Re: Simple question about cleaning up ground line

I hadn't thought about the static discharge issue - that's all I need is for
someone to scuff their feet, touch the test switch, and zap all of my eproms
at once :)

Thanks for the help!

-atw
----- Original Message -----
From: "Rodger Boots" <rlboots@cedar-rapids.net>
To: <rasterlist@synthcom.com>
Sent: Saturday, March 30, 2002 3:28 PM
Subject: Re: RASTER: Simple question about cleaning up ground line

> Half a volt of noise won't mean squat to a relay with 5 volts across the
> coil (a couple of volts MAYBE). Plus "noise" (a microsecond here, a
> millisecond there) is going to be ignored by the relay. Don't forget to
> put a diode across the coil. A capacitor wouldn't hurt either.
>
> To make the board work without the relay you could try a capacitor from
> the EPROM line to ground ON THE BOARD. About 10 uF should do it.
>
> The advantage of the relay is it also keeps static discharge off the
> EPROM input.
>
>
> Andrew Wilson wrote:
> >
> > Won't I have the same problem (noise on the switch gnd line causing the
> > relay to open/close)? Or is the relay automatically more resistant to
noise?
> >
> > -atw
> >
> > ----- Original Message -----
> > From: "Rodger Boots" <rlboots@cedar-rapids.net>
> > To: <rasterlist@synthcom.com>
> > Sent: Saturday, March 30, 2002 3:07 PM
> > Subject: Re: RASTER: Simple question about cleaning up ground line
> >
> > > Sometimes the "old school" ways are the best. Have your switch
control
> > > a relay on the board and let the relay ground the EPROM line. Radio
> > > Shack should have some really nice 5 volt relays.
> > >
> > >
> > > Andrew Wilson wrote:
> > > >
> > > > I have a problem that's almost embarassingly simple.
> > > >
> > > > I just finished up hacking my Gauntlet board to run both Gauntlet
and
> > > > Gauntlet II (basically, a bunch of the roms are replaced with
> > double-sized
> > > > roms, with the high address line attached to a switch that toggles
> > between
> > > > +5v and GND).
> > > >
> > > > So, essentially I have a circuit like the following:
> > > >
> > > > +5V ----/\/\/\/\/\-------X----[switch]----GND
> > > > 10k ohm
> > > >
> > > > 'X' is where I've attached the high address lines from my ROMs. This
> > works
> > > > great - when the switch is open, X is at 5V, and when the switch is
> > closed,
> > > > X is at GND. I've got this wired up so [switch] is actually the test
> > switch
> > > > for my JAMMA cab, and it works nicely.
> > > >
> > > > The problem is that the test switch on my JAMMA cab shares a ground
line
> > > > with the control panel. When I press buttons on the control panel,
it's
> > > > apparently introducing a little bit of noise into the ground line,
> > causing
> > > > the game to crash sporadically (since the high address line for the
ROMs
> > > > isn't remaining at a stable ground value).
> > > >
> > > > I'm trying desperately to remember my late-80s college electronics -
I
> > > > *think* I can put a capacitor in this circuit somewhere to smooth
out
> > any
> > > > noise on the GND line. I'm guessing that putting it between X and
ground
> > > > should do the trick (it'll act as if it's debouncing the [switch] to
> > smooth
> > > > out any momentary spikes in the ground line) - is this correct?
What's a
> > > > good value for the capacitor (I'm thinking something like .1
> > microfarads,
> > > > which gives me a RC time constant of 1 sec).
> > > >
> > > > Am I on the right track?
> > > >
> > > > Thanks again,
> > > >
> > > > -atw
> > > >
> > >
> >
> --------------------------------------------------------------------------
> > -
> > > > ** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE"
in
> > the
> > > > ** message body to rasterlist-request@synthcom.com. Please direct
other
> > > > ** questions, comments, or problems to neil@synthcom.com.
> > >
> >
> --------------------------------------------------------------------------
> > -
> > > ** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE"
in
> > the
> > > ** message body to rasterlist-request@synthcom.com. Please direct
other
> > > ** questions, comments, or problems to neil@synthcom.com.
> > >
> >
>
> --------------------------------------------------------------------------
-
> > ** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE" in
the
> > ** message body to rasterlist-request@synthcom.com. Please direct other
> > ** questions, comments, or problems to neil@synthcom.com.
>
> --------------------------------------------------------------------------
-
> ** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE" in
the
> ** message body to rasterlist-request@synthcom.com. Please direct other
> ** questions, comments, or problems to neil@synthcom.com.
>

---------------------------------------------------------------------------
** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE" in the
** message body to rasterlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Sat Mar 30 15:42:09 2002