Re: Simple question about cleaning up ground line

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
> >
>
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Received on Sat Mar 30 15:32:11 2002