Student research opportunities
Upgrading an electronic weighing system
Project Code: CECS_602
This project is available at the following levels:
Engn4200
Please note that this project is only for undergraduate students.
Supervisor:
Malcolm MacdonaldOutline:
Background:
Electronic weighing systems combined with automated livestock identification are used on many modern farms to, for example, collect individual animal weights and then optimise feed regimes, or in my case, to measure individual sheep fleece weights to assist with our Merino breeding programme - fleece weight/yield is one of many important selection criteria.
Commercial units are available (see reference section) but are very expensive and often don't provide quite the right requirements and/or flexibility.
In the past I have used a set of prehistoric scales (discrete electronics, car battery driven etc.) with a rather unfriendly RS232 interface. The scales themselves are very good (accuracy of about 0.1%), but the electronics have become unreliable and it is now time to upgrade the system and to interface it directly to a PC/laptop.
The task:
To develop an upgraded system which uses the existing load bars but with completely new (and simpler) electronics with a USB interface that provides the power, connected to a PC/laptop running say, Windows XP. Support software will need to be written for the PC/laptop.
Details of existing system:
The existing system consists of 2 load bars each with a pair of strain gauges. These connect to a "sender" box which incorporates a standard wheatstone bridge/op-amp arrangement, and provides temperature compensation, calibration adjustment etc.
The sender connects to a "receiver" box which provides battery power, switches/buttons for Range, Zero and Hold functions, debouncing/settling of the signal and displays it on a 3 digit LCD panel and also sends it to the RS232 interface.
The Range function selects for weights of either up to 1999Kg to the nearest Kg, or up to 199.9Kg to the nearest 100 grams.
Details of upgraded system:
On the PC/laptop the user should be presented with a window displaying a "digital" readout and "buttons" for Zero, Hold and Calibrate. (The Zero button resets the offset, and Calibrate, the scaling factor in the conversion algorithm.) For the Calibrate function, the user needs to be able to enter the value of the calibration weight.
Debouncing/settling of the weight value should also be done in the software package. There is no need to consider temperature compensation since any drift may be easily cancelled by using the Zero and Calibrate functions.
Range selection is probably best achieved by a switch on the electronics box since it simply changes the gain of the op-amps - there may be some reverse engineering of the existing system needed here.
Extension work:
Combine manual or automated animal identification with the weighing system to record data directly into a simple database.
Further, read the database to show, as well as current weight, the animal weight gain, or fleece quality factors such as micron etc.
References:
The following websites provide a good idea of the range and functions of commercially available units:
http://www.nrrbs.com.au/ruddweigh.htm
http://www.nrrbs.com.au/animalhealthtrutest.htm
