[sdiy] ground & power on pad-per-hole solder breadboard

[Jim Patchell]

    Grounding is almost more of an art than it is science.  At the very
least, you are headed in the correct direction.

    Creating a star connection on a PCB can be a big problem, because it
takes up lots of space.  In general, you only need a star when you a passing
"significant" amounts of current in the traces.  The deffinition of
"significant" is difficult to pin down, because, it depends on the
situation.

    Example of insignificant current: Current flowing into or out of an
op-amp input.  Even in bipolar parts, this current is down in the nano-amp
range.  These currents will not cause any significant voltage drop.

    Example of significant current: Current flowing  out of the ground pin
on a 555.  Even worse, it is not constant.  Another example of significant
current is the current flowing out of the ground pin of most logic chips.

    The main problem that drops in your ground may cause is when there is
something that can use that voltage as it's input.  Sometimes finding out
how these signals are being amplified by the circuit can be difficult.

    Also, another aspect to all this is proper bypassing, to get rid of the
voltage spikes.  To properly bypass the current on a chip, you need to
provide the shortest path possible between the bypass capacitor and the chip
being bypassed.  This, for the most part, can be difficult to do because the
power supply pins are generally positioned to make it difficult to put a
capacitor directly accross the pins.

    Anyway, this is a very big subject.  I am sure others will add their
thoughts to this as well.  People who specialize in EMC compliance (and, I
seem to recall we have a few on the list), would know a lot more about this
subject than I do.

    -Jim

Kenneth Martinez wrote:

> I started soldering a vco on a solder breadboard with a copper pad per
> hole...it doesn't have any copper ground or power busses, but I aligned
> the ICs and components so that leads could be connected to ground by
> soldering them to wires running in straight lines down the board between
> the rows of ICs and components, and then connecting these ground lines
> at the edges of the board.  For power, I'd planned to "daisy-chain" the
> + and - supplies for the 5 ICs, connecting IC1 to the board's power
> input, connecting IC2's power pins with short wires from IC1's power
> pins, etc.
>
> I'm wondering now if it would make any difference if I used a star
> arrangement to connect each IC directly to the board's power input?  And
> would it be better to run separate ground wires from some or all
> components to a central point instead of connecting them to those wires
> running down the board to simulate ground busses?