Back in my motor control days, we called them "motor starters". But that may
have been local slang. :-)

On Wed, 15 Jun 2005 09:43:58 -0500, Joe User wrote:

I wast just browsing a DC thread where "magnetic switches" are
discussed. Not the first time I've seen the term, and I know what they
were talking about, but I DAGS and the first 40 or 50 hits mostly
related to burglar alarm type switches, and none referred to the "punch
red for off, punch green for on, don't power the tool up after a power
failure" type switch that makes sense for woodworking and other
machinery. Grizzly's web site lists them as magnetic switches, but a
search at Grainger's web site for "magnetic switch" returned alarm type
switches and relays, and at McMaster-Carr returned alarm switches. I
didn't keep searching very long, so I didn't find what I was looking for
at either site.

I guess what I'm getting around to is a question: Is there another name
for this type of switch?

They're very simple devices. The actual switch for power to the tool is
a relay. The relay's coil gets power either through a set of contacts
on the relay itself, or applied via a normally open momentary switch
(the "on" button). A normally closed momentary switch in series with
the coil power is the "off" switch.

A relay with a 110VAC coil and appropriately rated contacts, a NC
pushbutton (red for off) and a NO pushbutton (green for on) and an
appropriate enclosure are all you need to make one of these.

If one wanted a separate start/stop switch for the dust collector at
every tool, it would be easy for the electrically inclined woodworker to
build a switch that would support a remote start/stop pair for the DC at
every station. All of the start buttons would be in parallel, while all
of the stop buttons would be in series (this could be obnoxious if you
have a bad connection on the "stop" side). I'd probably use a 24VAC for
the control side, which would mean a 3 pole relay or an extra 24VAC
transformer.

There are also current sensing controls. Attach one of these devices to
a power wire on a tool (there is no electrical connection, it senses the
magnetic field caused by the current flowing through the wire) and use
it to apply power to the DCs relay. I couldn't find these right off,
either. anyone know what they're called?

just random thoughts and questions....

-j

____________________
Bill Waller
New Eagle, PA