Custom measuring instrument dedicated to microbial fuel cell characterization

Microbial fuel cell(MFC) is a rising energy harvesting technology that can be used to supply low power devices for many purposes and applications like Wireless Sensor Network(WSN) for ambient monitoring or precision agriculture. An MFC is a bioreactor that turns the energy stored in chemical bonds of organic compounds into electrical energy. Due to its property, MFC could be useful to many different applications in term of biobattery, bioremediator or biosensor. Efforts are needed to improve MFC with various set up, substrates used and reactor configurations. An original measurer board was developed to allow self-managed long-time measurements for the electrical characterization of MFCs. The custom measuring instrument consent to set up a complete electrical performance analysis of MFC charge and discharge phase. It consents to understand the sensitivity of major parameters that affect MFC behavior, performing the charge and discharge phase or using a wide collection of loads, collecting easily the steady state, pseudo steady state and real time values. The components chosen were a PIC18F4550 and three electromagnetic relays LEG-5 that permit to switch between the three measurement options: discharge phase imposing short-circuit, charge phase imposing open-circuit, and as resistorstat switching resistance values. All the measurement can be managed by the feature of the graphical unit interface, written in C++ code. A precision operational amplifier LMP7721 is used to compare input values and an REF192 to obtain an accurate reference voltage of 2.5V. The board is supplied by +5V provided through USB port. All tests can be timed, or the software can self-manage it. One original advantage is the sensitivity to the measurement state, as resistorstat it can automatically switch load value after the measured value is stabilized.