Detection systems for power equipment
Methods to detect when a human body contacts a predetermined portion of a machine are disclosed. The methods distinguish contact with a person from contact with other materials. The methods are particularly applicable in woodworking equipment such as table saws to distinguish contact between a person and the blade of the saw from contact between the blade and wet or green wood. The methods and woodworking equipment may include predictive blade stop algorithms that prevent unnecessary activations of a safety brake during coast down of a blade and continued protection in the event a main power switch is turned off.
1. A woodworking machine comprising:
a cutting tool adapted to move to cut a workpiece;
a motor configured to move the cutting tool;
a motor control circuit adapted to selectively power the motor, where the motor control circuit includes a start/stop switch to allow a user to turn the motor on and off;
a safety system configured to detect a dangerous condition between the user and the cutting tool and to perform a predetermined action upon detection of the dangerous condition to mitigate the dangerous condition;
a power supply configured to provide power to at least a portion of the safety system;
a main power switch configured to control delivery of power to the power supply and to at least a portion of the motor control circuit by allowing a user to turn the main power switch on and off; and
a power control system associated with the start/stop switch and the main power switch and configured to prevent the interruption of power to the power supply if the main power switch is turned off while the cutting tool is moving.
2. The woodworking machine of claim 1 , where the cutting tool is adapted to spin, and further including a rotation sensing system to detect when the cutting tool is spinning.
3. A woodworking machine comprising:
a cutting tool adapted to move to cut a workpiece;
a motor configured to move the cutting tool;
a motor circuit adapted to power the motor, where the motor circuit includes a start/stop switch to turn the motor on and off;
a safety system configured to detect a dangerous condition between a person and the cutting tool and to perform a predetermined action upon detection of the dangerous condition to mitigate the dangerous condition;
a main power switch to turn on and off power to at least a portion of the motor control circuit and to the safety system; and
a control circuit to prevent the interruption of power to the safety system if the main power switch is turned off while the cutting tool is moving.
4. The woodworking machine of claim 3 , further comprising a motion sensing system to detect when the cutting tool is moving.
5. The woodworking machine of claim 3 , further comprising a motion sensing system to detect when the cutting tool is moving.