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The Non-Military User's Guide to Military Connectors - Part 2

This is part two of a series of stories in which we investigate why military specification connectors might be useful for industrial customers.

The MIL-Spec connector market might look large and confusing at first, but there are a few tips that we can give you to make the choice a little easier.  Hopefully, part one of the series has sold you on the idea that military connectors might be the solution for your commercial application.  Let’s take a look at a few lesser-known aspects of the MIL-Spec market and see how they might make your life a little easier.

It’s All in The Part Number

Buying a connector under a military specification provides you with a whole list of additional paperwork that you might not need.  If you are not in the military market, you might not care about the enhanced traceability that a MIL-Spec provides.  You might not need to know about the additional inspection or the increased liability protection that it provides.  You might not need the spare contacts that you might receive.  Our advice is simple: if you do not need a MIL-Spec product, don’t buy one.

This is not as crazy as it sounds.  Every manufacturer will sell the same connector under several part numbers.  The connector itself is the same – it is made from the same materials, on the same production line, and under the same conditions.  However, a connector that is purchased under the MIL-Spec brings with it the additional certification that you might need if it is to be fitted into safety-critical locations, such as aboard an aircraft or in a fighting vehicle.

Therefore, if you like the idea of MIL-Spec performance but do not want to pay a premium, search for the manufacturer’s own part numbers.  Instead of a D38999 series III connector, look for the Souriau 8D part number.  The Amphenol PT family will give you the commercial equivalent to the MIL-DTL-26482 Series 1.  And if you are buying a D-sub connector, don’t search for D24308 if you don’t need military standards – there are plenty of excellent commercial equivalents that will work just as well.

  • Our top tip:  Check if you can buy your connector using the manufacturer’s part number.  Seriously, you could save some money…

It’s All About the Accessories, Darling…

In many industrial applications, how you treat the cable is just as important as which connector you choose.  Some level of protection must be provided to the rear of the connector where the cable is anchored.  This can be as simple as a rubber boot or as complex as a shielded, waterproof cover.

Customers who purchase industrial connectors from manufacturers like Phoenix Contact or Bulgin are used to connectors that offer built-in cable support.  However, this is not true of most military connectors, where the backshell must be specified separately. 

Backshells for Military Connectors

In a world dominated by packaged products and holistic solutions, this might seem a little old-fashioned, but there is a reason.  While a military standard defines in detail how the front of the connector is designed to ensure compatibility, it does not define the use to which the connector is put.  The same product could be used on a simple power cable or might be designed into sensitive communications equipment.  In each case, how the cable is protected will differ enormously.  By providing backshells to perform a specific role, the industry has given users the greatest possible flexibility.

Choosing a backshell is not as tricky as it sounds.  As long as you have selected the correct connector type, it is then just a matter of deciding the function you need it to perform.  If all you need is basic strain relief, then a simple clamp solution will be perfect.  However, if shielding is vital to protect against electromagnetic interference (EMI), then choose a solution that enables the termination of the cable screen.

  • Our top tips:  Double check your connector type, know your cable size, and understand your application.

The Same, Only Smaller

Over the years, many criticisms have been levelled at military circular connectors, not least being their general bulky design.  If there is one barrier to using them in an industrial environment, this might be it.  Although their design promotes robustness, their overall size can be a concern.  Manufacturers have understood that users appreciate the features of traditional military designs but need a more compact design.

This has led to a broad range of connectors that are inspired by their military counterparts, share some of their components, but no longer conform to a military specification.  They are designed to provide the same performance and durability but in a smaller package.  As the military adopts more wearable technology, from helmet cameras to cooling vests, there is an increased need for connectors to be smaller and lighter.

Miniature Connectors – Designed for the battlefield, ideal for industry

Amphenol has developed the Terrapin series of miniature circular connectors to address these challenges.  Using the same contact technology as the D38999 family, but mounted in slim, waterproof shells.  Terrapin offers push-pull plugging technologies that are not normally available in traditional military connectors.  The ability to make or break the connectors in low light conditions makes them ideal for use in soldier systems.

For a more traditional approach to circular connectors that still save space and weight, Glenair has developed the Mighty Mouse family, and Amphenol has the 2M series.  Both types take their inspiration from the D38999 series III connector standard.  Smaller in both diameter and body length, these are the solution for users who want military connector familiarity in a slimline design.

  • Our top tips:  There may well be a smaller connector that you can use.  Do your research and remember that smaller does not mean less capable.

The Final Part – Filters and Other Oddities

Having explored MIL-Spec connectors and seen how they might be suitable for commercial and industrial applications, in the final part we will look at some special connectors.  Military designers have been solving some of the most challenging problems in electronics for decades.  There might be a product out there that’s perfect for you…

If you haven't already read it, check out Part 1 in this series now.

Connector Geek is Dave in real life. With 29 years in the industry, Dave still likes talking about connectors almost as much as being a Dad to his two kids. He still loves Lego too...

20 May 2020, 8:57