> > So, it is like the most useless machine, where one flips a toggle and > > then it immediately shuts itself off? The difference being that the > > saw is a useful machine. > > Yes, but that would be safe. ;-) > > My 7x12 horizontal bandsaw has the same setup as described. A tab of > metal hangs down and contacts the on-off toggle switch when the saw > swings down all of the way. > > It is very simple. > > Another way to do it electrically is to use a contactor to switch the > motor power on and off and then construct a control circuit around the > contact so pushing one button energized the contactor and seals it on > with an auxilary contact, and then > a stop button and a "saw off" switch break the seal on the contactor. > The saw off switch would need to be normally closed, push to open etc. > > Here is an example of a seal-in circuit. > http://www.allaboutcircuits.com/vol_4/chpt_6/4.html > > Push the Forward button and M1 stays on. Ignore the line below that > has M2 as the output. > > Picture putting a normally closed stop pushbutton where the normally > closed M2 contact is, and also put in series a normally closed saw stop > switch. > > You lift the saw and push the start button, M1 comes on and stays on and > the saw runs, you push the stop button or the saw closes (contacts the > saw stop switch) and the saw goes off. > > The OL normally closed contact to the far right is the motor overload > contact for M1, which is not needed to create the functionality you want. > > The wiring shows it being driven by L1 and L2 which normally means line > voltage, usually 230 volts and up in the US, but the same thing could be > done with 24 volts DC or AC. > > Dave
Hi, The original power switch arrangement used the toggle switch but had to be changed when the requirement in certain jurisdictions became that the saw did not restart after a power outage. The people making these saws changed the power switch to a double button arrangement with a magnetically latching "ON" button and a separate "OFF" button in a small plastic pod near where the toggle switch was previously located. The action of these was arranged similar to the toggle switch with the saw starting when the "ON" button was pressed and the tab of metal on the saw frame pressed the "OFF" switch at the end of cut. This is somewhat less satisfactory when you need to switch the saw off from the button panel especially close to the end of cut. - better to switch off at the power switch? If you wished to go all stops out the ultimate setup I saw on a site recommending changes to the circuitry for use in schools saw a "Klockner Moeller" surface mount emergency stop button (big red and about 150 mm dia) mounted on the free end of the saw and a "Telemechanique" direct on line starter (DOL) in surface mount on the frame above the hinge. The DOL starter had on/ off buttons as part of the package. As this starter was a three phase unit, the usual arrangement of converting to single phase use by looping the active through two poles of the contactor and the neutral through the third would need to be adopted to defeat the single phasing protection of the thermal cutout. -- Regards, David ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense.. http://p.sf.net/sfu/splunk-d2d-c1 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
