Re: [CAD_CAM_EDM_DRO] Another EDM Approach

Greetings

Grab any blown PC powersupply and you can salvage at least one toroid, somes
times three from it that will make a nice current transformer.

Have used these on heat pump compressors to monitor the amps. Used a AST
386SX-20 laptop and a wire wraped Maxim 186 or 7 ADC chip to the printer
port. 0 - 4.096 volts in gives 0 to 4096 counts per conversion cycle. 1 or
8 channel imput.

I stripped the windings and replaced with wirewrap wire for the secondary
winding. Dip the toriad in the tool handle dip several times for some extra
insurance. Salvaged a schocky diode from the same powersupply for the AC to
DC rectifier.

Installed them by just unhooking the wires from the contactor and running
the wire through them. For low amps or to scale the amps to a common factor
just make more loops through with the primary.

You could use the existing windings if you can count them. I calibrated
them by reading the amps on an amprobe.

I got the idea from a several years old Circut Cellar Ink magazine article.

Hugh

----- Original Message -----
From: Jon Elson <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, July 30, 2001 1:26 PM
Subject: Re: [CAD_CAM_EDM_DRO] Another EDM Approach


> Alexandre Guimarães wrote:
>
> > Hi,
> >
> > > I had wondered whether it would be possible to pick up enough current
for
> > > sensing by wrapping a few turns of wire around the power wire to the
> > > electrode and limiting the voltage on this by using a fast zener diode
or
> > > something.
> >
> > What about a hall-effect sensor ? At the currents involved it would
be
> > probably bery effective and best of all, completely isolated from the
> > current path ! Allegro has some nice linear parts.
>
> hall effect devices are pretty good for sensing currents, but they are not
> fast. A bare hall device provides only a couple of mV of signal. Most
> amplified hall devices would be slow to respond to the kinds of pulses
> we are looking at. I think a current transformer might be a lot easier to
> get working properly.
>
> Jon
>
>
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