Re: Simple question about cleaning up ground line

Andrew Wilson wrote:
>
> So, essentially I have a circuit like the following:
>
> +5V ----/\/\/\/\/\-------X----[switch]----GND
> 10k ohm
>
> 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).

Does this happen only when the switch is in a certain position?

> 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

That won't do anything when the switch is closed, because the switch
will short the capacitor. (I'm assuming you're saying the cap is in
parallel with the switch. If it's in series with the switch then it
will act as a high-pass filter, which is the opposite of what you want.)

Maybe the cap should be between +5V and GND, connected to the GND end of
the switch and the +5V end of the resistor??
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Received on Sat Mar 30 18:22:12 2002