What's the best way to terminate very fine stranded wire

[Bob Engelhardt]

I'm using a 9 pin D-sub connector with attached cable. The conductors
are stranded 30 guage (7/38). What's the best way to terminate these
conductors?

- crimp (I don't have connectors sized that small, but I'm sure that I
could crush larger ones enough to hold)
- solder (I've heard that this is bad, but there will be minimal flexing
as the cable has strain relief)
- capture under a screw with washer

Thanks,
Bob

 

[Rich Webb]

I'm using a 9 pin D-sub connector with attached cable. The conductors
are stranded 30 guage (7/38). What's the best way to terminate these
conductors?

- crimp (I don't have connectors sized that small, but I'm sure that I
could crush larger ones enough to hold)

Pick up a bag of Molex 016-02-0096 (Digikey WM2562-ND). They're pretty
inexpensive and are sized for 24-30 AWG. Fit connector housings, e.g.
for 10-position 50-57-9010 (WM2808-ND).

 

[petrus bitbyter]

I'm using a 9 pin D-sub connector with attached cable. The conductors are
stranded 30 guage (7/38). What's the best way to terminate these
conductors?

- crimp (I don't have connectors sized that small, but I'm sure that I
could crush larger ones enough to hold)
- solder (I've heard that this is bad, but there will be minimal flexing
as the cable has strain relief)
- capture under a screw with washer

Thanks,
Bob

Terminate to what? Another connector? A PCB?

Generally speaking, crimping is the best way... If only you have the right
tooling and material.

Soldering to another connector is no problem. Finish with a piece of heat
shrink tubing.

Soldering to a PCB is also easy but strain relief is more critical. A solder
junction should never be loaded mechanically.

Capturing stranded wire under a screw, even with a washer, is not a good
idea. There are however connection blocks that are prepared to handle
stranded wire.'

IMHO yoo'll need strain relief anyway.

petrus bitbyter

 

[Bob Engelhardt]

Terminate to what? Another connector? A PCB?

Yeah, another usenet'er asking for help without saying what the problem
is. <G>

What I'm doing is connecting a control box to a separate box with
switches & lights. The D-sub connector is on the control box & I need
to connect the cut wires on the other end to the switches & lights.
Which have rather bulky screw connections. So I need to interface the
30 ga (7/38) wires. I can add a Jones strip, a piece of perf board,
whatever.

Generally speaking, crimping is the best way... If only you have the right
tooling and material.

The smallest crimp fitting I have is 22-16ga. How about if I "sister" a
piece of stranded 22 ga beside my 30 ga & crimp the 2 together. Would
that make a secure connection?

....

Soldering to a PCB is also easy but strain relief is more critical. A solder
junction should never be loaded mechanically.

I could do that with a piece of perf board.

Capturing stranded wire under a screw, even with a washer, is not a good
idea. ...

OK, I can see there might be some strands that are not captured.

IMHO yoo'll need strain relief anyway.

The cable has strain relief where it enters the switch box, but there
will be a 6" or so run inside the box. How close does the strain relief
need to be to the connection?

Thanks,
Bob

 

[Bob Engelhardt]

I've always felt a certain security with soldering, but you have to
strain relief it further back up the wire. Crimping is great but you
need the right tools. Screw and washer is for thick single strand
wire. At least you didn’t mention insulation displacement. (I hate
that!)

Thanks. What do you think of adding strands to get enough to fill a
crimp connector? Otherwise, it look like solder.

Bob

 

[Bob Engelhardt]

Here's what I did: I took a small piece of perf board (1" x 2"), wove
the wire through a couple of holes, & soldered it. The weaving provides
very good strain relief - no amount of tugging affects the solder
joint. It will be mounted on a standoff.

http://home.comcast.net/~bobengelhardt/PerfBoard.jpg

Thanks to all the Reply'ers,
Bob

 

[Shaun]

To terminated a thin wire you have to bash it several times with a hammer.
Many things can be terminated that way.

 

[Bob Engelhardt]

Bob E wrote

Bad how?

That the solder can wick up the wire from the joint & stiffen it such
that it's more likely to break from flexing.

Bob

 

[Bob Engelhardt]

With no other strain relief, perhaps.

Right. Strain relief "upstream" of all solder would fix it. That's
what I did.

Your perf board thing took care of that, sort of.

Even that creates a focused flex point doesn't it?

Yes, where the wire exits the board there is focused strain. But there
is no solder anywhere near that.

Bob

 

[Rich Grise]

I'm using a 9 pin D-sub connector with attached cable. The conductors
are stranded 30 guage (7/38). What's the best way to terminate these
conductors?

- crimp (I don't have connectors sized that small, but I'm sure that I
could crush larger ones enough to hold)
- solder (I've heard that this is bad, but there will be minimal flexing
as the cable has strain relief)
- capture under a screw with washer

Shop around for a crimp connector that's sized for the wire.

Don't tin this stuff - that makes it brittle.

Good Luck!
Rich

 

[petrus bitbyter]

Yeah, another usenet'er asking for help without saying what the problem
is. <G>

What I'm doing is connecting a control box to a separate box with switches
& lights. The D-sub connector is on the control box & I need to connect
the cut wires on the other end to the switches & lights. Which have rather
bulky screw connections. So I need to interface the 30 ga (7/38) wires.
I can add a Jones strip, a piece of perf board, whatever.


The smallest crimp fitting I have is 22-16ga. How about if I "sister" a
piece of stranded 22 ga beside my 30 ga & crimp the 2 together. Would
that make a secure connection?

...

I could do that with a piece of perf board.


OK, I can see there might be some strands that are not captured.


The cable has strain relief where it enters the switch box, but there will
be a 6" or so run inside the box. How close does the strain relief need
to be to the connection?

Thanks,
Bob

Combining strands of different diameters does not look like a good idea.
I've tried incidentally but sometimes the thinner wires could easily pulled
out while the thick ones fitted thight. Doubling the strands by bending the
stripped part of the wires by 180 degrees worked fine for me but might not
be enough for you.

I've used "soldereyes" or "solderlips" to connect stranded wires to screw
connections. There may be other names for it but they look like washers
with a large hole for the screw and a protuberance with a small hole to
solder the wire. Finish with a piece of heat shrink tubing.

Perfboard will do well. Pull the wire two times trough the board before
soldering. That will give plenty of strain relief for 6" of wire as the
mechanical stress pulls on the bends in the wire rather then on the
solderjunction itself.

petrus bitbyter