Connecting with reliability

4 mins read

Electric vehicle racing team finds affordable solution to connectivity requirements.

The old Formula One proverb says that, to finish first, you must first finish and this applies equally to any form of motor sport, including the Institution of Mechanical Engineers' Formula Student. This competition challenges university students to design, build, develop and market a small single seater racing car as a team. A team from Imperial College London, Imperial Racing Green, has already built an enviable reputation, winning the 'Most Innovative Engineering Design' award at Formula Student 2009. The team is now entering Formula Student's new Class 1(A) event, where it will compete against other universities to build the fastest, most efficient low emissions vehicle. The new full size race vehicle, called IRG04, is using an interconnection system from Harwin to ensure this reputation for reliability is maintained. Reliability is vital, not just for competition, but also for general automotive use. However, it is while under race conditions that systems are stressed to the limit, so all component parts of the system must be closely scrutinised to ensure that they perform reliably. During Formula Student races, karts will regularly hit speeds of up to 60mph, causing a great deal of vibration, and the full size fuel cell race cars which are being developed must withstand forces of several g. One of the most vulnerable parts of any electronics programme is the interconnect system. Conventional connectors, which may have been designed for computers, mobile phones, audio or other entertainment systems – are simply not adequate for any application that will see extremes of shock vibration and temperature. On the other hand, products designed for such usage, such as Mil-C-38999 circular connectors, are often bulky, heavy and expensive. When designing the battery management system – one of the key modules of IRG04, Imperial Racing Green evaluated a number of different options before settling on Harwin's 2mm pitch high reliability Datamate connector system. Many connector systems exist that have been specially developed for use high reliability applications. Often, these have outstanding shock, vibration, temperature and other signal integrity performance specifications, but also carry an outstanding price tag – usually with very high contact prices. However, there is a large and growing demand for a high performance connector system that performs well under testing environmental conditions, yet is priced in line with commercial products – and demand is not just coming from the autosport sector. Datamate from Harwin is just such a system. The connector has been proven many times in applications where harsh operating conditions are the norm, including: the 'Nano' space program (also termed Cubesats), with satellites that measure just 10 x 10 x 10cm; the Neutrino telescope buried deep in the polar ice; Bowman military radio; missile guidance systems; dialysis equipment; and patient monitoring systems. And the connector has also been used in Formula 1 telemetry systems. All of these projects call for very robust electronic systems, since the equipment simply cannot fail – either, in the case of nano satellites, because it cannot be replaced, or because it is in a critical application, such as a medical system. Datamate includes board to board, cable to board and cable to cable versions. High performance is delivered by Harwin's patented contact design, which features a stamped, four- fingered, gold plated beryllium copper clip with highly stressed contact beams. The clips reside in the female half of the connector clasping a round pin tightly, ensuring the integrity of electrical connection even under severe conditions. This design ensures that Datamate connectors meet the exacting requirements of BS9525-F0033, as well as MIL-C-55302 and CECC 75101-008. The design also allows Datamate to be rated for operation between -55 and 125°C with a vibration sensitivity of 10Hz to 2000Hz, 0.75mm, 10g for a duration of six hours. Bump severity is 40g, 4000±10 bumps; shock severity is 100g for 6ms and acceleration severity is 50g. Environmental classification is 55/125/56 days at 95% relative humidity. Mechanically, Datamate is guaranteed for 500 operations. Mating and separation forces per contact pair are 2.8N max, 0.2N min (M80-xxx), 1N max, 0.2N min (M83-xxx). Contacts are rated at up to 3A for signal purposes. This compares with other commercially priced, twin beam 2mm connectors, whose contacts may only be able to handle 1A. The interconnection system comes in a number of different families. Datamate L-Tek offers friction latch, locking latch and no latch mating options. Datamate J-Tek includes the security of jackscrews, and Datamate Mix-Tek includes signal, power (up to 20A) and coax (up to 6GHz) contacts. All devices are available with 100% in process testing (Datamate Plus) and, for customers who require full BS9525-F0033 approval, there is Datamate BS. A variety of termination styles is available, including through hole, pc tail, crimp, vertical and horizontal surface mounting. All Datamate connectors are RoHS compliant and all board mounted versions are available in non RoHS versions with tin/lead plating. Recent developments include Datamate Trio-Tek. Performing to the same high reliability standards as conventional Datamate contacts, Harwin's Datamate Trio-Tek open barrel crimp contact automates the crimp process to save on assembly time and reduce process costs. The crimp design, which features a latching mechanism, also simplifies the insertion of contacts into the housing. The Datamate Trio-Tek autocrimp contact uses a triangular form that is the key to providing a simplified crimping process while, at the same time, enabling the customer to automate crimping in medium and high volume applications. Trio-Tek is suitable for both medium and high volume processes and inexpensive hand crimping tools are available for lower volume, product development and prototyping applications. Harwin has also launched a Datamate connector with fibre optic contacts. The Datamate EBO-TEK connector is offered with two EBOSA contacts, two power and four signal contacts. Further models will be added to the range in the near future. The Datamate EBO-TEK optical system is high endurance and requires zero contact pressure to mate the optical contacts. The rear removable optical inserts are non rotating and designed to ensure minimum insertion losses and optical stability. The contacts are also compact, self aligning and facilitate simple mating, featuring a design that greatly reduces sensitivity to particulate contamination, vibration and temperature changes. Imperial Racing Green chose to use Datamate J-Tek, which has the additional security of jackscrew fixings. Currently, the connectors are performing very well, according to team member Amit Meghani. He said: "We are very satisfied with the performance of the product and the support that we have had from Harwin's applications team. We are proud to have Harwin as a bronze sponsor for our race campaign." Author profile: Wendy Bourne is a technical support engineer with Harwin