Unmanned Systems Technology 024 | Wingcopter 178 l 5G focus l UUVs insight l CES report l Stromkind KAT l Intelligent Energy fuel cell l Earthsense TerraSentia l Connectors focus l Advanced Engineering report

88 For example, the JST-SH connector has a 1 mm pitch, can come with two to 20 contacts, and is a fairly common feature on small multi-rotor autopilot PCBs, as well as some data link transmitters and receivers. It can provide for 1 A signals and crimp wires of 28 to 32 AWG to its contacts, which are typically copper alloy, tin and gold-plated, with copper undercoating. Another type, the JST-GH, is often used in 5.8 GHz video transmitters, and has two to 15 contacts 1.25 mm apart and compatibility with wires sized 26 to 32 AWG, also with a 1 A current rating. It typically comes with a plastic locking tab that seats the plug into the receptacle. By contrast, the JST-XH carries 3 A per pin, with a 2.5 mm spacing between them. Between one and 20 circuits can be connected, from AWG size 30 to 22 (0.255-0.644 mm). These connectors are most often used on battery balance leads. Circular connectors Circular connectors are less suited to PCBs owing to their size requirement relative to rectangular or strip connectors. They cannot be flattened or ‘stretched’ to hold a high number of contacts in the way that rectangular connectors can. That said, they can still cost less to manufacture and have a smaller footprint than rectangular connectors, while offering somewhat greater modularity, partially as a natural result of their geometry. If eight to 10 contacts are required, for example, then arranging them in a circular connector takes up less space than in a rectangular one. While screw-locking circular connectors can require the same number of fasteners (or more) as rectangular connectors, the circular shape is better suited to many of the aforementioned tool-free locking methods, such as threaded, push-fit and bayonet types. They are also suitable for designing a set screw inside their cylindrical housings, while rectangular shapes cannot be designed in this way. Their shape tends to make them easier to grip and therefore to mate and un-mate, which can be vital for quick data uploads across repeated survey or surveillance missions, for example. Their shape also makes it easier to manufacture sealing rings for them, as required for IP67 and IP68 protection. Circular connectors are also used for delivering high-speed signals such as USB, Gigabit Ethernet and HDMI. Small but data-dense sensors, cameras and actuators gain faster comms and response times with the twisted-pair, differential signal processing methods of the USB 3.0 standard. The general limitation on how many contacts a circular connector can hold is not a significant bar to their application in high-speed data. USB 2.0 connectors require only four pins, Gigabit Ethernet needs just eight, and the USB 3.0 standard needs nine. And while HDMI ports contain 19 contacts, and USB Type-C connectors (for carrying USB 3.1 signals and power of 10 Gbit/s and 100 W) need 18 pins, it is important to note that some circular connectors can now be made with upwards of 20 contacts – some with more than 40. Improvements in design software and tooling advances over the past several years have enabled these density increases, and in time, circular connectors could encroach on the pin counts of micro-D connectors. Advances in payload resolutions, frame rates and data rates, boosted by embedded computer vision or analytics software, are likely to drive the evolution and adoption of circular connectors. February/March 2019 | Unmanned Systems Technology Focus | Connectors Advances in design software and tooling mean that circular connectors can now be designed to carry HDMI and USB Type-C (Courtesy of Fischer) The ideal fluid connector for UAVs – to deliver fuel, say – should differ from those typically used in aerospace in a number of ways