Arduino LCD Bargraph Voltmeter

Arduino based LCD Bargraph Voltmeter can be easily assembled with Arduino Mega 2560/Arduino Uno or compatible boards. This design is basically the same circuit I’ve shown in Bargraph Voltmeter except for  2 main differences. Current design uses 2×16 LCD with parallel interface instead of vacuum fluorescent display (VFD) for outputting the input voltage. In my opinion VFD looks better for this purpose, however an LCD is much more common, relatively cheap and widely available. The second one is the target microcontroller. Previously PIC16F877 was used but now I’ve modified the code to run on ATmega chip. Design schematic diagram is shown in the next figure.


Arduino sketch can be downloaded here. Basically the analog input voltage supplied at A0 is converted to 10 bit number, then normalized for 5v full scale operation and divided to 16 ranges to fit the available display segments. A short video demonstrating this circuits operation is available on the bottom of the page.

Arduino-LCD-Bargraph-Voltmeter-Prototype-BoardInput voltage can be increased by adding a simple resistor voltage divider to A0 input. In this case the sketch will require some modifications. +5V and GND are taken directly from the Arduino board as can be seen from the schematic diagram. Although LCD backlight connections are omitted from the schematic you still need to supply 5v to A (LED+) and GND to K (LED-).


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