INTERCONNECTION
How to turn your connector into a filter
There is an invisible force at work in electronics. Although it cannot be touched or seen, it has the power to disable or even destroy electronic equipment.
A
lmost all of us come across this force; the crackle you hear while listening to a car radio when a thunderstorm is nearby or the vacuum cleaner that makes the TV picture go fuzzy. These are examples of Radio Frequency Interference, shortened to RFI, also known as Electromagnetic Interference (EMI).
One method of protecting electrical and electronic devices is to provide them with shielding. Shielding takes the form of an electrically conductive covering that encloses the equipment, preventing electromagnetic interference from getting in or out.
However, electromagnetic radiation is hard to contain. It can be very difficult to prevent interference, despite the best efforts of the engineer. Most electronic and electrical installations make use of cables and connectors, which bring power into a device and transmit signals. All these connectors and cables create the potential for EMI interference. There is a quick and easy solution that can be used: filtered seals. Filtered seals like the EESeal and EESeal+ product lines from Quell, which are available from stock in Europe through Powell Electronics, work in the same way as traditional filtered connectors. The innovative feature of filtered seals is how
they are packaged and installed. From a distance, the filter seal looks deceptively simple. It is a thin silicon rubber shape that contains the capacitors and wiring circuitry required to provide an effective filtering solution. It is designed to fit over the pins of a male connector and, once in place, is almost invisible. It takes seconds to install and does not require anything else to be taken apart to do so. All that is required for installation is to unmate the connector pair. The seal is pushed over the pins of the male contacts and then the connector is mated. This quickly installs the filtering circuitry directly into the connector without the need for any additional work.
This versatility means that filter seals are not only ideal as a production solution, but they are also ideal for retrofitting into legacy equipment. For example, governments around the world are constantly upgrading their existing military fleet. Vehicles that may be 30 or even 40 years old are being fitted with the latest generation of communications equipment to perform tasks for which they were not originally designed. This mismatch of old and new technology has created a range of EMC challenges that vehicle contractors are struggling to solve. Using filter seals within existing interfaces removes the
headache that obsolete components would cause.
Filter seals are not only useful for retrofitting or problem solving. In recent years, a major commercial aircraft began to be manufactured with a composite fuselage. Composite materials are light and strong, but they are not conductive. This is important because EMC in aircrafts used to be easier to solve; the metal of the fuselage could be used for shielding. The use of so much composite material meant losing this shielding benefit. To solve this issue, the commercial aircraft manufacturer now uses more than 80 EESeal filter seals in each aircraft to protect the electronics. In contrast to a traditional filtered connector, samples of Quell’s EESeals can be sourced very quickly through Powell Electronics, making them ideal as quick solutions for testing or operational problems. All that the engineer needs to do is provide a few key pieces of information: the connector p/n, the frequency of the signal that needs to be filtered, the voltages, data rates and any transient specifications.
EESeal filter seals are a versatile solution to a range of different EMI problems. Each pin can be treated uniquely to meet the needs of the application. They can be used to turn any connector into a filtered connector to pass a failed EMC test. They can be used during the refit of legacy equipment and can be installed as an integral component in brand new devices.
OCTOBER 2024 | ELECTRONICS FOR ENGINEERS
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