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'[EE] Dumb mistake report'
2006\04\22@201510 by Timothy Weber

face picon face
Perhaps a different kind of dumb mistake than the ones we were talking
about a while ago, but also related to the recent discussion of
over-voltage and reverse-voltage protection:

My two-year-old daughter likes to play in my office.  I give her a
breadboard and wires and some old chips, and we plug them in at random
and move them around.  See e.g. <http://tinyurl.com/hzaqr>.
Occasionally we wire up a LED, resistor, and switch to a 2xAA battery pack.

The point is to make her feel comfortable in that environment, and she
is.  Often she goes through my shelves and demands to know what every
part and tool is.  "I want... something... NEW," she says, staring up at
the parts drawers.  Pointing: "That drawer."  My plan is that eventually
she will start building increasingly complex projects on her own without
really noticing it, and then she will become a geek and have good job
prospects but no social life, so that she will be emotionally dependent
on me and I will be able to control her.  Or perhaps there could even be
a positive outcome; who really knows.

I digress.  Today I was talking on the phone and not paying close enough
attention.  I did notice when she had a screwdriver and was finding
screws to push it onto - she was perilously close to some live AC
outlets, so I put a stop to that and reminded her not to get near them
because they're very, very hot.  So I wasn't totally ignoring her.  And
when she looked at the voltage switch on my small variable-output
switching power supply and decided to move it, I was watching - but not
fast enough to catch her before she moved it from 3V to 12V.

That power supply was running a breadboard containing an XBee radio
module, which has a max Vcc of 3.4 V.

I immediately grabbed the supply and shut it off.  Gently told her that
I thought she had broken it (because I think she should know that sort
of thing), but that it wasn't her fault, but that she shouldn't move
switches without asking.  And vowed silently to turn ALL accessible AC
outlets OFF when she's playing, because there are far worse
possibilities than burned out chips.

Went and checked later: Yes, the XBee was done.  When I plugged it into
a different carrier board, I could smell the remnants of its magic smoke
and feel it getting way too warm.  Pulled it out fast and wrote a eulogy
on it with marker ("TOAST").  A $36 lesson.

On the plus side, the PIC (688) was unscathed - popped in another XBee
and the gadget worked fine.  Good old sturdy PICs!  By comparison, this
is the third piece of my 7-piece MaxStream dev kit to die, and the first
with an observed cause; both an XBee and the USB carrier board just
seemed to become bored with life at different points.  So it goes.
--
Timothy J. Weber
http://timothyweber.org

2006\04\22@204705 by Hector Martin

flavicon
face
Timothy Weber wrote:
> On the plus side, the PIC (688) was unscathed - popped in another XBee
> and the gadget worked fine.  Good old sturdy PICs!  By comparison, this
> is the third piece of my 7-piece MaxStream dev kit to die, and the first
> with an observed cause; both an XBee and the USB carrier board just
> seemed to become bored with life at different points.  So it goes.

I once wired a board up the wrong way, where the net result was that the
12V and 5V lines got shorted together. I didn't notice for a while,
until I saw it wasn't working right. Board had two PICs: a 16F877A PLCC
version, and a 16F876 DIP version. Some 74HCxx logic thrown around too.
The 876 went toast, but everything else survived. The 7805 that was
regulating the 5V line from the 12V one just got hot, but was otherwise
undamaged. Good thing too, since I really didn't want to resolder the
PLCC chip (the 876 was on a DIP socket).


--
Hector Martin (spam_OUThectorTakeThisOuTspammarcansoft.com)
Public Key: http://www.marcansoft.com/hector.asc

2006\04\23@082003 by Howard Winter

face
flavicon
picon face
Timothy,

On Sat, 22 Apr 2006 20:15:08 -0400, Timothy Weber wrote:

>...
> I did notice when she had a screwdriver and was finding
> screws to push it onto - she was perilously close to some live AC
> outlets, so I put a stop to that and reminded her not to get near them
> because they're very, very hot.

It still faintly astounds me that US mains sockets are completely unprotected - they're such an obvious place
for screwdrivers in little hands, that there must be a number of tragedies each year.  I realise that 110V is
less dangerous than 240, but it can still be fatal.  In a country that does so much to protect its children
(school busses, for example) this seems a curious omission.  Are shielded outlets even available as an option?

Cheers,


Howard Winter
St.Albans, England


2006\04\23@101417 by Herbert Graf

flavicon
face
On Sun, 2006-04-23 at 13:19 +0100, Howard Winter wrote:
> Timothy,
>
> On Sat, 22 Apr 2006 20:15:08 -0400, Timothy Weber wrote:
>
> >...
> > I did notice when she had a screwdriver and was finding
> > screws to push it onto - she was perilously close to some live AC
> > outlets, so I put a stop to that and reminded her not to get near them
> > because they're very, very hot.
>
> It still faintly astounds me that US mains sockets are completely unprotected - they're such an obvious place
> for screwdrivers in little hands,

Very few screwdrivers most people own are small and long enough to get
into the danger are. However, there are MANY other things in a home
which are.

> that there must be a number of tragedies each year.  

I've never heard a statistic, but I'm sure there are.

> I realise that 110V is
> less dangerous than 240, but it can still be fatal.  In a country that does so much to protect its children
> (school busses, for example) this seems a curious omission.  Are shielded outlets even available as an option?

Yes, but usually as a cover on the outlet.

I was very impressed with where Europe is on this issue these days.
Every extension cord I could find had a built in mechanism that blocked
the holes unless two pins were trying to get in. Very neat. I'm assuming
that's also part of the building code over there?

Generally most people over here, who have small children, plug covers
into unused outlets. They stick in there pretty tightly and I'm sure
they help. However, this will do nothing to prevent a child from pulling
a cord out of an outlet and then sticking something in. The fact that
our outlets aren't recessed make things even worse since a plug can be
part ways out of an outlet and yet still be in electrical contact.

Also, I'm not sure of all of Europe, but I know in some places houses,
as part of the code, have a house wide GFCI, I'd imagine that helps
reduce the chance of anyone dieing from electrocution. Is a house wide
GFCI common in all of Europe?

Thanks, TTYL

2006\04\23@102650 by olin piclist

face picon face
Howard Winter wrote:
> It still faintly astounds me that US mains sockets are completely
> unprotected

They're not.  Just like you can buy outlet covers where there are open slots
for the two power leads and a sortof round one for the ground, you can buy
various protected covers.  These usually require you to insert then twist
the plug.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2006\04\23@102654 by Timothy Weber
face picon face
Howard Winter wrote:
> Timothy,
>
> It still faintly astounds me that US mains sockets are completely unprotected - they're such an obvious place
> for screwdrivers in little hands, that there must be a number of tragedies each year.  I realise that 110V is
> less dangerous than 240, but it can still be fatal.  In a country that does so much to protect its children
> (school busses, for example) this seems a curious omission.  Are shielded outlets even available as an option?

Generally, anyone with small kids buys lots of little plastic caps that
plug into the outlets.  But, they're necessarily hard to remove, so you
tend to put them where the kid's going to be most of the time and not
where you're constantly plugging things in and out (e.g., a workbench).

How are they protected there?  I tried a quick Google but couldn't find
the right incantation.
--
Timothy J. Weber
http://timothyweber.org

2006\04\23@103850 by Wouter van Ooijen

face picon face
> I'm assuming that's also part of the building code over there?

not that I know

> Generally most people over here, who have small children, plug covers
> into unused outlets. They stick in there pretty tightly and I'm sure
> they help. However, this will do nothing to prevent a child
> from pulling
> a cord out of an outlet and then sticking something in. The fact that
> our outlets aren't recessed make things even worse since a plug can be
> part ways out of an outlet and yet still be in electrical contact.

Our newer plugs are all half isolated half metal, so when the plug is
plugged in deep enough to make contact you can't touch the metal any
more. This defeats my trick (IIRC 5y old): take a curtain hanger wire
piece, it is S-shaped, the bends are exactly at plug-pin distance, put
it the plug pins for which it seems to be designed, and plug in.

We use a lot of stick-on outlet protectors, which require that you push
the plug into the 1mm depth of the protector holes, turn 90 degress
(sorry, don't know the imperial equivalent) and the press through into
the outlet itself.

> Is a house wide GFCI common in all of Europe?

I don't even know what it is.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\04\23@111846 by Rolf

face picon face
Herbert Graf wrote:
{Quote hidden}

I have lived in the UK, and South Africa. I am more familiar with SA's
electrical systems, but I believe the UK has similar fail-safes. Yes,
you can get GFI (Ground Fault Interrupt) protected switches in Canada
(where I live now....), and the US. People are very familiar with them
because they are in almost every bathroom in North America with a "test"
and "reset" switch. In South Africa the complete house's supply is
protected the same way. The mechanism is pretty simple, yet very effective.

It works by comparing the current in the "hot" wire to that in the
neutral. If they don't sum to zero it "trips" the complete houses power
supply... the assumption being that all well-behaved circuits should
only return current through the neutral wire, and any missing current is
"leakage". In South Africa this switch is thus called the Earth Leakage,
or just the "Earth". The earth "trip" switch is very fast acting, and I
am sure has saved many many lives. It appears that South Africa was the
pioneer of this technology.... go figure:

http://www.cbi.co.za/papers/26/CBI4.pdf

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


Rolf

2006\04\23@122101 by Peter van Hoof

face picon face


--- Wouter van Ooijen <.....wouterKILLspamspam@spam@voti.nl> wrote:

[snip]
>
> > Is a house wide GFCI common in all of Europe?
>
> I don't even know what it is.
>
[snip]

US: GFCI=ground fault circuit interruptor (also GFI)
Dutch: Aardlek-schakelaar

There are three different ways they are applied. The most common being
built in an outlet (sometimes looped to additional outlets that are
also protected). There are devices such as a hairdrier that have them
built in the plug and finally the least common the housewide systems
where the main line coming into the house has one built in that
provides protection to the whole house.

Peter van Hoof


2006\04\23@122420 by Howard Winter

face
flavicon
picon face
Herbert,

On Sun, 23 Apr 2006 10:15:55 -0400, Herbert Graf wrote:

> On Sun, 2006-04-23 at 13:19 +0100, Howard Winter wrote:
>...
> > Are shielded outlets even available as an option?
>
> Yes, but usually as a cover on the outlet.

OK, but that needs a positive act - placing the cover in place - to be safe, and if the little person pulls
out an existing plug/cable, the socket is then open, obviously.

> I was very impressed with where Europe is on this issue these days.
> Every extension cord I could find had a built in mechanism that blocked
> the holes unless two pins were trying to get in. Very neat. I'm assuming
> that's also part of the building code over there?

I don't know about Continental Europe, but in the UK plugs and sockets have to conform to BS 1363, which
specifies various safety aspects.  About 12 years ago it was updated to include having shielding on the outer
half of the live & neutral pins, so if a plug is partially pulled out there can be no contact with the live
pins.  Sockets have shields blocking the live and neutral entries, which are either retracted by the Earth pin
(which is longer so always enters first) or in some designs will be retracted only by both L&N pins being
inserted together - pushing something into one side will not open it.  Extension sockets have to comply with
the same standards as installed ones.

> Generally most people over here, who have small children, plug covers
> into unused outlets. They stick in there pretty tightly and I'm sure
> they help. However, this will do nothing to prevent a child from pulling
> a cord out of an outlet and then sticking something in. The fact that
> our outlets aren't recessed make things even worse since a plug can be
> part ways out of an outlet and yet still be in electrical contact.

Ours aren't recessed, but with half-shielded pins the protection amounts to the same.  Also because the cable
enters at the bottom, pulling it doesn't tend to pull the plug out, so part-inserted plugs aren't often an
issue.

> Also, I'm not sure of all of Europe, but I know in some places houses,
> as part of the code, have a house wide GFCI, I'd imagine that helps
> reduce the chance of anyone dieing from electrocution. Is a house wide
> GFCI common in all of Europe?

Again I don't know about the Continent, but in the UK the latest standards say that any socket which could be
used to supply outside appliances (electric lawnmowers, hedge-trimmers, etc) must have protection by a
Residual Current Device (RCD), which trips if there is an imbalance of current between Live & Neutral of more
than 30mA.  Some people take this to mean any downstairs socket, although that isn't in the standard.  
Whole-house RCDs are thought to be a Bad Thing because that would take the lights out, which may cause more
danger.  So the usual way to do it is to have a split Consumer Unit, where half of the circuits are RCD
protected, and half not.  Typically the lighting circuits, upstairs sockets, and electric cookers would be off
the RCD, and fridge/freezers too if the wiring can be made to allow for it (so a nuisence trip wouldn't result
in ruined food if it happens when the occupiers are away).

Cheers,


Howard Winter
St.Albans, England


2006\04\23@122543 by Sean Schouten

face picon face
On 4/23/06, Herbert Graf <mailinglist2spamKILLspamfarcite.net> wrote:
>
> Is a house wide GFCI common in all of Europe?
>

It is in the Netherlands (dutch law has become very strict with such
matters) and I would imagine the rest of Europe with the modern
EU-legislation, in modern buildings anyway. We call it an GFCI "aardlek
schakelaar" in dutch.

Sean.

2006\04\23@122633 by Howard Winter

face
flavicon
picon face
Olin,

On Sun, 23 Apr 2006 10:26:46 -0400, Olin Lathrop wrote:

> Howard Winter wrote:
> > It still faintly astounds me that US mains sockets are completely
> > unprotected
>
> They're not.  Just like you can buy outlet covers where there are open slots
> for the two power leads and a sortof round one for the ground, you can buy
> various protected covers.  These usually require you to insert then twist
> the plug.

Right, but these aren't the usual ones you find, are they?  I've seen a number of homes in the US, and I've
never seen sockets like these.

Cheers,


Howard Winter
St.Albans, England


2006\04\23@123546 by Howard Winter

face
flavicon
picon face
Timothy,

On Sun, 23 Apr 2006 10:26:52 -0400, Timothy Weber wrote:

> Howard Winter wrote:
> > Timothy,
> >
> > It still faintly astounds me that US mains sockets are completely unprotected - they're such an obvious
place
> > for screwdrivers in little hands, that there must be a number of tragedies each year.  I realise that 110V
is
> > less dangerous than 240, but it can still be fatal.  In a country that does so much to protect its
children
> > (school busses, for example) this seems a curious omission.  Are shielded outlets even available as an
option?
>
> Generally, anyone with small kids buys lots of little plastic caps that
> plug into the outlets.  But, they're necessarily hard to remove, so you
> tend to put them where the kid's going to be most of the time and not
> where you're constantly plugging things in and out (e.g., a workbench).

Right, but as I said to Herbert, these aren't fail-safe - you have to buy them and insert them in all empty
sockets.  Murphy says that the one you forget is the one where the problem happens!  :-)

> How are they protected there?  I tried a quick Google but couldn't find
> the right incantation.

Since it's built-in to the sockets, it's not easy to see the mechanism.  I'll see if I can find a useful
picture...

OK, this: http://www.tlc-direct.co.uk/Images/Products/size_3/BG922.JPG doesn't show it terribly clearly, but
you should be able to see the grey-coloured shutter which closes the lower two holes, and the ramp in the
upper (Earth) hole.  When the (longer) Earth pin enters, it pushes the ramp down which opens the lower holes
for the Live/Neutral pins.  Here's an example of a plug:  
http://www.tlc-direct.co.uk/Images/Products/size_3/TLPT13.JPG

Cheers,


Howard Winter
St.Albans, England


2006\04\23@130002 by olin piclist

face picon face
Peter van Hoof wrote:
> There are three different ways they are applied. The most common being
> built in an outlet (sometimes looped to additional outlets that are
> also protected). There are devices such as a hairdrier that have them
> built in the plug and finally the least common the housewide systems
> where the main line coming into the house has one built in that
> provides protection to the whole house.

A fourth and fairly common scheme here is GFI circuit breakers for
individual circuits.  These fit in place like ordinary circuit breaker but
cost somewhat more and trip on a ground fault in addition to excess current.
I've used them on some new circuits I installed in the basement.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2006\04\23@133100 by Wouter van Ooijen

face picon face
> Dutch: Aardlek-schakelaar

OK, I know those :)

In the past we used to have one for the wet-area groups only. In newer
installations you will find one or more, covering all groups. Placed on
the main fuse panel.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\04\23@133309 by Howard Winter

face
flavicon
picon face
Olin,

On Sun, 23 Apr 2006 12:59:59 -0400, Olin Lathrop wrote:

{Quote hidden}

We have those too, known as "RCBO" (Residual Current Breaker, Overcurrent) but they are quite rarely used
because they are darned expensive!  If you replaced all the Miniature Circuit Breakers with RCBOs, you'd
probably multiply the parts-cost by 5 to 8 times.  It's the neatest solution, because it only shuts down the
circuit with the problem, but most people wouldn't want to pay the extra, and most electricians wouldn't
recommend it.

Cheers,


Howard Winter
St.Albans, England


2006\04\23@134841 by Timothy Weber

face picon face
Howard Winter wrote:
> Right, but as I said to Herbert, these aren't fail-safe - you have to buy them and insert them in all empty
> sockets.  Murphy says that the one you forget is the one where the problem happens!  :-)

Absolutely true.

> Since it's built-in to the sockets, it's not easy to see the mechanism.  I'll see if I can find a useful
> picture...

Ah, I get it!  Clever and simple.

Now, why we don't do something similar I couldn't say, other than that
it may have to do with Newton's First Law...
--
Timothy J. Weber
http://timothyweber.org

2006\04\23@140900 by Bob Axtell

face picon face
Howard Winter wrote:
> Timothy,
>
> On Sat, 22 Apr 2006 20:15:08 -0400, Timothy Weber wrote:
>
>  
>> ...
>> I did notice when she had a screwdriver and was finding
>> screws to push it onto - she was perilously close to some live AC
>> outlets, so I put a stop to that and reminded her not to get near them
>> because they're very, very hot.
>>    
>
> It still faintly astounds me that US mains sockets are completely unprotected - they're such an obvious place
> for screwdrivers in little hands, that there must be a number of tragedies each year.  I realise that 110V is
> less dangerous than 240, but it can still be fatal.  In a country that does so much to protect its children
> (school busses, for example) this seems a curious omission.  Are shielded outlets even available as an option?
>
>  
We use GFI outlets. They look like regular outlets but have a fault
detector which checks for an unbalanced line, even a few uA of a short
(child with a screwdriver) will trip the device. Very reliable and even
include a convenient test button, which forces a trip (at 2uA, if I recall).
They can deliver 10A easily yet protect instantly. I have 'em all over
the house.

--Bob

> Cheers,
>
>
> Howard Winter
> St.Albans, England
>
>
>  

2006\04\23@152408 by David VanHorn

picon face
>
>
> Generally, anyone with small kids buys lots of little plastic caps that
> plug into the outlets.  But, they're necessarily hard to remove, so you
> tend to put them where the kid's going to be most of the time and not
> where you're constantly plugging things in and out (e.g., a workbench).


As a child, back in the bad old days, I used to pull bits of wire from the
windowscreens (aluminum?) and insert into the outlets, shoving it home with
a stick.

Made a satisfying zap.

I don't ever remember being shocked, but I knew that was a possibility at
the time.

2006\04\23@154135 by Timothy Weber

face picon face
David VanHorn wrote:
>>
> As a child, back in the bad old days, I used to pull bits of wire from the
> windowscreens (aluminum?) and insert into the outlets, shoving it home with
> a stick.
>
> Made a satisfying zap.
>
> I don't ever remember being shocked, but I knew that was a possibility at
> the time.

Those who survive, become EEs.  ;)
--
Timothy J. Weber
http://timothyweber.org

2006\04\23@155834 by Peter

picon face


On Sun, 23 Apr 2006, Timothy Weber wrote:

{Quote hidden}

There is a clever plastic tongue inside that covers both holes and can
only be shifted if both prongs go in at the same time. Sometimes it is
acuated by the body (laterally). Also most protected repceptacles are
made such that the body is inside the plastic rim before any prongs
touch inside. This removes the possibility of (tiny) fingers across the
prongs feeling for the hole. I know this because when I was a kid they
did not have that feature yet and I found out that it is very unpleasant
to insert a plug blindly with a finger across the prongs to feel for the
holes. This is also why 'euro' 2-prong plugs have part of the prongs
covered in plastic.

Peter

2006\04\23@162041 by Wouter van Ooijen

face picon face
> As a child, back in the bad old days, I used to pull bits of
> wire from the
> windowscreens (aluminum?) and insert into the outlets,
> shoving it home with
> a stick.

onto the daddy-did-this-but-don't-try-this-yourselves section? when I
was young (8y?) we dug what called trapholes, 30 cm deep :), but we
lined them with the innards from the big elco's you could find in
television sets. I heared that that suff was irritation - so it must be
good stuff to line a traphole with.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\04\23@164422 by Randy Glenn

picon face
Apparently in Ontario (not sure about elsewhere) the electrical code
now requires these newfangled Arc Fault Circuit Interrupters for all
new dwelling areas:

http://en.wikipedia.org/wiki/Arc-fault_circuit_interrupter

I'm not sure if it's in the code or not, but it was recommended to us
that a different colour wire be used for AFCI-protected circuits. Blue
14/2 is a touch on the expensive side.

Still, during installation of a light fixture (my dad likes to do this
with the circuit on but the switch off) neutral and ground wound up
shorting and the unit tripped.

On 4/23/06, Bob Axtell <.....engineerKILLspamspam.....cotse.net> wrote:
{Quote hidden}

> -

2006\04\23@175950 by Dave Lag

picon face
Randy Glenn wrote:
> Apparently in Ontario (not sure about elsewhere) the electrical code
> now requires these newfangled Arc Fault Circuit Interrupters for all
> new dwelling areas:
>
> en.wikipedia.org/wiki/Arc-fault_circuit_interrupter
>
> I'm not sure if it's in the code or not, but it was recommended to us
> that a different colour wire be used for AFCI-protected circuits. Blue
> 14/2 is a touch on the expensive side.
>
> Still, during installation of a light fixture (my dad likes to do this
> with the circuit on but the switch off) neutral and ground wound up
> shorting and the unit tripped.
>

I wanted to verify this with the extremely good electrical_wiring_faq,

http://www.faqs.org/faqs/electrical-wiring/

sadly, it doesn't seem to have been updated since 2004.
:(

D

2006\04\23@180514 by Philip Pemberton

face picon face
In message <EraseME14e9333f0604230925m8808a15l9f876aa4e53a785fspam_OUTspamTakeThisOuTmail.gmail.com>>          "Sean Schouten" <dev.seantechspamspam_OUTgmail.com> wrote:

> It is in the Netherlands (dutch law has become very strict with such
> matters) and I would imagine the rest of Europe with the modern
> EU-legislation, in modern buildings anyway. We call it an GFCI "aardlek
> schakelaar" in dutch.

In the UK they're usually known as RCDs - Residual Current Devices, or (less
commonly) RCCBs - Residual Current Circuit Breakers. They were at one point
called ELCBs (Earth Leakage Circuit Breakers) which says a lot more about how
they work than "RCD". That said, I suppose RCD is a little less of a mouthful
than ELCB or RCCB.

So many names for the same basic thing...

--
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2006\04\23@180514 by Philip Pemberton

face picon face
In message <KILLspam200604231624.k3NGOK8k002337KILLspamspamfort-point-station.mit.edu>>          "Howard Winter" <RemoveMEHDRWTakeThisOuTspamH2Org.demon.co.uk> wrote:

> Whole-house RCDs are thought to be a Bad Thing because that would take the
> lights out, which may cause more
> danger.  So the usual way to do it is to have a split Consumer Unit, where
> half of the circuits are RCD
> protected, and half not.

That's not the case in this house (9 years old, new-build, built by Barratt -
say no more).

We found out a few weeks after we moved in (and got all the mess dealt with)
that if a lightbulb blows, it'll trip the RCD. This is incredibly annoying
when the kitchen spotlight blows out at 11:00 at night, in the middle of
winter, when you really want a cup of tea before bed, and instead you end up
having to make a midnight trek to the garage to reset the %#$*ing breaker.
Not to mention having to reset the VCR and all the alarm clocks. Guess how I
know this.

It's even more annoying if the computers are running...

All comes with the territory I guess.

--
Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
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http://www.philpem.me.uk/     | Tiger: Toshiba SatPro4600 Celeron700 256M+40G

2006\04\23@180839 by Philip Pemberton

face picon face
In message <000001c66713$63c767d0$0b00a8c0@PAARD>
         "Wouter van Ooijen" <TakeThisOuTwouterEraseMEspamspam_OUTvoti.nl> wrote:

> onto the daddy-did-this-but-don't-try-this-yourselves section? when I
> was young (8y?) we dug what called trapholes, 30 cm deep :), but we
> lined them with the innards from the big elco's you could find in
> television sets. I heared that that suff was irritation - so it must be
> good stuff to line a traphole with.

Somewhere in the Netherlands, Wouter's trapholes are polluting an underground
aquifer somewhere, unbeknownst to nearby residents....

:)

--
Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
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2006\04\23@203626 by Timothy Weber

face picon face
Philip Pemberton wrote:
> In message <200604231624.k3NGOK8k002337EraseMEspam.....fort-point-station.mit.edu>> >           "Howard Winter" <EraseMEHDRWspamH2Org.demon.co.uk> wrote:
>
> We found out a few weeks after we moved in (and got all the mess dealt with)
> that if a lightbulb blows, it'll trip the RCD. This is incredibly annoying
> when the kitchen spotlight blows out at 11:00 at night, in the middle of
> winter, when you really want a cup of tea before bed, and instead you end up
> having to make a midnight trek to the garage to reset the %#$*ing breaker.
> Not to mention having to reset the VCR and all the alarm clocks. Guess how I
> know this.
>
> It's even more annoying if the computers are running...

I feel your pain.  My parallel experience is that a faulty GFI [RCD]
breaker kept blowing and filling my basement up with water... The
solution was just to replace it, but at least during diagnosis I had an
excuse to build a little PIC project: <http://timothyweber.org/sumpalarm>.
--
Timothy J. Weber
http://timothyweber.org

2006\04\23@212649 by Howard Winter

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flavicon
picon face
Phil,

On Sun, 23 Apr 2006 23:04:53 +0100, Philip Pemberton wrote:

>...
> In the UK they're usually known as RCDs - Residual Current Devices, or (less
> commonly) RCCBs - Residual Current Circuit Breakers. They were at one point
> called ELCBs (Earth Leakage Circuit Breakers) which says a lot more about how
> they work than "RCD". That said, I suppose RCD is a little less of a mouthful
> than ELCB or RCCB.
>
> So many names for the same basic thing...

Actually that's not quite right - ELCBs were the earliest form of the thing, and they actually measured the
current flowing in the Earth conductor at the meter-point, and tripped if it was significant.  This meant that
getting someone connected between a Live wire and an Earthed item such as the metal case of an appliance would
trip the breaker, but getting between a Live wire and a natural Earth, such as a water pipe, would not!  They
weren't used for very long, but they still exist in some houses rewired in the 1970s.  They are a separate
unit, not built into the CU, they are quite large, and the giveaway is that they have the main Earth cable
running through them (and they are probably labelled "ELCB" :-)  Apart from the possibility of not tripping
with some kinds or fault, they had a tendency to nuisence-trip during thunderstorms...

RCDs don't need an Earth because they measure the current balance between L & N, and are a much better
solution all round.

Cheers,


Howard Winter
St.Albans, England


2006\04\24@021228 by Randy Glenn

picon face
One of the more authoritative mentions I've been able to find is the
PEO (Association of Professional Engineers of Ontario):
http://www.peo.on.ca/publications/DIMENSIONS/marapr2002/PP02.pdf

The article mentions that the usage of AFCIs will be expanded in the
next revision of the electrical code, which is probably due out this
year or next.

On 4/23/06, Dave Lag <RemoveMEdavescomputerEraseMEspamEraseMErogers.com> wrote:
{Quote hidden}

> -

2006\04\24@045114 by Alan B. Pearce

face picon face
>How are they protected there?  I tried a quick Google
>but couldn't find the right incantation.

In the UK there are covers over the holes for the live and neutral, which
require a pin to be inserted into the earth socket to move them and allow
the pins in.

Also the live and neutral pins on the plug have insulation for about half
their length so that it is pretty well impossible to contact the metal part
of the pin once it is far enough into the socket to be in contact with the
connections. On items which are double insulated, and hence do not have an
earth connection, there will be a plastic earth pin on the plug to move the
shield in the socket.

The European connectors have similar insulation on the pins, but do not
necessarily have protection to stop probing the socket, as not all plugs
have earth pins. However the pins are much smaller than UK ones, so it is
more difficult to find something to poke into the socket.

The side effect of all this is that the European 2 pin connectors are on a
pi spacing that will fit a UK socket - so the trick is to get a pencil and
poke it into the earth pin to move the protector so you can get the European
plug in and get power on your laptop or whatever ...

2006\04\24@065155 by Howard Winter

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Bob,

On Sun, 23 Apr 2006 11:08:47 -0700, Bob Axtell wrote:
>...
> We use GFI outlets. They look like regular outlets but have a fault
> detector which checks for an unbalanced line, even a few uA of a short
> (child with a screwdriver) will trip the device. Very reliable and even
> include a convenient test button, which forces a trip (at 2uA, if I recall).
> They can deliver 10A easily yet protect instantly. I have 'em all over
> the house.

Right, that sort of thing is available here, but they are so expensive that you would never use them
throughout the house.   Checking a catalogue I have handy here, they are 10 to 15 times the price of a normal
socket.  The cheapest ones I could find are UK£18.75 (say US$32) for a twin socket!

That was something I noticed when I was in Home Depot over there, your twin sockets were something like $0.85
in ones, and about a third of this in packs of ten, whereas ours start at about £1.25 ($2.20) for cheap ones,
up to about £3.45 ($6) for the best quality.  There are differences, of course - ours usually have a switch on
each socket, and the mechanism is mounted on the faceplate, rather than being separate as yours are (here's an
example: http://www.tlc-direct.co.uk/Images/Products/size_3/MKK2747.JPG ), but even so the costs are
dramatically higher here.  I'm really surprised they can make them to sell for 30c there - must be huge mass
production in action!  :-)

Cheers,


Howard Winter
St.Albans, England


2006\04\24@070430 by Howard Winter

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picon face
Phil,

On Sun, 23 Apr 2006 23:02:36 +0100, Philip Pemberton wrote:

{Quote hidden}

Ah yes, Barratt!  :-)  (for the non-Brits, this is a firm that mass-builds houses to a price, and they are
famous for producing really cheap houses...)  I'm not surprised the CU isn't the best available...

> We found out a few weeks after we moved in (and got all the mess dealt with)
> that if a lightbulb blows, it'll trip the RCD.

That's odd!  I've heard of MCBs tripping, due to the vapourised filament causing a current surge (usual
solution is to use a C-rated MCB rather than B-, which has a greater short-term overload capability), but I
can't see why an RCD should trip.  Are these low-voltage halogens?  I wonder if it's possible that the
electronic "transformer" is doing some sort of load-shedding to the Earth conductor?

> This is incredibly annoying
> when the kitchen spotlight blows out at 11:00 at night, in the middle of
> winter, when you really want a cup of tea before bed, and instead you end up
> having to make a midnight trek to the garage to reset the %#$*ing breaker.
> Not to mention having to reset the VCR and all the alarm clocks. Guess how I
> know this.

Is the garage attached to the house?  If not it's a strange place to put the CU.  Standard advice would be to
get it changed to a split CU with the lights and other circuits off the RCD... but initially perhaps you could
change that light unit - or are there multiple culprits?

> It's even more annoying if the computers are running...
>
> All comes with the territory I guess.

It shouldn't!  I'd be well annoyed if it kept happening to me.  Sadly we're now under Part P so you'll need to
get an electrician in if you do want the CU changed.  I'd guess a couple of hundred quid, minimum.

Cheers,


Howard Winter
St.Albans, England


2006\04\24@072158 by Howard Winter

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Timothy,

On Sun, 23 Apr 2006 20:36:26 -0400, Timothy Weber wrote:

{Quote hidden}

Are you sure that wasn't a burst pipe?  :-)))

> The solution was just to replace it, but at least during diagnosis I had an
> excuse to build a little PIC project: <http://timothyweber.org/sumpalarm>.

Excellent article!  I thought it looked like a smoke alarm from the first photo - I didn't realise it was a
cottage cheese carton :-)  Looks like a great solution.  I was going to suggest an addition, in the form of a
water-sensor towards the top of the sump, which would trigger a different alarm sound to indicate that the
pump was running but wasn't coping, but as you power the thing only when there's a power failure, that's not
feasible.  Neither was my other thought, a mobile-phone link so it could phone you when there's a problem
wherever you are at the time... I think that counts as overkill  :-)

Cheers,


Howard Winter
St.Albans, England


2006\04\24@075340 by Peter Todd

picon face
On Mon, Apr 24, 2006 at 02:12:28AM -0400, Randy Glenn wrote:
> One of the more authoritative mentions I've been able to find is the
> PEO (Association of Professional Engineers of Ontario):
> www.peo.on.ca/publications/DIMENSIONS/marapr2002/PP02.pdf
>
> The article mentions that the usage of AFCIs will be expanded in the
> next revision of the electrical code, which is probably due out this
> year or next.

I worked on a massive house renovation project last summer... Nearly was
the one who did all the wiring for the house, but the guy ran out of
money first... I can say for certain though that in most cases AFCI's
are now required for dwellings. There are exceptions, but as I recall
they are mandatory in bedrooms, bathrooms and kitchens.

Don't remember any mention about using different colored wire though,
sounds like a decent idea, though I assume the different color would be
the outer jacket, not the inner conductors.

--
peteSTOPspamspamspam_OUTpetertodd.ca http://www.petertodd.ca

2006\04\24@080303 by Alan B. Pearce

face picon face
>Neither was my other thought, a mobile-phone link so it
>could phone you when there's a problem wherever you are
>at the time... I think that counts as overkill  :-)

I have thought of doing this to send an SMS stating what the problem was
(burglary, fire, flood, etc) so one could phone a neighbour and get it
checked out when away on holiday.

2006\04\24@090708 by Timothy Weber

face picon face
Howard Winter wrote:
> Timothy,
>> I feel your pain.  My parallel experience is that a faulty GFI [RCD]
>> breaker kept blowing and filling my basement up with water...
>
> Are you sure that wasn't a burst pipe?  :-)))

<slaps forehead>  No wonder we had such a hard time fixing it!  :)

>> The solution was just to replace it, but at least during diagnosis I had an
>> excuse to build a little PIC project: <http://timothyweber.org/sumpalarm>.
>
> Excellent article!  I thought it looked like a smoke alarm from the first photo - I didn't realise it was a
> cottage cheese carton :-)

Thanks - I wasn't trying for a polished final product, but it doesn't
look too shabby in that top angle!

>  Looks like a great solution.  I was going to suggest an addition, in the form of a
> water-sensor towards the top of the sump, which would trigger a different alarm sound to indicate that the
> pump was running but wasn't coping, but as you power the thing only when there's a power failure, that's not
> feasible.  

The water sensor is the next logical addition, as it's more what we
really care about and would handle other root causes as well (hose
disconnected, too much volume, clogged pipe).

(Though the nice thing about the power loss indicator is that it can
warn you *before* the water rises to problem levels - if power loss is
the cause.)

> Neither was my other thought, a mobile-phone link so it could phone you when there's a problem
> wherever you are at the time... I think that counts as overkill  :-)

Definitely overkill.  I'll get started.  :)

No, we've gone through lots of phases and coping strategies with this
issue.  For a while, we knew that the pump didn't have enough capacity
to handle really big storms - say, one- or two-year events - but weren't
sure what to do about that.  So, I wrote a Windows system tray app that
would poll the regional climate data web page every hour just after it
was updated, parse out the amount of rainfall from the previous hour,
keep a running average, weight it somewhat to correspond with past
experience, and pop up a warning dialog on the desktop if it thought the
sump pump was going to be overtaxed.  Then I would know to go home and
start setting up the hand pump.

Hey, really solving the problem was going to require getting cold, wet,
and dirty... though eventually we did.  (And by 'we,' I mean my wife.)

Cheers.
--
Timothy J. Weber
http://timothyweber.org

2006\04\24@091016 by Timothy Weber

face picon face
Alan B. Pearce wrote:
>> Neither was my other thought, a mobile-phone link so it
>> could phone you when there's a problem wherever you are
>> at the time... I think that counts as overkill  :-)
>
> I have thought of doing this to send an SMS stating what the problem was
> (burglary, fire, flood, etc) so one could phone a neighbour and get it
> checked out when away on holiday.

A pretty simple, if expensive solution:
<http://www.sparkfun.com/commerce/product_info.php?products_id=280>

Throw a couple of speech chips at it and you could have it call the
neighbor directly!
--
Timothy J. Weber
http://timothyweber.org

2006\04\24@093157 by Howard Winter

face
flavicon
picon face
Alan,

On Mon, 24 Apr 2006 13:02:59 +0100, Alan B. Pearce wrote:

> >Neither was my other thought, a mobile-phone link so it
> >could phone you when there's a problem wherever you are
> >at the time... I think that counts as overkill  :-)
>
> I have thought of doing this to send an SMS stating what the problem was
> (burglary, fire, flood, etc) so one could phone a neighbour and get it
> checked out when away on holiday.

I wanted to do this as a car alarm.  For the Psion 3 I had (remember those?) you could get a link that would
connect to my Nokia Orange phone (remember those? :-) and it had software that would receive and send SMS
messages, and you could access those functions from home-written software so it would have been ideal.  Sadly
as time went on, the replacement equipment (Psion 5mx and Motorola "Time Port" phone) didn't have any of this,
so the idea died at that point.  A shame, but that's progress...

Cheers,


Howard Winter
St.Albans, England


2006\04\24@095729 by Alan B. Pearce

face picon face
>> I have thought of doing this to send an SMS stating what
>> the problem was (burglary, fire, flood, etc) so one could
>> phone a neighbour and get it checked out when away on holiday.
>
>A pretty simple, if expensive solution:
><http://www.sparkfun.com/commerce/product_info.php?products_id=280>
>
>Throw a couple of speech chips at it and you could have
>it call the neighbor directly!

I was thinking more along these lines - and it uses a PIC.

http://www4.tpg.com.au/users/talking/DialAlarm-1-Page1.html

although it is for a landline dialling application. There have also been
projects around for using a standard cell phone to do the same thing without
needing a GSM modem.

2006\04\24@112541 by Timothy Weber

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Alan B. Pearce wrote:
>> A pretty simple, if expensive solution:
>> <www.sparkfun.com/commerce/product_info.php?products_id=280>
>>
>> Throw a couple of speech chips at it and you could have
>> it call the neighbor directly!
>
> I was thinking more along these lines - and it uses a PIC.
>
> www4.tpg.com.au/users/talking/DialAlarm-1-Page1.html
>
> although it is for a landline dialling application.

I don't know why I was thinking about cell phones - a land line is
certainly available for my purposes!

Looks like a neat design - I shall peruse.  Thanks.
--
Timothy J. Weber
http://timothyweber.org

2006\04\24@115106 by Robert Ammerman

picon face
We do have some premium outlets and extension cords that have a little
spring loaded 'shutter' that covers the slots. You have to press a lever to
open the shutter before inserting the plug. This of course even handles the
case of pulling out a cord.

However, you more often see this in extension cords (where we do have a code
requirement for blocking unused outlets) than you do in fixed sockets.

The most common way manufacturers deal with blocking unused outlets on
extension cords is with a tight fitting plastic piece that plugs into the
slots.

Bob Ammerman
RAm Systems

{Original Message removed}

2006\04\24@193528 by Philip Pemberton

face picon face
In message <spamBeGone200604241104.k3OB4TWL017799STOPspamspamEraseMEfort-point-station.mit.edu>>          "Howard Winter" <KILLspamHDRWspamBeGonespamH2Org.demon.co.uk> wrote:

> Ah yes, Barratt!  :-)  (for the non-Brits, this is a firm that mass-builds
> houses to a price, and they are
> famous for producing really cheap houses...)  I'm not surprised the CU
> isn't the best available...

Still didn't stop the place going up quite markedly in value though. Probably
because over the past nine years, Dad's been slowly finding and fixing all
the little niggles.

> That's odd!  I've heard of MCBs tripping, due to the vapourised filament
> causing a current surge (usual
> solution is to use a C-rated MCB rather than B-, which has a greater
> short-term overload capability), but I
> can't see why an RCD should trip.  Are these low-voltage halogens?

240V/60W reflector spot bulbs actually. The ones shaped like CRTs with a
silver reflective coating on the inside. Not sure what the living room bulbs
are though.

> Is the garage attached to the house?

Yep.

> If not it's a strange place to put the CU.  Standard advice would be to
> get it changed to a split CU with the lights and other circuits off the
> RCD... but initially perhaps you could
> change that light unit - or are there multiple culprits?

Cheapest option was to just live with it.. One midnight trip every few months
isn't that bad, and it seems to be a roughly 1-in-4 chance that a bulb
blowing will trip the RCD in addition to the breaker. They certainly do a
good job of tripping the breakers on the lighting circuit though!

--
Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
EraseMEphilpemspamEraseMEdsl.pipex.com         | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G
http://www.philpem.me.uk/     | Tiger: Toshiba SatPro4600 Celeron700 256M+40G

2006\04\24@194546 by Philip Pemberton

face picon face
In message <@spam@200604241331.k3ODVuOJ014125@spam@spamspam_OUTfort-point-station.mit.edu>>          "Howard Winter" <spamBeGoneHDRWspamKILLspamH2Org.demon.co.uk> wrote:

> connect to my Nokia Orange phone (remember those? :-)

The 2110? I've got two of those :)
And a HP OmniGo 700LX palmtop - the one with the dock for the 2110, and a
built in Nokia Datacard modem.

These days I just use my Samsung V200 and an IrDA connection to my laptop.
Problem is, Virgin Mobile don't provide GPRS data, and when Huddersfield Uni
provide a free WiFi internet connection to students in the Computing and
Engineering department... well, there's just no point any more :)

I really don't like Samsung mobile phones though. My V200 has this rotten
tendency of completely losing the GSM signal and refusing to reconnect
without a power cycle. I also happen to know someone who had an E800 that
wouldn't make calls or send text messages.

Samsung should stick to what they do best - semiconductors.

If you want to play around with text message sending, get your mitts on a
Nokia 6210 and a DLR-3P data cable. You can send AT commands to the phone and
use it to send text messages or create dial-up data connections. Pretty old
tech these days, but still fun. You should be able to get a perfectly good
6210 for about £40 these days, or a fairly battered one for £20-£30. Like
most Nokias, they're built like tanks. Easy enough to scratch up the plastic,
but fairly hard to break by accident. Unless you sit on it.

--
Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
.....philpemspam_OUTspamdsl.pipex.com         | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G
http://www.philpem.me.uk/     | Tiger: Toshiba SatPro4600 Celeron700 256M+40G

2006\04\24@220459 by Jim Korman

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face
Timothy Weber wrote:
{Quote hidden}

<snip>
Not meaning to wag a finger or anything, but is an electronics bench
really safe for a two year old?

I didn't let my son around mine until he was about 6 or 7. By then I
knew that he understood that things could and should always be
considered dangerous. Even then we kept it at battery powered projects
for a while.

Just my $0.02US

Jim

BTW - Keep her interested.

2006\04\25@110807 by Russell McMahon

face
flavicon
face
> switching power supply and decided to move it, I was watching - but
> not
> fast enough to catch her before she moved it from 3V to 12V.

> Went and checked later: Yes, the XBee was done.

> On the plus side, the PIC (688) was unscathed - popped in another
> XBee
> and the gadget worked fine.  Good old sturdy PICs!  By comparison,
> this
> is the third piece of my 7-piece MaxStream dev kit to die, and the
> first
> with an observed cause; both an XBee and the USB carrier board just
> seemed to become bored with life at different points.  So it goes.

I once shorted a medium-high voltage power supply (can't recall -
probably 20V - 50V range) onto the ?5V? power supply rail of a
Motorola "D2 kit". This contained several dozen TTL and MOS ICs.
Processor, parallel ports, serial ports, glue, ... . The D2 stopped.

The IC's were all socketed. Murphy must have had an off day*. I marked
all the suspect ICs, took them all out, swapped in a set from another
D2, then successively swapped back in the ICs from the suspect set.
Every time the D2 stopped working again I put that IC aside and
continued. D2 repaired in gratifyingly little time.

The interesting (and relevant here) point was that the ICs that dies
all had 'power" capability. Anything that had little current sourcing
or sinking capacity lived. Anything that was able to drive 10 mA plus
died.

Interesting thought: The PIC breaks the above rule.



       RM


* odds are that for every problem solved by the sockets, 157 were
caused by bad contacts, so that Murphy won overall.
All things work together for good ... :-).


2006\04\25@111650 by Timothy Weber

face picon face
Jim Korman wrote:
> Not meaning to wag a finger or anything, but is an electronics bench
> really safe for a two year old?

It's a good question.  My current answer is yes, as long as I turn off
the power strip and supervise closely.  (Obviously I broke those rules
during the above story.)

> I didn't let my son around mine until he was about 6 or 7. By then I
> knew that he understood that things could and should always be
> considered dangerous. Even then we kept it at battery powered projects
> for a while.

Oh yes - batteries only for sure.

Right now the main thing we do is plug wires and (old) chips into a
breadboard, and look at other parts, pick things up with pliers, etc.
My impression is that she's already careful, bordering on a little
paranoid; of course no child is predictable at any age, let alone 2, but
for instance, she'll point to the pliers and look at me solemnly and
say, unprompted, "Only touch the red parts."  (Rubber grips - i.e., keep
fingers out of plier jaws.)  So I feel like her caution should be
rewarded with some slight responsibility.

And of course, I only let her use lead-free solder and a small 25W iron.  ;)

> BTW - Keep her interested.

I'll do my best!  I have a long way to go to repay the debt I owe *my*
father.
--
Timothy J. Weber
http://timothyweber.org

2006\04\25@115105 by David VanHorn

picon face
>
>
> And of course, I only let her use lead-free solder and a small 25W
> iron.  ;)


I'm surprised she has the dexterity to use a soldering iron at that age!


--
> Feel the power of the dark side!  Atmel AVR

2006\04\25@130300 by Timothy Weber

face picon face
David VanHorn wrote:
>>
>> And of course, I only let her use lead-free solder and a small 25W
>> iron.  ;)
>
> I'm surprised she has the dexterity to use a soldering iron at that age!

Sure... and she also flies small planes and recompiles her own Linux
kernel...

;)  ;)  ;)
--
Timothy J. Weber
http://timothyweber.org

2006\04\25@135057 by James Newton, Host

face picon face
> > BTW - Keep her interested.
>
> I'll do my best!  I have a long way to go to repay the debt I
> owe *my* father.
> --
> Timothy J. Weber
> http://timothyweber.org

I'm sure you sing to her and that will go a long way. I have "Calling the
Maid" and "Some kind of Truth" on my machine and I enjoy them greatly.

Just to keep this EE, music has been shown many time to increase children's
abilities in Math and Science.

For anyone who didn't know it, Timothy had some success as a singer /
musician in the past and makes a number of very nice mp3s available on his
old web site at
http://www.lightlink.com/tjweber/

---
James Newton: PICList webmaster/Admin
TakeThisOuTjamesnewton.....spamTakeThisOuTpiclist.com  1-619-652-0593 phone
http://www.piclist.com/member/JMN-EFP-786
PIC/PICList FAQ: http://www.piclist.com


2006\04\25@144543 by Timothy Weber

face picon face
James Newton, Host wrote:
> I'm sure you sing to her and that will go a long way. I have "Calling the
> Maid" and "Some kind of Truth" on my machine and I enjoy them greatly.

Hey, that's great to hear!  Thank you!

> Just to keep this EE, music has been shown many time to increase children's
> abilities in Math and Science.

I'm sure it's true.

> For anyone who didn't know it, Timothy had some success as a singer /
> musician in the past and makes a number of very nice mp3s available on his
> old web site at
> http://www.lightlink.com/tjweber/

<blush>  You're very kind.  Thanks!
--
Timothy J. Weber
http://timothyweber.org

2006\04\26@000829 by Russell McMahon

face
flavicon
face
> There is a clever plastic tongue inside that covers both holes and
> can
> only be shifted if both prongs go in at the same time. Sometimes it
> is
> acuated by the body (laterally).

Some sockets here have shutter on phase and neutral (live and return)
which are opened by the longer earth pin being inserted first.


       RM

2006\04\26@003150 by Russell McMahon

face
flavicon
face
>> As a child, back in the bad old days, I used to pull bits of wire
>> from the
>> windowscreens (aluminum?) and insert into the outlets, shoving it
>> home with
>> a stick.

>> Made a satisfying zap.

> Those who survive, become EEs.  ;)


Memories of university years :-)

<DTTAH>
Old ?TO66? metal can transistors make a very nice bang and broadside
of debris when mains-assisted. Turn power off before inserting. Check
thrice. Which I, long ago, once failed to do :-). But only once.

Those who survive become ... ?

Foil in lightbulb sockets also produces great results but alas tends
to also take out fuses.
"I'll just turn on the .." Bzzzt. Foosh.
</DTTAH>




       RM

2006\04\26@060131 by Howard Winter

face
flavicon
picon face
Russell,

On Wed, 26 Apr 2006 16:28:51 +1200, Russell McMahon wrote:

> Memories of university years :-)
>
> <DTTAH>
> Old ?TO66? metal can transistors make a very nice bang and broadside
> of debris when mains-assisted. Turn power off before inserting. Check
> thrice. Which I, long ago, once failed to do :-). But only once.
> </DTTAH>

Did you mean TO3?  And were you aware that some of the large power transistors, such as 2N3055, contain
Beryllium, which is something that you *really* don't want to breathe in, or otherwise ingest?

Cheers,


Howard Winter
St.Albans, England


2006\04\26@172559 by Peter

picon face

On Wed, 26 Apr 2006, Russell McMahon wrote:

>> There is a clever plastic tongue inside that covers both holes and can
>> only be shifted if both prongs go in at the same time. Sometimes it is
>> acuated by the body (laterally).
>
> Some sockets here have shutter on phase and neutral (live and return) which
> are opened by the longer earth pin being inserted first.

The 2-prong protector works by being wedged against dogteeth left or
right inside if only one prong pushes it. Only if both go in at the same
time does the tongue-like cover shift into a recess between the
dog-teeth. It is very simple and very clever (and you can push against
with with a nail and it won't open because the opening movement is
aside, not in).

Peter

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