What are the most critical considerations when designing electronics for use in harsh environments?
By Mike O’Connor, Red Lion Controls, Director Hardware Engineering, Automation Team
When designing electronics for harsh environments the top considerations are temperature, electromagnetic interference (EMI), electrical abnormalities, and mechanical strength. Temperature in harsh applications can vary greatly from what average electronics will ever see. For example, an electronic control system on an oil rig or gas pipeline could be located in a sweltering desert or sub-zero temperatures, unlike consumer electronics that are designed for milder environments. Therefore, industrial electronics need to use components rated to broader temperature extremes, such as -40 C to +85 C. Additionally, designs must employ methods to eliminate excess heat through conduction (heat sinks), convection (air flow) or radiation (heat fins).
The second element to address is protection from EMI, which is emitted from power switching circuits, wireless devices, sun flares, thunderstorms, and more. EMI can be conducted through physical means or radiated through air. The EMI in industrial environments is typically much worse than in-home or commercial areas, as consumer electronics must meet different standards and therefore generate less noise. Also, industrial applications tend to utilize more electrical devices with higher voltages and currents. Designers must therefore employ shielding, filters, special layout techniques, bypass capacitors, and other methods of protecting against EMI.
The third consideration for electronics in harsh conditions is protection against electrical abnormalities like power surges, brownouts, fast transients, and electrostatic discharge. These can enter through any connections on the electrical device, including the ground. The use of fuses, surge suppressors, and chokes are the typical solution of choice for this protection. Finally, the electronics must physically hold up to the harsh environment, which can mean using a metal case instead of plastic, corrosion protection such as conformal coating, water-tight seals, or even shock absorbers. Given the variety of challenges present in harsh environments, it’s vital that designers consider all the elements involved, and design to mitigate the threats each pose.
By Scott Flower, Product Strategy Manager and designer of the Gecko 1.25mm interconnection system, Harwin Inc.
Shock, vibration, and temperature fluctuation are the three biggest killers of electronic systems. Harsh environments often encompass all those conditions. Consider, for example, a satellite. On launch, the onboard systems will experience intense shock and severe vibration. When deployed in space, the satellite may alternately be extremely cold, for example when shielded from the sun by the moon, or very hot when directly exposed to the sun’s scorching heat.
Similarly, defense systems also provide challenging shock, vibration, and temperature conditions, but even automotive applications must be able to survive a sub-zero winter and elevated under-the-hood temperatures, as well as continuous vibration. Motor sport is more regulated, but vibrations are more severe as cars are pushed to the absolute limit of performance, and robotics are often used where conditions are hazardous to human life, so it must be prepared for all events.
Such conditions are challenging for any electronic component but for the interconnection, the issue is even more difficult since the connector often forms not only an electrical but also a physical connection. Simply put, a connector designed for a consumer application is very unlikely to be fit for purpose of even an industrial environment such as an Industry 4.0 Smart Factory installation, let alone a defense, aerospace, or space program.
There are two key issues: robustness and continuity of signal. It is relatively easy to determine whether a connector is physically robust enough to withstand harsh environment deployment. The ability of a connector to maintain continuity of signal under shock, vibration, and temperature extremes depends primarily on the contact design. There are many different types of contact, such as check shock, vibration, and temperature performance. Remember, harsh operating conditions often mean you don’t get a second chance.
By Doug Patterson, VP, Marketing & Business Development, Aitech Defense Systems
Today, the most critical consideration is the choice of the electronic components used in the design, and the relative age of those components from their “born-on” dates. Yet, the experience of the subcontractor ranks a high second, and is actually very closely tied to component choice.
If you are procuring some aspect of a board- or system-level product from a subcontractor, are you 100 percent certain they have all the product lifecycle management procedures, processes, and safeties in place to ensure the long-term availability of those commercial off-the-shelf (COTS) products?
If you’re not using the latest and greatest component parts available today in your electronic designs, chances are the parts you’ve “lovingly” selected for your latest creation will be obsolete in 12 to 18 months. If you’re designing for the rugged industrial or military, where it can take many years before an electronic embedded system is finally tested, qualified, and makes it into production, over 50% of the active component will most likely be obsolete, or replaced by an alternate part that – you guessed it – mandates that the entire system be requalification tested – even before you make it to production!
A full requalification can take months–and more than a million dollars– to complete all the testing (again) and produce all the supporting test documentation on the contractually mandated, Subcontracts Data Requirements Lists (SDRLs).
To protect company’s investments in IP and products, we have developed a series of comprehensive component obsolescence management programs, based on technology management and insertion. The COTS Lifecycle + program, one of the first of its kind in the rugged defense markets, helps control operational and maintenance issues as well as reduce overall program lifecycle costs.
A solid relationship is just as important a consideration as component selection to ensure you have partners that can deliver market-leading software, applications, expertise, and innovative product solutions that help you navigate the morass of limiting technology insertions or redesigns.
By Rick Wietfeldt, Ph.D, Chairman of the MIPI Alliance Technical Steering Group and Senior Director, Technology at Qualcomm
The harsh environment that probably escapes many of us is the smartphone in our pocket or purse. The “harsh” arises because these devices contain concurrently operating radios and their support interfaces.
Today, all smartphones use concurrently operating Bluetooth, WiFi, and cellular radios, each operating in its own spectrum. When the radio operating frequencies overlap or are sufficiently close to each other, interference may arise in the radio receivers. Furthermore, the low- and high-speed interfaces, including those with a dedicated clock line whose spectral emissions can fall into the receive band of radios, can cause havoc to radio or interface receivers.
A system solution can operate on “solution knobs” involving time, frequency, space, and power. Let us begin with frequency. Sufficient separation of the transmitting frequencies may mitigate interference, although in some cases operating frequency is determined by the network and other factors. Next is space, where sufficient physical separation of components such as the antennas may help; and time, where time multiplexed radio operation may help; and power, where a reduction of the radio transmitters may help. Similarly, interference from wired interfaces can be mitigated in time via slew-rate control, in frequency via spread spectrum clocking, in space via suitable physical design practices, and power via variable voltage levels.
The venerable smartphone is ripe with computing power and communications capability. But, very careful control of radio and interface operation is needed to avoid the harshness created by their concurrent operations.
By Ashish Gokhale, Isolation Products Manager, Silicon Labs
Electronic products are now so ubiquitous we seldom think twice about them, let alone ponder the challenges that electronics designers face. As the world becomes smarter and more connected, it is imperative that designers use technologies that can provide a reliable shield to protect sensitive, expensive electronics from harsh environments that can fatally damage sensitive electronic components or cause data corruption. This is especially true in applications such as process control and factory automation for chemical manufacturing plants or automotive assembly lines. Harsh conditions are also prevalent in fast-growing sectors such as solar inverters as well as power supplies and telecommunication systems. Here are some of the hazards that a harsh environment can present:
- High voltages – In many demanding applications, sensitive low-voltage electronic components must communicate with other components that are rated for high-voltage use. In such cases, sensitive components are liable to be damaged in case of an electrical fault.
- Electrical fast transients – These are caused when a relatively high voltage is switched on and off, such as in a high-power inverter that delivers controlled switched power to heavy duty motors. These transients can cause permanent damage to sensitive electronic components that are not designed to sustain them. Even if the component escapes permanent damage, these transients can cause data corruption, leading to system failure or a system down situation.
- Common mode differences – This comes into play when communication between subsystems with different reference voltages is necessary. Let’s say, for example, a subsystem circuit powered by a 3V power supply must be able to communicate with other subsystems that may be referenced to a 240V mains supply. In this case, the communication link can be severely corrupted, and data may be lost if adequate care is not taken to account for the different reference voltages.
Fortunately, for all these cases, there is one common solution that is easy to implement. Galvanic isolation of these sensitive components protects them from high voltages, fast transients as well as common mode differences. Plug-and-play, CMOS-based digital isolation solutions make it easy to ensure that sensitive components are adequately protected not only from data corruption but also from fatal damage, thus ensuring a reliable and long lasting system even in harsh environments.
By Mark Horner, National Applications Manager, Sharp Microelectronics of the Americas
When designing for harsh environments, component and material selection is a critical element of the process. Whenever possible, enabling a de-rating factor between the product and component specifications can go a long way toward ensuring there is adequate design margin. However, the product specifications are often at the limits of the components and materials used in the design. In this case, using quality suppliers can have a substantial impact on overall product reliability and robustness. This certainly holds true for display applications.
A display supplier’s sub-component and material selections can extend across a wide spectrum of available options. Many trade-offs exist when trying to balance performance parameters, cost and long-term material availability. In order to meet cost targets, suppliers may pick materials or sub-components that are on the edge of the design specifications for environmental performance such as temperature/humidity, shock, and vibration. Quality suppliers will employ design rules that de-rate subcomponents and materials to ensure there is adequate margin. This is a key factor in providing displays that enable final product designs capable of withstanding the harsh environments required in many display applications today; for example, Automotive, Ag/Construction Equipment, and Industrial Automation.
Employing Highly Accelerated Life Testing (HALT) early in a product design cycle can be an effective tool to expose marginal areas of a product design. If a display failure is identified, a quality supplier will be able to assist in the failure analysis process to help determine if it is a sub-component/material issue or an application issue. Based on the FA results, decisions can be made between the system designer and the supplier to determine the best course of action to resolve the issue. Early and comprehensive supplier support can make a substantial difference in bringing a quality product to market, under budget and on schedule.