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TEACHING IN THE LABORATORY

Low-cost computer-controlled current stimulator for the student laboratory

Biomedical Engineering Institute, Boaziçi University, stanbul, Turkey

Address for reprint requests and other correspondence: B. Güçlü, Biomedical Engineering Institute, Boaziçi Univ., Bebek, Istanbul 34342, Turkey (e-mail: burak.guclu{at}boun.edu.tr)

Electrical stimulation of nerve and muscle tissues is frequently used for teaching core concepts in physiology. It is usually expensive to provide every student group in the laboratory with an individual stimulator. This article presents the design and application of a low-cost [about $100 (U.S.)] isolated stimulator that can be controlled by two analog-output channels (e.g., output channels of a data-acquisition card or onboard audio channels) of a computer. The device is based on a voltage-to-current converter circuit and can produce accurate monopolar and bipolar current pulses, pulse trains, arbitrary current waveforms, and a trigger output. The compliance of the current source is ±15 V, and the maximum available current is ±1.5 mA. The device was electrically tested by using the audio output of a personal computer. In this condition, the device had a dynamic range of 46 dB and the available pulse-width range was 0.1–10 ms. The device is easily programmable, and a freeware MATLAB script is posted on the World Wide Web. The practical use of the device was demonstrated by electrically stimulating the sciatic nerve of a frog and recording compound action potentials. The newly designed current stimulator is a flexible and effective tool for teaching in the physiology laboratory, and it can increase the efficiency of learning by maximizing performance-to-cost ratio.

Key words: voltage-to-current converter; audio output; neurophysiology; frog; sciatic nerve