Contact detection system for power equipment
A woodworking machine having one or more dangerous portions of the machine is disclosed. The machine also includes a safety system configured to detect accidental contact between a person and at least one of the dangerous portions by electrically coupling a signal to the person's body, and detecting if the signal becomes coupled to the dangerous portion.
1. A method for detecting accidental contact between a person and a dangerous portion of a woodworking machine, the method comprising:
providing a first electrode electrically coupled to the person;
providing a second electrode electrically coupled to the dangerous portion;
transmitting a signal by one of the first or second electrodes;
receiving the transmitted signal by the other of the first or second electrodes; and
performing a step of sampling the signal a plurality of times to determine if the signal has at least one predetermined characteristic indicative of contact between a person and the dangerous portion.
2. A method for detecting accidental contact between a person and a dangerous portion of a woodworking machine, the method comprising:
providing a first electrode electrically coupled to the person;
providing a second electrode electrically coupled to the dangerous portion;
transmitting a signal by one of the first or second electrodes;
detecting whether the transmitted signal is received by the other of the first or second electrodes; and if so,
sampling the signal a plurality of times within 200 microseconds to determine if the signal has at least one predetermined characteristic indicative of contact between a person and the dangerous portion.
3. The method of claim 2 , where the step of transmitting includes transmitting the signal by the first electrode through the person.
4. The method of claim 2 , where the step of transmitting includes transmitting the signal by the second electrode through the dangerous portion.
5. The method of claim 2 , where the woodworking machine includes at least one cutting tool, and where the step of providing a second electrode includes providing a second electrode electrically coupled to the at least one cutting tool.
6. The method of claim 2 , where the woodworking machine includes at least one guard, and where the step of providing a second electrode includes providing a second electrode electrically coupled to the at least one guard.
7. The method of claim 2 , where the step of transmitting includes transmitting an alternating electrical signal.
8. The method of claim 7 , where the alternating electrical signal has a particular frequency, and further comprising identifying contact if an electrical signal having the particular frequency is received.
9. The method or claim 2 , where the step of transmitting includes transmitting a ground electrical signal.
10. The method of claim 2 , where the dangerous portion is a blade with cutting teeth, and where the sampling occurs while a single tooth is in contact with the person.
11. The method of claim 2 , where the sampling occurs within 100 microseconds.
12. The method of claim 2 , where the sampling occurs in less than 100 microseconds.
13. The method of claim 2 , where the predetermined characteristic indicative of contact between a person and the dangerous portion distinguishes such contact from proximity between a person and the dangerous portion.
14. The method of claim 13 , where the predetermined characteristic indicative of contact between a person and the dangerous portion involves peak-to-peak amplitude.
15. The method of claim 13 , where the predetermined characteristic indicative of contact between a person and the dangerous portion involves phase.
16. The method of claim 13 , where the predetermined characteristic indicative of contact between a person and the dangerous portion involves a positive value.
17. The method of claim 13 , where the predetermined characteristic indicative of contact between a person and the dangerous portion involves a negative value.