The modular Interscale enclosure platform is based on a parametric model and can therefore be easily adapted to the requirements and size of the board as well as the installed components in height, width and depth.

© Pentair

The networking of machines, services and people across the entire production and value chain as part of the 4th industrial revolution is also increasing the use of embedded systems.

These are used in particular as IoT gateways and as a collection or interface between control and sensor data and higher-level IT systems for analysis and aggregation. Pentair has developed a comprehensive concept - based on its Interscale product platform - with which users can build their individual hardware application for the realization of industrial IoT systems. This shortens time-to-market, increases flexibility and security and improves quality and efficiency.

The board selection

The central unit of such a system is either a small form factor board with a specific board standard, such as ATX, Micro-ATX, Mini-ITX and Pico-ITX, a single-board computer, such as Embedded-NUC, Raspberry Pi and Arduino, or a proprietary board provided by the user. These boards differ not only in size, but also in functionality or slot configuration. The user selects a suitable board depending on the application and the associated requirements.

The board is selected on the basis of various criteria: Which processor and which processor performance are required? Which RAM is sufficient? Which interfaces are required or which interface cards should be connected? It is important to note that standard industrial mainboards also offer a different number of PCIe slots: An embedded NUC board has no PCIe slots, a Mini-ITX has one PCIe slot, a Micro-ATX has up to four slots and an ATX can accommodate up to eight PCIe cards.

The right housing

A suitable enclosure is then configured based on the selected board, for example based on the flexible and modular Schroff Interscale enclosure platform. The type of board or board standard selected for the application is irrelevant, as the flexible enclosures of the Interscale family can be adapted to a wide range of conditions.

Depending on the board, two, three or four-part enclosures can be realized. Mini-ITX, Micro-ATX and ATX boards only have interfaces on one side, which are led to the outside through a cut-out for the supplied interface panel, so a two-part housing consisting of a base plate with side panels and housing cover is possible here.

An example of a three-part housing are boards such as Raspberry Pi or the embedded NUC board, which have interfaces on two sides and therefore require a three-part housing in order to lead the interfaces to the outside through cut-outs and ensure EMC protection. In the case of a four-part housing, it is also possible to provide the housing cover with a cut-out and insert a heat sink that sits directly on the processor - an example of this is the Schroff complete solution for COM Express modules including COM carrier integrated in a housing with cooling and power supply.

The special interlocking design of the housing ensures integrated EMC protection of 20 dB at 2 GHz without the need for additional EMC seals and guarantees a degree of protection up to IP30.

Integrating electronic components

In the next step, electronic components and interfaces are selected for integration.

For the power supply, for example, power supply units with different outputs are available: A desktop power supply unit with 19 V and 65 W (external or also integrated in the housing), various Pico PSU kits for passively cooled systems with 80 W, 120 W and 160 W, a space-saving 1 U ATX power supply unit with 300 W or ATX power supply units in PS2 form factor with 300 W or 500 W. Depending on the choice of board, processor, memory and PCIe cards, a power supply unit is selected that covers the overall performance of the components.

Installation options or slots for PCI or PCIe cards can be integrated depending on the selected board form factor. In addition, the height of the housing can be reduced accordingly if either half-height PCIe cards are used or full-height PCIe cards are installed horizontally via riser boards.

Various solutions are available for mounting the drives, depending on the board used. The housing concept allows several drives to be mounted using brackets inside the housing. They can also be mounted using a hard disk holder that can be removed from the outside. For example, mounting under the mainboard is also possible without restricting the maintenance properties. If necessary, Schroff also offers an illuminated power switch including connection cable.

Customize cooling solutions

Flexible heat-conducting elements FHC in 20 mm (left) and 70 mm (right) versions. The integrated springs enable vertical length compensation.

© Pentair

Various options are available for embedded systems depending on the power dissipation. In some systems, the power dissipation is so low that no cooling is required. Factors such as the ambient temperature, processor performance and thermal design power (TDP) of the processor determine the necessary cooling to be applied. The Raspberry Pi board, for example, can be operated fanless under normal ambient temperature conditions with only housing perforation. If the power dissipation increases, i.e. processors from approx. 15 W TDP upwards, it is necessary to dissipate the heat, either by active or passive cooling. Enclosures can be equipped with perforations and fan kits. Fan cooling enables effective and cost-effective heat dissipation.

However, if high IP protection, quietness or a long service life of the entire system is required, passive cooling has advantages. The heat is dissipated by conduction cooling using integrated heat sinks and/or flexible heat conductors (FHC). Different heat sink geometries are available for specific power losses and areas of application, for example heat sinks integrated into the housing cover with cooling fins at different heights, which are adapted to the processor and the ambient temperature accordingly. Pentair has developed a flexible heat sink FHC made of aluminum especially for the area of high power dissipation. Processors can form a continuous heat path to the housing through the FHC, as the FHC creates tolerance compensation thanks to its innovative design. Integrated springs enable vertical length compensation of the aluminum block and reduce the thermal resistance so that no thermal pad is required.

Execute interfaces

Depending on the selected board standard or individually developed board, various interfaces are routed to the outside, which require a corresponding cut-out and optional printing at different positions on the housing. These include, for example, display elements, power switches, USB and Ethernet connections, which are positioned on the outside, or the cut-out for the interface panel of industrial motherboards, which require a corresponding modification of the housing. The new concept includes the mechanical processing of the enclosures and comprises an extensive CAD library for standard cut-outs, but also offers the option of implementing other individual cut-out geometries in the enclosure. It is important here that the interfaces of the board are attached to the base of the enclosure in order to be able to continue to guarantee EMC protection.

A wide range of powder coating and printing options are also available to customize an Indus-trial IoT system. This gives customers the opportunity to realize the housing color as well as design elements and colored logos up to photorealistic images according to their corporate design.

The wide range of standard accessory components for the enclosures enables a variety of assembly and expansion options. Four standard accessory elements are available for mounting or positioning PCBs and components in the enclosure: a simple mounting plate, a mounting plate with integrated fans, flexible PCB holders or adhesive bases. With the flexible PCB holder, PCBs can be mounted anywhere in the enclosure.

Accessories and services

In addition to standard plastic feet, stand-up feet or a stacking aid are also available. 19-inch brackets or a clip for top-hat rail mounting are available for mounting the enclosures, for example in a control cabinet.
The concept developed for the enclosure platform also includes accompanying services. For example, enclosures can be supplied fully assembled on a project-specific basis, including all selected mounting and accessory parts. Components provided by the user can also be included here.

It is also possible to have thermal simulations carried out in Pentair's own laboratory to ensure optimum heat dissipation on the one hand and optimum use of the room space on the other. This and other test options, such as shock and vibration tests as well as tests for IP protection and thermal tests, support customers with the certification of their products and the necessary documentation.

Author:
Linly Fou is Field Marketing Specialist EMCA Europe at Pentair.

A practical example

The concept developed by Pentair for the Schroff interscale housing platform is illustrated by a customer example. A small, powerful PC unit was to be configured and set up for use as an IoT edge gateway for automation, visualization or monitoring. The customer chose an embedded NUC board suitable for industrial applications. It combines many PC functions on a baseboard measuring only around 10 cm × 10 cm and takes into account the interfaces relevant for industrial applications, the long-term availability of processors and other electronic components as well as fail-safe cooling without fans via conduction cooling.

The housing configured for these applications consists of three parts (body, cover and front panel) including EMC protection and is 35 mm high, 110 mm wide and 103 mm deep. Looking at the size of the embedded NUC board (101.60 mm × 101.60 mm), it becomes clear that the integration of additional hardware components in a very small space was required. The housing had to be able to be used as a desktop device or installed in a control cabinet with a DIN rail, which was ensured by existing standard accessory components. The most effective cooling solution was determined through thermal simulation in the climate laboratory. The resulting power loss can be reliably dissipated via conduction cooling using a heat sink integrated into the housing. The board is attached directly to the heat sink so that no unnecessary thermal resistance is created.