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Designers are being asked to squeeze more functionality into increasingly awkward and confined spaces as part of size, weight, power, and cost (SWaP-C) optimization. This is especially true in portable devices, industrial robotic systems, and aviation systems where the interconnects are routing both power and data signals in close proximity.

While designers must be concerned with reliability and signal integrity, they must also ensure the interconnect system is easy to configure for different pinouts and use cases, can reliably connect and disconnect during setup and is easy to maintain when in use.

This article will explain how designers of electronics systems can ensure reliable connectivity by using the appropriate connector family for small and tight interconnect situations. It will discuss how SWaP-C optimization can be achieved for a broad range of interconnect challenges by standardizing on one interconnect family from Harwin. The application of two sample solutions that target interconnects for small systems will be described.

Why SWaP-C is needed for small systems
Designers of electronic systems such as portable devices and communications equipment are being tasked with squeezing more functionality into a smaller footprint. As a result, they must reduce the footprint required for existing components to shrink system size while also making room for more components in the same area. In addition, the interconnect system must be rugged enough to withstand being dropped onto a hard floor without cracking or damaging any interconnect. A hard fall can result in a connector developing intermittent connection issues, which if not diagnosed, can result in the device being discarded, a costly consequence for the user as well as the manufacturer’s reputation.

Industrial robotic systems are another example where SWaP-C optimization is desirable. While it may not appear obvious that a heavy robotic system would gain much by reducing the size of a few connectors, real SWaP-C gains are achieved not by one optimization but by the combined optimization of hundreds of subsystems. Lower weight and smaller size in robotics improve efficiency and translates into less power needed to move an arm or aperture, which reduces costs. Robotic arms are also often subjected to hard starts and stops, which over time can stress interconnect systems, resulting in intermittent failures. Robotic systems also need to carry both power and digital signals in the same wiring harness, resulting in an interconnect challenge in carrying both types of signals in the same connector reliably and without interference.

Aviation systems are an obvious area where SWaP-C is needed, as an interconnect that has a lower weight, smaller size, and can transfer more power results in a lighter aircraft with greater efficiency. Aviation systems are also subject to regular inspections where connectors are frequently unmated and mated. The interconnect system must be able to withstand a high number of mating/unmating cycles, while also having a variety of keying options to prevent an incorrect mating event when many connectors are in the same area.

SWaP-C optimization is particularly advantageous for drone designs where every ounce saved can have a noticeable improvement in battery life and time of flight. Drones are also very size conscious. The smaller the drone, the less power required to keep the drone balanced around its center of gravity.

Smart home appliances are another area where SWaP-C optimization is needed. Smaller and lighter appliances are always an advantage for installation in cramped kitchen spaces. A rugged interconnect system is needed for appliances such as dishwashers, washing machines, and clothes dryers where, over time, vibration can cause the wrong interconnect system to disconnect. Connectors must also have easy and reasonable mating/unmating cycles for ease of maintenance.

The requirements of these various applications have resulted in a variety of innovative interconnect design approaches, many of which can be applied together on a single line of interconnects to ensure optimum performance, reliability, and ease of use.

Screw lock interconnect for SWaP-C optimizations
For example, for ease of use, connectors should be easy to mate for fast equipment assembly, easy to unmate for ease of maintenance, yet still be strong enough to withstand shock and vibration, and lightweight enough that they don’t place any stress on the low-current wires in the cable assembly. For SWaP-C interconnect optimizations that require solid interconnect in any situation, Harwin has the Gecko SL 1.25 millimeter (mm) pitch screw lock interconnect system. These are high-reliability connectors that are designed to be up to 45% smaller and up to 75% lighter than the popular micro-D connector commonly used in equivalent applications.

An example of a mated pair of Gecko SL connectors is the Harwin G125-2241096F1 10-position receptacle and the Harwin G125-3241096M2 10-position panel mount plug (Figure 1). The plug housing on the right is recessed and keyed on the top and bottom surfaces. This prevents incorrect receptacle insertions which can lead to equipment failure. Gecko-SL connectors are available with a variety of keyed configurations to prevent incorrect insertions when multiple connectors in a system are grouped near one another.

The Gecko SL interconnect system uses crimp contacts and has two screw locks to secure the connectors in place. This is an advantage for systems subject to vibration and high impact shocks where connectors can be forcefully unmated. The stainless-steel screw locks ensure a tight connection in any situation. The connector system uses a mate-before-lock mechanism that provides a solid electrical connection even before the two screws are secured. This allows technicians to temporarily mate the connectors during maintenance and testing situations. As the interconnect system appears symmetrical on the horizontal axis, the top side of each connector has a triangular contact mark to make mating easier for technicians. The connectors are rated for 1000 mate/unmate operations, making them appropriate for aerospace applications where connectors may be unmated during regular inspection and maintenance.

Each of the ten pin positions is rated to handle a maximum of 2.8 amperes (A) in isolation. If all contacts are used simultaneously to carry current, each contact can handle a maximum of 2.0 A. With five power and five ground contacts, this gives the connector a maximum power transfer capability of 10.0 A.

When mated, the connector system has a high resistance to abuse and can withstand a 100 g, 6 millisecond (ms) shock as well as a 20 g vibration for six hours, making it appropriate for harsh robotic and industrial systems. The housings are made of glass-filled thermoplastic that can operate over a temperature range from -65°C to +150°C. This makes the connectors suitable for aeronautics systems that can see extremes in temperature from hot desert runway heat to the extreme cold of high altitudes. For systems that can see high-frequency vibrations, it is recommended to apply a back-potting compound to the crimp assemblies to provide further reinforcement.