How to Defend Yourself Against a Man Armed with a GrapefruitHow to Defend Yourself Against a Man Armed with a Grapefruit

Gaurang Kavaiya, a principal applications engineer at Microchip Technology, was trying to figure out what prop would best illustrate the features of the company's new family of PIC Microcontrollers featuring nanoWatt Technology. And get the attention of engineers at trade shows. Then, inspiration struck: What better way to showcase what Microchip claims is "the industry's lowest power technology for embedded systems" than to use fruit as the power source for a digital thermometer? Okay, he sort of cheated when he used a grapefruit. According to one experiment published on the web that employed zinc and copper electrodes, grapefruits average a 0.93V output, which tops oranges (0.89V), kiwis (0.85V), and the lowly tomato (0.62V). Though the type of electrodes matter more than the fruit, the sight of a grapefruit powering a nanoWatt microcontroller, temperature sensor (a thermistor), and a 3.5-digit LCD display has been drawing crowds at trade shows since Microchip introduced the nanoWatt line in February. Oh, and just in case anyone is wondering, the technology itself has been garnering interest from a wide range of design engineers, particularly those challenged by the need to extend battery life in mobile electronic devices. To help engineers come up to speed on nanoWatt, Microchip offers a host of tips on its website at http://www.microchip.com/download/tools/picmicro/demo/pdem4/41200a.pdf. And for those engineers who want a good party trick, Gaurang has graciously agreed to let Design News publish the instructions for his grapefruit-powered thermometer. Download them at http://www.manufacturing.net/contents/pdf/grapefruitdemo.pdf, along with a parts list. For those looking for more insight into edible power sources, check out Erika Lindstrom's "The Electric Fruits" at http://members.aol.com/dswart/ElectricFruits.pdf and www.madsci.org.