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Company Logo NXP Semiconductors

  • Digital 0V to 9V DC Voltmeter

  • Created: Sep 16, 2014

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A voltmeter is a device used to measure electrical potential difference in an electrical circuit. It is usually made of a moving coil galvanometer, a small coil of fine wire suspended in a strong magnetic field. But this project is different; it is built on integrated circuits made to measure from 0 to 9V DC only. This is applicable on checking batteries and circuits operating on or below 9V DC.

The output of this project is a single 7-segment numeric display counting 0, 1, 2, and so on; which is the project's disadvantage, it does not give decimal values. But the range can be expanded depending on the design. The IC LM3914 is a display driver that can sense analog voltage levels and provides ten linear output displays. In this project, the LM3914 is set to a linear output from zero to ten. But only nine output pins are used since the single 7-segment only gives a maximum number of nine.

The output of the LM3914 is then fed to the IC 74HC147D line encoder. It accepts data from nine active LOW inputs (A0 to A8) and provides a binary representation on the four active LOW outputs (Y0 to Y3). The outputs of the LM3914 passed through an inverter (74ABT04D) before the line encoder to match the assigned numbers. And another inverter (74ABT04D) is placed after the line encoder because of its active LOW outputs. The BCD (binary coded decimal) output is then inputted to the IC HEF4511BP decoder/driver; which converts the BCD signal to 7-segment numeric display, a single common cathode 7-segment display is used in this project.



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