEVICE
We can see by examining these diagrams - that operator intervention is simplified: simple display of
the destination and departure control Cavec the original device there
must hold the inverter one way or the other and command
in time to stop the bridge).

- that the bridge moves well on the shortest path - that it stops well in front of the requested lane - that the electronic control replaces exactly in place of the
original control button - do not modify the original bridge wiring.

The prototype was produced according to the figure -13- on which we recognize - reference 1 - the encoder disc - reference 2 - the sensor - reference 37 - the rotary bridge - reference 38 - the control console comprising the coding wheels 39 and
40, display decades 34 and 35, the double button of
switch on 41, the button for testing the dice segments
cades 36 - item 42 - the power transformer - item 43 - the power and control board for the bridge (figure -10
and figure -11-) - item 44 - the interface card (figure -7-) - item 45 - the computer circuit (figure -6-) - item 46 - the GRAY / BCD converter card for the position indicator
tion (figure -9-).

 The device, object of the invention, can be used in all cases where model makers, owners of rotary bridges, wish to automate them to make their operation conform to the real situation.

 On the other hand, this device is within the reach of all amateurs, even those with no knowledge of electronics and electricity, because the device plugs in place of the original system without any modification.

Claims (1)

 I - Device for controlling the rotary bridge by logic automation  with integrated circuits applicable in particular to railway model making  characterized by the fact that it includes a computer circuit  comparator (45) associated with a position reader (composed of a  encoder disc t1) and an opto-electronic sensor t2) and to a  consiqnes data system (39) and (40) composed of two wheels  coders.  II - Swing bridge control device according to claim (I)  characterized in that the detection of the position at the bridge  turning point is obtained by a digital opto-electronic assembly com  installed with an encoder disc t1) and a sensor C2). III - Swing bridge control device according to claims tI)  and (II) characterized by the fact that the address in clear of the desti  swing bridge nation is achieved by a coded wheel system  digital t39) and (40).  IV - Swing bridge control device according to claims f1)  and CII) characterized by the fact that the clear indication of the  position of the rotary bridge is obtained by two opto-electro decades  picnics (34) and (35) figure -9- controlled by integrated circuits  (31), t32) and t33) of Figure -9-.