Schematic of a voltage divider

Making Actually Useful Schematics In KiCad

[Andrew Greenberg] has some specific ideas for how open-source hardware hackers could do a better job with their KiCad schematics.

In his work with students at Portland State University, [Andrew] finds his students both reading and creating KiCad schematics, and often these schematics leave a little to be desired.

To help improve the situation he’s compiling a checklist of things to be cognisant of when developing schematics in KiCad, particularly if those schematics are going to be read by others, as is the hope with open-source hardware projects.

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Server racks branded with Internet Archive

Internet Archive Hits One Trillion Web Pages

In case you didn’t hear — on October 22, 2025, the Internet Archive, who host the Wayback Machine at archive.org, celebrated a milestone: one trillion web pages archived, for posterity.

Founded in 1996 by Brewster Kahle the organization and its facilities grew through the late nineties; in 2001 access to their archive was greatly improved by the introduction of the Wayback Machine. From their own website on Oct 21 2009 they explained their mission and purpose:

Most societies place importance on preserving artifacts of their culture and heritage. Without such artifacts, civilization has no memory and no mechanism to learn from its successes and failures. Our culture now produces more and more artifacts in digital form. The Archive’s mission is to help preserve those artifacts and create an Internet library for researchers, historians, and scholars.

We were curious about the Internet Archive technology. Storing a copy (in fact two copies!) of the internet is no mean feat, so we did some digging to find out how it’s done. The best information available is in this article from 2016: 20,000 Hard Drives on a Mission. They keep two copies of every “item”, which are stored in Linux directories. In 2016 they had over 30 petabytes of content and were ingesting at a rate of 13 to 15 terabytes per day, web, and television being the most voluminous.

In 2016 they had around 20,000 individual disk drives, each housed in specialized computers called “datanodes”. The datanodes have 36 data drives plus two operating system drives per machine. Datanodes are organized into racks of 10 machines, having 360 data drives per rack. These racks are interconnected via high-speed Ethernet to form a storage cluster.

Even though content storage tripled over 2012 to 2016, the count of disk drives stayed about the same; this is because of disk drive technology improvements. Datanodes that were once populated with 36 individual 2 terabyte drives are today filled with 8 terabyte drives, moving single node capacity from 72 terabytes (64.8 T formatted) to 288 terabytes (259.2 T formatted) in the same physical space. The evolution of disk density did not happen in a single step, so there are populations of 2, 3, 4, and 8 T drives in the storage clusters.

We will leave you with the visual styling of Hackaday Beta in 2004, and what an early google.com or amazon.com looked like back in the day. Super big shout out to the Internet Archive, thanks for providing such an invaluable service to our community, and congratulations on this excellent achievement.

Photo of [DENKI OTAKU] with his test circuit and oscilloscope

Exploring The Performance Gains Of Four-Pin MOSFETs

Over on YouTube [DENKI OTAKU] runs us through how a 4-pin MOSFET works and what the extra Kelvin source pin does.

A typical MOSFET might come in a 3-pin TO-247 package, but there are 4-pin variants which include an extra pin for the Kelvin source, also known as source sense. These 4-pin packages are known as TO-247-4. The fourth pin provides an additional source for gate current return which can in turn lessen the effect of parasitic inductance on the gate-source when switching current, particularly at high speed.

In the video [DENKI OTAKU] uses his custom made testing board to investigate the performance characteristics of some 4-pin TO-247-4 MOSFETs versus their 3-pin TO-247 equivalents. Spoiler alert: the TO-247-4 MOSFETs have better performance characteristics. The video takes a close look at the results on the oscilloscope. The downside is that as the switching speed increases the ringing in the Vds waveform increases, too. If you’re switching to a 4-pin MOSFET from a 3-pin MOSFET in your design you will need to be aware of this Vds overshoot and make accommodations for it.

If you’d like to go deeper with MOSFET technology check out Introduction To MOSFET Switching Losses and MOSFETs — The Hidden Gate.

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[Usagi Electric] and his home brew computer

TMS9900-based Home Brew Computer

[Usagi Electric] is known for minicomputers, but in a recent video, he shows off his TMS9900-based homebrew computer. The TMS9900 CPU was an early 16-bit CPU famously used in the old TI-99/4A computer, but as the video points out, it wasn’t put to particularly good use in the TI-99/4A because its RAM was hidden behind an inefficient interface and it didn’t leverage its 16-bit address space.

The plan is for this computer to have 2K words of ROM, 6K words of RAM, and three serial lines: one for the console terminal, another for a second user console terminal, and the third for access to a tape drive.

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A photo of a brushed motor and brushless motor with a brushless controller board

An Introduction To DC Motor Technology

[Thinking Techie] takes us back to basics in a recent video explaining how magnets, coils, brushed DC motors, and brushless DC motors work. If this is on your “to learn” list, or you just want a refresher, you can watch the video below. It’ll be ten minutes well-spent.

The video covers the whole technology stack behind the humble DC motor in its various incarnations. Starting with basic magnetic effects, it then proceeds through 2-wire brushed DC motors and finally into 3-wire brushless DC motors (BLDC motors).

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A photo of the LEGO sorter

Making A Machine To Sort One Million Pounds Of LEGO

You know what’s not fun? Sorting LEGO. You know what is fun? Making a machine to sort LEGO! That’s what [LegoSpencer] did, and you can watch the machine do its thing in the video below.

[Spencer] runs us through the process: first, quit your day job so you can get a job playing with LEGO; then research what previous work has been done in this area (plenty, it turns out); and then commit to making your own version both reproducible and extensible.

A sorting machine needs three main features: a feeder to dispense one piece at a time, a classifier to decide the type of piece, and a distributor to route the piece to a bin. Of course, the devil is in the details.

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A photo of some drives with their controller boards

Installing An 84MB Hard Drive Into A PDP-11/44

Over on YouTube [Usagi Electric] shows us how he installed an 84MB hard drive into his PDP-11/44.

In the beginning he purchased a bunch of RA70 and RA72 drives and board sets but none of them worked. As there are no schematics it’s very difficult to figure out how they’re broken and how to troubleshoot them.

Fortunately his friend sent him an “unhealthy” Memorex 214 84MB hard drive, also known as a Fujitsu 2312. The best thing about this hard drive is that it comes complete with a 400 page manual which includes the full theory of operation and a full set of schematics. Score!

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