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Advanced Engineering 2021

NEC Birmingham(B40 1NT)

03/11/2021 - 04/11/2021

Join us in our 12th and most important edition to date, as we invite engineers and management from all (more)

Touchless two-part sensor for innovative agricultural machine

Touchless two-part sensor for innovative agricultural machine The British manufactured Big Bale Transtacker is an innovative agricultural machine that provides a highly efficient, simple and effective solution for collecting and stacking straw bales in the field as well as transporting bales to and from storage locations on the farm. The tractor towed machine collects and stacks its payload continuously as it is driven through the field with the operator controlling the entire machine from the tractor cab.

The Transtackers efficiency is largely due to both the 'auto pick up' and the 'auto tie' functions that allow the machine to work seamlessly with minimal operator input. These functions work through a series of rotary sensors logging the position of the machines components and then relaying the data back to the ECU, whereby the next sequence of events is actuated.  

Alex Baylis from Big Bale Transtacker says: "We had to reassess the Transtacker at the end of the 2012 harvest due to several reliability issues that were beyond Big Bale Transtackers control. After a lot of deliberation we decided to bring the entire R&D 'in house' and I now control all of the production from my desk rather than outsourcing it. This meant we were able to create a five year 'R&D' plan, with the hope that by 2017 our product will be a world leader in the straw handling market. One of the issues encountered during the 2012 harvest was the reliability of the 'Hall effect sensors' that we used. Not only were these expensive, they weren't water proof and also struggled with the precision that we were after. These issues meant that a lot of machines were experiencing problems and therefore weren't operating efficiently, causing both the farmer and Big Bale Transtacker a lot of unnecessary problems."

Big Bale Transtacker discovered the Novotechnik RFC4800 series angle sensors, specified and supplied by Variohm. The RFC4800 solution utilises a two part design with non-contact 'touchless' technology, comprising an encapsulated magnet position marker that is attached to the rotating shaft and a physically separate sensor which is encased in a robust IP69 rated, sealed housing made from high-grade and temperature resistant plastic. With no mechanical coupling required, installation is very straightforward with generous alignment tolerances. Without traditional bearing seals to wear, the sensor offers an effectively unlimited life for the mechanical parts and the 50000 hour MTBF quoted figure for the electronics. The robust and compact solution provides a 12-bit resolution (0.09 degrees) analogue output which is absolute and therefore does not require recalibration after initial set-up or after complete power loss.

With its wide choice of supply voltages, output formats and electrical angle selection, the application flexibility available for the RFC4800 also allowed Big Bale Transtacker to exactly match their requirements which had not been possible with the alternative solutions that they had looked at. With a prerequisite to operate the control system from 12 or 24V DC supplies, and provide a 4-20mA output, a standard option with a 9 to 34V input capability was perfectly suited. Other standard supply options are 5 or 12V DC with output options of 0-10V DC as well as 0.5-4.5V DC ratiometric. The RFC4800 was also supplied with a limited electrical angle. As standard, the unit has a 360 degree output with optional 30 degree increment version specials available as well as redundant output versions.

"The touchless technology sensor has answered all of the issues stated above; with it offering very high levels of precision, being IP69K rated, and also very good value for money," says Baylis. "Its two-part design has increased our confidence for much improved reliability - a very important factor for our equipment which is shipped world-wide."

The Big Bale Transtacker is in use in many different countries and is designed to withstand the rigours of a variety of agricultural conditions. High shock and vibration as well as extreme variation in temperature and humidity are factored into the performance specification with reliability and the need to perform faultlessly being of upmost importance. Variohm designs, specifies and supplies a wide range of position, load/force, pressure and temperature sensors for the agricultural machinery industry as well as construction equipment, motorsports, aerospace and many other demanding areas.
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