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Hackaday Links: July 27, 2025

Sad breaking news late this Sunday afternoon of the passing of nerd icon Tom Lehrer at 97. Coming up through the culture, knowing at least a few of Tom’s ditties, preferably “The Elements” or “Poisoning Pigeons in the Park,” was as essential to proving one’s bona fides as committing most Monty Python bits to memory. Tom had a way with words that belied his background as a mathematician, spicing his sarcastic lyrics with unusual rhymes and topical references that captured the turbulence of the late 50s and early 60s, which is when he wrote most of his well-known stuff. First Ozzy, then Chuck Mangione, now Tom Lehrer — it’s been a rough week for musicians.

Here we go again. It looks like hams have another spectrum grab on their hands, but this time it’s the popular 70-cm band that’s in the crosshairs. Starlink wannabe AST SpaceMobile, which seeks to build a constellation of 248 ridiculously large communication satellites to offer direct-to-device service across the globe, seeks a substantial chunk of the 70-cm band, from 430 to 440 MHz, to control the satellites. This is smack in the middle of the 70-cm amateur radio band allocation here in the US, but covers the entire band for unlucky hams in Europe and the UK. The band is frequently used for repeaters, which newbie hams can easily access using a cheap hand-held radio to start learning the ropes.

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Create Custom Gridfinity Boxes Using Images Of Tools

Exhibit A: A standard-issue banana.

We love it when a community grabs hold of an idea and runs wild with it despite obvious practicality issues. Gridfinity by YouTuber [Zach Freedman] is one of those concepts. For the unaware, this is a simple storage system standard, defining boxes to hold your things. These boxes can be stacked and held in place in anything from a desk drawer to hanging off the side of a 3D printer. [Georgs Lazdāns] is one such Gridfinity user who wanted to create tool-specific holders without leaving the sofa. To do so, they made a web application using node.js and OpenCV to extract outlines for tools (or anything else) when photographed on a blank sheet of paper.

The OpenCV stack assumes that the object to be profiled will be placed on a uniformly colored paper with all parts of its outline visible. The first part of the stack uses a bilateral filter to denoise the image whilst keeping edge details.

Make a base, then add a banana. Easy!

Next, the image is converted to greyscale, blurred, and run through an adaptive threshold. This converts the image to monochrome, again preserving edge details. Finally, the Canny algorithm pulls out the paper contour. The object outline can be given an accurate scale with the paper contour and paper size specified. The second part of the process works similarly to extract the object outline. The second contour should follow the object pretty accurately. If it doesn’t, it can be manually tweaked in the editor. Once a contour is captured, it can be used to modify a blank Gridfinity base in the model editor.

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