Abstract:
The present invention relates to providing bus control for relays and more particularly relates to a method of monitoring and/or controlling a relay, a module for exchanging data with a relay, and a relay provided with such a module.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to providing bus control for relays and more particularly relates to a method of monitoring and/or controlling a relay, a module for exchanging data with a relay, and a relay provided with such a module.  
         DESCRIPTION OF THE PRIOR ART  
         [0002]    Relays are widely used in numerous applications. In many of those applications there is a need to monitor the functioning of the relay and, if necessary, to influence or correct its functioning as the need arises. Relays are normally connected to a control unit, which may include a simple switch or a more complicated device. Most traditional control units, however, are not designed to provide status information of the associated relay to a remote computer or a similar monitoring device. Likewise these traditional control units normally do not allow remote control by such a monitoring device.  
           [0003]    To allow the remote monitoring and/or controlling of relays it is of course possible to modify or replace each control unit. This is, however, expensive and laborious.  
         SUMMARY OF THE INVENTION  
         [0004]    It is therefore an object of the present invention to overcome these disadvantages and to provide a method of monitoring and/or controlling a relay or a plurality of relays which does not require the existing relay control units to be replaced and/or modified.  
           [0005]    It is a further object of the present invention to provide means for monitoring and/or controlling a relay.  
           [0006]    It is a yet further object of the present invention to provide a relay which is capable of being remotely monitored and/or controlled.  
           [0007]    Accordingly, the present invention provides a method of monitoring and/or controlling a relay having an excitation coil operating an electrical switch. The relay is connected to a control unit via a control line. The method having the steps of providing a data exchange module connected to a data exchange line, inserting the module in the control line, connecting the data exchange line to a data exchange device capable of transmitting and/or receiving data, and transmitting data to the relay and/or receiving data from the relay via the data exchange module and the data exchange line.  
           [0008]    By inserting a data exchange module in the control line between the relay and its control unit, it is possible to receive data from the control line, allowing a monitoring of the control line and thus of the relay. It is also possible to feed data into the control line, thus controlling the relay via the data exchange module and possibly overriding any control signals originating from the control unit. As the data exchange module is connected to a data exchange line, remote monitoring and/or control by a (remote) data exchange device is possible.  
           [0009]    The method of the invention does not require the relay&#39;s control unit to be modified. Still, additional control functions may be provided through the data exchange module.  
           [0010]    The present invention also provides a module for exchanging data with a relay via a control line connected to the relay, the module comprises a first connection for connecting the module to the control line, a second connection for connecting the module to a data exchange line, a data transmission device for transmitting data to the data exchange line, and/or a data reception device for receiving data from the data exchange line. In addition, the present invention provides a relay provided with such a module.  
           [0011]    The present invention further provides a system for monitoring and/or controlling at least one relay connected to a control unit via a control line, the system includes at least one data exchange module, at least one data exchange line capable of being connected to at least one data exchange module, and at least one data exchange device capable of being connected to a data exchange line and of transmitting and/or receiving data. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The invention will further be explained below with reference to the accompanying drawings in which:  
         [0013]    [0013]FIG. 1 schematically shows a relay circuit according to the Prior Art.  
         [0014]    [0014]FIG. 2 schematically shows a relay circuit according to the present invention.  
         [0015]    [0015]FIG. 3 schematically shows, in perspective, an arrangement of relays according to the present invention.  
         [0016]    [0016]FIG. 4 shows a schematic diagram of a data exchange module of the present invention.  
         [0017]    [0017]FIG. 5 shows a schematic circuit diagram of a data exchange module according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    The Prior Art relay circuit schematically shown in FIG. 1 comprises a relay  1 , of which only the excitation coil  2  and the electrical switch  3  are shown for the sake of clarity of the drawing. In practice the relay will include an anchor on which electrical contacts are mounted, which contacts are part of the electrical switch shown.  
         [0019]    The excitation coil  2  is connected to a control unit  10  by a control line  11 . For this purpose the control unit  10  has terminals A 1  and B 1  which are connected by the respective wires of the control line  11  with terminals A 2  and B 2  of the relay  1 . The control unit  10  may be an existing conventional control unit and may for instance be as simple as a hand-operated switch.  
         [0020]    A load (not shown) may be connected to the terminals C 1  and C 2  of the switch  3  which is operated by the excitation coil  2 .  
         [0021]    Although a relay circuit of this kind may be adequate for many applications, it is normally not possible to control and/or monitor the relay  1  by means of a computer without replacing the control unit  10 . It will be evident that such a replacement is expensive and therefore generally not desirable. Still, it is often advantageous to be able to (remotely) monitor the relays, for instance for safety reasons. In addition, it may be desirable to override the control  10  in certain circumstances. It would therefore be very advantageous to be able to connect the relay  1  to a data bus or similar structure without having to replace the control unit  10 .  
         [0022]    An exemplary embodiment of a relay circuit according to the present invention is shown in FIG. 2. Here a data exchange module  20  is inserted in the control line  11 . As a result, the control unit  10 , the data exchange module  20  and the relay  1  are connected in series wherein all signals exchanged between the control unit  10  and the relay  1  pass through the module  20 .  
         [0023]    The module  20  is connected to a data exchange line  21  which may be a serial or parallel bus. In a preferred embodiment the data exchange line  21  is suitable for transmitting infra-red light and may therefore contain one or more optical fibres.  
         [0024]    Several modules  20  may be connected in series to a single data exchange line  21 , each module being associated with a relay  1 . In turn, several data exchange lines  21  may be connected in parallel to a single data exchange device  22 . In this way, a plurality of modules  20  may be connected to a single data exchange device  22 .  
         [0025]    The data exchange device  22  is preferably a computer provided with a suitable interface, for example an infra-red serial interface operating in accordance with the well-known RS 232  protocol.  
         [0026]    An example of a relay arrangement in which the present invention is applied is shown in FIG. 3. Two relays  1  are each mounted on a base or socket  12 . The bases  12  are, in turn, mounted on a support rail  13 . In each base  12  a data exchange module  20  according to the present invention is inserted. The modules  20  are both connected to a data exchange line  21  which is, in the embodiment shown, an optical fibre cable.  
         [0027]    A control line  11  links the relay bases  12  with a control unit (not shown) and a power supply (not shown).  
         [0028]    In the embodiment shown, the control lines are integrated in the relay bases  12 . The bases  12  each have openings for receiving contact pins of the relays  1 , allowing a relay  1  to be plugged into a base  12  without the need for separately connecting wiring. The invention preferably utilises two pairs of unused openings to accommodate the four terminals of the module  20 .  
         [0029]    The generic circuit  50  of the module  20  schematically shown in FIG. 4 comprises a connection  25  for connecting the module to the control line  11 , a coupling  26  for coupling the module  20  to a data exchange line  21 , a data transmission device  27  for transmitting data to the data exchange line  21 , and/or a data reception device  28  for receiving data from the data exchange line.  
         [0030]    The circuit diagram of FIG. 5 shows a preferred embodiment of the electrical circuit of a module  20  according to the present invention. The circuit  50  comprises a group  25  off our terminals a 1 , a 2 , b 1  and b 2  which are to be connected to the terminals A 1 , A 2 , B 1  and B 2  in FIGS.  2  respectively. As can be seen, terminal a 1  is directly coupled to terminal a 2 . An integrated circuit  51  receives an input signal from the terminal pair a 1 -b 1  via a voltage regulator  52 . A first capacitor  53  and a second capacitor  54 , arranged on either side of the voltage regulator  52  serve to dampen any transients.  
         [0031]    The integrated circuit  51  is preferably a commercially available PIC 12C 509 control circuit. One of its terminals is connected, via a first resistor  55 , to the base of a transistor  56 . The collector of transistor  56  is connected to terminal b 2 .  
         [0032]    Another output of integrated circuit  51  is connected to the collector of a phototransistor  58 . This phototransistor  58  becomes conductive upon receiving (infra-red) light emitted by a free end  26   a  of the fibre optic data exchange line  21 . As a result, the phototransistor  58  provides a first optical coupling between the data exchange line  21  and the circuit  50 , allowing the circuit  50  to receive data from the line.  
         [0033]    Yet another output of integrated circuit  51  is connecting to a photodiode  57  which emits (infra-red) light when activated. This light is received by a free end  26   b  of the fibre optic data exchange line  21 . As a result, the photodiode  58  provides a second optical coupling between the data exchange line  21  and the circuit  50 , allowing the circuit  50  to transmit data to the line.  
         [0034]    It will be understood by those skilled in the art that the present invention is not limited to the embodiments shown and that many additions and modifications are possible without departing from the scope of the present invention as defined in the appending claims.