Build It
Do-it-yourself science and technology projects: physics experiments, electronics, home lab, software and sensors.
Measure Gravity With a Phone and a Pendulum
A walkthrough for finding g with phyphox and a string: the formula, a T-squared graph, how to cut swing-angle and length errors,…
systemd Timers vs Cron: Schedule Jobs With a .timer and .service Pair
Compare cron with systemd timers, then copy a working .service and .timer pair. Covers OnCalendar syntax, Persistent=, RandomizedDelaySec, systemctl list-timers and journalctl…
Wireshark First Capture: Filters, DNS Lookups and TCP Streams
A question-and-answer guide to a first Wireshark capture: what you may legally capture, capture versus display filters, spotting a DNS lookup and…
How to Test a Fuse, Diode and Capacitor With a Multimeter
Plain answers on testing a fuse (continuity), a diode (diode-test mode) and a capacitor (capacitance mode), including why capacitance alone cannot catch…
PM2.5 Air-Quality Monitor With a PMS5003 and an ESP32
How a laser-scattering PM2.5 sensor counts particles, what the PMS5003 datasheet promises, how to parse its 32-byte frame on an ESP32, and…
Build a Spectroscope and Identify Common Light Sources
Two ways to build a diffraction-grating spectroscope, how to calibrate it with a fluorescent lamp, and a table for reading LED, CFL,…
How to Use git bisect to Find the Commit That Broke Your Build
A worked git bisect example: mark good and bad commits, automate the search with git bisect run, understand the exit codes, and…
How to Set Up WireGuard to Reach Your Home Network
Keys, two config files, one forwarded UDP port and a routing setting get a laptop onto a home network. A tutorial, plus…
How to Solder Through-Hole Parts Without Cold Joints
Wetting, flux and temperature explained, with a do and don't list, a look at good versus cold joints, and a troubleshooting table,…
Measure the Speed of Light With a Microwave and Chocolate
Find the speed of light from melted chocolate spots and the frequency on your oven's label, with a worked calculation, safety notes…