Arduino DC Volt and Frequency Meter with Data Logger Functionality

 

Having on several occasions the need for another dc voltmeter, and while owning a really good one and a cheap one that was at best intermittent, it was time for another decent meter.   I thought why purchase one when I could build an Arduino based voltmeter with parts I have on hand. Thus born is my latest project, The Arduino based dual input DCV meter.

The project however was quickly a victim of feature creep. Originally just dc voltages, I decided to add another input for frequency and add in a data logger function. 

This came about after a few years of completing several pages of data from characterizing various IC’s and circuits and then entering that data manually into a spreadsheet for further analysis. 

The present specs for this project are:

Input 1 and 2, 0-15vdc

Input 3, up to 30mHz

Data Logging to export data into a spreadsheet automatically on demand

The DCV function went fairly smooth in the scheme of things.  Originally, I was playing around with the idea of using an opamp to invert a negative voltage on one of the inputs for reading negative voltages. I determined however that this was not a practical function and while it gave me a better insight to opamp behavior, the idea was abandoned.

The data logging routine went well and after a couple of days of hacking Arduino code I was able to get the dcv being measured exported to a spreadsheet via the serial port to my computer.  At first it was a constant stream of data and I put in a pushbutton debounce routine that allowed me to send data one line at a time at the push of the button.  Perfect.

Now I can turn my efforts to figuring out how to use the Arduino to read frequencies up to 30mHz.  I have the code working now up to about 4mHz.  The need for frequency divider circuit is apparent and I have never played around with these type of circuits before. 

Spending the last few days watching videos, reading what I can on the subject, not really understanding too much of it yet, I put in an order for a few IC’s that should get me what I need.  The practical experience will help with my understanding of these circuits. 

Along with counter IC’s I ordered a couple of Schmitt triggers as well. Mainly because I have seen where they are sometimes used in these circuits and since its all new to me and they are inexpensive, why not.  Should be here in a day or 2. With any luck I hope to have a working circuit by the weekend.

Another thought I have had lately is to get away from using the Nano board. While they are cheap and convenient, I am thinking about just adding in the couple of components required directly onto the pcb along with the rest of the circuit.  I have breadboarded such circuits years ago using the Atmega 168 IC so I know I can do it. Not tried the 328 though. I have a couple of 328 chips doing nothing so this might be the project to do this.

73, Peter