Sub-milliamp mechanical relay control

Abstract

A relay driver circuit, suitable for controlling a bistable relay, includes .[.a storage device which is charged to a first voltage level by a low current flow voltage source..]. .Iadd.a transformer which handles both an information signal and a control signal and a storage device. The control signal is provided by a low current low voltage source. .Iaddend.A first switching circuit couples the storage device to the bistable relay when the first voltage level exceeds a predetermined value. The charge on the storage device is dumped into the relay and forces it into a first state (set). A second switching circuit is coupled to sense the voltage on the storage device and the voltage on the low voltage source. When the voltage on the low voltage source falls below the voltage on the storage device, current flows from the storage device and forces the relay into a second state (reset). The reset time is within 100 μs.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent is: 
     
       1. A control circuit suitable for .Iadd.attaching a station to a serial communication network by .Iaddend.driving the set and reset energization coils of a bistable relay comprising: .Iadd.a bistable relay including a switch means having a first and second state connected to the communications network; said bistable relay also including a set energization coil responsive to a first energization current to set the bistable relay and switch means to the first state in which the station is inserted into the network and a reset energization coil responsive to a second energization current to reset said bistable relay and switch means into the second state in which the station is bypassed;   a transformer means including a primary winding means for receiving time varying data signals and a direct current control signal from a station which wants to communicate time varying data signals over the said network and a secondary winding means for applying said time varying data signals to said switch means;   a control circuit means coupled to the bistable relay means and a primary winding means, said control circuit means having .Iaddend.a first circuit means disposed in parallel with the set and reset coils; said first circuit means being operable .Iadd.in response to the direct current control signal .Iaddend.for setting a first reference voltage level;   at least one storage means coupled to the first circuit means and the set and reset coils, said first storage means being operable .Iadd.in response to the direct current control signal .Iaddend.for storing a predetermined electrical charge with .Iadd.a value of .Iaddend.sufficient magnitude for setting and resetting the bistable relay;   a first switching means coupled to the set energization coil and the storage means; said first switching means being operable .Iadd.when the charge on said storage means exceeds the value .Iaddend.for causing the storage means to discharge a portion of its charge into the set energization coil to set the .Iadd.bistable .Iaddend.relay .Iadd.and switch means .Iaddend.into .[.a.]. .Iadd.the .Iaddend.first sate .Iadd.in which a path is established for time-varying signals between the station and the network.Iaddend.; and   a second switching means coupled to the storage means and the reset coil; said second switching means being operable .Iadd.when the direct current control signal is discontinued .Iaddend.for causing the storage means to discharge the remaining portion of its charge into the reset coil to reset the .Iadd.bistable .Iaddend.relay .Iadd.and switch means .Iaddend.into .[.a.]. .Iadd.the .Iaddend.second state .Iadd.in which the path for time-varying signals between the network and the station is interrupted. .Iaddend.   
     
     
       2. The control circuit of claim 1 further including an excitation means coupled in parallel with the energization coils. 
     
     
       3. The control circuit as recited in claim 2 wherein the excitation means is a low current/low voltage source. 
     
     
       4. The control circuit of claim 1 wherein the first circuit means includes a zener diode having one electrode connected to the first switching means and the other electrode coupled to the storage means. 
     
     
       5. The control circuit of claim 1 wherein the first circuit means includes a pair of series resistors connected to the first switching means. 
     
     
       6. The control circuit of claim 1 wherein the storage means includes a capacitor. 
     
     
       7. The control circuit of claim 6 wherein the capacitor is sized so that the charge accumulating thereon is of sufficient magnitude to set and reset the energization coils of the relay. 
     
     
       8. The control circuit of claim 1 wherein the first switching means includes a silicon control rectifier (SCR). 
     
     
       9. A control circuit suitable for .Iadd.attaching a station to a serial communication network by .Iaddend.driving set and reset energization coils of a bistable relay comprising: .Iadd.a bistable relay including a switch means having a first and second state connected to the communications network; said bistable relay also including a set energization coil responsive to a first energization current to set the bistable relay and switch means into the first state in which the station is inserted into the network and a reset energization coil responsive to a second energization current to reset said bistable relay and switch means into the second state in which the station is bypassed;   transformer means connected to the switch means; said transformer means providing a transmission path between the station and the switch means when the station provides a control current;   a control circuit means coupled to the switch means and the transformer means; said control circuit means including .Iaddend.a first circuit means disposed in parallel with the set and reset coils; said first circuit means being operable for setting a first reference voltage level;   at least one storage means coupled to the first circuit means and the set energization coil, said .[.first.]. storage means being operable for .Iadd.responding to the control current from the transformer means for .Iaddend.storing a predetermined electrical charge;   a first switching means coupled to the .Iadd.set .Iaddend.energization .[.coils.]. .Iadd.coil .Iaddend.and the storage means; said first switching means including a programmable unijunction transistor (PUT), a transistor switch and a diode interconnecting the cathode of said PUT to the base electrode of the transistor switch and being operable for periodically discharging the storage means into the .Iadd.set .Iaddend.energization coil to set the .Iadd.bistable .Iaddend.relay into .[.a.]. .Iadd.the .Iaddend.first state; and   a second switching means coupled to the storage means and the reset coil; said second switching means being operable to periodically discharge the storage means into the reset coil .Iadd.to set the bistable relay into the second state.Iaddend..   
     
     
       10. The control circuit of claim 1 wherein the second switching means includes a PUT; said PUT having its cathode electrode connected to the reset coil, its anode electrode connected to the storage means and the gate electrode coupled to sense an excitation voltage wherein the PUT conducts and dumps current into the reset coil when the excitation voltage is less than a voltage on the storage means. 
     
     
       11. The control circuit of claim 1 wherein the first switching means discharges the storage means when the voltage on the storage means is greater than the first reference voltage level. 
     
     
       12. In a communication network system having a communication link wherein bistable relays are being utilized for inserting a plurality of network ports into the link with the relays being responsive to an enabling electrical signal generated from a device connected to said ports an improved circuit arrangement for controlling the bistable .[.relay.]. .Iadd.relays .Iaddend.comprising: a storage means operable to receive the electrical signal;   and to store a charge of sufficient magnitude to set and reset the bistable relay;   a circuit means coupled in parallel with the storage means and operable to limit the charge thereon;   a first switching means having a control electrode connected to the circuit means and an anode electrode connected to a set coil of the bistable relay; and   a second switching means having at least three electrodes with one of the electrodes being coupled to sense the enabling electrical signal, a second electrode being coupled to .[.the.]. .Iadd.a .Iaddend.reset coil of the bistable relay and a third electrode being coupled to the storage means whereby the first switching means conducts and dumps a portion of the charge on the storage means into the set coil when the quantum of charge thereon exceeds a predetermined level and the second switching means conducts and dumps the residual charge on said storage means into the reset coil when the level of the enabling electrical signal falls below the residual charge on said storage means.   
     
     
       13. The improved circuit of claim 12 further including a diode and a capacitor connected in series with the reset coil and operable to provide a low resistance electrical discharge path during an interval when current is flowing from the storage means into the reset coil. 
     
     
       14. The improved circuit of claim 12 further including a resistor, a diode connected in series to the resistor; wherein the series resistor-diode is coupled in series with the storage means and operable to limit the rate at which said storage means is being charged. 
     
     
       15. In a communication network system having a communication link wherein bistable relays are being utilized for inserting a plurality of network ports into the link with the relays being responsive to an enabling electrical signal generated from a device connected to said ports an improved circuit arrangement for controlling the bistable .[.relay.]. .Iadd.relays .Iaddend.comprising: (1) a pair of input .[.operable coupled.]. .Iadd.terminals .Iaddend.to receive the input signal;   (2) a reference voltage means for defining a reference voltage coupled across the input terminals;   (3) a first storage means coupled across the input terminals, said first storage means being in parallel with the reference means and .[.the.]. .Iadd.a .Iaddend.set of the relays;   (4) a switching means coupled in series with the set coil and operable to discharge the storage means periodically into the set coil;   (5) a second storage means connected to at least one of the input terminals; and   (6) a first comparator means coupled to the switching means; said comparator means being operable to monitor the voltages on the reference voltage means and the second storage means and to initiate a current flow in the switching means when the voltage on the second storage means is greater than the voltage on the reference voltage means whereby the current flow in the switching means causes the charge on the first storage means to be dumped into the set coil.   
     
     
       16. The improved circuit arrangement of claim 15 further including a second comparator means coupled to the reset coil of the relay, the first storage means and at least one of the input terminals; said comparator means being operable to sense the voltage on the first storage means and the enabling electrical signal and periodically discharging the first storage means into said reset coil. 
     
     
       17. The improved circuit arrangement of claim 15 wherein the switching means includes a transistor switch. 
     
     
       18. The improved circuit arrangement of claim 17 wherein the first comparator means includes a programmable unijunction transistor (PUT) having an anode electrode connected to the second storage means, a gate electrode connected to the reference voltage means and a cathode electrode coupled to the transistor switch. 
     
     
       19. The improved circuit recited in claim 18 further including a resistor interconnecting the cathode to the emitter electrode of the transistor switch. 
     
     
       20. The improved circuit recited in claim 19 further including a diode interconnecting the cathode to the base of the transistor switch. 
     
     
       21. A circuit arrangement for use in a telecommunication system to insert a station into the system comprising: signal generating means associated with the station and operable to generate an enabling signal indicative of the station's desire for inserting into the system;   at least one storage means operable to receive the signal and develop an electrical charge therefrom;   a bistable relay having a set and a reset coil arranged in parallel with the storage means and operable for energizing the relay between first and second positions;   a first switch means coupling the storage means with the set coil and operable to monitor the charge on the storage means and causing said storage means to discharge into the set coil to set said relay into a first state when the charge exceeds a predetermined value; and   a second switch means having a controlling electrode coupled to detect the enabling signal and the charge on the storage means and to discharge the storage means into the reset coil when the level of the enabling signal falls below the charge on the first storage means thereby switching the relay into its second position.   
     
     
       22. A control circuit suitable for .Iadd.attaching a station to a serial communications network by .Iaddend.driving the set and reset coil of a bistable relay comprising: .Iadd.a station including .Iaddend.a supply voltage source;   .Iadd.a bistable relay having a first and second state operatively coupled to the communications network, said bistable relay including a set coil responsive to a first energization current for setting the bistable relay to the first state in which the station is coupled to the network and a reset coil responsive to a second energization current for setting the bistable relay to the second state in which the station is bypassed;   transformer means coupled to the bistable relay, said transformer means providing a transmission path between the network and the station when the station provides a unidirectional control current from said supply voltage source; .Iaddend.   at least one storage means coupled to the supply voltage source .Iadd.by said transformer means.Iaddend., said storage means being operable .Iadd.by the control current from said supply voltage source .Iaddend.for storing a charge with sufficient magnitude for setting and resetting the bistable relay;   a first switching means coupled to the storage means and the set coil, said first switching means being operable when activated for causing the storage means to discharge a portion of its stored charge into the set coil thereby setting the .Iadd.bistable .Iaddend.relay .Iadd.to the first state.Iaddend.;   a second switching means operable for coupling the storage means to the reset coil; said second switching means being operable for monitoring voltage differences between the supply voltage source and the storage means and to cause said storage means to discharge the remaining portion of its charge into the reset coil so that said relay is reset to the second state when the voltage differences fall below a predetermined level.   
     
     
       23. The control circuit of claim 22 further including a first circuit means coupling the storage means and the first switching means; said first circuit means being operable for setting a reference voltage level and for energizing said first switching means when the stored charge on the storage means is greater than the reference voltage.