Automated, Hands Free Weighing
Masters Student Ben Walters came to me with a problem. The Brown-Headed Cowbirds he works with needed to be weighed several times over a period of a few weeks, and the weights at each time interval needed to be accurately compared for his experiment. The issue? The stress from being handled by humans causes the cowbird's weight to fluctuate for several weeks. He needed a hands free solution, and the systems already available were far too costly.
Over the next few weeks I collected the requirements from Ben. The system needed to be as cheap as possible, accurate within 0.1 grams, and function outdoors in all elements for extended periods at a time. What we came up with was a feeding/weighing station consisting of an RFID reader and load cell being run by the Raspberry Pi. The load cell had a perch attached that the bird could land on to begin feeding from the feeder hanging above. When the bird landed on the perch, the RFID tag we attached to the bird's leg would be read by the RFID reader, which in turn also activated the load cell and began logging several samples of the bird's weight on the Raspberry Pi. We then apply statistical procedures to the data captured to account for variables such as wind and bird movement and extract the bird's true weight from the samples.
Eight separate feeding/weighing stations were constructed, and the experiment began June 2014; it has run through all trials successfully, with software and hardware performing as expected. The cost of the project came in under 25% of the cost of hands-free solutions already on the market.
Ben Walters, Masters Student in Biology at the University of Western Ontario
Raspberry Pi Model B running Raspbian, Java, Phidget USB Sensors, BASH Script