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
