small connectors with strain relief?

[Mike Noone]

Hi - I seem to be looking for something that doesn't exist. I want a small
connector (2mm pitch or smaller, ideally) that has strain relief built in.
I probabaly will want it to be a crimp housing style connector. A ribbon
cable connector would not work for my application. Does such a thing exist?
I've looked and looked - and everything I find either is huge, or doesn't
have strain relief. Thanks,

-Mike

 

[Donald]

Hi - I seem to be looking for something that doesn't exist. I want a small
connector (2mm pitch or smaller, ideally) that has strain relief built in.
I probabaly will want it to be a crimp housing style connector. A ribbon
cable connector would not work for my application. Does such a thing exist?
I've looked and looked - and everything I find either is huge, or doesn't
have strain relief. Thanks,

-Mike

Is this for internal wiring ??
or
Is this for connecting external wiring into a bulkhead ??

 

[mw]

Hi - I seem to be looking for something that doesn't exist. I want a small

connector (2mm pitch or smaller, ideally) that has strain relief built in.

www.jst.com

 

[Ken Smith]

Hi - I seem to be looking for something that doesn't exist. I want a small
connector (2mm pitch or smaller, ideally) that has strain relief built in.
I probabaly will want it to be a crimp housing style connector. A ribbon
cable connector would not work for my application. Does such a thing exist?
I've looked and looked - and everything I find either is huge, or doesn't
have strain relief. Thanks,

Samtec and others make sort of what you need at 0.1" centers. The strain
relief is just the crimp pin grabbing the insulation of the wire, not a
clamp on the housing.

In the past, I have glued heat shrink to the body of connectors to strain
relief ones I was abusing. It works but needs a lot of extra labor.

 

[Mike Noone]

Is this for internal wiring ??
or
Is this for connecting external wiring into a bulkhead ??

Hi Donald. I'm not sure what you mean by internal vs. external. The
application is that I have two circuit boards connected to each other. They
are constantly in motion relative to each other, so I am worried that the 5
wire connection between them will wear out. I'm using wire designed
specifically to be bent many times, but I'm worried about there being
excess stress on the connectors.

-Mike

 

[John Fields]

Hi Donald. I'm not sure what you mean by internal vs. external. The
application is that I have two circuit boards connected to each other. They
are constantly in motion relative to each other, so I am worried that the 5
wire connection between them will wear out. I'm using wire designed
specifically to be bent many times, but I'm worried about there being
excess stress on the connectors.

 

[Tim Shoppa]

Hi Donald. I'm not sure what you mean by internal vs. external. The
application is that I have two circuit boards connected to each other. They
are constantly in motion relative to each other, so I am worried that the 5
wire connection between them will wear out. I'm using wire designed
specifically to be bent many times, but I'm worried about there being
excess stress on the connectors.

Mike -
Look at the "flat flex jumper" category in the Digikey catalog. These
are typically flexible PCB's, with rectangular (fine pitch, one or
two-row) connectors very securely attached at the ends. Usually the
cable will be clamped to limit the maximum curvature as your boards do
their motion (e.g. even though they say "flexible" you still cannot
kink them.) And because they're flat, they are more flexible in one
directon than the other.

Tim.

 

[Donald]

Hi Donald. I'm not sure what you mean by internal vs. external. The
application is that I have two circuit boards connected to each other. They
are constantly in motion relative to each other, so I am worried that the 5
wire connection between them will wear out. I'm using wire designed
specifically to be bent many times, but I'm worried about there being
excess stress on the connectors.

-Mike

OK, so its internal.

How far apart are these boards ?

If these board are "constantly in motion", the answer is, "make a single
board".

Any two connectors may be higher that the distance of the two boards.


This is one of those, "it depends" problems.

Unless you are willing to post all the dimensions of these boards and
the packaging involved, we may never truly understand what you need to do.

Good luck

Donald

 

[Mike Noone]

OK, so its internal.

How far apart are these boards ?

about 10cm.

If these board are "constantly in motion", the answer is, "make a
single board".

Not possible in this application. I could go into detail, but it's
really not necessary. Just understand that it wouldn't work.

Any two connectors may be higher that the distance of the two boards.


This is one of those, "it depends" problems.

Unless you are willing to post all the dimensions of these boards and
the packaging involved, we may never truly understand what you need to
do.

There is a primary board (10x6cm) connected to 6 motor controller boards
that are all 1.5x5cm by a 5 conductor cable. I'm using a simple Molex
2mm pitch crimped pin style connector right now, but I do not believe it
was designed for this constant movement.

Good luck

Donald

Thanks,

-Mike

 

[Donald]

There is a primary board (10x6cm) connected to 6 motor controller boards
that are all 1.5x5cm by a 5 conductor cable. I'm using a simple Molex
2mm pitch crimped pin style connector right now, but I do not believe it
was designed for this constant movement.


Thanks,

-Mike

I guess I still don't understand the problem.

But,first I'll say, I don't know of any connectors that will help you.

If all these 7 boards are mounted, then where is the movement ?

Unless your saying that the wires are flopping around because of the
movement ??!!

Is the entire cabinet/enclosure moving ??

Would some RTV or other silicone rubber help here ??

I would think that the connection of the wire in the crimp pin is where
it will wear.

So a little RTV at that junction would be easy and still allow for
removal of the connector.

Good Luck

Donald

 

[Paul Hovnanian P.E.]

Mike -
Look at the "flat flex jumper" category in the Digikey catalog. These
are typically flexible PCB's, with rectangular (fine pitch, one or
two-row) connectors very securely attached at the ends. Usually the
cable will be clamped to limit the maximum curvature as your boards do
their motion (e.g. even though they say "flexible" you still cannot
kink them.) And because they're flat, they are more flexible in one
directon than the other.

Tim.

That's what they use inside those 'floating number' clocks with the LED
wand that swings back and forth (at about 10 Hz) and 'paints' the date
and time as it goes. Mine has been running for a couple of years now and
the ribbon cable seems to be fine.

 

[Mike Noone]

Mike -
Look at the "flat flex jumper" category in the Digikey catalog.
These
are typically flexible PCB's, with rectangular (fine pitch, one or
two-row) connectors very securely attached at the ends. Usually the
cable will be clamped to limit the maximum curvature as your boards do
their motion (e.g. even though they say "flexible" you still cannot
kink them.) And because they're flat, they are more flexible in one
directon than the other.

Tim.

Problem for me is that the boards are moving with respect to each other in
two different axes, thus I have to use really stranded cable.

-Mike

 

[Mike Noone]

I guess I still don't understand the problem.

But,first I'll say, I don't know of any connectors that will help you.

If all these 7 boards are mounted, then where is the movement ?

They are on a robot with 6 legs. There is one primary board mounted in
the center of the robot, while each leg has it's own controller onboard.
The legs are set up much like a human's leg - in that there's a ball
joint at the top (2 axes of freedom) and another single joint further
down (like a knee). The boards are mounted between the ball joint and
the single joint. The wires are looped above so they won't get caught,
but they do move.

Unless your saying that the wires are flopping around because of the
movement ??!!

Is the entire cabinet/enclosure moving ??

Everything possible is moving.

Would some RTV or other silicone rubber help here ??

I would think that the connection of the wire in the crimp pin is
where it will wear.

So a little RTV at that junction would be easy and still allow for
removal of the connector.

That's what I've been thinking, but I was hoping there'd be a
"prettier" solution.

Good Luck

Donald

Thanks,

-Mike

 

[Mike Noone]

www.jst.com

Any products at particular? Their website is clumsy at best.

-Mike

 

[Mike Noone]

[email protected] (Ken Smith) wrote in

Samtec and others make sort of what you need at 0.1" centers. The
strain relief is just the crimp pin grabbing the insulation of the
wire, not a clamp on the housing.

In the past, I have glued heat shrink to the body of connectors to
strain relief ones I was abusing. It works but needs a lot of extra
labor.

The crimp pins in the connectors I'm using also grab the insulation. But I
don't think that will be enough. I've been thinking I might do something
along the lines of first putting some kinda of sealing in the connectors -
something along the lines of hot glue. Then I'd put some heat shrink that
would cover the edge of the connector and hopefully go up tight on the
wires - but that would mean the heat shrink would have to shrink quite
alot. I'm not sure if I have any that good, I'll have to look around.

-Mike

 

[Mike Noone]

Design the "cable" so that it's essentially a service loop where
flexure at the point where the wire joins the connector doesn't
exist.

Hi John - I've looked at trying to do this, but it's proving to be very
tricky as I have very little space to work with on the boards. I was hoping
to find a connector that could handle the problem for me, but if necessary
I'll do my best to implement a solution to hold the wires in place at the
connector.

-Mike

 

[Tim Shoppa]

Problem for me is that the boards are moving with respect to each other in
two different axes, thus I have to use really stranded cable.

Not necessarily. The flat flex cable can be turned around a corner and
then you can flex it on a second axis. It requires some thought and
some "corner" to be turned around, and you may be too late in
mechanical design to handle that.

Look inside, for example, a tape library robot to see the principles
applied.

Tim.

 

[Mike Noone]

Not necessarily. The flat flex cable can be turned around a corner and
then you can flex it on a second axis. It requires some thought and
some "corner" to be turned around, and you may be too late in
mechanical design to handle that.

Look inside, for example, a tape library robot to see the principles
applied.

Tim.

Early on in mechanical design I looked at the possibility of using flat
flex cable. Problem is I didn't have the space to get it to turn on two
axes. I understand the principle of giving it two places to rotate - I just
don't have the space for it.

-Mike

 

[Donald]

They are on a robot with 6 legs. There is one primary board mounted in
the center of the robot, while each leg has it's own controller onboard.
The legs are set up much like a human's leg - in that there's a ball
joint at the top (2 axes of freedom) and another single joint further
down (like a knee). The boards are mounted between the ball joint and
the single joint. The wires are looped above so they won't get caught,
but they do move.




Everything possible is moving.




That's what I've been thinking, but I was hoping there'd be a
"prettier" solution.




Thanks,

-Mike

OK, now is get it.

I don't think your going to get any better than the RTV.

Its cheap and it works.

I worked on a three-axis milling machine in another life.
With the coolant flowing, cables had to be protected as well as strain
reliefed. ( external connections )

Good Luck again,

Donald

PS: got any pics

 

[Tim Shoppa]

Early on in mechanical design I looked at the possibility of using flat
flex cable. Problem is I didn't have the space to get it to turn on two
axes. I understand the principle of giving it two places to rotate - I just
don't have the space for it.

I think any of the discrete-wire small rectangular connectors are
"pretty good" in terms of flexibility. And you get wiggle room in any
dimension, unlike the flexible-PCB cables. You don't get the
umpteen-bazillion cycles of operation that the flexible PCB's give you,
but the may well outlast your mechanism . These are available not
just in 0.1" pitch but also 2mm and 1.5mm and 1.25mm.

For the smaller sizes of discrete-wire connectors, you really DO need
the "correct" crimper. Otherwise you do not get the wire crimp or the
insulation crimp correct. The correct crimp tool will set you back
several hundred dollars. Without the right crimp tool, you will not get
the crimp right. With the 1.25mm pitch ones there's no way any
hardware-store crimper is gonna do the crimp right - the 1/8" width of
those tools completely dwarfs the proper crimp.

The IDC ribbon cable fine-pitch connectors are much more easily
attachable without a multi-hundred-dollar crimp tool. But you might not
get all the flexibility in all axes that you desire.

Unlike the others I recommend AGAINST kludging these up with hot glue
or silicon or heat shrink as a "strain relief". All these will do is
concentrate the strain at the end of the "relief" and guarantee a wire
break there, and give you less overall length to flex. A properly
crimped discrete wire gets the CORRECT amount of strain relief from the
insulation crimp and the connector housing.

And of course with the smaller pitches you do NOT get to use wire any
thicker than 24AWG. If you are powering motors then you might not be
able to carry enough current over such skinny wires (usually they're
rated at 1Amp and I would personally consider that optimistic). If you
get up to the couple amps of current arena, then I highly recommend
that you make enough area on your PCB's for Waldom Micro-Fit connectors
or AMP Mini-Universal Mate-N-Locks which give you 5 to 9Amps of current
per circuit (and let you use appropriately sized wire, like 16AWG.)

Tim.