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. 2012 Apr;83(4):044303.
doi: 10.1063/1.3700977.

Continuous-waveform constant-current isolated physiological stimulator

Mark R Holcomb  1 , Jack M Devine, Rene Harder, Veniamin Y Sidorov
Affiliations

Continuous-waveform constant-current isolated physiological stimulator

Mark R Holcomb et al. Rev Sci Instrum. 2012 Apr.

Abstract

We have developed an isolated continuous-waveform constant-current physiological stimulator that is powered and controlled by universal serial bus (USB) interface. The stimulator is composed of a custom printed circuit board (PCB), 16-MHz MSP430F2618 microcontroller with two integrated 12-bit digital to analog converters (DAC0, DAC1), high-speed H-Bridge, voltage-controlled current source (VCCS), isolated USB communication and power circuitry, two isolated transistor-transistor logic (TTL) inputs, and a serial 16 × 2 character liquid crystal display. The stimulators are designed to produce current stimuli in the range of ±15 mA indefinitely using a 20V source and to be used in ex vivo cardiac experiments, but they are suitable for use in a wide variety of research or student experiments that require precision control of continuous waveforms or synchronization with external events. The device was designed with customization in mind and has features that allow it to be integrated into current and future experimental setups. Dual TTL inputs allow replacement by two or more traditional stimulators in common experimental configurations. The MSP430 software is written in C++ and compiled with IAR Embedded Workbench 5.20.2. A control program written in C++ runs on a Windows personal computer and has a graphical user interface that allows the user to control all aspects of the device.

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Figures

Figure 1
Figure 1
Custom PCB. Shown with the four jumpers removed that connect the custom PCB to the USB power, CP2102, TTL inputs, and serial LCD, and stimulator output.
Figure 2
Figure 2
Stimulator schematic.
Figure 3
Figure 3
1 Hz-50 kHz noise spectra. Measurements were taken across a 1 kΩ load resistor with the stimulator set at constant currents of 1.0 mA, 5.0 mA, and 10.0 mA using a Hewlett Packard 3562A signal analyzer. The SNRs over the full bandwidth are 60 dB, 72 dB, and 75 dB, respectively.
Figure 4
Figure 4
Stimulator output. Voltage measured across a 1 kΩ resistor with a Tektronix TDS 2012B oscilloscope. (A) (Upper trace) S1-Sine mode example. Three 3.0 mA S1 pulses of 10.0 ms duration and period 50.0 ms, followed by a 25.0 ms delay, followed by a 300.0 ms duration 50 Hz sine stimulus of amplitude 8.0 mA with a −4.0 mA offset and 270° starting phase. (B) (Lower trace) Streaming mode example. A damped sine wave specified by 5000 currents loaded from a text file in the GUI. Values are updated every 175 μs. This trace was recorded at 100 ms per division and overlaid to make efficient use of the figure.
Figure 5
Figure 5
Induction of Arrhythmia in a Rabbit Heart using S1-sine mode. Electrogram was recorded using two Ag-AgCl pellet electrodes (EP8, Word Precision Instruments) placed on opposite sides of the heart. Six 1.0 mA S1's of 2.0 ms duration and 300.0 ms period followed by a 300.0 ms delay precede a sine wave with 4 mA amplitude, 90 ms period, 0° offset, 0.0 mA offset, and 2.0 s total duration.
See this image and copyright information in PMC

References

    1. Holcomb M. R., Woods M. C., Uzelac I., Wikswo J. P., Gilligan J. M., and Sidorov V. Y., Exp Biol Med. 234, 11 (2009).10.3181/0902-RM-47 - DOI - PMC - PubMed
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