How to Build a Digital Voltmeter of your Own?

How to build a voltmeter for DC voltage measurements without using multimeter testing? This is a simple digital voltmeter circuit that can measure voltages from 0V to 9V.The main part of this circuit is a dot bar display driver IC LM3914. Input voltage applied to this IC generates an output which is converted into a binary value by the priority encoder IC 74147. It is then displayed on the seven segment display by the help of a common anode seven segment display driver IC 7447.However the voltmeter accuracy of this digital voltmeter schematic is limited to a sensitivity of 1V.

Circuit diagram of digital voltmeter

Click on the circuit for enlarged view

Components required

IC LM3914
IC 74147
IC 7404
IC 7447
7810
Resistors(1.2k,3.3k,220)
Common anode Seven segment display

Working

IC LM 3914 is a bar dot display driver which has 10 output pins (1 to 10). This IC has 10 comparators with a reference voltage each (1/10 to 10/10 of reference voltage)

Each comparator output is low if the voltage to be measured is greater than the corresponding comparator’s reference voltage.

Output of this IC is connected to a priority encoder IC 74147 which converts it into corresponding binary value.

Since the binary output is inverted, this voltmeter uses an inverter IC 7404 before giving it to the seven segment display driver IC 7447.

Here all IC’s supply is +5V, so for that you can use 7805 connected in a similar way as 7810 in the circuit diagram.

Components Pin out

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