Author: John Elliot V

133 Articles

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

An Introduction To DC Motor Technology

November 16, 2025 by No comments

[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

November 16, 2025 by 19 Comments

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

November 12, 2025 by 8 Comments

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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[Gerry] holding up a DIP IC

Emulating A 74LS48 BCD-to-7-Segment Decoder/Driver With An Altera MAX 7000 “S” Series Complex Programmable Logic Device

November 11, 2025 by 24 Comments

Over on the [Behind The Code with Gerry] YouTube channel our hacker [Gerry] shows us how to emulate a 74LS48 BCD-to-7-segment decoder/driver using an Altera CPLD Logic Chip From 1998.

This is very much a das blinkenlights kind of project. The goal is to get a 7-segment display to count from 0 to 9, and that’s it. [Gerry] has a 74LS193 Up/Down Binary Counter, a 74LS42 BCD to Decimal Decoder, and some 74LS00 NAND gates, but he “doesn’t have” an 74LS48 to drive the 7-segment display so he emulates one with an old Altera CPLD model EPM7064SLC44 which dates back to the late nineties. A CPLD is a Complex Programmable Logic Device which is a kind of precursor to FPGA technology.

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Photo of breadboards and bench oscilloscope

Programming The 6581 Sound Interface Device (SID) With The 6502

November 10, 2025 by 6 Comments

Over on YouTube, [Ben Eater] pursues that classic 8-bit sound. In this video, [Ben] integrates the MOS Technology 6581 Sound Interface Device (SID) with his homegrown 6502. The 6581 SID was famously used in the Commodore line of computers, perhaps most notably in the Commodore 64.

The 6581 SID supports three independent voices, each consisting of a tone oscillator/waveform generator, an envelope generator, and an amplitude modulator. These voices are combined into an output filter along with a volume control. [Ben] goes into detail concerning how to configure each of these voices using the available facilities on the available pins, referencing the datasheet for the details.

[Ben]’s video finishes with an 8-bit hit from all the way back in October 1985: Monty on the Run by Rob Hubbard. We first heard about [Ben’s] musical explorations back in June. If you missed it, be sure to check it out. It seems hard to imagine that demand for these chips has been strong for decades and shows little sign of subsiding.

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A photo of [nanofix]'s bench including his FNIRSI soldering station.

Investigating Soldering Iron Phantom Voltage

November 10, 2025 by 16 Comments

Just because you are paranoid doesn’t mean people aren’t out to get you. Do you think your soldering iron is after you? Well, [nanofix] asks (and answers): Is My Soldering Iron Dangerous?

He has a look at his cheap FNIRSI soldering station and measures a “phantom voltage” of nearly 50 volts AC across the tip of his iron and earth ground. He explains that this phantom voltage is a very weak power source able to provide only negligible measures of current; indeed, he measures the short circuit current as 0.041 milliamps, or 41 microamps, which is negligible and certainly not damaging to people or components.

He pops open his soldering iron power supply (being careful to discharge the high voltage capacitor) and has a look at the switched mode power supply, with a close look at the optocoupler and Y-class capacitor, which bridge the high voltage and low voltage sides of the circuit board. The Y-class capacitor is a special type of safety capacitor designed to fail open rather than fail short. The Y-class capacitor is there to remove high-frequency noise. Indeed, it is this capacitor that is the cause of the phantom voltage on the iron tip.

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The two types of LED candle, side by side.

2025 Component Abuse Challenge: Heat Activated LED Candles

November 8, 2025 by 6 Comments

[Miroslav Hancar] wasn’t satisfied with abusing just a single component for our Component Abuse Challenge. He decided to abuse a whole assembly, in particular, some LED candles.

In this project, LEDs are abused as temperature sensors. When the temperature gets hot enough for long enough, the microcontroller will turn on its LEDs. How? A diode’s forward voltage is temperature-related. By monitoring the forward voltage, the microcontroller can infer the temperature and respond appropriately.

This particular project is really two projects in one, centered around a common theme, heat activation. The first version has four LEDs and, in response to heat, four LEDs flicker to simulate a real candle. The second version is also heat-activated, but it has only one LED. You can snuff out this LED by pinching the top of it with your fingers. You can see a demo of each version in the videos below.

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