Dual Volt Amp Meter

Overview

This writeup is from the GitHub pages for the VoltsAmpsLogger project and from the hackster.io project page. The code is in the VoltsAmpsLogger GitHub Code Repository

The Dual Channel Voltage and Current Monitor project was created as I needed a way to look at the voltage and current going into an Adafruit Powerboost 1000c module and through the soft switch circuit that I built from Mosaic Industries Raspberry Pi ON/OFF Power Controller. I wanted to be able to monitor the voltage and current coming out of the controller and going into the Raspberry Pi.

The project is based on the Adafruit INA219 High Side DC Current Sensor Breakout and a Raspberry Pi Pico. The Raspberry Pi Pico is a bit overkill for this project, but I have a few on hand so that is what I choose to use.

Hardware Build

Parts List

• Adafruit INA219 High Side DC Current Sensor Breakout – 26V ±3.2A Max – STEMMA QT
  QTY: 2
  NOTE: I had the older version of these on hand without the STEMMA QT connecters.
• Adafruit Monochrome 1.3″ 128×64 OLED graphic display – STEMMA QT / Qwiic
  QTY: 2
  NOTE: I had the older version of these on hand without the STEMMA QT connecter.
• Raspberry Pi Pico
  QTY: 1
• Adafruit Panel Mount Extension USB Cable – Micro B Male to Micro B Female
  QTY: 1
• Adafruit Panel Mount USB Cable – B Female to Mini-B Male
  QTY: 2
• Adafruit Panel Mount USB Cable – A Male to A Female
  QTY: 2
  NOTE: I had some similar ones on hand that plug into PC Motherboards, which I used instead.
• Adafruit Adafruit Perma-Proto Half-sized Breadboard PCB – Single
  QTY: 2
  One was used for the Raspberry Pi Pico and the other for the 2 INA219 breakout boards.
• Radio Shack 10A/250V AC Binding Posts (2-Pack)
  QTY: 4 (4 packs for a total 8 binding posts with 4 red and 4 black)
• Radio Shack Project Enclosure Box – 8 x 6 x 3″ Catalog №: 2701809
  QTY: 1
• Glowforge Draftboard™ 12 x 20″
  QTY: 1
  Used for inside front panel and mounting plate for Perma-Proto boards
• Glowforge Clear Acrylic 12 x 20 x 1/8″
  QTY: 1
  Used for outside front panel
• Miscellaneous mounting hardware. Screws, nuts, and binding posts.
• Heat Shrink Tubing
• Hookup Wire

Next Steps/Going Further

The data transfer rate is extremely slow. It is good enough for what is being done here but it would be nice to capture more data points over the same period. Right now, the rate is about one set of measurements per minute. (It takes about 1.2 seconds to send one set of measurements.) One way to speed this up would be to move away from JSON and sending tab delimited data. I may create another version of the Raspberry Pi Pico and Windows software to send delimited data and see if there is an improvement. I would expect to get 4 to 5 times as many measurements in the same amount of time. It still is not very fast, but it would be an improvement.

References

• TaW had a good reply to SunAwtCanvas’s question regarding Chart Auto Scroll (Oscilloscope Effect). While I did not use the code verbatim, it did point me in the right direction.

External Project Pages

• hackster.io – Dual Channel Voltage and Current Monitor