Indian Institute of Technology Hyderabad THE BENCH SAW BRAKE SYSTEM ATUL S VIVEK ME12B1004 JOPHIN GEORGE JOSEPH CH12B1010

INTRODUCTION  By this project,we intend to make a system which automatically switches of a working bench saw if a person ‘ s limbs comes into contact the blades of the saw.  This is accomplished by using an electronic touch sensor which is activated when a person touches the saw blades & this touch sensor in turn activates an electric circuit which switches off the saw and triggers a stopping mechanism which is used to bring the saw blades rotating at speed of 1000 RPM [on an average],to rest instantaneously.  The touch sensor works by detecting the small potential associated with the human body and thereby creating a potential difference which activates a relay controlled stopping mechanism

NEED FOR AN AUTOMATIC SAW STOP SYSTEM  Bench saws are devices which are crucial for furniture and construction industries, for they make wood working a much less tedious task  But along with this ease comes an inherent danger of accidental amputation of limbs of personnel involved in this business.  Globally a saw accident happens every 9 minutes  The automatic saw stop system provide a simple but effective solution to this problem WWSSD

CHALLENGES IN THE PROJECT There are number of challenges which arises with this project, some of them are listed below : SA  The project’s prime concern is to reduce the risk of injuring one’s hand while cutting wood using a bench saw.So the touch sensor must be designed in such a way that it is not triggered when wood comes into contact with the saw  The second major thing to be taken into consideration is the response time of the system & The stopping mechanism. Ideally the stopping mechanism should have a reaction time of not more than.05 seconds or else it won’t effective and the risk of injury is not eliminated

WORKING OF TOUCH SENSOR  The touch sensor is a circuit which amplifies the small potential associated our body.  It employs two IC 741 amplifier circuits to amplify this voltage. IC V GND -5V 2 I/P From blade O/P to relay circuits

SCHEMATIC DIAGRAM SAW BLADE CONDUCTING WIRE ELECTRONIC CIRCUIT WHICH MONITORS SIGNAL FROM THE BLADE MOTOR POWER ON DETECTING TOUCH, A POTENTIAL IS DEVOLOPED RELAY CIRUITS CONTROLLING SUPPLY TO THE MOTOR SWITCHES OFF THE MOTOR STOPPING MECHANISM TO BRING THE BLADE TO REST TOUCH

STOPPING MECHANISM  Stopping mechanism is used to bring the saw blade rotating at a very high speed suddenly to a halt,thereby reducing damage to limbs  Here, we are designing a stopping mechanism which works with the help of an electromagnet  When the touch sensor is activated, it triggers the stopping mechanism using a relay circuit  The stopping mechanism has a metal strip attached to a permanent magnet kept close to an electromagnet,the whole system is kept close to the saw blade.  When the electromagnet is powered using an AC supply, the metal strips oscillates with a very frequency of the AC.During this oscillation,It continuously hits the blade and stops the blade within a short period,without causing much damage to the blade as well as the person touching it

PROs OF THE SYSTEM  T he system is activated only the touch of human limbs or such bodies with a small associated potential.  Even though it may cause slight Damage the saw blade, It does not do much damage to the saw as a whole.  It can be reused without replacing many parts, In the extreme case the saw blade or the metal strip used for stopping may have to be replaced  Most importantly it keeps the limbs of the saw operator intact. CONs OF THE SYSTEM  The saw brake cannot be use with wet or newly cut wood or metals  Even though it reduces the chance of damage to the body, one cannot escape without a slight cut.