Waiting To Connect |
|||||||||||||||||||||||||||
|
The purpose of a connector is easy to describe: connectors bridge the gap between individual pieces of electronic equipment in order to make the assembly, repair and upgrade of the equipment easier to accomplish. Instead of struggling with a gordian knot of soldered circuits and spliced wiring, connectors enable electrical technicians to interconnect the wires, cables, boards and subassemblies of an electronic system with ease and convenience.
Connectors function at the circuit level. They bridge the gap between individual wires to provide contact between two conductive elements of an electronic system. The connection they make enables electrical current (or light waves in the case of fiber optics) to flow from one conductor to the next. Edward's Publishing's indespensible Encyclopedia of Connectors defines the connector as "an electromechanical device which permits two or more circuit elements to be electrically and mechanically separated and reconnected at will without disturbing any other elements of the circuit. A connector performs no circuit function and should have no effect on the electrical performance of the device to which it is attached. If the connectors of a device were eliminated and the corresponding wires joined together, the circuit would not be affected".
Connectors appear throughout an electronic system. When they are used to connect one set of wires to another, they are called wire-to-wire connectors. Wire-to-board connectors connect
a wire to a Printed Circuit Board (PCB). And board-to-board connectors are designed to directly interconnect PCB's.
Connectors improve the manufacture and assembly of electronic products by enabling designers to treat each subassembly as a unique, modular unit. Interconnection can then be accomplished at the most convenient time and place in the production process. The knee bone gets connected to the leg bone when the production engineer says so, not just because it's the next link in the schematic. For this same reason, connectors also facilitate the equipment repair process by allowing technicians to quickly and easily replace suspect components. Without opening black box cabinets and without introducing contaminants like solder and flux into the system, technicians can swap out suspect equipment and have a system back on line in a matter of minutes. Connectors also permit upgrades to electronic equipment without major disruptions to the overall system. Connectors give engineers the flexibility to design and integrate new products and components into existing systems simply by maintaining a consistent connector specification. While there is great variety in the makeup and design of each type of connector, as a family they generally share a common set of design elements and component parts. In fact, in order to function as a separable interconnect device, a connector usually has the following features:
Connectors are selected with consideration to electrical, mechanical and environmental requirements. Electrical requirements include contact resistance, transfer impedance and current rating. Mechanical specifications, such as thermal shock, vibration and durability indicate how well a connector will perform under critical stress factors. Environmental requirements include moisture absorption, temperature resistance, corrosion and resistance to electromagnetic interference. Environmentally resistant connectors are required for interconnect systems which are subjected to fluids in combination with vibration, shock, thermal extremes and corrosion. All three categories of performance requirements must be addressed when matching a particular connector to its application environment.
While the same basic connector design may be used for both signal and/or power distribution, power connectors use contacts designed specifically for the unique requirements of power distribution. This is due to the relatively higher current/voltage requirements of power applications and the temperature rise experienced by power connectors. A disk drive in a personal computer, for example, uses both signal and power connectors. The power connector bridges the circuit that drives the unit. The signal connector carries the digital data, generally over a low current (sub 3 AMP) circuit. While the signal and power contacts may be combined into a single connector housing, each contact type is uniquely suited for its role in transmitting either signal or power electrical energy.
Optimized for High-Reliability: The Military Standard Connector The multi-contact electrical connector used in Air force, Navy and other high reliability aerospace applications is a critical subassembly within the interconnect wiring system. The military connector finds many diversified applications due to severe environments, mobility of equipment and field repairability. The key attribute of these connectors is their relatively better reliability when compared to less expensive commercial connectors. The reliability of a system is dependent on the failure rate of its components. Connectors can fail due to plug dependent mechanisms, wear mechanisms or corrosion mechanisms. Total system life, power on-hours (POH) and system on/off cycles (number of times that a product powers on and off) are important factors determining system reliability. Military standard connectors (and their commercial equivalents) are chosen for their performance and reliability even in the most severe interconnect applications.
The military standard connector is made up of two separate component assemblies known as the "plug and receptacle" which intermate to connect wires with pin and socket contacts. Connector families are defined in this high-reliability world by the military detail specifications which spell out the exact requirements for every aspect of the connector's design and performance. Connector families are distinguished by their coupling mechanisms, physical shape, contact types, environmental classes and termination methodologies.
Plug and receptacle connector pairs are available in various mounting configurations to accommodate different levels of interconnection and different application requirements. The most common configurations are for in-line (wire-to-wire) applications, or for various bulkhead, chassis and enclosure mountings. In general, connector designs are available to accommodate any fixed mounting or in-line requirement.
Circular connectors are selected because of their compact, rugged design and their ability to effectively seal the connector from environmental hazards. Circular connectors may incorporate bayonet couplings, threaded couplings, ball detent couplings (push/pull), and/or breech lock couplings as their mechanism for locking the mated pairs together.
Rectangular connectors are selected to maximize the number of contacts possible in a restricted space. However, rectangulars are not as easily sealed against fluid damage and other environmental hazards. Spring style rack/panel couplings as well as standard jackscrew fasteners are both common coupling styles in rectangular connectors. Both circulars and rectangulars can accommodate multiple contact types including power or high-voltage contacts, signal contacts, coaxial and triaxial contacts, or fiber-optic termini. High reliability contacts are usually made from gold plated, copper alloy material. Large diameter power contacts and solder type contacts may be either gold or silver plated copper alloy. Crimp style contacts are preferred for all aerospace and other high reliability applications (except those requiring a hermetic seal) due to their relative ease of assembly and maintenance. Crimp contacts can be removed from the connector for servicing or in order to replace a bad contact. Solder type contacts, which are permanently fixed in the connector, are usually selected when cost is the primary consideration and repairability secondary. Solder type contacts are also used in hermetic connectors and in applications with unique termination requirements, such as high-voltage power connectors. Installation of both crimp and solder type contact connectors requires unobstructed working room behind the connector rear-end. Rear release crimp contacts require additional working room to install the extraction tool to remove the contact. Another important design feature of crimp type contact connectors is the connector insert wire sealing grommet. The grommet is permanently fixed to the connector insert, and provides moisture sealing around each individual wire.
The shell of a circular connector is a cylinder available in incremental sizes starting as small as .375" diameter up to 3.25" diameter and larger. The most common shell sizes are available in .0625" increments starting at shell size 8 (.50") to shell size 36 (2.25"). Shell size may be determined by multiplying the shell size number by .0625. Shell size 24, for example, has a 1.50" outside diameter (24 x .0625" = 1.50"). This nomenclature becomes significant, as backshells (accessories which attach onto the connector shell) must intermate with the connector shell rear-end geometry. Connector and accessory manufacturers both use the term "shell size" to designate the size of their respective products.
Making Sense of Connector Part Numbers Military standard connectors are organized under specification series numbers: MIL-DTL-5015, MIL-C-38999 and so on. The specification series number identifies the master document which explains in detail everything concerning the particular connector family. The actual part numbers of connector components are designed to call out the physical connector type and the dimensional attributes of the connector. For example, a MIL-DTL-5015 receptacle connector designed to be mounted on a box would have a part number such as MS3402DS28-21PY. The part number can be dissected as follows: The first 4 digits after the MS (Military Standard) designate the physical connector type, like so:
3400 - Wall mounted receptacle The single character which follows indicates the connector service class:
D - High Shock The next character, S in our example, indicates the shell material; in this case stainless steel. The next two characters, 28 in our example, identify the shell size. The following pair of numbers, 21 in our example, identifies the contact arrangement. If this pair of characters is followed by an "S", it indicates female-style (socket) contacts. If they are followed by a "P", it indicates male contacts (Pin). The final character, Y in our example, indicates the choice of polarization keying. That's all there is to it. While there are many part number complexities and nuances throughout the various MS connector families, they all follow the same basic approach to part number development.
|
| Glenair QwikConnect Navigator | ||
|
|
 |
 |
 |
 |
 |
 |
 |
