 Evolution of Connector Systems for New Unmanned Equipment
By Bob Stanton, Director of Technology,
Omnetics Connector Corporation
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| Photo: courtesy of Harris bomb disposal team |
Unmanned equipment and technology are expanding into nearly all walks of our lives. We are developing new systems that can expand our reach and capabilities using remote controlled equipment, but we are also adding to the challenges and demands placed upon the electronics that serve and drive them. Connectors and cable systems have been changing rapidly to meet those needs. Conveniently, technology advancements have helped speed up the design and manufacturing of new cables and connectors for application-specific unmanned equipment. Remote devices now serve us, spanning from simple ground based robotics, to drones mounted with cameras, and rovers on Mars. Each new system starts by using COTs and standard connectors on its prototype modules. As the design evolves and enters into the systemization phase, new design needs arise. Emphasis changes include size reduction, shape fitting, and/or mounting requirements. Extremely rugged connectors may need to carry enough current to control heavy machinery used in dangerous conditions. See the photo attached of the Harris T7 Explosive Ordinance Disposal (EOD) System. Equipment like this will protect and save lives across the spectrum from Military to Civil Service agencies.
Circular connectors that have typically been used in ruggedized equipment and machinery have begun to evolve in many ways to serve these industries. To meet today’s demand for small diameter connectors, many manufacturers are scaling down older designs to add to their existing lines. The popular Mil-DTL-38999 Circular connector uses 18-20 size pins to carry up to 12 Amps on 20 AWG wiring. A smaller 38999 connector is being standardized by a number of companies working with the Defense Logistics Agency (DLA) for a down-sized Mil. Spec. version that will be a smaller, more universally available circular connector with a triple-start thread coupling system. It will also mate quickly and have EMI shielding. This new standard will likely use size 23 pins and handle about 10 Amps on 20-22 AWG wire. Many companies already offer a smaller Micro-Circular connector line with size 24 pins/sockets that support 3 Amps on 24-30 AWG wire. Some of the smallest circular connectors offer the use of size 30 pins, support 1 Amp and 30-32 AWG wiring. In this size, note that pin to pin spacing drops from over 75 millimeter pitch down to 25 millimeters. This reduces the diameter of both the connector and the cable involved. Cable flexibility is improving simultaneously.
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Many new circuits respond well to lower voltages and current flow, allowing the connectors to be more compact. The newer and smaller ratcheting connectors mate easily and lock quickly while offering additional features, such as waterproofing and using less panel mounting space on the instruments. Special ground wires and the use of braided cable shielding are often used to protect the cable from both electrical and physical damage by connecting the shielding onto the back-shell of the metal ratcheting style connectors.
Unmanned equipment systems often require easy disconnection and reinstallation of electronic modules that are mounted and carried within the equipment. Examples include image storage or Ethernet modules on hand-launched UAVs during Intelligence, Surveillance and Reconnaissance (ISR) missions. The fast-latching connectors are exchanged on the ground with fresh modules. The connector’s lighter weight allows for longer flight times and more maneuverability in hand-launched aerial systems. Many ISR circuits are using solid state chips that run at digital Gigabit speeds. In addition, high speed surveillance and image displays demand high signal integrity of the connectors. UAV video capture rates are climbing as we install devices that send 20 megapixel images at 60 frames per second and are compressed into transmission or storage onboard. This totals over 7 gigabits/sec transmission of digital data.
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| Omnetics SWaP Connectors |
Unmanned connector systems must focus on rugged performance to survive the rigors of their applications. Connector mating elements and housings are often critical. Frequent use of nickel plated 6061-T6 aluminum or hardened polymer shells contains the pin to socket elements inside. Beryllium Copper flex pins are made to ASTM B194 and tempered to over 17200 ksi and then plated with nickel/gold. Low resistance is critical while retaining contact during shock and vibration of the oft-moving equipment. Wires are most often strengthened copper coated with Teflon® insulation. Connectors are pretested for high reliability and long range performance.
Fortunately, the increasing demand for lighter and smaller cables and connectors is simultaneous with the change in circuit voltages and currents. More ruggedized Micro- and Nano-sized rectangular connectors are being used in UAVs as modern designs are being completed. The push for SWaP (Smaller, Lightweight, and Power) has been answered two ways. First, designers can begin with ruggedized military-quality Micro- and Nano-D connectors that allow them to tailor their designs on the fly. Second, solid models can be quickly adjusted and sent to automated machining equipment to build them to fit the new application exactly.
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Beyond customizing standard designs, connector designers now supply a wide range of mixed signal hybrid connectors. Size and weight are significantly reduced by using only one cable and connector carrying both power and signal in the same system. These new hybrid connectors are also adjusted to meet the application that is specifically needed. The new connector designations are still evolving but seem to be settling at SWaP-R or SWaP-C (Speed, Lightweight, Power, and either Reliability or Cost, whatever is most critical).
For more information visit: www.omnetics.com
Bob Stanton, Director of Technology, Omnetics Connector Corp.
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