I have got the PCBs for my Tougher INA3221 Power Monitor projects, which of course are matte black. I also took the time to assemble the first test board. So far, I have only tested the buck converter, and it operates as it should, providing +5V. Given that this is my first experience in KiCAD, I have expected that there will be some errors in footprints but, surprisingly, everything is correct and components fit just fine. The KiCAD design files are available on GitHub, and you can read more about the schematics and PCB design in another post.
Designing the PCB for Tougher INA3221 Power Monitor
This is my first project in KiCAD, and I am mostly using Altium and CircuitStudio, as I have written in one of my blog posts. So, even though the PCB itself is not complex, learning a new tool was a bit of a challenge. I have achieved what I wanted in my design, except for some PCB art work, since import of bitmaps is not directly supported in KiCAD. I can’t learn everything with a first design. Block diagram Up-to-date schematics I initially planned for the power monitor to be compatible with Feathers only (see the previous post), but then I realized that adding Arduino Nano support was possible. Except for this, I haven’t made any significant changes in the schematics. The design files are available on GitHub, you can also download schematics in PDF directly here. PCB design I wanted to keep the design 2-layer, and with some insignificant shortcuts, I kept it at two layers. I have tried to avoid large currents to pass around INA3221 to prevent ground bouncing, so I added some cutouts in the ground. Cutouts are made so that differential traces from current resistor don’t experience ground plane breaks. I didn’t add any ground …
Tougher INA3221 Power Monitor
Following my experiments with setting up a small-scale solar system for charging phones and laptops, I needed a better power meter. I am using a DFRobot I2C Wattmeter (SEN0291) to measure current and voltage of a battery, a solar panel and a load. It is INA219 based, and has as minimilastic design as other INA219 based boards from Adafruit, Sparkfun or other manufacturers. The problem with power meters The problem with all of these boards, is that there is no filtering implemented around the current sense resistor. The pins of INA219 are directly exposed to the voltage on a wire you are trying to measure the current of. If there is any transient voltage higher than 26V between the current sense resistor and ground, the INA219 will be destroyed. In my case, the module would get sometimes destroyed during connection of a load. I have measured the voltage between the current sense resistor and ground during load connection, and maximum voltage reaches 56.7V, which is way above 26V. My conclusion was that it is caused by the high inrush current oscillations. Another disadvantage with all these prototyping modules are the connectors. The screw terminals are low quality, too small and …