Table Top Saw Rips Wood Not Fingers

SawStop LLC is now in production with a new power table saw equipped with a revolutionary sensing and instant brake feature enabled by a Texas Instruments TMS320C2000 series of digital signal controllers, which were covered in the September, 2004 issue of EE Product News. Enabling greater safety in the workplace and at home, the saw detects accidental contact between the blade and a user to completely stop and retract the circular blade in less than 5 ms. As a result, many woodworking accidents will now require only minor treatment instead of emergency medical care.

Here’s how it works. The SawStop safety unit places a small charge on a standard saw blade, creating a steady 3V signal on the blade during normal use. When the blade comes into contact with a user’s skin, the capacitance of the human body changes the voltage level on the blade. The C2000 controller monitoring the blade voltage detects this change within 50 µs. The controller then trips a high-speed, high-force, single-use actuator that forces a brake into the teeth of the blade and stops it within 5 ms. This safety module can be replaced easily by the user after it has been used. The controller also performs self-tests of the module and prevents the saw from starting if it detects a problem with the safety feature. You can read more on this subject at http://focus.ti.com/docs/pr/pressrelease.jhtml?prelId=sc05036. To view a short video of the saw in action, point your browser to http://208.178.1.181/video.htm.