Your ultimate guide to connectors: master RF cable assembly selection, explore industrial cabling options, apply new standard connectors for LED lighting, and see how connectivity drives sustainable automation
We get technical
Connectors | Volume 11
The engineer’s guide to RF cable assembly selection and use Connector, gland, and grip options for industrial-automation cabling Understanding and applying the new standard connectors for indoor & outdoor LED-based lighting Connectivity – the backbone of sustainable automation
we get technical
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4 12 18
The engineer’s guide to RF cable assembly selection and use
An introduction to circular connectors and cables
Thermodynamics backgrounder
24 32 38 44 54 62 74 80
Connector, gland, and grip options for industrial-automation cabling
How to select 48 V connectors for medium-voltage automotive architectures
Special feature: retroelectro Genius and tragedy
Understanding and Applying the New Standard Connectors for Indoor & Outdoor LED-Based Lighting
What constitutes a heavy-duty connector and where are they used for industrial connectivity
Understanding and choosing GHz-range coaxial connectors and cable assemblies
Connectivity – the backbone of sustainable automation
Understanding USB specifications for selecting the correct cables, plugs, and jacks
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Editor’s note In this issue, we dive into the essential elements that drive today’s most sophisticated electronic systems. As engineers and designers, you know that choosing the right connectors, cables, and assemblies isn’t just about functionality—it’s about enhancing performance, reliability, and efficiency across all applications. We’ve compiled an expert guide to help you navigate the complex world of RF cable assemblies, GHz coaxial connectors, and USB specifications. Whether your project involves high-frequency applications or rugged outdoor conditions, our articles offer technical insights and practical tips on selecting components that meet the highest standards. You’ll find in-depth articles on medium-voltage connectors, critical for applications that demand robust power delivery and safety, as well as circular and heavy- duty industrial connectors designed for environments where reliability and resilience are paramount. We’ll also take a closer look at outdoor LED lighting connectors, an essential element for urban and industrial lighting systems. With so many options and specifications to consider, we hope this issue serves as a valuable reference for making informed choices and staying at the forefront of connector technology. Enjoy the read, and as always, we welcome your feedback and insights.
The engineer’s guide to RF cable assembly selection and use
By Kenton Williston Contributed By DigiKey's North American Editors
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RF cable assemblies are used in a wide range of applications, from well-established domains like aerospace and communications, to newer use cases like automotive, industrial, and the Internet of Things (IoT). This expanding list of applications has prompted the development of new types of RF cable assemblies, giving engineers further opportunities to optimize their RF system designs. However, all this growth is complicating the design process. With so many assemblies on the market, it is difficult to identify the best choice for a particular application. Also, the use of RF cabling in new applications is putting unfamiliar technology in front of more designers, installers, and maintenance technicians. Along with space and environmental considerations, those groups must now become familiar with frequency compatibility, impedance matching, voltage standing wave ratio (VSWR), magnetic coupling, and shielding. To ensure the performance and reliability of RF systems, engineers need an attentive approach and a clear roadmap of the options and potential pitfalls that await them.
Beginning with a brief overview of RF applications including their electrical characteristics, physical construction, and typical use cases, this article serves as a guide to the complex task of choosing, installing, and maintaining RF cable assemblies. Examples from Molex are introduced to illustrate key selection and usage criteria. The expanding use cases of RF cable assemblies RF technologies span a multitude of sectors, each with its unique challenges. Frequencies range from hundreds of hertz (Hz) to tens of gigahertz (GHz). Some applications require ruggedization. Others have extremely confined physical footprints. To illustrate the diversity of use cases, consider these common applications: ■ Aerospace and defense: Radar systems, communication channels, and GPS ■ Automotive and transportation: Infotainment systems,
■ Industrial: IoT sensors, automated assembly lines, and telemetry ■ Medical: Remote patient monitoring systems, advanced diagnostic machinery, and robotic surgery units ■ Test and measurement: Bench measurements, field tests, and quality assurance in manufacturing setups Due to the growing use of RF, more engineers and designers are engaging with high-frequency circuits, many without a background in this technology. Faced with tight deadlines and budgets, they need solutions that simplify their tasks while ensuring their systems perform reliably. That is where RF cable assemblies come in. These assemblies consist of pre-assembled connectors and cables that meet the specified performance requirements while reducing the engineering effort. Using premade RF cable assemblies can save time and cost during design and prototyping, and improve the quality and efficiency of production.
navigation, and vehicular communication networks
■ Telecommunications and broadcast: 8K video signals over Wi-Fi, LTE, and 5G networks
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The engineer’s guide to RF cable assembly selection and use
To achieve the desired performance, a cable assembly must handle the appropriate frequency range without significant signal loss or distortion. For example, the Society of Motion Picture and Television Engineers (SMPTE) sets stringent signal quality requirements under their 2082-1 guidelines, which limits loss to 40 decibels (dB) at half the clock frequency.
One way to meet these demands is with the Molex BNC Mini RF Cable Assemblies, which deliver high return-loss performance at frequencies of up to 12 GHz. This performance exceeds the requirements for serial transmission of 8K high-definition TV (HDTV) video, allowing for future bandwidth expansion without hardware changes.
Frequency compatibility, impedance matching, and VSWR Choosing the appropriate cable assembly requires careful consideration of multiple factors. First, the assembly must be able to accommodate the frequency range of the RF signal. These can vary from a few hundred hertz to the super high frequency (SHF) band of 3 to 30 GHz or higher (Figure 1).
Figure 1: RF cable assemblies come in a wide variety of designs, which can be categorized by the size of the connector and their maximum supported frequency, among other factors. (Image source: Molex)
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CONNECTOR-TO -CONNECTOR
VOLTAGE STANDING WAVE RATIO VSWR)
ORDER NO.
CABLE LENGTH
LENGTH
LENGTH
89762-1540
152.40 mm / 6.00"
1.00 dB
89762-1541
228.60 mm / 9.00"
1.43 dB
89762-1542
304.80 mm / 12.00"
1.85 dB
086 low-loss
1.50 max to 40 GHz
89762-1543
381.00 mm / 15.00"
2.15 dB
89762-1544
457.20 mm / 18.00"
2.85 dB
2.92 mm ST plug to 2.92 mm ST plug
98762-1580
152.40 mm / 6.00"
1.65 dB
89762-1581
228.60 mm / 9.00"
2.30 dB
89762-1582
304.80 mm / 12.00"
2.90 dB
047 low-loss
1.55 max to 40 GHz
89762-1583
831.00 mm / 15.00"
3.60 dB
89762-1584
457.20 mm / 18.00"
4.20 dB
Figure 2: Shown are examples of VSWR and insertion loss figures for efficient, low-loss, microwave-frequency cables. (Image source: Molex)
Impedance matching is another key parameter. RF signals are susceptible to interference from incident and reflected waves caused by an impedance mismatch along the signal line. To minimize signal loss, the cable assembly should have the same impedance as the connected load, typically either 50 or 75 ohms (Ω). It is good practice to design the connectors and cables together to achieve the best match.
A real-world example of this practice is the 0897629290 assembly that pairs Molex BNC connectors with a Belden 4794R cable for high-end 75 Ω applications.
ratio of an incident signal to the reflected signal that provides a measure of how efficiently RF signals are carried from source to load. Insertion loss is the amount of energy that a signal loses as it travels along a connector and cable. Figure 2 illustrates some examples of each.
For particularly demanding applications like test and measurement, it may be
necessary to carefully consider additional parameters like VSWR and insertion loss. VSWR is the
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The engineer’s guide to RF cable assembly selection and use
Figure 3: Shown is a typical shielded cable. Starting from the inside of the cable are the core conductor, a dielectric material that separates the core from the shield, a woven metal shield, and the cable jacket. (Image source: Molex)
There is also the form of shielding to consider. Metallic braids like those on the 0897616761 MCX assembly with RG-136 cables offer excellent mechanical strength and physical protection. In contrast, foil shields are typically made of aluminum laminated to a polyester or polypropylene film for a lightweight, inexpensive, and flexible alternative. There are other types, such as spiral, tape, and combinations, which vary in terms of percentage of frequency coverage, flexibility, lifespan, mechanical strength, cost, and ease of termination. There may also be unique application requirements to consider. For example, medical applications often involve sensors that can be affected by magnetic fields. Here, a solution
like the 0897616791 MMCX cable assembly is a viable choice, as these assemblies are available in non-magnetic coupling versions for better design compatibility. Space constraints, environmental hazards, and maintenance When considering physical parameters, limitations on space and routing are often the main obstacles. Consider defense applications, which are notoriously cramped. Here, a solution like the 0897611760 SSMCX cable assembly is practical. SSMCX connectors are some of the smallest on the market and are available with vertical and right-angle orientations to accommodate challenging space and routing constraints.
Shielding, magnetic coupling, and other considerations
Shielding is another important consideration. Any cable carrying RF signals can act like an antenna and broadcast or receive signals, creating interference. To minimize this interference, cables need to be shielded by a grounded metallic housing (Figure 3).
Shielding material choice is influenced by a range of
factors, including performance requirements, environmental conditions, and budget constraints. For example, copper is highly effective across most frequencies but also relatively heavy and costly, while aluminum is light and inexpensive but less effective and more prone to corrosion.
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Designers also need to consider the minimum bend radius when selecting an assembly. Due to their complex construction, RF cables tend to be rather stiff. For situations that require tight turns, look for solutions like the flexible microwave assemblies from Molex (Figure 4). These cables are specifically designed for a smaller static bend radius. Temperature extremes can also be an issue, particularly for outdoor applications like those in the telecom sector. For such applications, the thermoplastic jackets common on RF cable assemblies are not suitable.
STATIC BEND RADIUS (MIN.)
CABLE PART NO.
CENTER CONDUCTOR
OUTSIDE DIAMETER
CUTOFF FREQUENCY
IMPEDANCE VOP CAPACITANCE
INSULATION JACKET
0.20"
0.0113"
0.061"
112 GHz
100067-1047
70% 29 pF/ft
100067-1086
0.30"
0.0201"
0.101"
62 GHz
100067-1141
0.50"
0.036"
0.158"
41 GHz
100054-0007
23.0 pF/ft
0.30"
0.0126"
0.056"
143 GHz
PFA
FEP
50±1 Ohms
100054-0006
23.4 pF/ft
0.38"
0.0253
0.158"
42 GHz
100054-0008
0.75"
0.0453"
0.158"
42 GHz
87%
100054-0027
1.00"
0.0571"
0.210"
31 GHz
23.3 pF/ft
100054-0028
1.60"
0.0907"
0.310"
19 GHz
Figure 4: Shown is a sampling of RF cables with a small static bend radius. (Image source: Molex)
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The engineer’s guide to RF cable assembly selection and use
Instead, more durable materials are required. For example, the flexible microwave assemblies mentioned earlier use Temp-Flex fluorinated ethylene propylene (FEP) material for the jacket, which is a tough material similar to Teflon. Vibration and shock can compromise a design, particularly in applications like aviation. To ensure reliable operation, the RF cable assemblies used must have extraordinarily secure connections. A good example is Molex’s 0732306110 cable assembly, which utilizes I-PEX’s patented MHF® LK connector locking mechanism (Figure 5).
Maintenance must be considered as part of the design process. It is important to look at the mean time between failure (MTBF) for cable assemblies and consider how to arrange a design for ease of maintenance and repair with reasonable access to those subassemblies and connections that might need the most care. Designers should also consider creating inspection schedules for normal maintenance, and user checklists for signs that a cable assembly might need repair or replacement to proactively manage complications.
Common maintenance steps include checking assemblies for wear, as well as cleaning cables and connectors to remove contaminants that could penetrate connections and degrade performance. Finally, it’s important to evaluate the cable assembly manufacturer. Criteria include appropriate certifications, experience in producing the relevant assemblies, sufficient product options to support design flexibility, and quality assurance processes to avoid performance issues. For example, Molex has been a leading developer of cable and connector technologies with innovation supported by more than 8,100 patents and a strong reputation for quality and technical support, including a custom cable creator tool.
Figure 5: The MHF LK connector system from I-PEX uses a patented locking mechanism to ensure a secure connection. (Image source: Molex)
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Conclusion Selecting the right RF cable assembly is challenging as it requires an understanding and careful consideration of factors such as frequency compatibility, shielding, environmental conditions, space constraints, and maintenance. As shown, collaborating with a seasoned manufacturer that brings
expertise, quality assurance, and innovation to the table can be the key to navigating these challenges, particularly for engineers and designers who are new to RF. Such a partner can guide the process of selecting, installing, and maintaining these cables to ensure that devices and systems reliably operate at their peak.
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An introduction to circular connectors and cables
By Jeff Smoot, VP of Apps Engineering and Motion Control at Same Sky
Housing multiple pins or contacts for transferring electrical power, signals, or data, circular connectors are cylindrical electrical devices of varying sizes that are designed to withstand a range of harsh environments. Also referred to as circular interconnects, their circular construction affords them additional ruggedness and resistance to vibration and impact damage, outside signals or interference, incursion from environmental contaminants, and pressure or temperature extremes. Due to their high performance in these extreme conditions, circular connectors and cables find broad uses in industrial and factory automation applications, medical devices, security and defense systems, aerospace, and more. Circular connectors encompass a wide array of product offerings from standard circular connectors to DIN, Metric, Hermetic, Push-Pull, Keyed, Mixed Signal, and Micro or Nano versions. Hybrid options are also available that combine power, signal, and data into a single device. This article will primarily focus
on standard circular connectors and cables, including their basic construction, designations and codes, selection criteria, and more.
Circular connector construction
Thanks to their cylindrical shape, circular connectors have a higher strength-to-weight ratio than any other connector shape. As already mentioned, this enhanced strength gives them added resistance to impact damage, outside elements, and decoupling, while giving them durability in applications with frequent mating cycles. The number of internal contacts as well as the layout of those contacts varies by connector and application type to ensure correct alignment and insertion into a compatible mating device. Circular connector shells are often constructed with threads to allow for more secure screw-in connections where vibration or other factors would potentially cause unwanted decoupling. Other types of connection systems include bayonet locking, push/pull locking, and snap lock.
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An introduction to circular connectors and cables
Figure 1: Basic construction of a female circular connector. (Image source: Same Sky)
Figure 2: Basic construction of a male circular connector. (Image source: Same Sky)
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From a high level, each circular connector consists of four main areas (Figures 1 and 2): 1. Contacts: The internal pins and sockets housed in the connector used to form the electrical connection. A mated pair consists of male contacts and female sockets. 2.Insulator: This component encapsulates the contacts and insulates them from each other and the connector shell. It also provides proper spacing of the contacts and holds them in the correct position. 3.Shell: As the outer cover of the connector, the shell protects the contacts and insulator while providing the alignment and connection mechanism for pairing two connector halves.
“M” simply calls out the size of the metric thread on the coupling nuts and mating receptacles, which gives us the common M5 (5 mm diameter fasteners), M8 (8 mm), and M12 (12 mm) connector types. M12 circular connectors and cables are arguably the most common type found as they are a global standard for the automotive industry.
As a whole, M-style connectors are further divided into several categories that define the keying and shape of the contact body to ensure properly mated connections. These designations and codes are defined as follows (Figure 3):
4.Accessories: These can include pins, keys, rings,
clamps, gaskets, and additional components utilized to guide, secure, position, and seal parts of the connector. Common circular connector designations and codes Perhaps the most well-recognized type of circular connector is the M-style standard utilized for connecting sensors and actuators in industrial network applications.
Figure 3: A general overview of the various interface options for M-style connectors. (Image source: Same Sky)
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An introduction to circular connectors and cables
A – connectors for sensors, dc power and 1 Gbit Ethernet (protocol for connecting computer systems to form a network). B – connectors for Fieldbus (industrial computer network for distributed control) and Profibus (digital network standard providing communication between field sensors and a control system). C – connectors with a dual keyway for added security, used for ac power for sensors and actuators. D – connectors for 100 Mbit Ethernet and Profinet (protocol for data exchange between controllers and devices) systems. X – connectors for 10 Gbit Ethernet high speed applications as well as power over Ethernet (PoE). S – connectors for ac power (replacement for C – coded parts). T – connectors for dc power (replacement for A – coded parts).
Figure 4: Mating of a male and female circular connector pair. (Image source: Same Sky)
Circular connector selection criteria
There is a nearly endless list of specifications and considerations to take into account when selecting circular connectors and/or cables for a design. Outside of deciding whether a circular plastic connector (CPC) or circular metal-shell connector
Figure 5: How to designate jacks and plugs of different genders. (Image source: Same Sky)
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(CMC) is the better fit, here is a relatively comprehensive list of parameters to consider: ■ Gender (Male/Female): The male end incorporates the contact pins that plug into the female sockets (Figures 4 and 5). Most plugs and receptacles are designed to mate within their own brand or manufacturer. Connectors from different manufacturers typically do not interconnect, so in general, connectors will be sourced as a mated pair. ■ Number of Contacts: The number of conductive pins in the connector required to carry the signals, data, or power. This number can range from 1 into the hundreds. ■ Termination: How the wire or cable will mate with the conductive contacts in the connector, including solder, wire wrap, lugs, or crimping. ■ Contact Size: The diameter of the individual contacts or gauge of wire that can mate with each contact. ■ Voltage & Current Rating: The maximum voltage, expressed as volts (V), or current, expressed as amps (A), that the connector is designed to carry.
■ Insertion Frequency: How often the connector will be connected and disconnected. Also known as mating cycles, the frequency of connection may require a more robust connector or cable protection accessory. ■ Mounting Style: Common mounting options include cable mount, panel mount, or surface mount. ■ Coupling or Locking Style: Offers secure mating of the connector and can include bayonet, latch, push-pull, threaded, and quick-disconnect. ■ Backshell Type: Threaded onto the cable side of a circular connector to offer secure cable support, backshell types include straight, right angle, braid tail, spring, strain relief, sealed, and crimped. ■ Materials Used: Common materials used for the connector body are stainless steel, aluminum, plastic, composite, or brass, depending on design requirements and budget. ■ Ingress Protection: IP ratings are defined by the IEC 60529 standard that covers protection against solids and liquids entering the body of the connector. ANSI 60529 covers IP in the United States and EN 60529 covers it in Europe.
■ Plugs & Sockets: There is no standard naming convention so different manufacturers may use alternate terms, but typically sockets and jacks are associated with panel mounted circular connectors, while plugs relate to circular connector cable assemblies. Conclusion Will the connector be exposed to environmental contaminants or subject to immersion? Does the connector require protection from EMI or RFI signals? Will the connector be subject to excessive vibration or frequent impacts? The answers to each of these will help determine the quality, features, and accessories needed, but regardless, circular connectors have proven to be a reliable and rugged interconnect solution when dealing with harsh application conditions. Same Sky offers a diverse range of circular connectors and circular cable assemblies that can meet these design challenges head on.
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Thermodynamics backgrounder
Electronics engineers only have to study thermodynamics for a few short weeks in college, and in that time, it is common for confusion and forgetfulness to overcome deep and meaningful learning. What follows is a brief refresher on the physics of resistance and heat and how it applies to printed circuit board and component failures.
By Mark Hughes
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Mental metal mayhem Metals are collections of atoms arranged in an orderly crystalline lattice with one or more free electrons. This arrangement allows the outermost electrons to move freely from atom to atom. If the atoms were stuck rigidly in place, electrons could travel from atom to atom without much interruption. However, the quantum world is awash with wiggles, waggles, and wonder. Unless an object’s temperature is absolute zero, atoms are never completely still -- they translate, rotate, and vibrate. The macroscopic products of this microscopic movement is the basis for study of thermodynamics.
Metals are orderly collections of atoms that are able to easily share their outermost electron(s) with neighboring atoms.
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Thermodynamics backgrounder
Visualization Even with perfect eyesight and the best optical microscope, observing the movements of atoms and molecules is impossible. The movement occurs on the scale of picometers and at frequencies measured in terahertz. At the atomic level, those constant and slight movements will disrupt any uninterrupted path an electron might try to take through the lattice, causing a collision with another electron, and a significant change in direction of movement. These disruptions are the basis for resistance. Consider a game of pool or billiards: imagine taking a shot while all of the balls, the pockets, the bumpers, and even the table move and vibrate in every direction. In this analogy, the pool balls are electrons, and the pool table is the crystalline lattice structure of the metal. Just as the balls in the games wouldn’t follow predictable paths, electrons will not either. Unlike the sixteen pool balls on the table, there are far more electrons in one pool ball than there are pool balls in the world (perhaps ). So the pool table we need to visualize has a zillion balls on the table. The ball you strike with a cue will cause bulk motion in the direction of your
This AI imagined view of the copper grains that might exist in copper metal. Electrons experience a bit more resistance at grain boundaries.
pool cue, but the first ball you strike won’t go very far before a collision with another ball. Similarly, electrons suffer so many collisions per second that even in high speed circuits, an individual electron moves along a copper trace approximately as fast as your fingernails grow.
Electron movement and resistance As electrons travel through a crystalline lattice in the presence of an electric field, there is no predictable path for any single electron. This randomness
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causes collisions. The Coulombic attraction between Electrons and Protons means that these collisions transfer energy from electrons to lattice nuclei and back to electrons. The increase in energy is predominantly due to translational oscillations. These collective oscillations define the object’s Temperature. The more the atoms oscillate, the greater the likelihood that future collisions will occur, which leads to higher amplitude oscillations, and this feedback loop creates a condition known as Thermal Runaway. Thermal runaway continues until the temperature of the object rises so high that materials decompose into magic smoke and a variety of carcinogens.
The only way to stop this cyclic effect is to allow the lattice to transfer their energy somewhere else through some combination of three processes: conduction, convection, and radiation. Common language Temperature is the measure of the total kinetic energy of a group of molecules. Heat is the transfer of that energy from high-temperature (high energy) objects to low- temperature (low energy) objects. In everyday language, we call objects “hot” if when we touch them, energy transfers out of the object into our hands, and we call objects “cold” if when we touch them, energy transfers out of our hands into the objects.
heat energy out of your circuit or until something fails. Limit heat generation when you can, and when you can’t limit it, expel it from your design into the environment. Heat dissipation There are three passive methods of heat transport: Conduction, Convection, and Radiation. Conduction Conduction happens when objects are in direct contact. Heat energy transfers from the high temperature object to the lower temperature object. Convection Natural convection occurs when a high temperature object transfers heat to a surrounding lower temperature fluid, causing the fluid to expand, and in the presence of gravity, denser and colder fluid comes in and replaces the less-dense and warmer fluid in a cyclic process. Radiation Radiation occurs as atoms emit photons. The photon’s frequency depends on the temperature of the object. As photons leave the object, the parent atoms lose energy and temperature decreases. For better or worse,
Heat generation
Thermal runaway occurs when the heat entering a circuit is greater than the heat leaving a circuit. The temperature increases which leads to increased resistance. Resistance increases due to increasing temperature. This feedback loop eventually leads to temperatures high enough
Every common conductor is subject to Joule’s law of heating: , where P is “Power”, or the rate of heating, I is current, measured in Amperes, and R is the resistance, measured in Ohms. This is true of conductors that obey Ohm’s law, and PN junctions that don’t. If you want current to flow in your circuit, as electronic engineers are wont to do, your design will generate heat and the temperature of the PCB will rise until the rate of heat energy into the circuit matches the rate of
melt or sublimate the conductor and break the circuit.
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Thermodynamics backgrounder
energetic photons from the environment can arrive at the object and raise the temperature of the object.
The trouble with high temperatures High temperatures accelerate the rate of failure for PCB and components, sometimes in exciting ways. When possible, it’s always best to keep your PCB as close to room temperature as possible. But in the real world it’s not possible, so knowing the failure modes and designing mitigations can save your next design!
Other Methods Engineers have developed
methods to improve these three natural passive methods. For example, thermoelectric coolers take advantage of the Peltier effect to provide localized cooling at the expense of heat generation somewhere else. Heat Pipes absorb energy in one location in a liquid to gas phase change, and then transfer the energy back to the environment elsewhere when the gas changes back to liquid. Perflourinatedpolyethers (PTFE) use bulk liquid → gas phase changes and the subsequent convection to transfer heat from a circuit at the bottom of a tank up to the surface, where the gas quickly returns to liquid form. Application to electronic circuits Joule heating applies to ohmic (Q=I²R) and non-ohmic devices (Q=IV). If the generated heat exceeds the dissipated heat, the part will eventually reach a temperature that allows for the thermal decomposition of the material. Molecules will leave the material and enter the environment
Failure modes
Mechanical Failure of PCB and Components The most recognized PCB
-- often as “magic smoke” that is generated when silicon dies and their bonding wires reach a sufficient temperature to vaporize the epoxy die packages. The high temperatures then permanently damage the bonding wires and silicon fractions of a second later.
substrate material is called FR-4 - a NEMA designation for fire-resistant (FR) fiberglass reinforced epoxy resin (4). FR4 is an entire class of woven-fiberglass materials made with different weave patterns, epoxies, and thicknesses. Many materials fall under the FR4 umbrella, but they all have characteristics important to the discussion of thermal failures: the in-plane-of-weave coefficient-of- thermal-expansion (CTE) and the much greater out-of-plane CTE are both significantly greater than the CTE for copper. That means when the temperature of a PCB increases, FR-4 expands more than the copper. The differential CTE places stresses on the PCB
To keep your PCB from turning into a flaming ball of carcinogens, you have to balance the heat generated in the traces and components with the heat dissipated into the environment.
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components and interconnects eventually leading to mechanical failures: via barrel wall cracking in PCBs and solder metal fatigue and failure in the attached components. Remember, FR4 is an entire class of materials. And there are other classes of materials that don’t have fiberglass inside them. If high temperature use or multiple temperature fluctuations are expected in your use case, choose a material with an isotropic CTE closer to that of copper. Component Failure Chemists predict reaction rates using the Arrhenius equation.
Electronics engineers adopted that equation to predict the lifespan of components. When used correctly, the equation allows the prediction of mean-time- to-failure with some degree of accuracy. When used incorrectly by an unsupervised junior engineer, the predicted lifespans are often expressed in geological timescales. But if you’ve ever wondered how engineers determine that LEDs will last for 40 years without waiting 40 years for a failure, they accelerate failure in heated chambers and use the
Summary Heat at Temperature are different things, and a decent understanding of how both topics relate to resistance will help you improve your next high-reliability PCB Design. To learn more about designing “Heavy- Copper” PCBs, read another article in this issue titled “You Want to Put How Much Current in Your PCB?”
modified Arrhenius equation to work backwards to room- temperature failures.
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Connector, gland, and grip options for industrial-automation cabling
By Lisa Eitel Contributed By DigiKey's North American Editors
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Connector, gland, and grip options for industrial- automation cabling There are various connectors to join cables and components used in industrial automation. These connectors must transmit all power and data-signal streams carried over the cables while terminating the line in a way that keeps the conductors tightly connected and protected. The challenge is that equipment associated with industrial automation is often located in dirty, hot, mobile, and electrically noisy settings … so industrial cable connectors require a level of robustness and reliability not necessary for other applications. First, consider some industrial- connector basics: Connectors include the components classified as couplers (which join two cables) as well as systems that include both the plug and socket (or receptacle) halves of a connector assembly. In some contexts, the term connectors can also refer to cable glands — terminations that pass through enclosures … often with a free- spinning subcomponent that acts to compress an O-ring seal around the cable end to close it off from chemicals, flames, dirt, and extraneous currents.
IED 60529 INGRESS (or more properly) INTERNATIONAL PROTECTION (IP) RATINGS
Figure 1: Illustrated here is what the various IP ratings of IEC 60529 indicate. Cable connectors’ IP ratings are critically important. (Image source: connectortips.com)
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Connector, gland, and grip options for industrial-automation cabling
Industrial cable connectors join cables (more commonly) at front and rear-mount equipment receptacles. All connectors and cable glands have ingress protection (IP) ratings as defined by IEC 60529 that quantify their resistance to dirt and moisture. These ratings are the same as those used to describe the ruggedness of component housings as well as industrial equipment enclosures. An IP code has two digits, with higher values indicating a higher level of protection for both. The first IP-rating digit specifies the level of protection from solid objects such as dust — ranging from 0 for no protection to 6 for dust-tight sealing. The second IP-rating digit specifies the level of protection against fluids — ranging from 0 for no protection to 8 for continuous protection from water at a depth of 1 m. Comparing RJ and M12 ethernet connectors for automation Ethernet defined by IEEE 802.3 remains the most widely used local area network (LAN) technology anywhere. Ethernet- based communications standards for industrial automation include
ModbusTCP/IP, EtherCAT, Ethernet/IP, and Profinet. The connectors commonly associated with Ethernet cables are the ubiquitous registered jack (RJ)
connectors. Most RJ connectors include a plug having a simple plastic tab that clicks into mating geometry on an RJ socket to securely hold the two together.
Figure 2: This is a TL2253-ND hand crimper tool that allows in-field RJ-plug termination of four, six, and eight-wire Ethernet cable cut to length. With one squeeze the tool’s blades strip flat or round Cat5e and Cat6 and secure the connector body. (Image source: Tripp Lite)
Figure 3: RJ connectors such as the ones shown here are the most common on Ethernet cables. That said, there are other connector types available for use on Ethernet cable. (Image source: Getty Images)
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The plugs and sockets easily fit to cables — and installation personnel can simultaneously clamp them and make the electrical contacts using a special-purpose crimping tool. Crimping terminators allow for the construction of custom- cut cables (fitted onsite) that are reasonably reliable. Plug subcomponents designed for such onsite installation often have clear bodies to let installation personnel inspect all internal contacts before putting them into service. That said, the reliability of factory- assembled cables is unbeatable. Where RJ connectors aren’t rugged enough for a particular industrial environment, M12 connectors may be better. That’s because M12 connectors provide a more reliable and physically robust connection — with the added advantage of protection against the ingress of dust and fluids. Power over Ethernet (PoE) defined by IEEE 802.3 is a convenient way to obtain both data and electrical power through a single cable. PoE Alternative A (often called mode A) uses the same two twisted pairs to carry both data and power, so cables with fewer cores can be used — and bandwidth is limited to 100 Mbps (100BASE-TX). PoE Alternative B (often called mode B) uses a Cat 5 Ethernet cable
with four twisted pairs — two pairs carrying data and two pairs carrying power. This reduces the bandwidth available for data — limiting the data rate to 100 Mbps even when the cables are rated for Gigabit Ethernet. 4PPoE or four-pair cable requires a cable with four twisted pairs of conductor strands and all transmitting both power and data. This means that higher data rates (Gigabit Ethernet and beyond) and currents are supported. Devices accepting power over PoE must be configured to accept mode A or mode B as it’s supplied. That said, they may use fixed or alternating resistance across wire pairs to indicate compatibility and request a specific power configuration. Of course, it’s PoE power supplies (the sourcing equipment or PSE) that actually determine the system’s PoE mode.
Terminating both data and power cables (as well as network cabling such as industrial Ethernet, PROFINET, and Fieldbus) are M-series connectors — round mating connectors with a threaded female sleeve (to mount on a male receptacle) wrapped around an array of conducting pins. M8 (8 mm) and M12 (12 mm) threads are most common but M5, M16, and M23 are also familiar standards. The positive (screw-on) closure of M-series connectors ensures a highly reliable connection that minimizes intermittent signals even while protecting against the environmental debris so common to washdown and corrosive environments. No wonder M-series connectors are a top standard on the cables for actuators, PLCs, sensors, switches, and controls of industrial automation.
Figure 4: The connector design is largely dictated by the cable it terminates. M12 Ethernet-cable connectors such as the ones shown here are generally more robust than RJ connectors; some manufacturers color-code them to indicate compatibility with PoE modes and conductor arrangements. (Image source: Lumberg Automation)
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Connector, gland, and grip options for industrial-automation cabling
M8 and M12 connectors may have two, three, four, five , eight, or 12 pins (also called positions). Sensors and power supplies generally require three or four pins. For M-series connectors on the ends of Ethernet and PROFINET cables, four or eight pins are needed. In contrast, those on the ends of cables carrying Fieldbus, CAN bus, and DeviceNet data usually have four or five pins. Of course, cables carrying multiple data and power streams may require termination with an M-series connector having all 12 pins.
introduced by Molex so it is sometimes referred to as Molex interconnections in the vernacular. The proprietary Molex Brad series of connectors are based on M12 connectors but replace the threaded sleeve with a more convenient and reliable push-to- lock system. Because the locking does not depend on the operator tightening a thread, it ensures reliability and minimizes the risk of an intermittent signal. Brad connector variations include: ■ Brad Micro-Push M12 connectors — a push-on and pull-off connector providing IP65 protection ■ Brad MX-PTL M12 push-to- lock connectors offering IP65 protection ■ Brad Micro-Change M12 threaded connectors offering IP67 protection ■ Brad Ultra-Lock and Ultra-Lock EX M12 connectors with push-to- lock fittings and O-rings for full IP69K level of ingress protection. Coaxial connectors for high-frequency signals Coaxial cables (fitted with coaxial connectors) are also used in industrial automation for transmitting high-frequency signals — especially those
supporting vibration monitoring and analog signal transmission. Standards abound. BNC connectors have a bayonet fastening that requires a quarter turn to connect or disconnect. They can be used for frequencies of beyond 12 GHz and in some cases up to 18 GHz. DIN 0.4 to 2.5 connectors are very small push-fit connectors suitable for frequencies to 3 GHz. In contrast, DIN 1.0/2.3 connectors are small push-fit radio- frequency connectors widely used in digital telecommunications. Modular and custom cables proliferating for automated machinery With conventional system integration approaches, cables are “made up” — measured, cut, and terminated — onsite during the installation of the automated equipment. That usually means an onsite electrician cuts the required cables to length, strips all their conductors’ delicate sheathing, and fits the cables with the connectors required to join the components at hand. Such in-field cable preparation is time-consuming and leads to variable connection quality. That’s why the trend now is to source modular cable and connector systems consisting of standard cables and factory-fitted
Figure 5: This Brad Ultra-Lock 120108 right-angle connector is a proprietary adaptation of an M12 connector design to boost reliability. (Source: Molex)
In fact, one related connector- receptacle design that’s quite common in the industry is the pin- array-and-socket pair — originally
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connectors. Required cable lengths are determined during design and supplied ready to install. Some estimate that modular cables reduce onsite installation time by 60% to 70% while improving the reliability of the electrical connections. The special case of cable glands Cable connectors called glands are used wherever cables pass through an enclosure. Glands serve three purposes — securing the cable, preventing cable wear, and providing a seal around that cable to shield components inside the enclosure from environmental debris. The way in which cable glands secure the cable essentially prevents damage to electrical contacts from yanking or other disturbances. It also prevents the cable from scraping or rubbing against the sharp sheet- metal edge of the enclosure cutout. That’s important because sheet metal can easily saw through cable sheaths and eventually cause the cable cores to short. Less demanding applications often use lamellar glands having multiple fingers that clamp around the cable. This type of gland is less costly but requires regular retightening to maintain
ingress protection. Higher quality glands use a continuous seal that clamps around the cable. This type of gland is much less likely to loosen over time.
Construction of today’s industrial-power connectors Devices used for industrial automation often require a wired power supply in addition to a data connection. The relatively new technology of PoE mentioned earlier is preferable where it’s possible to use because it keeps cabling so simple. However, the vast majority of automation components and systems require traditional power cords.
Figure 6: General-purpose power cables include a variety of IEC and other standard connectors. (Image source: Getty Images)
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Connector, gland, and grip options for industrial-automation cabling
Figure 7: Notice the color coding (adherent to IEC 60309) of this high-power cable connector. (Image source: Railway Tech)
Connectors standardized by the International Electrotechnical Commission (IEC) are common on power cables for consumer and office as well as industrial applications. The IEC defines a range of non-locking connectors in the IEC 60320 standard with voltages to 250 V and current not exceeding 16 A. Here, the C13/C14 connector is commonly used for electronic equipment — including computer power supplies. Larger C19/C20 couplers are used
on the ends of cables carrying higher current — including server enclosures, for example. For more critical or demanding applications, IEC 60309 connectors are often preferred. These plugs, sockets, and couplers are expressly intended for industrial use and can carry voltages to 1,000 V, currents to 800 A, and frequencies to 500 Hz. All of these connectors provide some level of resistance against water ingress:
IP44 connectors are splash-proof, IP67 connectors are waterproof, and IP66/67 connectors can reliably prevent ingress even when subject to pressurized waterjets. Socket outlets may also be interlocked so that the socket cannot be energized unless it’s mated with a plug — and the plug cannot be removed until the power is switched off.
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Different sizes of IEC 60309 connectors are used for different current ratings. The connectors are also keyed and color-coded to indicate their voltage and frequency range: ■ Yellow indicates carriage of 100 to 130 V at 50 to 60 Hz ■ Blue indicates carriage of 200 to 250 V at 50 to 60 Hz ■ Red indicates carriage of 380 to 480 V at 50 to 60 Hz — often in a three-phase configuration
Conclusion
There are many geometry and integration options when it comes to selecting connectors and glands for industrial automation. During the specification of a cable for a given automated piece of machinery, the first consideration for design engineers must be the cable core count and the cores’ gauges. Ingress protection and the need for a positive lock to prevent intermittent signals are the next- most important considerations.
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How to select 48 V connectors for medium-voltage automotive architectures
Government mandates for lower CO 2 emissions and consumer demand for vehicle electronics have resulted in a transition from 12 V automotive systems to more efficient 48 V architectures. These mid-voltage architectures offer higher power delivery and lighter, lower-cost wiring harnesses.
The problem for designers is ensuring that the connectors meet the demanding electrical, safety, reliability, and physical requirements of 48 V systems while meeting cost and time- to-market constraints. The solution lies in developing an understanding of the
By Kenton Williston Contributed By DigiKey's North American Editors
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connectors. It then presents suitable solutions from Molex and describes how these solutions may be applied in practical scenarios. The benefits of 48 V automotive architectures Automakers can implement mild hybrid systems that recuperate energy during braking and coasting by moving to mid-voltage architectures. They can also deploy enhanced start-stop systems that reduce fuel consumption while city driving and in traffic jams. Additionally, because the higher voltage allows the use of lighter, smaller-gauge wires to deliver the same power at a lower current, 48 V systems reduce vehicle weight. All these factors translate to significant fuel savings, particularly in smaller vehicles. Higher-power wiring harnesses are also needed to accommodate the electrification of components such as power steering, air conditioning, and the adoption of advanced driver assistance systems (ADAS), such as adaptive cruise control and lane- keeping assist. Transitioning to a 48 V architecture meets this need without the costs and complexities associated with the high-voltage systems (i.e., 400 V and beyond) used in full hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs).
The 48 V architecture also serves as a bridge to greater vehicle electrification, allowing gradual integration of hybrid technologies without a complete electrical overhaul. These mid-voltage systems will remain valuable even in fully electric vehicles, as evidenced by their incorporation into designs like the Cybertruck. Cost considerations for 48 V connectors The question of which electrical connection system should be used for 48 V architectures can be answered by looking at the technical challenges arising from the increased voltage. Adopting the high-voltage connectors developed for use in electric and hybrid vehicles is technically feasible, but cost and package-space considerations make it inadvisable. In contrast, adapting 12 V connectors for mid-voltage architectures is an attractive cost and size proposition. It is worth noting that not all vehicle systems will switch to 48 V. Some smaller devices that consume less power will stay at 12 V. Therefore, it is useful to have consistent connectors across 12 V and 48 V systems to simplify tooling and technician training.
operational, regulatory, and safety requirements of mid-voltage automotive architectures before choosing from an appropriate supplier’s selection. This article reviews the benefits of 48 V architectures and outlines the challenges of selecting appropriate
Molex’s MX150 Mid-Voltage Connector System (Figure
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