eli5: How do some tablesaw know when to autamatically stop when it is about to cut you?
In: Engineering
It applies a 500-kHz sine-wave current to the blade and measures the voltage response every 6 msec. A sudden drop in voltage indicates a conductive foreign object, like a finger, is drawing current off the blade.
Once the touch is detected, analysis software acts to stop the blade as quickly as possible. When signaled, capacitor sends a surge of current into a fuse wire that holds back a mechanical spring. The current vaporizes the wire within 15 millionths of a second and releases the spring to force an aluminum “brick” into the teeth of the blade.
https://www.machinedesign.com/community/guest-commentary/article/21818329/capacitance-system-stops-table-saws-from-amputating-fingers
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