[sdiy] PCB / Panel Manufacture

Shawn Rakestraw shawn at epicpoolsga.com
Sat Feb 8 22:40:30 CET 2020

Here's a revision that improved things I believe. I'll stop bothering
everyone after this. I realize that my capacitor C1 label flew across the
board for some reason and I will fix that now.

I think I separated the ground planes like you were suggesting, Ingo. The
CT ground is on the bottom layer and connected to the other ground plane
through a single trace on the bottom.

I used the widest traces that I could. The positive rail will receive more
demand than the negative, so I'm not too worried about the negative traces
being slightly smaller. I didn''t need any vias after I reorganized the

[image: AC-DC Power Supply V1 Bot.jpg]
[image: AC-DC Power Supply V1 Top.jpg]

On Sat, Feb 8, 2020 at 3:09 PM Ingo Debus <igg.debus at gmail.com> wrote:

> > Am 08.02.2020 um 19:52 schrieb Shawn Rakestraw <shawn at epicpoolsga.com>:
> >
> > Thanks for pointing out the small via and acid trap, Vesa. I do not
> understand your comment about no thermals on the pads. Can you or someone
> else briefly describe what that means?
> Thermals, also called heat traps, make soldering easier. A pad inside a
> big copper plane (mostly a ground plane) is connected to that plane via
> four short traces rather than being just a part of the plane. You can heat
> up the solder joint without having to heat up the whole plane. I think I
> saw thermals on the pictures of your board. AFAIK Eagle places them
> automatically.
> > Ingo, I thought that I need all of my grounds connected to the center
> tap. If I separate them, the capacitors will form a "new" virtual ground
> for the DC output side?
> Sure there are different schools of thought, and if you ask n layouters
> you’ll get n+1 opinions :-)
> Of course all grounds have to be connected. But you can do this in
> different ways. Keep an eye on the currents flowing through the traces. In
> a power supply, the traces from the rectifier and the center tap of the
> transformer to the big electrolytics carry a hefty ripple current. The
> electrolytics are charged only during a short time around the peaks of the
> ac input voltage. No matter howthick these traces are, there’s always some
> voltage drop across them. This does not matter as long as these traces are
> not shared for other current paths.
> Ground planes, as on your layout, are a good thing. But it gets difficult
> to predict where the currents are flowing. So I like to keep the ripple-ly
> traces separate from the ground plane.
> Ingo
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[image: Our Website] <http://epicpoolsga.com/>
Shawn Rakestraw
shawn at epicpoolsga.com
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