Enclosures
Selecting enclosures to protect electronics indoors and outdoors
By Rolf Horn, applications engineer at DigiKey A
lthough the inside of systems may change, electronic printed circuit boards (pc boards) must be externally protected from the
environmental intrusions of heat, cold, light, water, dust, humidity, and chemicals. They also need mechanical isolation to protect them from tampering and prevent electrical shock and short circuits. In some cases, they may further require isolation from shock and vibration. Enclosures must also shield from electric and magnetic fields and electronic interference. Finally, electronic circuit boards need protection from catastrophic events like fires and flooding. While designers can build their own enclosures, doing so is time-consuming and doesn’t provide optimal results. The solution is to buy enclosures off-the-shelf from a reputable supplier with a wide range of options with respect to materials, sizes, mounting, and sealing.
This article discusses the selection criteria for plastic enclosures suitable for indoor and outdoor use. It uses examples from Hammond Manufacturing and focuses on selecting designs with appropriate sealing and flame-retardant characteristics.
Choosing an electronics enclosure Before selecting an enclosure, the device’s location and environment need to be specified. Will it be mounted indoors or outdoors? Will it be mounted on a wall, a pole, or a bench? Does it have to be waterproof, corrosion resistant, dustproof, sun tolerant, or flameproof? Will the mounted sub-assembly be a pc board or a DIN rail module? Selection can only begin once these questions are answered. Small electronic enclosures are available in a variety of materials. Hammond Manufacturing designs and builds small
38 November 2024
Figure 1: Shown are the key structural features of a Hammond Manufacturing 1555F series enclosure. (Image source: Hammond Manufacturing)
electronic enclosures made of steel, stainless steel, sheet and die-cast aluminum, ABS plastic, and polycarbonate. They are available in an assortment of sizes and geometric configurations. In recent years, plastic enclosures have gained prominence primarily due to their lower cost and lighter weight while offering increased environmental protection.
Plastic enclosures
The Hammond Manufacturing 1555F series (Figure 1) is an example of a series of plastic watertight enclosures designed to operate in harsh environments. Constructed of either ABS plastic or polycarbonate materials, they are intended for wall mounting and include an integral mounting flange, mounting bosses, and a sealing gasket.
The 1555F series includes many of the common features of Hammond Manufacturing plastic enclosures, including a smooth molded surface that is recessed to accept a label or a membrane keypad. All include integral bosses to mount pc boards, and some also include mounts for DIN rail modules. These modules are sealed using a tongue-and-groove slot
Components in Electronics
www.cieonline.co.uk
to accept a replaceable, high-temperature, UL-listed silicone gasket. Tongue-and-groove slots hold the gasket and provide a better seal than the simple lap-joint seal used on die-cast enclosures. All the hardware is corrosion resistant, including stainless steel or brass. The cover screws and gasket are included and are
Figure 2: The Hammond Manufacturing 1555H2F42GY is an IP68-rated watertight polycarbonate enclosure. (Image source: Hammond Manufacturing)
self-captivating to prevent loss.
Replacement hardware and gaskets are also available. The series enclosures are standard RAL-7035 light gray with an easy- to-clean satin finish, except for the keypad recess which is smooth. The molded-in mounting flange is a characteristic of the
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