By Majeed Ahmad, contributing editor

How do you select
the right enclosure for an embedded system? While size, weight, and power are still
key elements in choosing a suitable enclosure, there are more factors in play
in the design of instrumentation cases and enclosures.

For example, is
there sufficient space for the I/O devices? How does a cabinet protect itself
from the internal and external hazards? How does enclosure design simplify the
assembly work? Below is a sneak peek into what’s driving the enclosure design
and how it can serve the embedded system hardware more efficiently.

1. Shelf management options
The new enclosure
designs are now helping users to manage and monitor the shelf operation, including
power, cooling, and interconnect conditions on the shelf. It leads to greater
flexibility, which, in turn, creates more design options.

Take, for
instance, the Pigeon Point shelf management for AdvancedTCA enclosures offered
by LCR Embedded Systems. The design facilitates a drop-in replaceable
arrangement both mechanically and electrically. Moreover, it features dual-redundant
and hot-swappable fan trays in push-and-pull configurations and hot-swappable
power-entry modules capable of reporting voltage and current on each feed.

A shelf manager
can raise the fan level inside the enclosure if the temperature is exceeding a
pre-set value. And if that’s not sufficient, the shelf manager can even start
powering down the field replaceable units (FRUs) to reduce the heat load on the

LCR Embedded
Systems offers both Pigeon Point and Vadatech shelf management formats. And
besides AdvancedTCA chassis, the Norristown, Pennsylvania-based company also provides
shelf management options for the VPX form factors.

2. Cooling arrangements
Airflow is
crucial in ensuring a stable enclosure operation. The new enclosure and chassis
platforms now offer various front-to-rear, side-to-side, and bottom-to-top
airflow configurations. Take the case of 9U RiCool chassis platform from Pixus
Technologies that features up to 32 OpenVPX backplane slots. Here, reverse
impeller blowers reside directly above the boards.

The cooling
arrangement pulls air from below the card cage and blows the exhaust 90 degrees
to the back. Next, fans are individually hot-swappable, and it enhances
reliability and minimizes downtime. Enclosures like RiCool also provide various
power supply options in fixed, pluggable, and redundant modes.


Fig. 1: The rackmount chassis platform from Pixus offers various
cooling options.

Then there are
venting accessories offered by firms like Polycase that facilitate various
levels of airflow management and thus help equalize temperature and pressure in
the watertight enclosure. These vents come along with cable glands that help
maintain a watertight seal around the hole used for cables.

3. Enclosure lids
Enclosure designs
require more than just a box because you need to put components, controls, and
instruments inside the enclosure with wiring, cables, and conduits. Therefore,
many enclosures now come with snap-on lids for easy and cost-effective

These lids
feature a side-edge fold with half shears that allow a solid or perforated
enclosure cover to snap into place. Companies like Pixus Technologies offer
covers that have side notches for fitting into rails with 160- or 280-mm
depths. These snap-on lids also include the EMC gaskets.


Fig. 2: Cover lids on Pixus enclosures enhance the assembly and deployment

Polycase offers internal panels for its enclosures; these panels allow users to
secure components on a flat surface inside the enclosure without having to
puncture the box. The Avon, Ohio-based manufacturer’s EX Series aluminum
enclosures are a case in point.

The enclosures have
been designed to allow a standard PCB to slide into place with removable
end-caps, which can easily be modified for cables, connectors, and switches. Here,
gaskets sit between the end-caps and enclosure body to provide the IP66-level
protection from dust and water. The aluminum material also provides a degree of
EMI and RFI protection.

4. Outdoor applications
Besides meeting
the National Electrical Manufacturers Association (NEMA) ratings, enclosures
for outdoor use should be airtight, and for that, they need to have a gasket
between the base and cover to create a watertight seal.

Second, the
material used for outdoor enclosures is of vital consideration. Aluminum,
stainless steel, and painted steel are metal types commonly used for enclosures
in outdoor environments.


Fig. 3: The SB Series NEMA enclosures from Polycase comply with the
IP65 and IP 66 ratings.

Polycase has
introduced the SB Series stainless-steel enclosures that are waterproof,
weatherproof, and corrosion-resistant. These enclosures include an internal
panel, external mounting brackets, latch key, and grounding studs and wire. The
company is targeting these NEMA-rated enclosures at food and beverage,
pharmaceutical, and oil and gas industries.

Some outdoor
enclosure manufacturers also use polycarbonate plastic with a UV-stabilizer in
the resin. It’s worth noting that ABS plastic, which typically has a lower heat
tolerance than polycarbonate, is not suitable for outdoor enclosures unless the
resin has specifically been enhanced with a UV-stabilizer.

5. Enclosure displays
There are some
enclosure units that offer sufficient space and hardware slots for operating hardware
elements like displays. That’s critical in applications such as measurement and control, medical and
laboratory instrumentation, and environmental engineering.


Fig. 4: OKW’s
table-top and wall-mount enclosure can incorporate 7-in. touch displays.

Enclosures like OKW’s SMART-TERMINAL
are designed
to fit standard display and touch solutions ranging from 4.3-in. to a maximum
of 8-in. sizes. Additionally, the inside of the enclosure has several mounting
options on two assembly levels so that displays and PCBs can be optionally
mounted face up or face down.

above trends show that the enclosure design is evolving along with the backplane
and chassis platforms. It also shows how accessories are increasingly
complementing the overall enclosure designs.