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Subject: Re: laptop drill press (foot switch safety)

From: "starsnstripes_2003" <bwatson@...>
Date: 2003-07-26

YES! Ron has a VERY GOOD point!
I wasn't going to get into wiring basics, but for this you should be
aware of safety! Ron's idea is the best, but I'll use the phono plug
for mine.

I use stereo 3 conductor phono plugs/jacks for one of my projets, so
using the tip conductor for "Hot" and the center conductor
for "Neutral" would be one solution. If Hot is connected to the
center or shell conductors, You would get a JOLT when you plugged it
in under power!

Use the plastic insulated plugs. (Or use a proper Heat-shrink tubing
to insulate the metal ones.
Also, you should use a 3 conductor wire so that you
can carry the ground to the switch housing.
Connect the Green ground wire inside the power strip to the outer
shell and one conductor (shield if it has one) of the cable. At the
other end, connect this ground wire to the housing of the metal
footswitch.

You don't want the hot wire connected to the outer shell or switch
housing at any time!

The footswitch I mentioned only has a 2 conductor plug.
You would need to replace it and the cable with a 3 conductor rated
for the job, or as Ron suggested, use a low voltage relay rated well
over the current of your drill.


> If you do use a phono plug, make sure you put a relay and
transformer with it to avoid running the mains current on a
phonoplug.
>
> In the US, it seems about 20% of residential buildings are
wired backwords, and as such you could end up with 120V on the
phonoplug shell, so I'd make sure that a low voltage signal was
running through the footswitch which would enable a relay to turn on
the dremel. Make sure to use a decent relay, as the inductive
kickback from the dremel can fry contacts pretty easily if you don't
have the proper snubber.
>
> Another solution is a foot switch designed for mains operation
such that there are no safety concerns. Sometimes you can find them
surplus for under $10.
>
> Thanks
> Ron