This Low-Cost Raspberry Pi Pico-Driven Power Monitor Includes a 1.2–35V Benchtop Power Supply
All-in-one gadget can handle up to 1.5A draws, and chart the power usage on-screen in real time.
Pseudonymous maker "electronstogo" has designed a low-cost power monitor with a difference: it also provides an adjustable power output, adjustable smoothly from 1.2V to 35V at up to 1.5A.
"A while ago, I designed [a power monitor and supply]. I then built a new and improved version that is cheaper, smaller, and simpler," electronstogo explains of the project. "The ZK-4KX [buck-boost converter], with its display of current and voltage in the old version, is actually a redundant component. Current and voltage are already shown in the display above the [ZK-4KX], so it is sufficient to use a DC-DC step-up/down voltage converter without [its] own display. This also eliminates the need for the additional step-up converter that was necessary because the ZK-4KX module switches off immediately as soon as its input voltage falls slightly below 5V."
The redesigned power monitor is built around a 3.5" display connected to a low-cost Raspberry Pi Pico RP2040-based microcontroller development board. Texas Instruments' popular INA219 current sensor provides the power monitoring, while a cheap DC-DC buck-boost converter handles the power supply side of things.
"The DC-DC step-up/down voltage converter module used is normally adjusted via a potentiometer on the circuit board," electronstogo explains of this part of the project. "I removed this potentiometer and measured the range it covers. I then soldered on a potentiometer with the same value (10K ohms) that can be installed in the housing."
As well as a knob to adjust the output power in a range from 1.2V to 35V, the case also includes connections for the device-under-test. Once connected and powered, the INA219 monitors voltage and current while the Raspberry Pi Pico graphs both on the display — providing both at-a-glance and over-time readings for power profiling purposes.
The project is documented in full, complete with STL files to 3D-print the case, on Instructables; the source code is available on GitHub under an unspecified license.