Self-learning relay turn-off control system and method

A relay turn-off control system for use with an alternating-current (AC) signal input, comprising:

• a relay;
• a relay current load sensor connected to the relay;
• a rectifier circuit connected to the relay current load sensor and having an output;
• a microprocessor connected to the rectifier circuit output;
• and
• wherein the microprocessor is configured to set a relay turn-off signal output time based on an empirically determined duration time for the relay to turn-off and further based on determining a zero-cross period via use of a modulo operation;
• wherein the zero-cross period is determined by configuring the microprocessor to:
• a) define a plurality of successive time increments where each of the plurality of successive time increments combined are equal to a cycle time of the AC signal input;
• b) perform a modulo operation of (duration time) mod (half the cycle time), wherein a remainder of the modulo operation is one of a non-zero value and a zero value;
• c) store the remainder and an associated time increment in a memory coupled with the microprocessor;
• d) output a next relay turn-off signal to the relay at a next of the plurality of successive time increments;
• e) repeat steps b-d until the stored remainders of successive modulo operations transition from the non-zero value to the zero value or from the zero value to the non-zero value;
• and
• f) set a relay turn-off signal output time at the associated time increment where the remainder of successive modulo operations transitioned from the non-zero value to the zero value or from the zero value to the non-zero value.

A method performed by a microprocessor forming a part of a relay control system for use with an alternating-current (AC) signal input and where the relay control system includes a relay, a relay current load sensor connected to the relay, a rectifier circuit connected to the relay current load sensor and the microprocessor connected to a rectifier circuit output, comprising:

• a) outputting a first relay turn-off signal to a relay at a first of a plurality of successive time increments where each of the plurality of successive time increments combined are equal to a cycle time of the AC signal input;
• b) measuring a duration time, after step a or e, for the rectifier circuit output to indicate that the relay has turned off;
• c) performing a modulo operation of (duration time) mod (half the cycle time), wherein a remainder of the modulo operation is one of a non-zero value and a zero value;
• d) storing the remainder and an associated time increment in a memory coupled with the microprocessor;
• e) outputting a next relay turn-off signal to the relay at a next of the plurality of successive time increments;
• f) repeating steps b-e until the stored remainders of successive modulo operations transition from the non-zero value to the zero value or from the zero value to the non-zero value;
• and
• g) setting a relay turn-off signal output time at the associated time increment where the remainder of successive modulo operations transitioned from the non-zero value to the zero value or from the zero value to the non-zero value.