small connectors with strain relief?

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

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.

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kensmith@rahul.net   forging knowledge

Donald wrote in news:ZsOdnVGKFukpirPZnZ2dnUVZ snipped-for-privacy@forethought.net:

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

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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.

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.

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

Donald wrote in news:UK-dnYe92tOu0LLZnZ2dnUVZ snipped-for-privacy@forethought.net:

about 10cm.

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

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

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.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Think honk if you\'re a telepath.

"Tim Shoppa" wrote in news: snipped-for-privacy@e56g2000cwe.googlegroups.com:

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

Donald wrote in news:XZadnebzlrg8p63ZnZ2dnUVZ snipped-for-privacy@forethought.net:

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

mw wrote in news:eDvXf.10916$ snipped-for-privacy@newssvr27.news.prodigy.net:

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

-Mike

snipped-for-privacy@green.rahul.net (Ken Smith) wrote in news:e0m8ns$3fg$ snipped-for-privacy@blue.rahul.net:

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

John Fields wrote in news: snipped-for-privacy@4ax.com:

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

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.

"Tim Shoppa" wrote in news: snipped-for-privacy@i40g2000cwc.googlegroups.com:

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

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 :-)

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.