Simple Data Acquisition and Plotting for Wetware

My O'Reilly Biocoder article, A Simple Data Acquisition and Plotting System for Low Cost Experimentation.

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See my O'Reilly Biocoder #6 paper - "A Simple Data Acquisition and Plotting System for Low Cost Experimentation"

This paper details the design and construction of a simple data acquisition and plotting system for amateur or commercial use. The system uses a general purpose computer, a standardized USB-powered peripheral board, and small software application to measure, record, and plot a real time signal. The system is demonstrated in use with a biochemistry chromatography experiment; however, the system may be used in conjunction with any experiment which needs to measure and plot an electrical signal. Modifications to the hardware are discussed to adapt the circuit to various signal voltages. Total cost is about US $35 in parts, a few hours connecting common electronic components with a soldering iron, and a few hours entering software on any typical computer. This system does require a separate computer which supports USB, although a small, inexpensive, embedded computer may be substituted instead, such as the popular Raspberry Pi board (currently, US $25). In contrast, a commercial-grade chart recorder which performs the same functions might have a price tag of US $2,000. Building this basic data acquisition system also yields the understanding of how to design and use such systems, either for use in laboratory protocols, or in field experiments.

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    Step 1

    Refer to the full paper published in O'Reilly BioCoder issue 6.

    The circuit is simple enough to construct directly by soldering point-to-point onto a copper prototyping board. It is best to spatially separate analog circuits from digital circuits to reduce electrical noise. In general, analog circuits are best soldered on a copper board rather than prototyped in a solderless breadboard to reduce stray capacitance. Leads of components are trimmed to reduce length and reduce stray inductance. A copper prototyping board with bus traces is used to ease construction. The specific bus board used has 5 connections for each pin in a DIP IC footprint plus two power rails down the center. The power rails are helpful in higher speed digital circuits, to reduce digital noise, or in analog circuits like this one, as a large ground bus. In constructing this board, the two power rails are soldered together at a single point and used as a larger ground. The bypass capacitor in particular, used to reduce power supply noise, should have short leads and is often arranged diagonally across the top of the IC, to reach as close to the IC as possible while connecting power to ground.

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