Homebrew PCBs

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?  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.  Should any grounded part of the board be connected to the 
netural line on the AC?  Should there is some kind of connection such 
as through a transient supressor?  Any help is appreciated. Also, 
should there be any type of noise supression on the AC side of the 
board?  What about grounding planes on the AC side?  Thanks!

Hi J,

I'm no expert, but I've gutted many devices for parts which were 
equipped with PCB-mounted transformers. I've got a small cable box 
here that I'm using for an enclosure, and am going to clone the board 
dimensions and probably re-use the xformer. Most of the stuff I've 
gotten has been the type with the bottom exiting pins. On the cable 
box, for instance, they just go straight down into the board (looks 
like about a .04-.06" thick single-sided), and the pads are average to 
medium sizes, with the exception of the ground lines, which drop 
directly into a large surrounding copper pour area. The hole sizes, of 
course, will likely be a bit larger.

You sound as if you're dealing with the type with the top exit wires, 
instead of pins. I've seen those on boards too, and they just drop 
through wherever they go, like the rest of the parts. That was usually 
on cheaper small stuff like clock radios. I'm guessing the pin style 
ones are preferred, but may be more expensive(?). I've got some 
massive ones from amps and monitors, which are also thru-hole mounted, 
directly to the single sided board, maybe with heavier pins. I think 
all of them use the two "mount ears" coming off the sides, and have 
screws protruding through the board into the metal chassis.

I guess your only real concerns are heat, current (no extra thin 
traces), and proper electrical placement. The cable boxes and stuff 
usually have them mounted near the rear, close to some vents in the 
back or top of the chassis.

Good Luck,

George

----- Original Message ----- 

From: "J" <wyninejr@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, February 19, 2006 3:04 AM
Subject: [Homebrew_PCBs] AC to PCB


> 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?  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.  Should any grounded part of the board be connected to the
> netural line on the AC?  Should there is some kind of connection such
> as through a transient supressor?  Any help is appreciated. Also,
> should there be any type of noise supression on the AC side of the
> board?  What about grounding planes on the AC side?  Thanks!

AC mains voltage, presumably. I'd put an IEC filtered connector on the 
enclosure, with suitable terminals on the PCB. I like the two part ones 
which plug together, like these:

< 
http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=30236&STK_PROD_CODE=M34159&XPAGENO=1 >

Leon 

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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

In a message dated 2/20/2006 1:35:13 P.M. Central Standard Time,  
wyninejr@... writes:

Does  anyone have idea about how to attach an AC line to a PCB  board?<<
Any good, solid, well-isolated soldered connection is  fine.  Common sense 
stuff!

I have a  transformer that is actually on the board itself.  Is this a 
good/bad  idea?<<
Very common practice.  Perfectly fine, if done  properly.

Do I  basically drill a whole and stick the wire through the hole and solder 
it  one?<<
That would be OK in situations where the board will be  mounted, and the 
AC-lines not flexed often, as they might be if an "AC  line-cord" is used here.
 

Should  any grounded part of the board be connected to the 
netural line on the  AC?<<
NO!

Should  there is some kind of connection such as through a transient 
supressor?   Any help is appreciated. <<
What KIND of connection do you mean, here?  Use of a  transient suppressor is 
fine.  That's what they are FOR.  But not  necessary in every case.  Depends 
on what you are doing!  Again,  "common sense" is a serious factor, here!

Also,  should there be any type of noise supression on the AC side of the  
board?  What about grounding planes on the AC side?   Thanks!<<
see the previous response. 
 
Be  careful!        Lotsa  luck!        Jan Rowland, Been there;  DONE that.


[Non-text portions of this message have been removed]

In article <dtd94k+6ej7@...>,
   dl5012 <dl5012@...> wrote:
> You should always ground the chassis of your equipment to earth 
> ground. 

Absolutley

> 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 I understand correctly what you are saying here the answer is no, no,
no.

You /must never/ connect the incoming neutral to earth within any piece of
equipment you build.

I have a picture of how I did it in Photos->Mickey. The AC cord comes
in from the left, you can kind of make out where the three leads go.

Mickey
 

--- 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?  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.  Should any grounded part of the board be connected to the 
> netural line on the AC?  Should there is some kind of connection such 
> as through a transient supressor?  Any help is appreciated. Also, 
> should there be any type of noise supression on the AC side of the 
> board?  What about grounding planes on the AC side?  Thanks!
>

small safety note

[snip]

> 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.


I think I must've misunderstood what you said. But after re-reading this
post a couple of times, what you said still sounds a bit dangerous. So let
me try to clarify a couple of points.

Whet talking about AC power, there are generally three lines - hot, neutral
and ground.

Hot is self-explanatory.

Neutral is, as the poster noted, connected to ground at the circuit breaker,
but that's THE ONLY PLACE where it should be connected. No "shortest path to
ground" argument applies here. This is probably the most basic rule that the
electricians who wired up your house had to follow if they had any hope of
the house passing the inspection. I am not sure what the poster meant by
"floating" the neutral, but if you "float" it, you won't have any current
flowing (unless you use the ground instead, which is a big no-no).

Ground exists for *safety* only. Under normal circumstances no current
should ever be present in that wire. If any current is present, something is
wrong. So, never connect it to anything but the case or the enclosure of
your project. (ok, that's a generalization, so there are exceptions, but it
is a pretty good and safe generalization to start with).

Vlad


--
Vlad's shop
http://www.krupin.net/serendipity/index.php?/categories/2-metalworking


[Non-text portions of this message have been removed]

Hi Vlad,

After thinking about it, you're right.  What I said about connecting 
neutral to earth ground was wrong.  It should only be connected at 
the panel.

Earth ground should be connected to the chassis so that would 
provide the shortest path for a short condition...

Sorry for the confusion...

Regards,
Dennis

--- In Homebrew_PCBs@yahoogroups.com, "Vlad Krupin" <vlad.cnc@...> 
wrote:
>
> small safety note
> 
> [snip]
> 
> > 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.
> 
> 
> I think I must've misunderstood what you said. But after re-
reading this
> post a couple of times, what you said still sounds a bit 
dangerous. So let
> me try to clarify a couple of points.
> 
> Whet talking about AC power, there are generally three lines - 
hot, neutral
> and ground.
> 
> Hot is self-explanatory.
> 
> Neutral is, as the poster noted, connected to ground at the 
circuit breaker,
> but that's THE ONLY PLACE where it should be connected. 
No "shortest path to
> ground" argument applies here. This is probably the most basic 
rule that the
> electricians who wired up your house had to follow if they had any 
hope of
> the house passing the inspection. I am not sure what the poster 
meant by
> "floating" the neutral, but if you "float" it, you won't have any 
current
> flowing (unless you use the ground instead, which is a big no-no).
> 
> Ground exists for *safety* only. Under normal circumstances no 
current
> should ever be present in that wire. If any current is present, 
something is
> wrong. So, never connect it to anything but the case or the 
enclosure of
> your project. (ok, that's a generalization, so there are 
exceptions, but it
> is a pretty good and safe generalization to start with).
> 
> Vlad
> 
> 
> --
> Vlad's shop
> http://www.krupin.net/serendipity/index.php?/categories/2-
metalworking

> 
> 
> [Non-text portions of this message have been removed]
>

What do you mean by IEC?  I'm going to use this one because this is 
an actual prototype for an upstart company.  After this baby is 
done, we're going to hook it up to an oscope and see how much costs 
we can eliminate.  For now this is what we are using:  
http://www.americanelectrical.com/pdfs/GreenBlock/T-212-350Mx.pdf

Once again, what kind of filter are you referring to and why should 
there be one.  Thanks!

jimmy

--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" 
<leon.heller@...> wrote:
>
> ----- Original Message ----- 
> From: "J" <wyninejr@...>
> To: <Homebrew_PCBs@...m>
> Sent: Sunday, February 19, 2006 3:04 AM
> Subject: [Homebrew_PCBs] AC to PCB
> 
> 
> > 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?  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.  Should any grounded part of the board be connected 
to the
> > netural line on the AC?  Should there is some kind of connection 
such
> > as through a transient supressor?  Any help is appreciated. Also,
> > should there be any type of noise supression on the AC side of 
the
> > board?  What about grounding planes on the AC side?  Thanks!
> 
> AC mains voltage, presumably. I'd put an IEC filtered connector on 
the 
> enclosure, with suitable terminals on the PCB. I like the two part 
ones 
> which plug together, like these:
> 
> < 
> http://www.rapidelectronics.co.uk/rkmain.asp?
PAGEID=80010&CTL_CAT_CODE=30236&STK_PROD_CODE=M34159&XPAGENO=1 >
> 
> Leon 
> 
> ---
> [This E-mail has been scanned for viruses but it is your 
responsibility 
> to maintain up to date anti virus software on the device that you 
are
> currently using to read this email. ]
>

----- Original Message ----- 

From: "J" <wyninejr@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, February 21, 2006 7:19 AM
Subject: [Homebrew_PCBs] Re: AC to PCB


> What do you mean by IEC?  I'm going to use this one because this is
> an actual prototype for an upstart company.  After this baby is
> done, we're going to hook it up to an oscope and see how much costs
> we can eliminate.  For now this is what we are using:
> http://www.americanelectrical.com/pdfs/GreenBlock/T-212-350Mx.pdf
>
> Once again, what kind of filter are you referring to and why should
> there be one.  Thanks!

IEC connectors are the three pin ones often used on computer equipment. They 
are available with mains filters built-in.

Leon 

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