Non-contact proximity switch for machine safety

1. A non-contact proximity switch having a first part and a second part, wherein

the first part is arranged to be connected to a reset circuit comprising an indicator light and a reset switch having a reset button;

the first part comprises a reset mechanism for machine safety;

the reset mechanism comprises a signal generator and a signal detector; and

the signal detector is arranged to detect when the state of a connected reset switch corresponds to a state where the reset button is being pressed, characterized in that

the first part comprises a first I/O interface arranged to be connected to said reset circuit;

the reset mechanism is arranged to, upon a detected absence of a response signal from the second part, generate a modulated signal at an output of the first I/O interface; and

the signal generator is arranged to, upon indication that a reset is required, generate a signal so as to switch-on said indicator light.

2. The non-contact proximity switch of claim 1 ,

the first part further comprises:

a first I/O interface arranged to be connected to said reset circuit;

the reset mechanism is arranged to, upon a detected absence of a response signal from the second part:

alter the output from the signal generator so that a signal at an output of said first I/O interface changes;

detect a re-appearing response signal from the second part;

detect a reset operation, the detection comprising detecting, in the signal detector, that a signal at an input of the I/O interface has changed to a signal, which corresponds to the reset button being pressed.

3. The non-contact proximity switch of claim 1 , wherein

the first part further comprises a first I/O interface arranged to be connected to said reset circuit; and

the signal detector is arranged to detect a reset operation if the potential at the input of said I/O interface has changed to a potential corresponding to the reset button being pressed.

4. The non-contact proximity switch of claim 1 , wherein

the output and the input of the first I/O interface is provide with a single connection point;

an output of the signal generator is connected to said single connection point;

and an input of the signal detector is connected to said single connection point.

5. The non-contact proximity switch of claim 1

wherein the reset mechanism is at least partly implemented by means of a processor, the processor being arranged to:

detect an absence of an expected response signal from the second part;

instruct the signal generator to generate a signal so as to switch-on said indicator light;

detect a re-appearing response signal and

detect a reset operation.

6. The non-contact proximity switch of claim 5 , wherein said at least one processor is arranged to perform the detection of a reset operation by

receiving a signal indicative of the potential at the input of the first I/O interface;

comparing said signal with a potential expected, at said input, if the reset button of the reset circuit which is connected to the non-contact proximity switch is being pressed; and

if said signal represents said expected potential, then

checking whether the duration of said expected potential at said input exceeds a pre-determined period of time; and

detecting, via said signal indicative of the potential at said input, that the potential has returned to a potential expected when said reset button has been released.

7. The non-contact proximity switch of claim 1 , further comprising

a signal generator arranged to generate a CLOSED-signal at a second I/O interface in response to the reset mechanism having detected a re-appearing response signal and a detected reset operation.

8. The non-contact proximity switch of claim 7 , wherein

said signal generator arranged to generate a CLOSED-signal is arranged to only generate a CLOSED-signal if both an input signal and a response signal has been received, the response signal either having been received at an expected point of time, or if received later, the received response signal was followed by a detected reset operation.

9. The non-contact proximity switch of claim 7 , wherein

said output arranged to output a CLOSED-signal is a data port arranged to be connected to a data bus; and

the signal generator to which said data port is connected is arranged to generate said CLOSED-signal as a digital signal.

10. The non-contact proximity switch of claim 1 , further comprising a housing wherein said housing houses:

the reset mechanism; and

a receiver for receiving a response signal from the second part.

11. A machine safety systems comprising a safety controller and at least two non-contact proximity switches according to claim 1 .

12. The machine safety system of claim 11 further comprising a signal generator arranged to generate a CLOSED-signal at a second I/O interface in response to the reset mechanism having detected a re-appearing response signal and a detected reset operation, wherein

at least two of the at least two non-contact proximity switches are connected to a safety controller via said second I/O interface connected to said signal generator arranged to generate a CLOSED-signal.