Start/stop a 3-phase motor on a saw

I need a schematic and PCB-layout for a SIMPLE CHEAP and stable way to

START, fast STOP a 3 X 400V motor 2800W

on my saw.

The other day it just didn't function any more and I can see it's made of just a few pure standard components !

Beside I think I can use the circuit for some other of my machines - a small saw (0,25 HP) and a bigger lathe (5 HP).

Get one of these.. .I know this doesn't answer your question, but interesting non the less.

TMD

www.sawstop.com

Seaching the USPTO using Stephen Gass as the search key turned up 24 patents by Gass, assigned to SD3, LLC.

This will give you all of them, in list form, using Google Patents.

Extracting the patent numbers therein, and inputting them to pat2pdf.org will give you all of Gass' patents. Some are NOT for the Saw Stop product.

Gass' patents are large, as few as 7 pages and as many as 39 pages, with most being towards the high end.

The following list will get you all of Gass' patents in PDF form. Input this list to pat2pdf.org.

6536536; 6826988; 6857345; 6834730; 5676319; 7137326; 6994004; 6945149; 6945148; 6920814; 6957601; 7077039; 7171879; 6880440; 7055417; 6877410; 7000514; 7093668; 7121358; 6813983; 7098800; 7024975; 7100483; 6997090

They're all "cached", right now.

Use Download Them All, or an equivalent tool to down load them.

It appears that US Pat. 6,997,090, Gass, et. al., is the basic patent for the Saw Stop protection system, although other patents, also by Gass, et. al., adapt this concept to so-called "Contractor's" saws. Also to miter saws.

Gass' patent contains perhaps the largest list of "prior art" which I have yet seen.

Essentially, Gass' invention incorporates literally hundreds of other inventive devices into his own, in addition to his own unique protection system.

US Pat. 7,024,975 extends Gass' basic invention to saws of all kinds, including band saws, etcetera. Several hundred earlier patents are cited as "prior art".

Herein is disclosed the capability to protect the operator from a very wide saw, such as a stacked dado.

The actual "firing circuit" is disclosed in US Pat. 7,100,483.

The "proximity detector" is disclosed in US Pat. 7,171,879.

Dr. Gass certainly has been a busy boy!

Where can I find a forum - like this practicalmachinist - for people experimenting with modern components like thyristors to "Start/stop a 3-phase motor and reversing them" ?

Do you have any links ?

Motorola, Teccor and pretty much all other Triac/Thyristor manufacturers offer schematics for forward/reverse switching of 3 phase induction motors using power triacs.
From there it's a simple addition of a centrifical switch and a NOR gate to stop the motor.
You basically reverse the polarity until the switch cuts-off. Note that this will work on relatively small motors. For larger ones you pretty much have to include a transformer and supply reduced braking voltages, OR use current limiting resistors. This can get slightly more complicated, but only by having to have a second set of switching devices and some additional logic to determine the rotational direction. I can even imagine using non-zero crossing triacs, and use delayed firing to reduce the reverse currents.
Now, I have not played with this for a very very very long time, but I do know that my school books gave clear description of the "old-school" method of the same thing, except it was timing relays, resistor-bank switching relays, etc etc.
Should be much easier today.
In fact would not be surprized if there is a one-IC solutions to this whole thing from the likes of Analog Devices, including on-board hall-effect sensors and all.

I don't know if anyone read the entire article on "Saw Stop", but the electronic circuit causes a rapid CRASH of a block of aluminum into the blade and that is really what does the stopping, not the electronics controlling the motor. Kind of like crashing a CNC machine !

TMD

That works too.