https://derek.engineer/ Recent content on derek.engineer https://derek.engineer/og-default.png https://derek.engineer/og-default.png Hugo en-us Sun, 11 Oct 2026 00:00:00 +0000 https://derek.engineer/posts/vornado-fan-on-home-assistant/ Sun, 11 Oct 2026 00:00:00 +0000 https://derek.engineer/posts/vornado-fan-on-home-assistant/ A Flipper Zero, an ESP32-S3 and a CC1101 put a fan with a perfectly good remote on Home Assistant: a transmit path with no data line, a logging bug that dropped MQTT every few minutes, and one receiver for the remote and the neighbors' weather sensors. https://derek.engineer/posts/what-limits-local-ai-speed/ Fri, 09 Oct 2026 00:00:00 +0000 https://derek.engineer/posts/what-limits-local-ai-speed/ Two weeks of measurements on an Arduino UNO Q, a Raspberry Pi 5 and a Mac mini M4, backed by real data: what limits how fast a small language model runs, where the usual rules hold and where they break, and what a token costs in energy. https://derek.engineer/posts/trmnl-x-part-2/ Tue, 06 Oct 2026 17:30:00 -0700 https://derek.engineer/posts/trmnl-x-part-2/ A first pass at a daily dashboard on my TRMNL X, running off my own server. What's on it and what keeps it fed. https://derek.engineer/posts/game-night-ogle-on-the-tv/ Sun, 04 Oct 2026 20:30:00 -0700 https://derek.engineer/posts/game-night-ogle-on-the-tv/ The board on the TV, everyone tracing words on their own phone, and a relay on the Mac mini keeping score, the way Netflix runs its party games. Built while I was out, then given music made in code and three more modes. https://derek.engineer/posts/samsung-tv-hdhomerun-app/ Sun, 04 Oct 2026 00:00:00 +0000 https://derek.engineer/posts/samsung-tv-hdhomerun-app/ There's no HDHomeRun app for Samsung TVs, so I built one with Claude Code. First picture at halftime, working app by the end of the game, with the setup steps and snippets to do it yourself. https://derek.engineer/posts/ogle-daily-word-game/ Wed, 30 Sep 2026 00:00:00 +0000 https://derek.engineer/posts/ogle-daily-word-game/ We got hooked on Netflix's Boggle in Tahoe, so I had Claude Code build our own: one board a day, our dictionary, our rules, and no server. First commit to live in under three days. https://derek.engineer/posts/aperture-mystery-carrier-dc-spike/ Mon, 28 Sep 2026 00:00:00 +0000 https://derek.engineer/posts/aperture-mystery-carrier-dc-spike/ A 916.381 MHz 'carrier' that looked like LoRa turned out to be the RTL-SDR's own DC spike; plus the bursts that are really there, a 2-hour hopping decode of 902-928 MHz, and what PG&E publishes about its meters. https://derek.engineer/posts/aperture-whats-on-the-air/ Sat, 26 Sep 2026 00:00:00 +0000 https://derek.engineer/posts/aperture-whats-on-the-air/ A full-spectrum sweep, a test of whether strong FM stations overload the receiver, and an AM station I chased through four attempts that turned out to be an empty channel. https://derek.engineer/posts/ota-antenna-rain-gauge/ Thu, 17 Sep 2026 00:00:00 +0000 https://derek.engineer/posts/ota-antenna-rain-gauge/ I logged an HDHomeRun's signal for two months to detect rain. It rained five times, my logger said it never did, and the signal didn't care. https://derek.engineer/posts/aperture-ships-and-aircraft/ Wed, 09 Sep 2026 00:00:00 +0000 https://derek.engineer/posts/aperture-ships-and-aircraft/ Three AIS runs and an ADS-B run from one RTL-SDR in San Francisco, cross-checked against vessel-tracking sites and ADSBdb, with dates and times so anyone can look for themselves. Updated with a second ADS-B run in late September. https://derek.engineer/posts/aperture-433mhz-weather-sensors/ Sat, 22 Aug 2026 00:00:00 +0000 https://derek.engineer/posts/aperture-433mhz-weather-sensors/ Starting with a $25 RTL-SDR: fixing an antenna-length calculation, sweeping the tuner gain, walking the 433 MHz band for eight hours, and finding that a weather sensor's transmit clock drifts with its own temperature reading. https://derek.engineer/posts/vornado-eos-9-rf-remote-reverse-engineering/ Tue, 04 Aug 2026 00:00:00 +0000 https://derek.engineer/posts/vornado-eos-9-rf-remote-reverse-engineering/ My Vornado EOS 9's remote has no documented protocol, so I reverse engineered it with a Flipper Zero: OOK, 1:3 PWM, a 20-bit address, no encryption. https://derek.engineer/posts/sf-apartment-thermal-lag/ Wed, 29 Jul 2026 00:00:00 +0000 https://derek.engineer/posts/sf-apartment-thermal-lag/ I bought an IKEA temp sensor for $8 while ordering batteries, stuck it in my living room, and ended up with a pretty clear picture of how SF apartments handle heat. https://derek.engineer/posts/hdhomerun-antenna-remote/ Sun, 19 Jul 2026 00:00:00 +0000 https://derek.engineer/posts/hdhomerun-antenna-remote/ Moved my antenna to a closet, wired up an HDHomeRun, and now I can stream or record live TV from anywhere over Tailscale. https://derek.engineer/posts/latex-resume-github-actions/ Fri, 10 Jul 2026 00:00:00 +0000 https://derek.engineer/posts/latex-resume-github-actions/ How I write my resume in LaTeX and let GitHub Actions compile and publish the PDF on every push. https://derek.engineer/posts/obsidian-sync-pi-tailscale/ Fri, 26 Jun 2026 00:00:00 +0000 https://derek.engineer/posts/obsidian-sync-pi-tailscale/ Setting up CouchDB + Obsidian LiveSync on a Pi 3B with Tailscale for free E2E-encrypted vault sync from anywhere. https://derek.engineer/posts/how-this-blog-was-built/ Fri, 12 Jun 2026 00:00:00 +0000 https://derek.engineer/posts/how-this-blog-was-built/ Hugo, PaperMod, Netlify, DNS, search, and the local writing workflow behind derek.engineer. https://derek.engineer/posts/reading-build-tony-fadell/ Fri, 29 May 2026 00:00:00 +0000 https://derek.engineer/posts/reading-build-tony-fadell/ Tony Fadell's Build is written for founders. The makers inside those companies get just as much from it. https://derek.engineer/posts/diy-ambilight-part-2-capture-and-led-planning/ Sun, 03 May 2026 00:00:00 +0000 https://derek.engineer/posts/diy-ambilight-part-2-capture-and-led-planning/ HDMI splitter arrived. Got a clean 1080p30 frame out of the B101, Hyperion preview working, and LED layout sketched out. 1080p60 is still broken. https://derek.engineer/posts/migrating-derekwelty-hugo-github-actions/ Sat, 02 May 2026 00:00:00 +0000 https://derek.engineer/posts/migrating-derekwelty-hugo-github-actions/ Replacing a Bootstrap 5 static site with Hugo and the Congo theme, deployed via GitHub Actions to GitHub Pages. Here are the gotchas. https://derek.engineer/posts/diy-ambilight-pi3-b101-setup/ Fri, 01 May 2026 00:00:00 +0000 https://derek.engineer/posts/diy-ambilight-pi3-b101-setup/ A working log of getting Hyperion-NG capture going on old hardware. HDMI timing detection works over a loopback, but no frame has been captured yet. Splitter arrives tomorrow, LEDs not yet wired. https://derek.engineer/posts/trmnl-x-byos-server-setup/ Thu, 23 Apr 2026 00:00:00 +0000 https://derek.engineer/posts/trmnl-x-byos-server-setup/ Setting up a FastAPI BYOS server for the TRMNL X e-ink display, with local DNS and Caddy reverse proxy, before the hardware even ships. https://derek.engineer/posts/ikea-varmblixt-home-assistant-automations/ Mon, 13 Apr 2026 00:00:00 +0000 https://derek.engineer/posts/ikea-varmblixt-home-assistant-automations/ Turning the IKEA Varmblixt donut lamp into a context-aware status light with weather reactions, cycling alerts, door alerts, and three color scripts. https://derek.engineer/posts/molty-personal-ai-assistant/ Wed, 08 Apr 2026 00:00:00 +0000 https://derek.engineer/posts/molty-personal-ai-assistant/ How Molty works: Telegram interface, file-backed memory, scheduled checks, model routing, integrations, and the parts I would rebuild. https://derek.engineer/posts/spotify-concert-discovery/ Sun, 29 Mar 2026 00:00:00 +0000 https://derek.engineer/posts/spotify-concert-discovery/ Scraping SF venue calendars, matching artists against my Spotify library, and scoring shows by taste, venue, price, and distance. https://derek.engineer/about/ Mon, 01 Jan 0001 00:00:00 +0000 https://derek.engineer/about/ About derek.engineer: Derek Welty, an electrical engineer who builds things at home with an AI coding agent and tests them on the real hardware. https://derek.engineer/how-i-work/ Mon, 01 Jan 0001 00:00:00 +0000 https://derek.engineer/how-i-work/ How the projects on derek.engineer get built: I direct an AI agent that writes most of the code, and the real hardware is the test.