Re: Simple question about cleaning up ground line

Andrew Wilson wrote:
>
> Yeah, I wasn't very clear - I meant to put the cap between the EPROM address
> line and a ground line I brought up from the board, as Rodger suggested. You
> are correct, putting the cap between the EPROM address line and the ground
> line from the control panel (parallel to the switch) doesn't help me.

Why not just connect the switch itself to PCB GND instead of the noisy
GND?

> My other concern was that when the switch is open, the cap will charge up to
> 5V, but when you close the switch the cap will discharge very rapidly (won't
> it? There's no resistor in series with the cap). Will a cap hold up to this?

Good point. That's probably not ideal.

> The circuit will end up looking like this (with the cap connected to X)
>
> +5V ---/\/\/\/\/\/\/\/\--X----[switch]----<control panel gnd>
> |
> |
> +----[Capacitor]------<PCB gnd>

I think if you want to eliminate fluctuations in GND, you need the cap
between the GND and a stable reference point - like the +5V. ICs on
PCBs often have caps between their V supply and GND pins to keep the
voltage differential between them stable.
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Received on Sat Mar 30 19:22:36 2002