Hacker News: davidhoellhttps://news.ycombinator.com/user?id=davidhoellHacker News RSShttps://hnrss.org/hnrss v2.1.1Sun, 12 Apr 2026 19:27:17 +0000<![CDATA[New comment by davidhoell in "Phyphox – Physical Experiments Using a Smartphone"]]>The coolest thing I ever did with that was finding wires in a friends wall - we needed to drill a hole and it was unclear whether the wires went up (problem) or right from the outlet. I didn't have a cable finder on hand but did have the epiphany to put a large load on the outlet (we used a kettle, a hairdryer would also work, just needs a lot of watts) and use the Fourier transform magnet spectrum to find the 50 Hz grid frequency in the wall. Worked beautifully.

Sadly, since most smartphone magnetometers seem to have a sample rate of 100/s, this will not be applicable to Americans and everyone else with a 60 Hz grid frequency, the 50 Hz were already at the Nyquist–Shannon limit.

]]>Sun, 12 Apr 2026 12:48:25 +0000https://news.ycombinator.com/item?id=47739032davidhoellhttps://news.ycombinator.com/item?id=47739032https://news.ycombinator.com/item?id=47739032