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LM3914 analog display and resistance measurement - del20008U2A opamp LF353 is used here as a constant current source, R10-D13-D14 is for protection in case you measure voltage in the ohms range. U1 4052 helps digitally select four different currents, the currents pass thru the unknown resistor to be measured and an voltage developed across the resistor is measured.U2B is a buffer which passes on the voltage measured to U5A for inversion of polarity as current source is a negative current (current sink). U5B amplifies to the level required for the LM3914 display circuit. U7 555 is used as a de-bouncing for switch SW1 so as to advance counter 4029 to change the range of resistance measurement. To view the circuit below, Click the Link of PNG or PDF and view the Circuit, PNG can be Scrolled with Mouse and PDF can be Viewed-Zoomed in the Browsers with Acrobat plugin. The Javascript and Images must be enabled in your Browser. |
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Data sheets and info useful to study and build this circuit. National P N LM3914 - Dot Bar Display Driver National Semiconductor Products Catalog National Semiconductor Products LF353 - Wide Bandwidth Dual JFET Input Operational Amplifier The 4029 CMOS Counter IC ICs: CMOS - CD4000 Series |