Is this legal?

[Hammy]

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)?

 

[Eeyore]

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)?

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]

On Thu, 13 Mar 2008 23:04:50 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"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


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

 

[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]

On Thu, 13 Mar 2008 23:31:28 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"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


Well they say it's supposed to provide protection for incorrect outlet

wiring; line and neutral reversed.

 

[John Larkin]

On Thu, 13 Mar 2008 13:17:57 GMT, Hammy <spamme@hotmail.com> wrote:

On Thu, 13 Mar 2008 23:31:28 +1100, "Phil Allison"
philallison@tpg.com.au> wrote:


"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


Well they say it's supposed to provide protection for incorrect outlet
wiring; line and neutral reversed.

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]

On Thu, 13 Mar 2008 13:17:57 GMT, Hammy <spamme@hotmail.com> wrote:

On Thu, 13 Mar 2008 23:31:28 +1100, "Phil Allison"
philallison@tpg.com.au> wrote:


"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


Well they say it's supposed to provide protection for incorrect outlet
wiring; line and neutral reversed.

---
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 <spamme@hotmail.com> wrote:

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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. 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

 

[Sjouke Burry]

Phil Allison wrote:

"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



Protect equipment at all costs, up to the live of the operator??

Those engineers need a 20 million dollar lawsuit, and a better
education.

 

On Mar 13, 8:46 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Thu, 13 Mar 2008 13:17:57 GMT, Hammy <spa...@hotmail.com> wrote:
On Thu, 13 Mar 2008 23:31:28 +1100, "Phil Allison"
philalli...@tpg.com.au> wrote:

"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

Well they say it's supposed to provide protection for incorrect outlet
wiring; line and neutral reversed.

Yup, the fuse will indeed blow if the house is wired improperly.

This is almost as goofy as the Pic architecture itself.

John

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

 

[Hammy]

On Thu, 13 Mar 2008 21:18:28 GMT, "Ken Fowler" <ko6no@yahoo.com>
wrote:

On 13-Mar-2008, Hammy <spamme@hotmail.com> wrote:

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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. 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

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]

On Fri, 14 Mar 2008 12:09:45 +1100, "Phil Allison"
<philallison@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.

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

 

[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

 

[David L. Jones]

On Mar 13, 11:18 pm, Hammy <spa...@hotmail.com> wrote:

On Thu, 13 Mar 2008 23:04:50 +1100, "Phil Allison"



philalli...@tpg.com.au> wrote:

"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

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

Dave.

 

[Paul E. Schoen]

"Hammy" <spamme@hotmail.com> wrote in message
news:ll6it3p5cbsm4gmtedgghjuuvuic0scf1q@4ax.com...

On Thu, 13 Mar 2008 23:04:50 +1100, "Phil Allison"
philallison@tpg.com.au> wrote:


"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


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 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:

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SYMATTR InstName R1
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SYMBOL diode -16 352 R180
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SYMATTR InstName D2
SYMATTR Value UPSC600
TEXT -304 456 Left 0 !.tran 10s startup

 

[Jon Slaughter]

"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).

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.