eli5: How do some tablesaw know when to autamatically stop when it is about to cut you?

Question

eli5: How do some tablesaw know when to autamatically stop when it is about to cut you?

In: Engineering

Answer 1

Sawstops have a low voltage current running through them and the blade. When you complete the circuit by touching the blade with your finger, (or running through a nail in old wood, or accidentally touching the blade with anything conductive), a piston fires, instantly dropping the blade below the table and stopping it.

It ruins the blade and the cartridge, but a $75 cartridge and a $100 blade are a lot cheaper than a finger.