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Past Project in Detail

Ranger Instruments (now Rinstrum) - design of electronic (DSP) device

30/06/2003

L to R: Alan McFadyen (Ranger Instruments) and Rakesh Solanki (QUT student)   Rakesh's DSP 'noise' filter connected to a weighing instrument and LCD screen.  

RANGER INSTRUMENTS (now Rinstrum)

Project duration: 1st semester, 2003

Student: Rakesh Solanki, QUT B.Electrical Engineering and Computer Science

BACKGROUND

Ranger Instruments specialises in the design, manufacture and marketing of electronic instrumentation for the weighing industry. Their products include high performance digital indicators, intelligent setpoint controllers, batching consoles and weight transmitters, as well as a range of remote displays. They also provide a design and manufacturing service for larger OEM users involved in fabrication of machinery associated with the measurement and control of weight and force.

Alan McFadyen, Design Engineer, Ranger Instruments looked to CEED as a cost-effective way in which to conduct research. He believes that it is also useful for Ranger Instruments to have access to a pool of bright, enthusiastic young engineering students and they are keen to offer training opportunities for them. Alan added that Ranger have a track-record of employing students who have performed well on projects for them.

PROJECT OBJECTIVES

This project was focussed on building a Digital Signal Processor (DSP) to read the weight of an object (such as cattle) and display it on the LCD screen. Then the DSP chip is used to develop filtering algorithms for removing large amounts of input mechanical/electrical ‘noise’ (eg. conveyor belts, diesel engine trucks) during the weighing process.

The objective was to prove that this method would produce a better result (i.e. a more accurate weight, due to reduced noise) than the currently used non-digital filter (simple moving average filter).

METHODOLOGY

Rakesh investigated all available digital filters, concentrating on variations of FIR (finite impulse response) filters. He then narrowed the choice down to the ‘Equiripple’ filter, which best suited the desired specifications and standards.

Half-way through his project, Rakesh wrote a feasibility study to present his research and recommendations, and help plan the rest of his project. He then gained approval to build the filter using the FIR filter that he recommended.

He then built a prototype board that can be connected to a weighing instrument and LCD display. Rakesh then moved on to writing the software so that the DSP chip could be programmed and tested against the non-digital filter. He then ran the tests in Matlab using live data.

During this phase, Rakesh learnt a great deal about DSP’s and moving from the design to production of a prototype stage….and the various challenges associated with it! His test results were often not conclusive and so he had to go back and look at the design many times, before being happy that the test was accurate.

Eventually, the test results consistently proved that the FIR DSP filter gave improved noise reduction (~25-30%) when compared to the moving average filter – a “significant improvement” according to Alan McFadyen.

Ranger Instruments is now looking at taking Rakesh’s design to the next level of testing, and if all goes well, then full production.

Future applications have already been identified for the product and Alan McFadyen is very happy with Rakesh’s results and performance during the project. Alan said that “Rakesh quickly became a regular member of the team, getting on well with his colleagues. He has been enthusiastic and pro-active in his approach”. “Rakesh has given us the first couple of rungs on the ladder, which were the most critical part of the entire project”.

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