This is a new revision of 10 bit Digital Voltmeter. Recently I’ve published a few voltmeter designs ranging from a simple LED display voltmeters with 8 bit of resolution to a more complex with 10bit and improved input stage. Current project incorporates a number of improvements including the use of CU16025 VFD Display and voltage reference NCV1009ZG instead of referencing the measured voltage to a positive supply voltage that varies due to changing load conditions thus influencing the measurement. Also the source code was written in C using Microchip MPLABX and XC8 compiler making it easier to understand in my view. I’ve removed the input stage OP amplifier to simplify the design. The Input voltage is divided by 1:10 to obtain a full scale reading of 25 Volts. As you can see the schematic is not too complicated.
In the next figure you can see a prototype board I’ve used to build this circuit,click it for higher resolution image.
I’ve also published another version of this design at this link. It uses a standard 4 digit LED Display instead of VFD module. It has the same characteristics, meaning the same input range, same 10 bit of resolution and display update rate and A/D convention functions. Hex file for VFD volmeter can be downloaded here. If you need a C source code and all necessary library header files use this link. Just open it in your MPLAB X and rebuild.