USB-C PD Decoded: A DIY Meter And Logger For Power Insights

September 15, 2025 by Matt Varian 9 Comments

As USB-C PD becomes more and more common, it’s useful to have a tool that lets you understand exactly what it’s doing—no longer is it limited to just 5 V. This DIY USB-C PD tool, sent in by [ludwin], unlocks the ability to monitor voltage and current, either on a small screen built into the device or using Wi-Fi.

This design comes in two flavors: with and without screen. The OLED version is based on an STM32, and the small screen shows you the voltage, current, and wattage flowing through the device. The Wi-Fi PD logger version uses an ESP-01s to host a small website that shows you those same values, but with the additional feature of being able to log that data over time and export a CSV file with all the collected data, which can be useful when characterizing the power draw of your project over time.

Both versions use the classic INA219 in conjunction with a 50 mΩ shunt resistor, allowing for readings in the 1 mA range. The enclosure is 3D-printed, and the files for it, as well as all the electronics and firmware, are available over on the GitHub page. Thanks [ludwin] for sending in this awesome little tool that can help show the performance of your USB-C PD project. Be sure to check out some of the other USB-C PD projects we’ve featured.

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From Paper To Pixels: A DIY Digital Barograph

September 14, 2025 by Matt Varian 6 Comments

A barograph is a device that graphs a barometer’s readings over time, revealing trends that can predict whether stormy weather is approaching or sunny skies are on the way. This DIY Digital Barograph, created by [mircmk], offers a modern twist on a classic technology.

Dating back to the mid-1700s, barographs have traditionally used an aneroid cell to move a scribe across paper that advances with time, graphing pressure trends. However, this method has its shortcomings: you must replace the paper once it runs through its time range, and mechanical components require regular maintenance.

[mircmk]’s DIY Digital Barograph ditches paper and aneroids for a sleek 128×64 LCD display that shows measurements from a BME280 pressure sensor. Powered by an ESP32 microcontroller — the code for which is available on the project page — the device checks the sensor upon boot and features external buttons to cycle through readings from the current moment, the last hour, or three hours ago. Unlike traditional barographs that only track pressure, the BME280 also measures temperature and humidity, which are displayed on the screen for a more complete environmental snapshot.

Head over to the project’s Hackaday.io page for more details and to start building your own. Thanks to [mircmk] for sharing this project! We’re excited to see what you come up with next. If you’re inspired, check out other weather display projects we’ve featured.

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The schematic on the left and the assembled circuit on the right.

How To Make A Simple MOSFET Tester

September 13, 2025 by John Elliot V 22 Comments

Over on YouTube our hacker [VIP Love Secretary] shows us how to make a simple MOSFET tester.

This is a really neat, useful, elegant, and simple hack, but the video is kind of terrible. We found that the voice-over constantly saying “right?” and “look!” seriously drove us to distraction. But this is a circuit which you should know about so maybe do what we did and watch the video with subtitles on and audio off.

To use this circuit you install the MOSFET you want to test and then press with your finger the spare leg of each of two diodes; in the final build there are some metal touch pads attached to the diodes to facilitate this. One diode will turn the MOSFET off, the other diode will turn the MOSFET on, and the LED will show you which is which.

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Reify Your GitHub Commit History With Contrib Cal

September 12, 2025 by John Elliot V 3 Comments

Over on Instructables, [Logan Fouts] shows us the Contrib Cal GitHub desk gadget. This build will allow you to sport your recent GitHub commit activity on your wall or desk with an attractive diffuse light display backed by a 7×4 matrix of multicolor LEDs. Motivate yourself and impress your peers!

This humble project is at the same time multifaceted. You will build a case with 3D printing, make a diffuse screen by gluing and cutting, design a LED matrix PCB using KiCad, solder everything together, and then program it all with Python. The brains of the operation are a Raspberry Pi Zero W.

The Instructables article will run you through the required supplies, help you to print the case, explain how to solder the LEDs, tell how to install the heat-set inserts for high quality screw attachments, explain wiring and power, tell you about how to use the various screws, then tell you about where to get more info and the required software on GitHub: Contrib Cal v2.

Of course this diffuse LED matrix is only one way to display your GitHub progress, you can also Track Your GitHub Activity With This E-Ink Display.

How The TI-99/4A Home Computer Worked

September 11, 2025 by John Elliot V 59 Comments

Over on YouTube [The 8-Bit Guy] shows us how the TI-99/4A home computer worked.

[The 8-Bit Guy] runs us through this odd 16-bit home computer from back in the 1980s, starting with a mention of the mysterious extra “space” key on its antiquated keyboard. The port on the side is for two joysticks which share a bus, but you can find boards for compatibility with “newer” hardware, particularly the Atari-style joysticks which are easier to find. The AV port on the back is an old 5-pin DIN such as was typical from Commodore and Atari at the time (also there is a headphone port on the front). The other DB9 port on the back of the device is the port for the cassette interface.

The main cartridge interface is on the front right of the machine, and there’s a smaller expansion socket on the right hand side. The front interface is for loading software (on cartridges) and the side interface is for peripherals. The system boots to a now famous “press any key” prompt. (We know what you’re thinking: “where’s the any key!?” Thanks Homer.)

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This Ouija Business Card Helps You Speak To Tiny Llamas

September 9, 2025 by Seth Mabbott 7 Comments

Business cards, on the whole, haven’t changed significantly over the past 600-ish years, and arguably are not as important as they used to be, but they are still worth considering as a reminder for someone to contact you. If the format of that card and method of contact stand out as unique and related to your personal or professional interests, you have a winning combination that will cement yourself in the recipient’s memory.

In a case study of “show, don’t tell”, [Binh]’s business card draws on technological and paranormal curiosity, blending affordable, short-run PCB manufacturing and an, LLM or, in this case, a Small Language Model, with a tiny Ouija board. While [Binh] is very much with us in the here and now, and a séance isn’t really an effective way to get a hold of him, the interactive Ouija card gives recipient’s a playful demonstration of his skills.

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Electronic Wizard in his lab wearing his wizards hat

How To Use The AT24C32 EEPROM For 4KB External Memory For Microcontrollers

September 8, 2025 by John Elliot V 27 Comments

Over on YouTube [Electronic Wizard] explains how to use the AT24C32 EEPROM for external memory for microcontrollers.

He begins by explaining that you don’t want to try modifying your microcontroller flash memory for storing settings, you want to use a separate EEPROM for that. Sometimes your microcontroller will have EEPROM memory attached, but you might still find yourself needing to attach more. The AT24C32 EEPROM is a 4KB non-volatile memory chip. It’s available in various 8-pin packages and two voltage levels, either 2.7 to 5.5 volts or 1.8 to 5.5 volts, and it’s programmed using the I2C protocol.

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