FEATURE INTERCONNECTION
GOING AGAINST THE ELEMENTS ARMED WITH D-SUB CONNECTORS
Harsh industrial conditions place high demands on the connectors used. Bob Hart from In2Connect UK explores the latest D-sub miniature connectors and how they have been design to meet industry needs
O
utdoor or wet indoor environments can destroy electronic equipment. The
ubiquitous HD15 VGA D-sub connector was never intended to withstand contaminants such as water and dust, but industry demand for A/V everywhere has introduced such connectors into less tolerant environments. To achieve IP67 or higher most protected connector designs work on the same principle where the aim has been to reduce the number of components that make up the connector, hence remove all possible leakage paths, and manufacturers have generally added a mounting plate with a silicone O-ring to create a watertight seal at the panel interface, and back potted screw machined contacts to prevent water ingress through the connector body. IP67 connectors must allow no ingress of dust with complete protection against contact. They must also prevent ingress of water in harmful quantity when immersed in water under defined conditions of pressure and time. IP67 is intended for applications that will get ‘rained on’, or occasionally washed/drenched. They are not intended for use under continuous pressure. In consideration of the broad range of ‘rained on’ definitions, the industry appears to have agreed to a ‘test of immersion for 30 minutes, at a depth of 1 metre, or the equivalent air test at 1.45psi. That is the qualification test (Protected against the effects of temporary immersion between 15cm and 1metre, duration of test 30minutes). UL and CSA Approved waterproof D-Sub
miniature connector ‘systems’ from In2Connect include the standard D configuration as well as High Density, mixed layout, and Filtered options, all of which can be used in applications where moisture, high humidity, water or dust could be a problem.
The connector contacts are rear sealed to
the shell, which means that D-sub socket and plug connectors are available with solder cup, straight or right-angled PCB, but not “crimp” contacts. Designed with a one-piece solid body zinc diecast housing to resist mechanical impacts during installation and operation and minimise possible leakage paths; these connectors comply to current solder requirements with
20 JULY/AUGUST 2018 | ELECTRONICS
the elements. Positioning near power lines etc. requires protection from EMI. Filtered connectors are used to provide system immunity from external noise sources. EMI or RFI can be broadly defined as an
Figure 1:
IP67 SlimCon filter connectors
Figure 2:
IP67 D-sub hood connector
RoHS compliant solder temperatures. Back-potted and ‘O’ ring mounted panel connectors always ensure full IP67 conformity whether mated or unmated and in especially harsh environments can be further protected by a waterproof end cap when unmated. The mating D-sub cable end connector can have a waterproof hood. This has a compression ring to stop the ingress of water via the cable entry point at the rear and a sealing skirt at the connector interface to prevent liquids from reaching the connectors. The fitted jackscrews are sealed with O rings. The cable-end connection will not itself meet IP67 when unmated unless a waterproof cap with an internal rubber seal is fitted. Once mated, then the total D-sub connection interface, not just the panel mount D-sub connector will conform to IP67. Unless the sealing skirts or other forms of IP67 protection are added around the interface of the two connectors, any moisture getting into the mating zone could track across the pins and cause shorting. But the use of electronic equipment outside not only requires protection from
unwanted electrical or electromagnetic energy that causes undesirable responses, degraded performance or failure in electronic equipment. A filtered connector is widely recognised as the most effective point to filter noise either entering or exiting an EMI enclosure. Noise induced on a signal line within the box can be stripped off as it passes through the shielding enclosure, preventing radiation to adjacent equipment. Filters integrated into D-sub connectors to achieve a reduction in conducted EMI have evolved over the years using a variety of elements and materials to achieve varying degrees of noise suppression. These filters are broadly identified as low-pass filters. A low-pass filter allows lower frequencies to pass through the filter with minimal reduction in signal strength, while attenuating signals with higher frequency. The four basic types of EMI filters include capacitive feed-through, L filters, Pi filters, and T filters, each with their own performance characteristics.
THE SOLUTION In2Connect has introduced the CONEC family of filtered, IP67 rated D-sub connectors. These devices have one integrated low-pass filter per contact in the very compact CONEC SlimCon connector. The integrated filters will be offered with capacity values of 370pF, 820pF and 1200pF. The low-pass filter is realised by completely encapsulated capacitor elements, connected from each contact to the connector housing. These SlimCon filter connectors are
designed for back panel mounting and are mechanically attached to the panel via four surfaces of the housing, guaranteeing an even mounting pressure to the seal. The sealing to the housing is achieved by a conductive EMC gasket or optionally by a silicone gasket.
In2Connect
www.in2connect.uk.com T: 01962 773004
/ ELECTRONICS
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