Is this legal?
Hammy
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)?
Eeyore
Hammy wrote:
Unbelievable.
Graham
Phil Allison
"Hammy"
> This is a pic from an app-note from Microchip.
>
> http://i29.tinypic.com/5b193d.png
** You are kidding ?
Can you supply a link to the actual note ?
> 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)?
** It break every basic safety rule in the damn book.
Incredibly lethal.
Plus, would trip any ELCB ( aka GFI ) immediately it was plugged in.
Strewth !!!!!!!!!!!
........ Phil
Hammy
Yes I know.This is from the engineers from Microchip.Scary Eh?
As requested here is the full note.
Phil Allison
"Hammy"
> 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
** For the life of me, I cannot see any ( even twisted ) logic that gives
a sane purpose to that fuse.
Can you ?
...... Phil
Hammy
Well they say it's supposed to provide protection for incorrect outlet
wiring; line and neutral reversed.
John Larkin
Yup, the fuse will indeed blow if the house is wired improperly.
This is almost as goofy as the Pic architecture itself.
John
John Fields
---
Not necessarily outlet wiring, since they say:
"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, more than likely it's intended to protect the
downstream stuff, including the user, from mains hot accidentally
connected to the common portions (grounds) of the circuit.
--
JF
Ken Fowler
On 13-Mar-2008, Hammy <spa...@hotmail.com> wrote:
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> Subject: Is this legal?
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If you're lucky, the GFCI feeding the outlet might trip due to part of the
Neutral current being diverted to the Safety Ground. The really dangerous
result would occur if the AC plug or outlet feeding this device had the
grounded and ungrounded conductors reversed. This could connect the device
ground to the AC Line voltage - 120 VAC so that a user touching a metal
part of the device sharing that ground and the AC Line Ground (Earth or
Water Pipe or Conduit, etc.) might receive a shock. If the AC outlet
contains a GFCI, the shock might be limited to the ~5 mA trip current, but
the fuse would not likely fail. However, nothing in NEC rules stops a user
from making an improper connection between the non-grounded (Neutral)
conductor and the Safety Ground conductor. Good Luck if you do this.
Ken Fowler, KO6NO
Phil Allison
"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.
Seems you suffer from the same delusion of the innate benefit of fuses the
Microchip writer did.
...... Phil
Phil Allison
"Ken Fowler"
>
>> 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)?
>
> If you're lucky, the GFCI feeding the outlet might trip due to part of the
> Neutral current being diverted to the Safety Ground.
** It is certain to trip.
> The really dangerous
> result would occur if the AC plug or outlet feeding this device had the
> grounded and ungrounded conductors reversed. This could connect the
> device
> ground to the AC Line voltage - 120 VAC .....
** Nonsense - the device ground in on a separate pin.
> If the AC outlet
> contains a GFCI, the shock might be limited to the ~5 mA trip current, but
> the fuse would not likely fail.
** Nonsense - the fuse would immediately explode, as it is then
connected from active to ground.
> However, nothing in NEC rules stops a user
> from making an improper connection between the non-grounded (Neutral)
> conductor and the Safety Ground conductor.
** More nonsense !!!!
Safety earth must not be linked to a current carrying conductor in an
appliance.
Bloody ham.
...... Phil
mrda...@gmail.com
That is an interesting set of circuits.
Would these be safe circuits for a beginner to experiment with,
without the fuse of course?
Also, I think there's a typo in Figure 3. I'm pretty sure the top 25V
cap is 330 microfarads, not 330 millifarads...
Michael
Sjouke Burry
Those engineers need a 20 million dollar lawsuit, and a better
education.
Hammy
wrote:
I have no intention of doing this. I came across it while looking into
how to generate a cheap low power supply on the primary side of an
SMPS. I was curious as to whether are not it is even legal in any
developed countries.
The fuse would blow if you plugged that into an improperly wired
outlet; Line to ground dead short.
The way I think it's supposed to work is for load protection. The
circuit that's getting power from this supply uses the neutral line as
its ground, zero volt reference. So if you were to switch the lines
around the ground would be at the RC attenuated line voltage (AC)
assuming the load draws any current in this case. The zener wouldn't
regulate (likely fail) the polarized electrolytic would blow
overvoltage and reversed polarity take your pick. I did some
simulations on it switching the ground around which is the same as the
neutral conductor which is grounded at the utilities transformer C.T
and that's what happened. With the fuse there depending if it's fast
enough and where the AC line is at when you plug it in and the type of
load you have; it may save the load. I could be wrong but that's my
take on it.
But still even if the wiring is correct you're not supposed to be
pumping 40mA in this case into the safety ground. When it is
functioning correctly you have a neutral to safety ground short. If
your A/V systems hums check if you have any devices designed by
Microchip into the same branch as your stereo.
Phil Allison
"Hammy"
>>> http://i29.tinypic.com/5b193d.png
> I have no intention of doing this. I came across it while looking into
> how to generate a cheap low power supply on the primary side of an
> SMPS. I was curious as to whether are not it is even legal in any
> developed countries.
** Absolutely NOT !!
> The fuse would blow if you plugged that into an improperly wired
> outlet; Line to ground dead short.
>
**Correct.
> The way I think it's supposed to work is for load protection.
** Nonsense.
>The
> circuit that's getting power from this supply uses the neutral line as
> its ground, zero volt reference.
** WRONG - it uses the safety ground.
YOU are just as confused as the dope from Microchip.
The fuse protects NOTHING !!
> But still even if the wiring is correct you're not supposed to be
> pumping 40mA in this case into the safety ground.
** Correct.
It is a 100% LETHAL arrangement.
...... Phil
Hammy
<phila...@tpg.com.au> wrote:
>
>** WRONG - it uses the safety ground.
Right my mistake no need to get worked up about it.
> YOU are just as confused as the dope from Microchip.
Not quite that bad. I would never do that.
David L. Jones
I think the guy who designed this was on drugs while simultaneously
watching 2001: A Space Odyssey
Dave.
Phil Allison
"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
Paul E. Schoen
"Hammy" <spa...@hotmail.com> wrote in message
news:ll6it3p5cbsm4gmte...@4ax.com...
I thought this might be a forgery, but here is the same app note on the
official site:
http://ww1.microchip.com/downloads/en/AppNotes/91008b.pdf
Sometimes it is OK to use a transformerless power supply for a PIC. I have
done this for a voltage relay, which determines if line voltage is within a
certain permissible range, and it provides an output to the control
circuitry via an optoisolator. It is enclosed in a plastic octal relay
enclosure, and is externally fused at about 1 amp. It is important that the
capacitor is rated for across the line duty, but the small fuse limits any
major disaster, and the opto is rated at 2500 volts, so it is safe. There
is still some chance of failure, as always, but as long as the external
circuitry is grounded, or you use a GFCI, it is OK.
But, I have had problems with using a series capacitor (2 uF for 120 VAC,
two in series for 240 VAC), wherein an 18 ohm 1 watt series resistor
overheats, and the zener diode in series shorts out. At 60 Hz, the current
should be about 90 mA and less than 1/4 W. But a square wave of 240 VRMS
produces 800 mA and 12.8 watts in the resistor. I think the customer may
have used the test set on a generator or possibly an inverter supply, which
may have had considerable distortion and noise, so that is another
consideration for a circuit like this.
It's strange, but I recently did a simulation for this, and I did not get
much increase in current with a square wave. I will have to go back to the
circuit I used for that and see where the discrepancy may be. It is greatly
dependent on the rise time of the square wave.
I did an LTSpice simulation for the exact circuit proposed by Microchip,
and I get about 232 mA with a 120 VRMS square wave, which puts 2.5 watts
into the 47 ohm resistor.
But this is really an extreme condition. A square wave into a standard
switching power supply would also cause an overload. And a square wave with
800 uSec rise and fall puts out only 89 mA, or 0.37 watts in the 47 ohm
resistor.
Paul
ASCII file follows:
Version 4
SHEET 1 880 680
WIRE -192 128 -208 128
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WIRE -32 128 -80 128
WIRE -208 160 -208 128
WIRE -32 224 -32 192
WIRE 32 224 -32 224
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SYMBOL zener 320 336 R180
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WINDOW 0 24 72 Left 0
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SYMATTR Value UPSC600
TEXT -304 456 Left 0 !.tran 10s startup
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.
Phil Allison
"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.
** Geeez - now that explains everything !!!
ROTFLMAO ...
.... Phil
David L. Jones
Looks like he's been "promoted" to "Technical Fellow".
Dave.
Tim Wescott
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
Phil Allison
"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".
** 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
ehsjr
> "Hammy" <spa...@hotmail.com> wrote in message
> news:s25it3508vsbq2vla...@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).
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
John Fields
<phila...@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.
---
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.
--
JF
Phil Allison
"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.
> but by wiring in a fuse, like this:
** 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.
** What a MASSIVE BLATANT LIE.
What a fucking dishonest turd you are - Fields.
Classic symptom of congenital autism.
....... Phil
John Fields
<phila...@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.
---
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.
---
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.
---
Couldn't figure out the schematic, huh?
---
>Classic symptom of congenital autism.
---
Something I'm sure you've got a lot of experience with, having
struggled with it for so long...
--
JF
Hammy
That makes sense thanks for thethorough explanation.
NewsGroups
"Phil Allison" <phila...@tpg.com.au> wrote in message
news:63v8ohF...@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.
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.
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.
Do you suffer from anal leakage ?
John Fields
---
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
Paul E. Schoen
"John Fields" <jfi...@austininstruments.com> wrote in message
news:7tmlt3hq5aln6olmc...@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 :-)
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
Phil Allison
"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.
** 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.
** Christ, you are a gutless, wanking
PITA BLOODY IDIOT - Schoen.
........ Phil
Ken Fowler
On 14-Mar-2008, John Fields <jfi...@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.
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