Wire connector?

[BobK]

Hello,

This is pretty basic. I have a small on/off switch that controls some
box lighting. There are two thin single-strand wires running to the
on/off switch (red and black). I noticed that one of the wires
disconnected from its terminal. It appears to have been soldered with
a piece of shrink tubing over it. There is no connector as such - just
a little thin post that the wire attaches to.

The problem is that the wire is very short and the switch is located
in the back of the box making it very difficult to reach. I have to
use long tweezers just to reach it.

Is there any clever way to try and re-attach the wire to the post? I
was thinking that liquid solder or something might be possible. Any
ideas?

Thanks,

Bob

 

[Paul]

Hello,

This is pretty basic. I have a small on/off switch that controls some
box lighting. There are two thin single-strand wires running to the
on/off switch (red and black). I noticed that one of the wires
disconnected from its terminal. It appears to have been soldered with
a piece of shrink tubing over it. There is no connector as such - just
a little thin post that the wire attaches to.

The problem is that the wire is very short and the switch is located
in the back of the box making it very difficult to reach. I have to
use long tweezers just to reach it.

Is there any clever way to try and re-attach the wire to the post? I
was thinking that liquid solder or something might be possible. Any
ideas?

Thanks,

Bob

What are the consequences, if the wire falls off while the device
is running ? Can someone get a shock ? Could a fire start ?

"Fix it right" comes to mind.

Solder is not the best means, in the first place. It all depends
on the environment. For example, if the wire is subject to
stress and strain, pulling on solder can lead to eventual failure.
It can also concentrate stress in the wire (at the "bend point"),
causing the wire to break. And that might be why it broke in
the first place.

Take this as an example. Two pieces of wire laying next to each
other. With insulation removed.

--------------
----------------

If you soldered the joint there, the solder would be the sole means
of mechanical support. If the solder cracks, the two ends flop about.

On the other hand, you could twist the wire together. In that case,
the contact of the wire to wire, is helping with the mechanical
support, so there is less stress on the solder in the joint.
And even if the solder joint was "cold" or a bad joint, the wire
can provide secondary support.

---------+ +---------
\ /
X
/ \ Twisted wire helps provide mechanical
\ / support.
X
/ \

Some switch terminals, have a hole in the tab, and the wire can
go through that. That is much more secure, than surface solder,
like my first drawing above.

Note that solder is also not a good candidate, for things where
there are other kinds of obvious stresses. Like, say, an item
that could get hot enough, that the solder could remelt and
drip off.

If the terminals on the switch were thin rectangles, of the
appropriate size, you could use these. A stranded wire is
crimped underneath the insulated part. The "jaw" part on the
other end, slide over the thin rectangle.

http://www.radioshack.com/product/index.jsp?productId=2104091

If the switch terminal is "dirty", you cannot use a connector like that.
Solder debris on the rectangular terminal, will prevent that
connector from gripping properly. So the crimp style connector,
should only be used on a new, clean, switch.

Just do it right, and sleep better at night. Imagine a
house full of "half right" repairs... What risk would you
run ? What are the house insurance implications, of a
bad user repair that causes a fire ?

Paul

 

[BobK]

Hello,

What are the consequences, if the wire falls off while the device
is running ? Can someone get a shock ? Could a fire start ?

"Fix it right" comes to mind.

Solder is not the best means, in the first place. It all depends
on the environment. For example, if the wire is subject to
stress and strain, pulling on solder can lead to eventual failure.
It can also concentrate stress in the wire (at the "bend point"),
causing the wire to break. And that might be why it broke in
the first place.

Take this as an example. Two pieces of wire laying next to each
other. With insulation removed.

--------------
----------------

If you soldered the joint there, the solder would be the sole means
of mechanical support. If the solder cracks, the two ends flop
about.

On the other hand, you could twist the wire together. In that case,
the contact of the wire to wire, is helping with the mechanical
support, so there is less stress on the solder in the joint.
And even if the solder joint was "cold" or a bad joint, the wire
can provide secondary support.

---------+ +---------
\ /
X
/ \ Twisted wire helps provide mechanical
\ / support.
X
/ \

Some switch terminals, have a hole in the tab, and the wire can
go through that. That is much more secure, than surface solder,
like my first drawing above.

Note that solder is also not a good candidate, for things where
there are other kinds of obvious stresses. Like, say, an item
that could get hot enough, that the solder could remelt and
drip off.

If the terminals on the switch were thin rectangles, of the
appropriate size, you could use these. A stranded wire is
crimped underneath the insulated part. The "jaw" part on the
other end, slide over the thin rectangle.

http://www.radioshack.com/product/index.jsp?productId=2104091

If the switch terminal is "dirty", you cannot use a connector like
that.
Solder debris on the rectangular terminal, will prevent that
connector from gripping properly. So the crimp style connector,
should only be used on a new, clean, switch.

Just do it right, and sleep better at night. Imagine a
house full of "half right" repairs... What risk would you
run ? What are the house insurance implications, of a
bad user repair that causes a fire ?

Thanks for the advice. This is single strand wire and the terminal
looks like it is the same size as the wire. That is, the terminal is a
small wire sticking out of the device. There does not seem to be any
crimping type connector on the wire.

So if I did something like adding a connector, it would have to be
crimped to the wire and have a very small female to catch the
terminal.

Does something like that exist?

Thanks Again,

Bob

 

[Paul]

Thanks for the advice. This is single strand wire and the terminal
looks like it is the same size as the wire. That is, the terminal is a
small wire sticking out of the device. There does not seem to be any
crimping type connector on the wire.

So if I did something like adding a connector, it would have to be
crimped to the wire and have a very small female to catch the
terminal.

Does something like that exist?

Thanks Again,

Bob

If you have two wires to join together, you can use
"wire nuts". These work best with stranded wire. There
is a thing, like a coil spring, inside the plastic. The
coil spring grips the wire, as the nut is twisted onto
the ends of the wire(s). You twist the wires together first,
then twist the wire nut onto the wire ends. The direction of
twist of the wires, should be consistent with what the wire
nut is going to do to the wire when twisted on - the wire
nut should serve to twist the wires in the same direction
as the original twisting.

http://www.productdose.com/phpwiki/uploads/EricMeeks/10acfb1d417f5a1fecb9c218e3c2530d_pop.jpg

You can see some wire nuts in this picture.

http://www.bfranker.badz28.com/fbody/scan36.JPG

In my personal experience with wire nuts, their performance
is quite variable. For example, if I took one solid wire and
one stranded wire, the wire nut would not stay on the end of
the twisted together bare wire ends.

When selecting wire nuts, you select them according to the
number of wires to be connected, and the gauge of each wire.
In my own case, I like to buy a "variety pack", which contains
samples of various size wire nuts. Then I check the charts, and
experiment with the two closest sizes, to find one that seems
the most secure.

I'd repaired appliances, like lamps for illuminating your home,
with wire nuts. I put the thing all back together again, then
disassembled, only to find a wire nut had worked loose. So
I consider them to be dangerous, and in fact, you're relying
on the twisting together of the original wires ends, about
as much as you're relying on the wire nut.

The benefit of the wire nut, is it compresses the wires, without
replying on the stiffness of the twisted wires. So in theory,
it should provide a superior, gas tight connection. But the
devil is in the details - if not fitted correctly, they
just don't grip very well.

I hope I've made their deficiencies clear enough.

Are you sure you cannot remove the switch, and fit
a new switch which is compatible with crimp fittings ?

Even with crimp fittings, it takes good tools to do
a good crimp. If you're going the crimp route, buy
plenty of extra materials (wire and crimp terminals),
and practice until you're no long breaking strands of
wire, or leaving strands loose outside the crimp. It
takes some practice before you get good at it. How
good the job has to be, depends on the amount of
current the circuit is carrying. For example,
a bad connection in a heating device, will result in
high wire temperatures, and even if the wire has
high temperature insulation, it can bake off.

There is another kind of crimp, but this one makes
me nervous as well. Especially if you were working
in a cramped location, and were unable to check for
damage to the wire caused by the crimping. Any time
you work with wire, you have to check for nicks that
cause the wire to break. If you have a thin wire,
and the crimp requires a lot of force to be applied to
the tool, it would be easy to transfer some of that
force to the wire, while working on it. While I have
some of these in crimp variety packs I've bought, I
don't use these.

http://www.radioshack.com/product/index.jsp?productId=2151268

Crimp terminals come in male and female. Now, think
about these for a moment. If you connected one of
the males to one of the females, the metal ends would
not be covered by insulation. So this would not be safe,
unless extra insulation was applied some how. These would be
better in a situation, where the device you were connecting
to, was bolted to the chassis, and could not move.

http://www.radioshack.com/product/index.jsp?productId=3060975

So not everything you find at the Radio Shack, is safety minded.
Some of the stuff, is downright dangerous.

Another thing you can find at Radio Shack, is heat shrink
tubing. This stuff is usually made from Polyolefin (a name you
can use as a search term, if necessary). It shrinks to half
its normal diameter, when heated. So what is the problem with
this stuff ? Well, the temperature at which it shrinks, can be
higher than the melting point of ordinary wire insulation.
When you apply hot air to the polyolefin, the rest of the wire
insulation pulls away from the wire. So again, not the
best material for every application. I still use it, but
like in the other examples - practice, disassemble, and inspect
for damage or deficiency, before making a final repair. I consider
this stuff to be more reliable than electrical tape, which can
become gooey and migrate away from where it is applied.

http://www.radioshack.com/product/index.jsp?productId=2062662

The store I buy my Polyolefin from, sells it in 3 foot lengths,
and I keep about five or six different diameters in stock. The
temptation is usually to make it fit too tight when you buy it,
so buy the size you think would fit, and also buy a piece of the
next largest one.

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

Paul

 

[BobK]

Even with crimp fittings, it takes good tools to do

a good crimp. If you're going the crimp route, buy
plenty of extra materials (wire and crimp terminals),
and practice until you're no long breaking strands of
wire, or leaving strands loose outside the crimp. It
takes some practice before you get good at it. How
good the job has to be, depends on the amount of
current the circuit is carrying. For example,
a bad connection in a heating device, will result in
high wire temperatures, and even if the wire has
high temperature insulation, it can bake off.

There is another kind of crimp, but this one makes
me nervous as well. Especially if you were working
in a cramped location, and were unable to check for
damage to the wire caused by the crimping. Any time
you work with wire, you have to check for nicks that
cause the wire to break. If you have a thin wire,
and the crimp requires a lot of force to be applied to
the tool, it would be easy to transfer some of that
force to the wire, while working on it. While I have
some of these in crimp variety packs I've bought, I
don't use these.

http://www.radioshack.com/product/index.jsp?productId=2151268

Crimp terminals come in male and female. Now, think
about these for a moment. If you connected one of
the males to one of the females, the metal ends would
not be covered by insulation. So this would not be safe,
unless extra insulation was applied some how. These would be
better in a situation, where the device you were connecting
to, was bolted to the chassis, and could not move.

http://www.radioshack.com/product/index.jsp?productId=3060975

So not everything you find at the Radio Shack, is safety minded.
Some of the stuff, is downright dangerous.

Another thing you can find at Radio Shack, is heat shrink
tubing. This stuff is usually made from Polyolefin (a name you
can use as a search term, if necessary). It shrinks to half
its normal diameter, when heated. So what is the problem with
this stuff ? Well, the temperature at which it shrinks, can be
higher than the melting point of ordinary wire insulation.
When you apply hot air to the polyolefin, the rest of the wire
insulation pulls away from the wire. So again, not the
best material for every application. I still use it, but
like in the other examples - practice, disassemble, and inspect
for damage or deficiency, before making a final repair. I consider
this stuff to be more reliable than electrical tape, which can
become gooey and migrate away from where it is applied.

http://www.radioshack.com/product/index.jsp?productId=2062662

The store I buy my Polyolefin from, sells it in 3 foot lengths,
and I keep about five or six different diameters in stock. The
temptation is usually to make it fit too tight when you buy it,
so buy the size you think would fit, and also buy a piece of the
next largest one.

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

Thanks again for the lesson and the links.

A couple of points of clarification: The wire I am dealing with is not
stranded. It is one solid piece of wire. It is about the same gage as
the thin individual wires running all around the box. Also, there is
no push or pull stress on the switch or wires. The switch is just
sitting there by itself.

Having said that, I appreciate the cautions you gave me and will
proceed in that direction.

Of all the connectors you linked to, the one that seems most likely is
the Crimp-on Butt Connector at
http://www.radioshack.com/product/index.jsp?productId=2151268 . The
only problem is going to be getting the crimping tool into the tight
space. I may have to pull things apart to get to it.

Thanks Paul,

Bob