Pocobor.

Strain Relief for Rough Prototypes

Most of Pocobor’s projects involve integration of electronics and software into a physical, mechanical system. Any single weak point in this integration can jeopardize the entire design; with the individual subsystems already complicated enough, we can’t afford to have weak interconnections between them. Of all the possible failure points, there is one that stands out to me as being both particularly devious and simple to mitigate: loose wires. A loose electrical connection can be extremely difficult to find and can wreak havoc on any electrical system. But there is hope for all those loose wires out there — strain relief!

I like to think of strain relief as a mentorship program for loose wires. Without a sturdy companion to provide guidance and assistance, a loose wire may find itself getting caught up in undesirable activities (maybe a rotating motor shaft or a passing foot). Sometimes this mentor is another, larger wire — there’s safety in numbers — or sometimes it’s a sturdy mechanical component in the system. A link is made between the loose wire and the mentor, and future snags are much less-likely to cause significant damage. Sure, our little loose wire might get pulled in dangerous directions, but his mentor will be right there beside him to provide support.

Three simple ways to add effective strain relief to essential wire connections in rough prototypes: zip ties, heat shrink, and hot glue. I’m focusing on rough, quick prototypes in this post (hot glue probably isn’t the best solution for manufactured products), but many of these techniques can apply for finished products as well.

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Zip ties can significantly reduce the forces on electrical connections. Here, the red zip tie is linking the large and small black wires together well below the electrical connection within the red wire nut.

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The yellow zip tie shows the strain relief for the wire bundle leaving the breadboard. In this case, I’ve zip-tied the bundle to a hole drilled in the edge of the breadboard.

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The yellow heat-shrink joins the small black wire to the larger grey wire to reduce forces on the electrical connection. Heat shrink used in this way also reduces the chance of an electrical short circuit.

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This very rough prototype shows the value of hot glue for strain relief. In this example, I’ve soldered small wires (green) to a surface-mount sensor (small and delicate connections!) and have used hot glue to keep them from moving around and breaking loose. You can also see the strain relief for the green wires’ heat-shrink connection to the wires leaving the board. Those (larger) black, white, and teal wires are going to protect the delicate connections if they ever get yanked.

Loose wires can get snagged, pulled, bent, melted, or trampled. Whether you’re connecting to a breadboard or a PCB, wires that enter or leave the electronics should be properly strain relieved. The small amount of time it takes to strain relieve a wire can save hours of stressful troubleshooting and/or repairs down the road. The important thing to remember is that strain relieving wires is not necessarily going to prevent them from getting yanked or twisted or snagged, but it will prevent the force of that snag from reaching a critical electric connection in your design.

As Engineers, there are many things that we can’t easily control (stray electro-magnetic fields, the weather, apostrophe usage). Therefore it is essential that we take relentless control of the variables within our grasp. The universe tends to favor the chaotic monotony of loose, poorly-managed wires — fight back with strain relief!

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