Isolator circuit
View Patent ↗An isolator circuit ( 25 ) for a unit of a safety system ( 10 ) includes a power control line ( 14 ) connectable to a first loop of a safety system and a power connection ( 16 ) connectable to a second loop of the safety system. A switch ( 26 ) is connected to the power control line ( 14 ), and the switch has a closed configuration and an open configuration. A controller ( 28 ) controls the configuration of the switch ( 26 ). If a voltage across the circuit ( 10 ) from the power connection ( 16 ) to the power control line ( 14 ) falls below a predetermined level, the controller ( 28 ) opens the switch ( 26 ), thereby causing a disconnection to occur in the first loop.
1. A detection system comprising:
a plurality of units connected to each other; and
a central control unit connected to each of the plurality of units, wherein each unit comprises an isolator circuit, the isolator circuit comprising:
a power control line;
a first and a second power connection;
a switch in the power control line, the switch having a closed configuration and an open configuration; and
a controller for operating the switch;
wherein the central control unit is configured such that, upon entry of instructions by a user, it sends an isolation signal to a relevant unit, and
wherein the controller is arranged such that, when it receives the isolation signal, the controller opens or closes the switch, thereby causing a disconnection to occur in the power control line.
2. The system according to claim 1 , wherein the switch in the isolator circuit comprises a solid-state switch.
3. The system according to claim 1 , wherein the switch in the isolator circuit comprises a pair of field-effect transistors connected in series.
4. The system according to claim 1 , wherein the power control line is arranged to carry a negative voltage.
5. The system according to claim 1 , wherein the controller is arranged to receive power from the power control line on both sides of the switch.
6. An isolator circuit according to claim 5 , wherein the controller includes a diode arrangement to separate the power control line on each side of the switch.
7. The system according to claim 1 , wherein the isolator circuit is incorporated into an ASIC.
8. The system according to claim 1 , wherein the isolator circuit further comprises a second power control line, and wherein the controller is such that, if a voltage between the power control lines falls below a predetermined level for less than a predetermined period of time, the controller does not open the switch.
9. A system according to claim 1 , further comprising a visual indicator for indicating when the switch is open.
10. A system according to claim 9 , wherein the visual indicator is an LED.