Robust rotary position sensor for fast paddle gearshift system

Variohm EuroSensor is supplying a reliable and robust rotary sensor to Life Racing Limited, producers of high-quality and reliable products for the professional motorsport industry with a specialist product range that includes engine controllers, power distribution units, custom wiring design and gearshift systems.

Early in 2003, the Essex-based electronics designer and manufacturer began looking to produce its own paddle-controlled sequential gearshift system that required a rotary sensor to provide position feedback from the gear input shaft to their own control unit. From the outset of the development phase, Life Racing identified that they needed a gear position sensor that would be compact, accurate, reliable and could withstand the environmental challenges of motor racing. Like all companies embarking on new product design they could not release a product that might harm valuable reputation, and tested many rotary sensors from various companies who claimed their own particular product was best suited for the application. Unfortunately, the early batch of tested sensors all failed randomly and prematurely.

However, later in 2003 they tested the Novotechnik SP2800 series from Variohm EuroSensor and quickly realised that they had found the right product for the job, as Karl Duchesne of Life Racing confirms: "As soon as we started to test the Variohm sensors we could tell straight away that we were on to a winner, as early data analysis indicated that the electrical trace showed very little noise due to vibration compared with other sensors we tried."

The SP2800 is a competitively priced contacting potentiometric sensor that features multiple layer conductive plastic tracks in combination with precious metal multi-fingered wipers arranged in a preloaded design that ensures reliable operation under characteristic motorsport shock and vibration conditions. The sensor elements are housed in a robust IP65 sealed high-grade plastic housing, capable of withstanding continuously hot ambient environments up to 125degC with an intermittent rating to 150degC. With a choice of electrical angles up to 345 degrees, single track or dual track redundant versions, a very low effective temperature coefficient and a life of 50 million movements, the SP series is well suited to the high demands required in the paddle gearshift application, as Karl Duchesne confirms: "The chosen SP2800 series sensor did not fail during a single test - in fact, we couldn't believe how well this sensor coped."

Following the full release of its sequential gear shift system, Life Racing's sales grew quickly and after several years of production continues with equal success across the industry from small single-seat formula teams to large Le Mans Prototype teams.

Dependable sensors

With reliability a key issue for Life Racing and, of course for the motorsport industry in general, Karl Duchesne and his team were able to dispel their fears about the dependability of contact type angle sensors. He says: "It's strange looking back, as we used to carry many spares to the track for failed sensor replacement, but now it is common for these to last easily over two seasons - we only change them out of precaution. In fact, there are teams out there that are still running the original sensors purchased in the early paddle shift production kits."

Life Racing's work in engine, chassis and gearbox control systems for the motorsport industry now uses a variety of Variohm sensors for other position-sensing areas. Karl Duchesne says: "We are so happy with the quality and reliability of the Variohm sensor range that we now use them for all of our position sensing including throttle angle and steering wheel angle."

Other types of sensor from Variohm's motorsport range which find good use at Life Racing include the non-contacting Euro-X series rotary sensor for angular position measurement up to 360 degrees as well as the ELPM series linear position sensor.

The 28mm diameter Euro-X uses a non-contacting Hall effect and magnet design for durability against shock and vibration with an integral plastic housing and bearing set that is fully sealed and IP67 rated for maintenance-free operation. A variant of the Euro-X is also available with a digital interface that allows user programming of angular resolution in 2-degree increments from PC-based graphical interface software.

Variohm also supplies a "touchless' technology Hall-effect sensors from its German distribution partner Novotechnik that consist of a separate magnet and detector. This design, without bearings or housings and with fully encapsulated and inherently protected components, allows robust, compact and long-life operation. The touchless sensor also facilitates position measurement through obstructions such as gearbox walls where the magnet may be fixed to the rotating gearbox barrel shaft - which does not need to protrude through the casing - and the detector sits outside on the housing wall. This arrangement has benefits in motorsport and commercial gearbox design for improved sealing, fewer parts, reduced weight and higher efficiency.

Variohm's ELPM series slimline linear position transducers suit demanding applications in steering position feedback and ride height measurement on race cars and bikes with travel ranges from 12.5-150mm and independent linearity to +/- 0.5 per cent. With IP67 protection and a strong resilience to shock and vibration, this contacting potentiometric sensor uses a similar preloaded brush design as the SP2800 series.

Sensors for motorsports

Variohm EuroSensor supplies an extensive range of specialist sensors and transducers across the motorsport industry including Formula 1, A1GP, WTCC, GP2, Champ, Nascar, ALMS, Superbike, and many others. The complete range includes pressure and temperature sensors for fuel, oil, coolant and brakes as well as force, torque and position measurement sensors for suspension travel, steering angle, ride height, throttle and gearbox. Laser and infrared technologies are also supplied for ride height position and tyre condition.

To find out more about the Novotechnik SP2800 series of contacting potentiometric sensors and other Variohm EuroSensor specialist sensors and transducers, go to the website at www.variohm.com.