Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Hi J,

--- In Homebrew_PCBs@yahoogroups.com, "J" <wyninejr@...> wrote:
>
> Does anyone have idea about how to attach an AC line to a PCB
board?
> I have a transformer that is actually on the board itself. Is
this a
> good/bad idea? Do I basically drill a whole and stick the wire
> through the hole and solder it one?

That will work, I've seen many pieces of equipment do that.
Normally you'd have a switch and fuse in series with "hot" line.

> I can't seem to find any
> connector type stuff on digikey. Also, I plan to have a floating
> ground on the other side of the transformer...i.e. electrical
> isolation.

Most connectors you find will be for connecting molded power cords.
Power cords with pig tails are usually soldered directly to
appropriate points -- switch, fuse, transformer, pads, etc.

> Should any grounded part of the board be connected to the
> netural line on the AC?

You should always ground the chassis of your equipment to earth
ground. The neutral line will be connected to earth ground at the
circuit breaker, so you don't need to connect it yourself; but many
will to make sure that the path to earth ground is as short as
possible.

If you're going to float your neutral, you should make whoever does
it jump through some hoops so you can avoid liability for
electrocuting someone.

> Should there is some kind of connection such
> as through a transient supressor?

Only if your circuit requires it.

> Any help is appreciated. Also,
> should there be any type of noise supression on the AC side of the
> board?

Only if your circuit requires it. There can be some high frequency
signals on the power line, so it really depends on what you're doing
with the AC line. If you're only using it for power, any filtering
your put on your DC supply should be sufficient to suppress any
noise on the AC line. If you're using the AC directly or stepping
it down, you may want to filter high frequency stuff.

On the other hand, if you're trying to use high frequency signals
superimposed on the AC line, you wouldn't want any
suppression/filtering...

>What about grounding planes on the AC side?

Ground planes and shielding are usually only required for high
frequency work. If you do need to shield your circuit, a ground
ring with breaks for signals to pass through will also work. The
breaks in the ground ring need to be calculated so the frequencies
you're trying to block can't easily pass through...

Regards,
Dennis