Re: micro wire-edm project (and software solution)

Dave in my times the silicon diode drop voltage was .7 volts. Hope
still the same
Jose

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<dave_mucha@y...> wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler"

<eexgs@n...>

> wrote:
> >
> >
> > > A current sense resistor has to be able to handle the total

current.

> > > diodes are cheap in comparison. They have a high voltage drop

which

> > > is not always a good thing, but can make monitoring the current

easy.

> > > But, did I mention they are cheap ?
> > >
> >
> > I am still a little confused as the voltage drop over a diode

will be

> > its forward voltage and that is not normally very large. The

voltage

> > drop will not be proportional to current and as you would still

need

> > to limit the current you could use the current limiting resister.
> >
> > > Many of the low end RC EDM machines use them as the sense

voltage

> > source.
> >
> > So they are not using them as a voltage references?
> >
> > I will probably measure gap voltage anyway to be quite honest and

if I

> > were to use a shunt it could be a tiny value, at the low intended
> > currents it would not need to be all that big or expensive.
> >
> > Graham
> >
>
>
> ummm..... I have to check the schematics. I know of at least two
> very widly known circuits that use diodes between the part and

ground

> and connect an op-amp or comparator across it.
>
>
> Dave
>