I need a relay which would be able to act in this way:
State 1: When there is no power supply on the coil, the COM contact of the relay is placed on the N/C contact (default state);
State 2: When I apply a power supply (12 volt) on the coil, the COM contact of the relay immediately switch to N/O contact and must keep this state indefinitely;
State 3: When the power supply is removed, the COM contact of the relay, switch again to the N/C contact (default state), and will remain in this position for a certain time (eg settable between 5 and 10 mins); when the power supply is applied again on the coil, the relay should keep the State 3 (as I've said for a certain settable time) and then back to State 2.
I need this relay to trigger a buzzer; the power supply of the relay will be “controlled” by a magnetic reed switch (like this one: http://s14.postimg.org/ouxbb05sx/magnetic_switch.jpg): when a magnet is placed near to the magnetic switch, the current is free to flow on the coil of the relay (the magnetic contact will set the its COM to N/C) – State 2 for the relay -;
when the magnet is far from the magnetic switch, the magnetic contact will set the its COM to N/O and the power supply will be interrupted – State 3 for the relay -;
when the magnet will be near again to the magnetic switch (COM on N/C), the State 3 of the relay should be keep for the settable time (eg 5 mins) and then the relay will back to the State 2.
I heard of Time-delay relays (http://www.allaboutcircuits.com/textbook/digital/chpt-5/time-delay-relays/) but I'm not sure of which kind of TDR I need for my purposes, if they have a large time settable (in terms of minutes), if they work with low voltages and if they are easy to find and if they are cheap to buy. I also heard of the possibility to implement a latching relay, but is not very clear to me the logic.
Or maybe can I achieve my needs using a timer? I'd wish to keep everything as simple as possible, so would be fine to find something of assembled (eg on ebay).
Thank you.
State 1: When there is no power supply on the coil, the COM contact of the relay is placed on the N/C contact (default state);
State 2: When I apply a power supply (12 volt) on the coil, the COM contact of the relay immediately switch to N/O contact and must keep this state indefinitely;
State 3: When the power supply is removed, the COM contact of the relay, switch again to the N/C contact (default state), and will remain in this position for a certain time (eg settable between 5 and 10 mins); when the power supply is applied again on the coil, the relay should keep the State 3 (as I've said for a certain settable time) and then back to State 2.
I need this relay to trigger a buzzer; the power supply of the relay will be “controlled” by a magnetic reed switch (like this one: http://s14.postimg.org/ouxbb05sx/magnetic_switch.jpg): when a magnet is placed near to the magnetic switch, the current is free to flow on the coil of the relay (the magnetic contact will set the its COM to N/C) – State 2 for the relay -;
when the magnet is far from the magnetic switch, the magnetic contact will set the its COM to N/O and the power supply will be interrupted – State 3 for the relay -;
when the magnet will be near again to the magnetic switch (COM on N/C), the State 3 of the relay should be keep for the settable time (eg 5 mins) and then the relay will back to the State 2.
I heard of Time-delay relays (http://www.allaboutcircuits.com/textbook/digital/chpt-5/time-delay-relays/) but I'm not sure of which kind of TDR I need for my purposes, if they have a large time settable (in terms of minutes), if they work with low voltages and if they are easy to find and if they are cheap to buy. I also heard of the possibility to implement a latching relay, but is not very clear to me the logic.
Or maybe can I achieve my needs using a timer? I'd wish to keep everything as simple as possible, so would be fine to find something of assembled (eg on ebay).
Thank you.
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