Is this legal?

"Jon Slaughter"
The point there is to blow the fuse if the outlet is wired up backwards.
(replace N with L and you get a short to ground which will blow the fuse).

I have no idea why this matters except that the first diode to ground
would be shorted if the outlet is wired up wrong(hence that is the reason
for the fuse). But the circuit definitly could be improved by placing a
diode before the first diode so that if its wired up wrong it won't short
the diode... that or place another fuse there.

In any case its not really a good circuit and in some cases N is not g and
substantial current could flow. (I'm going by the note on why the fuse
exists and its easy to see why they added it to that circuit but makes no
sense why they made such a sorry circuit in the first place.
Click to expand...


** Geeez - now that explains everything !!!


ROTFLMAO ...




..... Phil
 
On Mar 14, 1:36 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:
"David L. Jones"



Yes I know.This is from the engineers from Microchip.Scary Eh?

As requested here is the full note.

http://www.e-sonic.com/whatsnew/Microchip/power/TB008.pdf

I think the guy who designed this was on drugs while simultaneously
watching 2001: A Space Odyssey

** Stan D'Souza ( the author ) was and still is Microchip's main
applications engineer.

His bio says educated at the University of Cincinnati, between '81 and
83 - most likely in computer engineering.

So he is probably about 46 years old.

......... Phil
Click to expand...
Looks like he's been "promoted" to "Technical Fellow".

Dave.
 
On Thu, 13 Mar 2008 11:48:59 +0000, Hammy wrote:

This is a pic from an app-note from Microchip.

http://i29.tinypic.com/5b193d.png

They are using a fuse between the neutral line and earth (safety)
ground. Among other things like ground loops wouldn't this also exceed
the max allowable amount of ground leakage (0.5mA)?
Click to expand...
That's impressive.

Not in any positive sort of way, but it is impressive.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
 
"David L. Jones"

** Stan D'Souza ( the author ) was and still is Microchip's main
applications engineer.

His bio says educated at the University of Cincinnati, between '81 and
83 - most likely in computer engineering.

So he is probably about 46 years old.


Looks like he's been "promoted" to "Technical Fellow".
Click to expand...

** Being a " technical fellow " is a position of high honour in firms like
Microchip and Microsoft.

Means one is considered to be a learned individual and a leading light in
the firm.

http://en.wikipedia.org/wiki/Technical_fellow




........ Phil
 
Jon Slaughter wrote:
"Hammy" <spamme@hotmail.com> wrote in message
news:s25it3508vsbq2vlabnd9igbav3nn5pij2@4ax.com...

This is a pic from an app-note from Microchip.

http://i29.tinypic.com/5b193d.png

They are using a fuse between the neutral line and earth (safety)
ground. Among other things like ground loops wouldn't this also exceed
the max allowable amount of ground leakage (0.5mA)?


The point there is to blow the fuse if the outlet is wired up backwards.
(replace N with L and you get a short to ground which will blow the fuse).
Click to expand...
Ok, so now the fuse is blown. But what difference does that
make? Leave the fuse out - what difference does it make??
The fuse does absolutely nothing to protect anything.

Ed


I have no idea why this matters except that the first diode to ground would
be shorted if the outlet is wired up wrong(hence that is the reason for the
fuse). But the circuit definitly could be improved by placing a diode before
the first diode so that if its wired up wrong it won't short the diode...
that or place another fuse there.

In any case its not really a good circuit and in some cases N is not g and
substantial current could flow. (I'm going by the note on why the fuse
exists and its easy to see why they added it to that circuit but makes no
sense why they made such a sorry circuit in the first place.
Click to expand...
 
On Fri, 14 Mar 2008 09:35:03 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"John Fields"

"Note that the neutral is connected to ground through a fuse. This
would guard against improper AC wiring."

That could also mean the AC wiring on the plug side, and while it
does both jobs,



** You failed to explain HOW it protects anyone or anything.
Click to expand...
---
Hmmm... OK.

First, let's look at an unisolated, ungrounded power supply
connected across the mains properly:

+--------+
LINE<------| SUPPLY |---+
+---+----+ |
| [LOAD]
| |
NEUT<----------+--------+

No problem.


Next, let's look at an unisolated, ungrounded power supply connected
across the mains backwards:

+--------+
NEUT<------| SUPPLY |---+
+---+----+ |
| [LOAD]
| |
LINE<----------+--------+

Still no problem, as far as the load is concerned.


Next, let's look at an unisolated, ungrounded power supply connected
across the mains properly, with a with a scope with an isolated
supply connected across the load:


SCOPE PROBE TIP
+--------+ /
LINE<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
NEUT<----------+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

Still no problem, as far as the load and/or the scope is concerned.


Finally, let's look at an unisolated, ungrounded power supply
connected across the mains backwards, with a scope with an isolated
supply connected across the load:


SCOPE PROBE TIP
+--------+ /
NEUT<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
LINE<----------+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

BIG problem since the scope shorts HOT to GND.


So, you ask, "How does the PIC supply protect against that
happening?"

It doesn't, but by wiring in a fuse, like this:


SCOPE PROBE TIP
+--------+ /
NEUT<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
LINE<--[FUSE]--+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

When the supply is connected to the mains backwards, as shown, the
fuse will blow, disconnecting LINE from everything. ---

Seems you suffer from the same delusion of the innate benefit of fuses the
Microchip writer did.
Click to expand...
---
Well, while it's usually not Kosher to let GND carry load current,
the Microchip writer did, at least, provide a method whereby it
would be less likely that an amateur would kill himself or his
equipment by making a simple wiring error.

--
JF
 
"John Fields"


( snip tedious red herrings)


So, you ask, "How does the PIC supply protect against that
happening?"

It doesn't,
Click to expand...

** Game over.

What a fucking dishonest turd you are - Fields.



but by wiring in a fuse, like this:
Click to expand...
** Got SFA to do with the point raised.

What a fucking dishonest turd you are - Fields.



Seems you suffer from the same delusion of the innate benefit of fuses
the
Microchip writer did.


Well, while it's usually not Kosher to let GND carry load current,
the Microchip writer did, at least, provide a method whereby it
would be less likely that an amateur would kill himself or his
equipment by making a simple wiring error.
Click to expand...

** What a MASSIVE BLATANT LIE.

What a fucking dishonest turd you are - Fields.

Classic symptom of congenital autism.




........ Phil
 
On Fri, 14 Mar 2008 23:18:17 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"John Fields"


( snip tedious red herrings)


So, you ask, "How does the PIC supply protect against that
happening?"

It doesn't,


** Game over.

What a fucking dishonest turd you are - Fields.
Click to expand...
---
Couldn't figure out the schematic, huh?
---

but by wiring in a fuse, like this:

** Got SFA to do with the point raised.

What a fucking dishonest turd you are - Fields.
Click to expand...
---
Couldn't figure out the schematic, huh?
---

Seems you suffer from the same delusion of the innate benefit of fuses
the
Microchip writer did.


Well, while it's usually not Kosher to let GND carry load current,
the Microchip writer did, at least, provide a method whereby it
would be less likely that an amateur would kill himself or his
equipment by making a simple wiring error.


** What a MASSIVE BLATANT LIE.

What a fucking dishonest turd you are - Fields.
Click to expand...
---
Couldn't figure out the schematic, huh?
---

Classic symptom of congenital autism.
Click to expand...
---
Something I'm sure you've got a lot of experience with, having
struggled with it for so long...

--
JF
 
On Fri, 14 Mar 2008 06:48:10 -0500, John Fields
<jfields@austininstruments.com> wrote:


Hmmm... OK.

First, let's look at an unisolated, ungrounded power supply
connected across the mains properly:

+--------+
LINE<------| SUPPLY |---+
+---+----+ |
| [LOAD]
| |
NEUT<----------+--------+

No problem.


Next, let's look at an unisolated, ungrounded power supply connected
across the mains backwards:

+--------+
NEUT<------| SUPPLY |---+
+---+----+ |
| [LOAD]
| |
LINE<----------+--------+

Still no problem, as far as the load is concerned.


Next, let's look at an unisolated, ungrounded power supply connected
across the mains properly, with a with a scope with an isolated
supply connected across the load:


SCOPE PROBE TIP
+--------+ /
LINE<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
NEUT<----------+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

Still no problem, as far as the load and/or the scope is concerned.


Finally, let's look at an unisolated, ungrounded power supply
connected across the mains backwards, with a scope with an isolated
supply connected across the load:


SCOPE PROBE TIP
+--------+ /
NEUT<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
LINE<----------+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

BIG problem since the scope shorts HOT to GND.


So, you ask, "How does the PIC supply protect against that
happening?"

It doesn't, but by wiring in a fuse, like this:


SCOPE PROBE TIP
+--------+ /
NEUT<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
LINE<--[FUSE]--+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

When the supply is connected to the mains backwards, as shown, the
fuse will blow, disconnecting LINE from everything. ---

Seems you suffer from the same delusion of the innate benefit of fuses the
Microchip writer did.

---
Well, while it's usually not Kosher to let GND carry load current,
the Microchip writer did, at least, provide a method whereby it
would be less likely that an amateur would kill himself or his
equipment by making a simple wiring error.
Click to expand...
That makes sense thanks for thethorough explanation.
 
"Phil Allison" <philallison@tpg.com.au> wrote in message
news:63v8ohF28re1uU1@mid.individual.net...
"John Fields"


( snip tedious red herrings)


So, you ask, "How does the PIC supply protect against that
happening?"

It doesn't,


** Game over.

What a fucking dishonest turd you are - Fields.
Click to expand...


Got your panties in a twist ?




but by wiring in a fuse, like this:

** Got SFA to do with the point raised.

What a fucking dishonest turd you are - Fields.
Click to expand...

Or did your boyfriend cheat on you ?



Seems you suffer from the same delusion of the innate benefit of fuses
the
Microchip writer did.


Well, while it's usually not Kosher to let GND carry load current,
the Microchip writer did, at least, provide a method whereby it
would be less likely that an amateur would kill himself or his
equipment by making a simple wiring error.


** What a MASSIVE BLATANT LIE.

What a fucking dishonest turd you are - Fields.
Click to expand...


Do you suffer from anal leakage ?




Classic symptom of congenital autism.




....... Phil
Click to expand...
 
On Fri, 14 Mar 2008 17:48:28 GMT, Hammy <spamme@hotmail.com> wrote:

On Fri, 14 Mar 2008 06:48:10 -0500, John Fields
jfields@austininstruments.com> wrote:


Hmmm... OK.

First, let's look at an unisolated, ungrounded power supply
connected across the mains properly:

+--------+
LINE<------| SUPPLY |---+
+---+----+ |
| [LOAD]
| |
NEUT<----------+--------+

No problem.


Next, let's look at an unisolated, ungrounded power supply connected
across the mains backwards:

+--------+
NEUT<------| SUPPLY |---+
+---+----+ |
| [LOAD]
| |
LINE<----------+--------+

Still no problem, as far as the load is concerned.


Next, let's look at an unisolated, ungrounded power supply connected
across the mains properly, with a with a scope with an isolated
supply connected across the load:


SCOPE PROBE TIP
+--------+ /
LINE<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
NEUT<----------+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

Still no problem, as far as the load and/or the scope is concerned.


Finally, let's look at an unisolated, ungrounded power supply
connected across the mains backwards, with a scope with an isolated
supply connected across the load:


SCOPE PROBE TIP
+--------+ /
NEUT<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
LINE<----------+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

BIG problem since the scope shorts HOT to GND.


So, you ask, "How does the PIC supply protect against that
happening?"

It doesn't, but by wiring in a fuse, like this:


SCOPE PROBE TIP
+--------+ /
NEUT<------| SUPPLY |---+ <-------+
+---+----+ | |
| [LOAD] [SCOPE]--+----+
| | | | |
LINE<--[FUSE]--+--------+ <-------+-----+ |
\ |
SCOPE PROBE GND |
|
GND<-----------------------------------------+

When the supply is connected to the mains backwards, as shown, the
fuse will blow, disconnecting LINE from everything. ---

Seems you suffer from the same delusion of the innate benefit of fuses the
Microchip writer did.

---
Well, while it's usually not Kosher to let GND carry load current,
the Microchip writer did, at least, provide a method whereby it
would be less likely that an amateur would kill himself or his
equipment by making a simple wiring error.

That makes sense thanks for thethorough explanation.
Click to expand...
---
Oops... I put the fuse in the wrong place:

Here's how Microchip has it wired:


+--------+
LINE<------| SUPPLY |---+
+---+----+ |
| |
| |
NEUT<--[FUSE]--+ [LOAD]
| |
| |
| |
GND<-----------+--------+

This not only causes load current to flow in the earth ground
connection, which is a no-no, it also connects ground and neutral of
everything else that's plugged into the same leg of the mains
together. That's very, very bad.


With the device connected backwards:


+--------+
NEUT<------| SUPPLY |---+
+---+----+ |
| |
| |
LINE<--[FUSE]--+ [LOAD]
| |
| |
| |
GND<-----------+--------+

The fuse will still blow and isolate everything downstream from
LINE, but because of the current sharing with earth ground when it's
connected "properly" I'd never use it or recommend that it be used.

Phil was right; this is a very bad circuit.

Thanks, Phil :)

--
JF
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:7tmlt3hq5aln6olmcibrkmel1ng984c065@4ax.com...
Here's how Microchip has it wired:


+--------+
LINE<------| SUPPLY |---+
+---+----+ |
| |
| |
NEUT<--[FUSE]--+ [LOAD]
| |
| |
| |
GND<-----------+--------+

This not only causes load current to flow in the earth ground
connection, which is a no-no, it also connects ground and neutral of
everything else that's plugged into the same leg of the mains
together. That's very, very bad.


With the device connected backwards:


+--------+
NEUT<------| SUPPLY |---+
+---+----+ |
| |
| |
LINE<--[FUSE]--+ [LOAD]
| |
| |
| |
GND<-----------+--------+

The fuse will still blow and isolate everything downstream from
LINE, but because of the current sharing with earth ground when it's
connected "properly" I'd never use it or recommend that it be used.

Phil was right; this is a very bad circuit.

Thanks, Phil :)
Click to expand...
Right. It should never have been proposed for any case in which the load
will be exposed to the user's world. In principle, it is OK when the PIC
can float on the line, and any external I/O is done with opto-isolators or
similar devices. And in such a case, the connection of line or neutral does
not matter, the fuse is not necessary, and the safety GND will only connect
to the user's enclosure.

I think I will discuss this on the Microchip forum:
http://forum.microchip.com/ This circuit is in their "Tips and Tricks"
document, and I think their tricky engineer was a bit tipsy when he
proposed this in this way.

Paul
 
"Paul E. Schoen"
"John Fields"
Phil was right; this is a very bad circuit.

Thanks, Phil :)

Right. It should never have been proposed for any case in which the load
will be exposed to the user's world. In principle, it is OK when the PIC
can float on the line, and any external I/O is done with opto-isolators or
similar devices. And in such a case, the connection of line or neutral
does not matter, the fuse is not necessary, and the safety GND will only
connect to the user's enclosure.
Click to expand...

** In principle, the scheme is totally ILLEGAL and likely to KILL someone.

Connecting the load from supply active to safety earth is the act of an
INSANE person.

Or, some damn fool who knows and cares nothing about electrical safety.

The fact that circuit has been on Microchip's site for about 8 years
suggests the author has enough authority in the firm to prevent it coming
down despite many complaints. If so, that makes him a criminal.

Note particularly that it has been referenced over 100 times on the internet
and is taken seriously by novices with PIC projects.



I think I will discuss this on the Microchip forum:
http://forum.microchip.com/ This circuit is in their "Tips and Tricks"
document, and I think their tricky engineer was a bit tipsy when he
proposed this in this way.
Click to expand...

** Christ, you are a gutless, wanking

PITA BLOODY IDIOT - Schoen.



......... Phil
 
On 14-Mar-2008, John Fields <jfields@austininstruments.com> wrote:

With the device connected backwards:


+--------+
NEUT<------| SUPPLY |---+
+---+----+ |
| |
| |
LINE<--[FUSE]--+ [LOAD]
| |
| |
| |
GND<-----------+--------+

The fuse will still blow and isolate everything downstream from
LINE, but because of the current sharing with earth ground when it's
connected "properly" I'd never use it or recommend that it be used.
Click to expand...
It's still unsafe to depend on the fuse and the GND wire. The worst case
is when the outlet is wired wrong so that Neut and Line are reversed AND
the GND is not connected (Think about a two-wire outlet with a three-prong
adapter.) In that case, the fuse will not blow, and any part of the
circuit which the user can touch is live. This circuit would need a
double-insulated case and a GFCI to be safe, in which case the fuse would
be unnecessary.

Ken Fowler, KO6NO
 
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