Graphical Current Analyzer With Adjustable Voltage Source

I built a current measurement device with a graphical display and adjustable supply voltage. It’s mainly designed to check the standby mode of microcontrollers, but it can also be used to measure the power consumption of electronic devices during different operating modes to observe their behavior.

Material

1. 3.5inch display with Raspberry Pico connection (link)
2. Raspberry Pico (link)
3. Sensor INA219 (link)
4. Voltage Regulator Buck-Boost ZK-4KX (link)
5. Switch (link)
6. Push button (link)
7. Connectors (link)
8. USB port (link)
9. Diode (e.g. 1N4001)
10. Step up module (link)
11. Wires

Tools

1. Soldering iron
2. 3D printer
3. Electronics pliers
4. Screwdriver
5. Hot glue gun

I tried to keep this device simple. It is powered via a USB C port at the back, as this is normally always available. If the circuit being tested requires a higher current, you should use a suitable USB power supply that can deliver this current.

The switch can be used to turn the device on and off. The ZK-4KX is used to set the desired voltage (0.5V - 30V). The consumer can be connected to the banana sockets. The current curve can be observed on the graph in the display. Pressing the button resets the device, deletes all recorded data, and the graph starts again from the beginning.

When the graph reaches the end, the data is updated as in a FIFO shift register. The scaling of the graph is regularly adjusted to the largest value in the data.

I'm not particularly good at designing 3D printed objects. Please bear with me if not everything is perfect. Especially for the smaller individual parts, it might have been possible to integrate some fixtures. I simply fixed the loose parts with hot glue, that works well for me.

The two files contain the housing and the cover, which is clipped onto the back of the housing.

With the display used, the Raspberry Pico only needs to be plugged in, which saves a lot of wiring effort.

The power supply line of the Raspberry Pico contains a diode that prevents the Pico from supplying other components when it is being programmed.

The step-up converter is not absolutely necessary; the ZK-4KX module can be supplied with 5V. Unfortunately, however, the ZK-4KX module goes into “low voltage mode” when switched on and cuts off the power supply if the output voltage has been set too high, because the inrush current is too high and the USB voltage drops briefly.

Source code: github

For display control the TFT_eSPI lib is used, for the use of the mentioned display, uncomment the following line in "User_Setup_selection.h" in the TFT_eSPI library folder:

"#include <User_Setups/Setup60_RP2040_ILI9341.h> // Setup file for RP2040 with SPI ILI9341"