Electronics & Computers

Distributed Control Standard Connects Industry Regardless of Bus

In the early days of modern automation, the use of microprocessor technology addressed the need for fast and efficient configuration of control logics through graphical methods that mimic the hardwired relay logics. Over the past 30 years, the automation community has put the emphasis on simplifying and standardizing the method of programming this new breed of controllers. From these efforts came the adoption of the IEC 61131-3 standard that specifies the programming languages for automation.

Posted in: Articles, Articles, Electronics & Computers, Architecture, Standardization, Automation
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Bringing Modularity to MicroTCA

MicroTCA is a new specification that offers very high performance packed in a small form factor. The new specification is expected to be used in a wide variety of applications, including mil/aero, telecom edge, medical, enterprise and data, and scientific applications. However, there are so many possible configurations, it can be overwhelming. How can one develop various systems and offerings without starting from scratch — and the time to market, high costs, and implementation issues this brings? One solution is using modularity in MicroTCA designs. Prototyping and development of a new system enclosure design can be a time-consuming and costly process. Building upon a proven modular platform allows a wide range of design options with significantly reduced effort.

Posted in: Articles, Articles, Electronics & Computers, Design processes, Downsizing, Architecture, Systems engineering
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Filtered Conduction Empowers Mil-Spec Desert Systems

As embedded computing systems become more powerful, so are the challenges to protect and cool the payload. In the past few years, we have seen the power of a single board increase in most cases to over 100W per slot. To further challenge the designers, these systems are being deployed in rugged environments with a push to use COTS (commercial off-the-shelf) products. Recently, liquid-cooled systems have been developed to combat these However, there are some challenges with liquid cooling that can make this technology prohibitive. For example, not all boards are available in conduction- cooled format, or there may not be an external chiller/pump available to implement the liquid approach. So how does a designer handle an environment where there is no liquid coolant available, ambient temperatures hover around 55°C, the enclosure has a payload of 500W, and the client wants the system to operate on numerous rugged platforms (ground vehicle, rotary wing, UAV, etc.)? Oh, and the enclosure has to be sealed to protect the COTS boards from the harsh environments and EMI concerns. And with all of this, there is a desire to monitor the temperatures/ health of the system to protect the expensive payloads.

Add Monitoring to ATR

One approach to this design challenge is to integrate an air-to-air heat exchanger into a standard ATR package with a monitoring system. We will look at this approach in a little more detail with the specifications as follows:

Top-load Enclosure COTS air-cooled payload dissipating up to 500W Ambient temperature up to 55°C Harsh environment to meet MILSTD- 810 EMI — Designed to meet MIL-STD 461 (CE101, CE102) Front-panel access to all power and I/O connectors An additional electronics package, dissipating more than 100 W, is mounted inside of the controlled environment of the enclosure. In addition to these requirements, there is a concern that the accumulation of fine dust particles on the boards would prevent proper cooling, and larger particles would cause abrasion of the boards and other electronic components.

Exterior Mechanical Design

The first challenge is providing a rugged outside housing for the payload. In this solution, we chose to go with an ATR-style (see Figure 1) form factor because it is a common platform that has had a proven record for many years. The other advantage to this style of form factor is that it will easily mount into many existing applications, and there are a number of readily available shock-isolated trays on the market that can help meet the rugged vibration environments. It is also important to find that optimal balance between the weight and ruggedness required. A designer could go with a brazing approach, but this typically adds unacceptable cost and lead time to the program. The more economical approach would be to go with a welded/bolted-together construction method. This still provides significant strength, but also reduces the weight, cost, and lead time. It is also very important to include a rugged military finish or paint on the outside surfaces to further protect the enclosure from the harsh environments. The paint for this solution was chosen for its UV reflective properties to reduce the heat load generated by external solar radiation. In addition to the structural integrity and resistance to the environments, serviceability plays a big factor in the final design. The air intake filters on this unit are important to get the air into the chassis, but just as important is the ability to remove these filters and service them in the field, eliminating costly depot maintenance time.

Internal Structure

The second challenge is the requirement that the internal air be isolated from the external environment. The COTS air-cooled cards are not robust against accumulation of airborne sand and dust, and must be protected against this environmental threat. In addition, many board sets can generate substantial EMI, which must not only be contained within the unit, but must also be prevented from interfering with sensitive components in the electronics package (see Figure 2). Directly beneath the card cage is a small volume approximately 1.5" high, which can be used for additional payload. This space is EMI-isolated by aluminum walls and a conductive plane on the backplane. Airflow into this space is provided by ventilation holes in the backplane on the pressurized side of the recirculation fan.

To meet the environmental isolation requirement, an air-to-air heat exchanger was designed to allow the unit to shed heat, while preventing interchange of internal and external air. In order to minimize total system volume, reduce weight, and increase structural stiffness of the chassis, the heat exchangers and exhaust air ductwork are used to form the side walls of the chassis. The third and probably most important challenge was cooling the payload (see Figure 3). Four fans are used to pull external air through the external side of the heat exchangers, while internal air is re-circulated through the inner air passages of the heat exchangers. Additional cooling is provided for the electronics package by applying four smaller fans to pull air across the electronics package heat sink. The heat exchanger is a dual-passage counter-flow design where the internal air flows in the opposite direction of the external air.

This heat exchanger design is built as a brazement of aluminum plates and folded fin stock used to increase the surface area available for heat transfer. The recirculating air fan and the four fans on the electronics package are uncontrolled, and run directly from the 28V DC nominal input power. The four exhaust fans are speed-controlled to reduce audible noise when full cooling capability is not required. When run at highest fan speed, enabling internal payload power dissipation of over 500W, the cooling system is able to maintain internal air temperatures low enough to operate the system up to 55°C ambient. Thermal modeling shows that the recirculating air exiting the heat exchanger is kept within 10°C of the ambient air temperature.

System Monitor

In RF Mil-Spec systems, system monitoring falls into five major categories: temperature monitoring, fan monitoring, voltage monitoring, remote access, and other options. Temperature monitoring is becoming more critical as the value of the payload continues to rise. To address this, strategically located thermistors feed temperature values to a system monitor. The monitor can then evaluate the temperatures and increase/decrease the fan speed as needed. If a specified temperature is reached, a warning can be sent, and more importantly, if a temperature level is reached, the system monitor can inhibit the power to the backplane, shutting down and protecting the boards. It is also important to monitor other functions such as the health of the fans or system voltages. If one of these should fail, the system could be jeopardized.

In addition to the basic monitoring functions, new system requirements are generated every day. As the cost of processing boards rises, users are more interested in alerts that may not require system shutdown, which is moving customers towards boards and systems that can self-monitor the performance of the electronics package in addition to environmental factors.

This article was written by Ryan Pellecchia, Senior Technical Application Engineer, at Hybricon Corp. in Ayer, MA. For more information, contact Mr. Pellecchia at rpellecchia@hybricon.com, or visit http://info.hotims.com/10968-401.

Posted in: Articles, Articles, Electronics & Computers, Design processes, Embedded software, Cooling, Military vehicles and equipment
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Multi-Cores: The Gateway to Next-Gen SBCs and Blades

With the introduction of Intel Core microarchitecture into embedded systems, history could very well repeat itself. The company that invented the microprocessor in 1971 and created the very first micro-controller in 1976 is about to revolutionize the embedded space once again. By bringing the power of parallel processing to embedded developers in an open-standards-based building block architecture, Intel is hoping to break down the cost barriers while taking embedded systems performance to new levels that once were reserved only for expensive computer systems specifically designed for symmetric multiprocessing (SMP), while also accomplishing unrivaled levels of efficiency.

Posted in: Articles, Articles, Board-Level Electronics, Electronics & Computers, Architecture, Embedded software
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Beamforming System Eases Crowded Wireless Spectrum

Beamforming is critical to enable initiatives by the U.S. Federal Communications Commission (FCC) to increase spectrum capacity and provide additional cellular service and coverage through satellite and terrestrial systems. The key technology for this application is beamforming, which electronically steers data streams to and from a satellite via a combination of an array of antennas on the satellite and very sophisticated, ground-based computational engines.

Posted in: Articles, Articles, Board-Level Electronics, Electronics & Computers, Antennas, Telecommunications, Waveguides, Satellites
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SOA in Practice: Model-Driven Repositories Fill the Gap Between Concept and Implementation

In the past, network-based applications were pretty simple. A networked server ran a monolithic application that users accessed via a basic GUI (graphical user interface). Today, organizations struggle to develop feature-rich, network-based applications while also facing business pressure to minimize timescales, maximize quality, and work with legacy systems hosted on different platforms.

Posted in: Articles, Articles, Board-Level Electronics, Electronics & Computers, Design processes, Architecture, Human machine interface (HMI)
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Sensor Interface Design Demystified

With the rapid expansion of available sensor elements driven by the growth of MEMS (microelectromechanical systems) sensors, the considerations of sensor interface design become ever more important. The design engineer needs to understand both the sensor as well as the application in order to make the proper design tradeoffs in this already tricky art of analog front-end design. The challenge is further compounded with the trend toward MEMS technologies and their inherently smaller signals. This article attempts to cover some of the basics of sensor interface design and gives a cursory overview of the challenges and trade-offs of the possible approaches. It's Not Just a Resistor Fundamentally, every sensor can be modeled as a simpler component, albeit a component with a value that changes over time. Usually this means we can treat them as either a simple passive impedance, such as a resistance, capacitance, or inductance, or as an active source, such as a current or voltage source. As these values change with time, we need to be able to convert that change into a time-varying voltage. Furthermore, we need to maintain the linearity of the sensor while we do this.
Posted in: Articles, Articles, Electronics & Computers, Design processes, Architecture, Microelectricmechanical device, Sensors and actuators
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Advanced Ceramic Heaters Improve IC Packaging and System Performance

The continuous increase in the consumption of semiconductor devices and the emergence of new applications in optical components — MEMS, LCD display, flip-chip, chip-onglass, and multichip modules — has created a vast demand for faster throughput and better die-bonding equipment for IC packaging. IC packaging requires a typical ramp rate of 100ºC per second to 400 to 500ºC ±2°C, and a cycle time of 7 to 15 seconds. Similarly, IC chip testing, which stresses chips between -40 to 125ºC while monitoring electrical parameters, also requires a faster cycle rate. To manufacture ICs of all types, a die bonder or die attach equipment is used to attach the die to the die pad or die cavity of the package's support structure. The two most common processes for attaching the die to the die pad or substrate are adhesive die attach and eutectic die attach. In adhesive die attach, adhesives such as epoxy, polyimide, and Ag-filled glass frit are used to attach the die. Eutectic die attach uses a eutectic alloy. Au-Si eutectic, one commonly used alloy, has a liquidous temperature of 370ºC, while another alloy, Au-Sn, has a liquidous temperature of 280ºC.

Posted in: Articles, Articles, Electronics & Computers, Semiconductor devices, Joining, Ceramics
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Accelerated Testing — Raising the Bar on Electronics Integrity

By now, most test engineers have recognized that both HALT (Highly Accelerated Life Testing) and HASS (Highly Accelerated Stress Screening) are the fastest and most effective new methodologies for quickly passing design verification and testing (DVT), and the most effective production screenings. Leaders across a broad range of industries have now embraced accelerated testing as a strategic move that can increase competitiveness and improve market share..

Posted in: Articles, Articles, Electronics & Computers, Electronic equipment, Systems engineering, Production, Quality control, Test procedures
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Multi-Fabric Switching Enables New Architectures for Military Systems

With multiple switched interconnects gaining momentum in the embedded space, selecting just one to address a wide range of military systems requirements is not easy.

Individually, switched fabrics such as Gigabit Ethernet (GbE), Serial RapidIO (SRIO), and PCI Express (PCIe) have their own particular technical merits, and each is poised to carve out a piece of the interconnect market. However, when combined in nextgeneration Serial Switched Backplanes (SSB) like VPX (VITA 46/48), multi-fabric switching can enable powerful new military architectures by leveraging 'best of breed' interconnect technology to address specific application requirements ( Figure 1).

Posted in: Articles, Articles, Electronics & Computers, Architecture, Embedded software, Switches, Military vehicles and equipment
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