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'[OT] Voltage drops (was Widlar Optimisation.. with'
2005\08\08@093218 by Howard Winter

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Tag & subject changed...

Jinx,

On Mon, 08 Aug 2005 23:12:41 +1200, Jinx wrote:

> > At my girlfriend's house in New York, I measured a 7 Volt
> > drop at the dining-room sockets when the microwave is
> > running in the kitchen
>
> Sigh, you're just a plain ole-fashioned romantic aren't you
> Howard ? A box of chocs, some roses and a Fluke.

Oh yes, trying to make her house wiring a tad safer than the (1937?) original is certainly something I do!

Like replacing the 2-pin sockets with 3-pin ones, so that the earthed appliances in her house are actually
connected to Earth...  I was amazed to find that almost all of the ground floor (lights and sockets) was
powered by one circuit with a 15A circuit breaker.  Only the fridge/freezer was on a seperate circuit.  It
means that she can't have the microwave and the toaster running at once, or the breaker trips (guess how I
found this out? :-)  I'm glad it's only rated at 15A though, as I suspect that the voltage drop I saw was a
symptom of grotty wiring.  Did you know they habitually join wires by twist-and-cap?  I thought it was a bodge
until I saw the stuff they sell at Home Depot - it seems to be the accepted practice!  :-#

> A friend of mine is having a battle with one of the Auckland
> electricity suppliers. His lights (and those in other suburbs he
> tells me) flicker. The first time I was at his place I thought
> there was a moth fluttering around the bulb, it's that noticeable.
> Apparently there's a major consumer causing voltage dips in
> vast swathes of housing

Slow-is flickering, I assume, rather than at mains frequency?  That suggests a "dirty" load, such as you'd get
from arc welding or an electric-arc furnace.  I wonder if someone has an illicit Aluminium smelter, in
competition with the chaps down South?  Or it could be arcing in a transformer or supply cable, of course, in
which case the problem will probably go away before too long!  :-)  Did you put a scope on it, to see if the
waveform suggests anything?

Cheers,


Howard Winter
St.Albans, England


2005\08\08@094059 by shb7

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>Did you know they habitually join wires by
>twist-and-cap?  I thought it was a bodge
>until I saw the stuff they sell at Home Depot - it seems to be the >accepted
>practice!  :-#

What is the accepted practice in the UK?

Sean

2005\08\08@101238 by Howard Winter

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On Mon, 8 Aug 2005 13:39:06 GMT, spam_OUTshb7TakeThisOuTspamnetzero.net wrote:

>
> >Did you know they habitually join wires by
> >twist-and-cap?  I thought it was a bodge
> >until I saw the stuff they sell at Home Depot - it seems to be the accepted
> >practice!  :-#
>
> What is the accepted practice in the UK?

Screw terminals, preferably in the accessories themselves (switches, sockets, ceiling roses) which are
generally designed to take at least three of the appropriate sized wire, or if that's not possible in
connecting blocks ("chocolate blocks") or junction boxes like this:
http://www.tlc-direct.co.uk/Images/Products/size_3/BG603.JPG but these have to be "accessible", and there's
much discussion of the interpretation of that!  If a join isn't going to be accessible (eg. extending a cable
to move a socket, and then plastering over the join) then it has to be crimped, which is regarded as a
permanent join so doesn't need to be inspected once it's been made and tested.

I believe twisted joins were disallowed in the regulations some time in the 1970s.

Cheers,


Howard Winter
St.Albans, England


2005\08\08@102929 by Michael Rigby-Jones

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{Quote hidden}

I didn't think is was possible to reliably crimp solid core wire?

Regards

Mike


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2005\08\08@143842 by Dwayne Reid

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At 07:32 AM 8/8/2005, Howard Winter wrote:
>  Did you know they habitually join wires by twist-and-cap?  I thought it
> was a bodge
>until I saw the stuff they sell at Home Depot - it seems to be the
>accepted practice!  :-#

Those "twist and cap" connectors (Marrettes or Murrettes - depending on age
of the box) are some of the most reliable connectors I've ever used.  The
wires are twisted into a helical spring within the cap which maintains
tension for decades.

On the other hand, I no longer use (or allow the use of) the
copper-plated-steel "Stak-on" crimp connectors designed for splicing house
wiring.  I have had to replace far to many of them that went resistive
after 10 or 15 years.  These were installed with the proper tooling and
duly inspected and passed - and some of them have failed.  The copper
conductors appear to deform (cold-flow) over long periods of time and
become loose.

But I have *never* seen a properly-installed Murrette connection
fail.  Properly-installed means that the wires are twisted uniformly after
removing the cap to inspect the connection.  And I always inspect every
splice that is done by a homeowner or do-it-yourself person who has asked
me for help.  It is distressing how often I find connectors that just
aren't tight enough.

As an interesting aside, Marr also still sells one of their earliest
products: the Marr connector.  This is a brass sleeve that clamps the
conductors with a large diameter set-screw through the side of the
sleeve.  A plastic cap then screws onto the sleeve for insulation.

The interesting thing about those Marr connectors is how I once saw them
used: aboard ships.  The electrician inserted the wires as usual (tighten
the set-screw until you hear it squeak), then got out a tiny flame torch
and proceeded to fill the whole brass sleeve with solder.  He told me that
was the secret to making connections that would not fail in a salt-mist
environment.

I believe him!

dwayne

--
Dwayne Reid   <.....dwaynerKILLspamspam.....planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
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2005\08\08@174626 by Jinx

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> Did you put a scope on it, to see if the waveform suggests anything?

Er no, he's not my girlfriend ;-)

But I did aks whether anyone from the power company had done
so. He said they knew what the long-standing problem was but
thought they just didn't have the will to fix it

2005\08\08@203536 by Russell McMahon

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> The interesting thing about those Marr connectors is how I once saw
> them used: aboard ships.  The electrician inserted the wires as
> usual (tighten the set-screw until you hear it squeak), then got out
> a tiny flame torch and proceeded to fill the whole brass sleeve with
> solder.  He told me that was the secret to making connections that
> would not fail in a salt-mist environment.

Sounds good.
But a caution.
Post soldering a connection like that so the wire is soldered to the
brass connectors should work.
BUT soldering a wire end to hold the conductors together in a "nice
tidy way" and then crimping it with the set screw is an invitation to
disaster. The original solder&wire bundle presents enough initial
resistance to the screw. But with time the solder creeps and the
connection fails. Dwayne will know this but many people don't. In most
countries soldering a wire in this manner for mains service is illegal
(and should be in all countries).

In automotive use *ALL* crimp connectors will fail. If you're lucky
the lifetime will exceed that of the vehicle. If it's in the engine
bay or near the battery or in any of the more adverse vehicular
environments it may well fail during the working lifetime. I recommend
that all auto crimp connectors be soldered after crimping just as your
marine contact did. A real pain. works well.



           RM

2005\08\08@214235 by Carey Fisher - NCS

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  > At 07:32 AM 8/8/2005, Howard Winter wrote:
  > >  Did you know they habitually join wires by twist-and-cap?
  > I thought it
  > > was a bodge
  > >until I saw the stuff they sell at Home Depot - it seems to be the
  > >accepted practice!  :-#
  >
  > Those "twist and cap" connectors (Marrettes or Murrettes -
  > depending on age
  > of the box) are some of the most reliable connectors I've ever
  > used.  The
  > wires are twisted into a helical spring within the cap which maintains
  > tension for decades.
  >

Commonly called "wire nuts" in the US and are used for 99.9999999 % of
Mains wiring in commercial and residential construction here in the states.

Carey

2005\08\09@062255 by Howard Winter

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On Mon, 8 Aug 2005 15:29:27 +0100, Michael Rigby-Jones wrote:

> I didn't think is was possible to reliably crimp solid core wire?

Not sure what you mean here, but you don't crimp the wires to each other - you crimp the two ends into a "butt
connector" (no sniggering in the gallery!) such as this:
http://www.tlc-direct.co.uk/Images/Products/size_3/CTBUTTSLASHY.JPG  and you have to do it with a proper
ratcheting crimping tool, not the cheap things you get in a car accessory shop!  This forms a gas-tight join
of the conductors, plus basic insulation of the joint, but you need further insulation (heat-shrink for
example) if it's going to be inaccessible.  

I stress that this is a last resort when there is no other way - replacing the whole length of cable is by far
the preferred method, rather than extending what's there, but sometimes that's impractical.  And it's
certainly better than burying a choc block, which is what some people would do if they didn't know better!

Cheers,



Howard Winter
St.Albans, England


2005\08\09@072351 by Alan B. Pearce

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> I didn't think is was possible to reliably crimp solid core wire?

My understanding is that a crimp does a cold weld of the various bits, and
as such is a reliable connection. It only gets unreliable if the crimp space
is not fully filled, so that the wires can move and work loose or allow
contamination in.

2005\08\09@075529 by Howard Winter

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Dwayne,

I'm not trying to start a "my electricity system is better than yours" match, honest!  :-)

On Mon, 08 Aug 2005 12:38:35 -0600, Dwayne Reid wrote:

{Quote hidden}

I have a feeling that when they were allowed here (*many* years ago) that the caps didn't have metal in them,
they were just ceramic.  This may explain why we don't have them any more, but you do!

> On the other hand, I no longer use (or allow the use of) the
> copper-plated-steel "Stak-on" crimp connectors designed for splicing house
> wiring.  

I don't actually know what these are - "Stak-on" isn't a name we have here.

>I have had to replace far to many of them that went resistive
> after 10 or 15 years.  These were installed with the proper tooling and
> duly inspected and passed - and some of them have failed.  The copper
> conductors appear to deform (cold-flow) over long periods of time and
> become loose.

The things I'm talking about shouldn't if crimped properly - they should form a gas-tight (cold weld) join
that can't flow, since it is effectively a single piece of metal.

> But I have *never* seen a properly-installed Murrette connection
> fail.  Properly-installed means that the wires are twisted uniformly after
> removing the cap to inspect the connection.  And I always inspect every
> splice that is done by a homeowner or do-it-yourself person who has asked
> me for help.  It is distressing how often I find connectors that just
> aren't tight enough.

What is the correct process?  Do you have to clean the wires before twisting?  Do you twist the wires together
"naked" then screw the cap on, or do you use the cap to act as a "handle" to twist the wires?  I wouldn't have
thought it was safe to remove and replace the cap after the joint is made, since undoing it would tend to
loosen off the twist, wouldn't it?

> As an interesting aside, Marr also still sells one of their earliest
> products: the Marr connector.  This is a brass sleeve that clamps the
> conductors with a large diameter set-screw through the side of the
> sleeve.  A plastic cap then screws onto the sleeve for insulation.

I don't remember ever seeing anything like that, except for use in high-powered car audio systems where a low
resistance power supply is needed.  And they tend to be gold plated!  :-)

> The interesting thing about those Marr connectors is how I once saw them
> used: aboard ships.  The electrician inserted the wires as usual (tighten
> the set-screw until you hear it squeak), then got out a tiny flame torch
> and proceeded to fill the whole brass sleeve with solder.  He told me that
> was the secret to making connections that would not fail in a salt-mist
> environment.
>
> I believe him!

I'm fairly sure that soldering isn't allowed on mains connections here, at least I've never seen them.  I can
see it being useful in a belt-and-braces situation as above, where the physical strain is taken by the metal,
and the solder is then just protecting it, but solder-only joints would be a problem as it's difficult to
detect dry joints, and cold-flow in solder is much more likely than in copper.

Cheers,


Howard Winter
St.Albans, England


2005\08\09@080042 by Michael Rigby-Jones

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>-----Original Message-----
>From: EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu [piclist-bouncesspamspam_OUTmit.edu]
>Sent: 09 August 2005 12:24
>To: Microcontroller discussion list - Public.
>Subject: Re: Re: [OT] Voltage drops (was Widlar Optimisation..
>with a voltage boost er)
>
>
>> I didn't think is was possible to reliably crimp solid core wire?
>
>My understanding is that a crimp does a cold weld of the
>various bits, and as such is a reliable connection. It only
>gets unreliable if the crimp space is not fully filled, so
>that the wires can move and work loose or allow contamination in.
>

I was taught in my apprenticeship at a railway signalling company that crimps were suitable only for stranded wire.  When crimped, stranded wire easily spreads out to fill the available space inside the crimp.  When a solid core wire is crimped, it will not flow in the same way unless extremem pressure is applied.  This means the gas tight connection occurrs only one two points of the wire, and as the wire flows with age into the remainging space within the crimp, the joint will loosen and fail.

They took their crimping very seriously, crimp tools were tested daily and re-calibrated regularly.  All crimped connections had to be inspected by an approved person and anything they didn't like was cut off and remade.  Soldering a crimped connection was absolutely forbidden.

Regards

Mike

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2005\08\09@081739 by Alan B. Pearce

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>I'm fairly sure that soldering isn't allowed on mains
>connections here, at least I've never seen them.

I don't know about the UK, but in NZ there is what is known as a "married
joint" where two pieces of 7 strand wire are to be joined, but I believe it
is only done with earth wires - certainly not with insulated wires.

The construction is to spread the outer six strands of each wire for about 4
inches length, and cut the centre strand off. Now butt the two wires so the
centre strands are almost touching, and the splayed outer strands interlace
with the strands of the other wire. Now wind the splayed strands over the
otside of the other wire, twisting in the original direction of twist. The
overall result is about an 8 inch length which is a 2 strand thickness
thicker than the original wire. This joint is then solidly soldered - an
action that requires a decent wattage iron to make the solder flow properly.

2005\08\09@082248 by Alan B. Pearce

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>>My understanding is that a crimp does a cold weld of the
>>various bits, and as such is a reliable connection. It only
>>gets unreliable if the crimp space is not fully filled, so
>>that the wires can move and work loose or allow contamination in.
>
>
>I was taught in my apprenticeship at a railway signalling company
>that crimps were suitable only for stranded wire.  When crimped,
>stranded wire easily spreads out to fill the available space
>inside the crimp.  When a solid core wire is crimped, it will not
>flow in the same way unless extremem pressure is applied.  This
>means the gas tight connection occurrs only one two points of the
>wire, and as the wire flows with age into the remainging space
>within the crimp, the joint will loosen and fail.

What you describe fails my description of the "crimp space being fully
filled", a process that the stranded wire does more or less automatically,
as you point out.

However if the crimp connection receiving the wire is correctly manufactured
for the diameter of the solid wire then a good crimp should be possible.

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