https://blog.hirnschall.net/ Deep technical articles on FEM simulation, PCB design, signal integrity, (embedded) C++, software engineering, mechanical engineering, FSAE, and applied mathematics by Sebastian Hirnschall. en Tue, 19 May 2026 12:15:13 +0000 https://blog.hirnschall.net/4x-sata-backplane/ https://blog.hirnschall.net/4x-sata-backplane/ Design, simulate, and build your own 4-drive SATA backplane PCB. Differential pairs, S-parameters, 3D FEM analysis, and full GitHub files for JLCPCB Sun, 29 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/perfect-looping-gif/ https://blog.hirnschall.net/perfect-looping-gif/ Random noise doesn't loop cleanly. By sampling higher-dimensional Perlin noise on a closed path, we generate perfectly looping procedural animations. Wed, 03 Mar 2021 00:00:00 +0000 https://blog.hirnschall.net/esp8266/ https://blog.hirnschall.net/esp8266/ Complete ESP8266 reference: module variants, wiring, code examples, deep sleep battery life, web server, EEPROM, and PCB layout — all in one place. Sat, 07 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/esp32-preferences/ https://blog.hirnschall.net/esp32-preferences/ Persist data on the ESP32 across reboots with the Preferences library. Key-value storage in NVS, read-only namespace, with full code example. Sun, 26 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/maze-generation-js/ https://blog.hirnschall.net/maze-generation-js/ Build a maze generator in JavaScript using the random walker algorithm. Annotated source code you can drop into a p5.js sketch or any canvas project. Sun, 30 May 2021 00:00:00 +0000 https://blog.hirnschall.net/gerber-to-step/ https://blog.hirnschall.net/gerber-to-step/ PCB STEP exports omit copper traces - unusable for EM simulation. Convert Gerber files to a simulation-ready STEP with full copper geometry (free tool). Sat, 21 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/calculating-eigenfrequencies-using-fem/ https://blog.hirnschall.net/calculating-eigenfrequencies-using-fem/ Calculate eigenfrequencies and modes using FEM and Rayleigh quotient minimization, with LOBPCG implementation in NGSolve applied to a tuning fork. Sat, 15 May 2021 00:00:00 +0000 https://blog.hirnschall.net/diy-useless-box/ https://blog.hirnschall.net/diy-useless-box/ A useless box with several switches and one stubborn arm — full Arduino code, custom PCB, and STL files. The build that takes the joke a step further. Fri, 07 Jan 2022 00:00:00 +0000 https://blog.hirnschall.net/esp8266-pcb-design/ https://blog.hirnschall.net/esp8266-pcb-design/ ESP8266 PCB rules from Espressif's guidelines — 15mm antenna keep-out, decoupling, and copper pour rules to keep WiFi working on your board. Mon, 09 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/esp8266-arduino-ide/ https://blog.hirnschall.net/esp8266-arduino-ide/ Program any ESP8266 using a spare Arduino as USB-to-serial bridge. Wiring, Arduino IDE setup, and the GPIO0-to-GND trick for firmware upload mode. Mon, 09 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/esp8266-5v-devices/ https://blog.hirnschall.net/esp8266-5v-devices/ ESP8266 GPIO is 3.3V — connect 5V sensors and Arduinos safely using voltage dividers. Includes circuit diagrams and resistor value calculations. Mon, 09 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/can-transport-layer/ https://blog.hirnschall.net/can-transport-layer/ Eliminate manual bit packing errors in CAN with compile-time validation and code generation. Full C++ implementation with filter and routing safety built in. Sun, 01 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/esp8266-vs-esp32/ https://blog.hirnschall.net/esp8266-vs-esp32/ Side-by-side ESP32 vs ESP8266 — specs, GPIO, ADC, deep sleep, price. Which chip wins in 2026, and the cases where the ESP8266 still beats it. Fri, 10 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/diy-smart-window-blinds/ https://blog.hirnschall.net/diy-smart-window-blinds/ Automate window blinds with an ESP8266 for under $10. Includes full schematic, Arduino code, and Homebridge setup for Alexa and Apple HomeKit integration. Fri, 14 Aug 2020 00:00:00 +0000 https://blog.hirnschall.net/gears-for-3d-printing/ https://blog.hirnschall.net/gears-for-3d-printing/ Design circular and non-circular gears for FDM using a circular tooth profile — simpler than involute, uniform teeth on any gear outline. Includes PDF. Sun, 30 May 2021 00:00:00 +0000 https://blog.hirnschall.net/diy-motorized-slider/ https://blog.hirnschall.net/diy-motorized-slider/ Build a WiFi-controlled motorized DSLR camera slider for under $100. Combines 3D-printed parts with metal rails — full BOM, wiring, and control code. Tue, 02 Aug 2022 00:00:00 +0000 https://blog.hirnschall.net/fem/ https://blog.hirnschall.net/fem/ From computing eigenfrequencies of a tuning fork to full-wave EM simulation of a PCB — practical finite element analysis, applied to real engineering problems. Wed, 05 Apr 2023 00:00:00 +0000 https://blog.hirnschall.net/automatic-chop-sticks/ https://blog.hirnschall.net/automatic-chop-sticks/ Build motorized chopsticks with Arduino and a single servo. A beginner electronics project with parts list, wiring diagram, and assembly steps. Under $10. Sat, 16 Nov 2024 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/ https://blog.hirnschall.net/cnc-mill-concept/ Design documentation for a fixed CNC milling machine targeting ≤ 10 µm accuracy in an apartment: structure, damping, sensing, electronics, and CAN software. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/software-architecture-can/ https://blog.hirnschall.net/cnc-mill-concept/software-architecture-can/ Firmware for distributed sensor nodes on STM32G4: YAML-driven CAN map code generation, type-safe CanManager transport, deterministic serialization, and DBC export. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/compliance-state-estimation-supervision/ https://blog.hirnschall.net/cnc-mill-concept/compliance-state-estimation-supervision/ Quasi-static compliance estimation from tilt, strain, and motor current; ECU state classification; and Schmitt-trigger feed-override supervision over RS-485. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/electronics-motion-and-electrical/ https://blog.hirnschall.net/cnc-mill-concept/electronics-motion-and-electrical/ ECU and distributed sensor PCBs on STM32G4 with CAN-FD, Duet 3 6HC open-loop stepper motion with HTD belts, and a DIN/EN 60204-1 electrical installation. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/deferred-and-future-work/ https://blog.hirnschall.net/cnc-mill-concept/deferred-and-future-work/ Out of scope for the current CNC mill build: closed-loop servos, glass scales, custom drives, 4th and 5th axis, thermal compensation, and manufacturing docs. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/mechanical-structure-and-passive-damping/ https://blog.hirnschall.net/cnc-mill-concept/mechanical-structure-and-passive-damping/ Welded steel box-section frame, gantry geometry, force loop from tool to frame, and four passive damping strategies on the spindle tower and X-carriage beams. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/enclosure-and-acoustics/ https://blog.hirnschall.net/cnc-mill-concept/enclosure-and-acoustics/ Apartment-compatible acoustic enclosure for the CNC mill: MDF outer panels, automotive foam, and a damped sheet metal liner forming a mass-spring-mass sandwich. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/vibration-sensing-and-metrology/ https://blog.hirnschall.net/cnc-mill-concept/vibration-sensing-and-metrology/ Vibration and sensing for the CNC mill: piezo microphones, MEMS accelerometers, strain gauge bridges over CAN-FD, and a flexure-mounted sub-100 nm laser tool probe. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/cnc-mill-concept/piezo-shunt-damping/ https://blog.hirnschall.net/cnc-mill-concept/piezo-shunt-damping/ Electromechanical damping for the CNC mill spindle tower using PZT elements bonded at modal antinodes, R-L shunt networks, and adaptive resistance tuning. Wed, 25 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/esp32-webserver/ https://blog.hirnschall.net/esp32-webserver/ ESP32 web server with WebServer.h — serve HTML, expose sensor data as JSON, read GET parameters, and access via mDNS. Full example included. Sat, 11 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/esp32/ https://blog.hirnschall.net/esp32/ Everything you need to add WiFi to Arduino: module comparison, wiring, code examples, power saving, web server, preferences, and ethernet — one reference hub. Sat, 11 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/esp8266-webserver/ https://blog.hirnschall.net/esp8266-webserver/ ESP8266 web server using ESP8266WebServer.h — connect to WiFi, respond to requests, and read GET parameters. Working Arduino code in 20 lines. Mon, 09 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/esp8266-on-battery/ https://blog.hirnschall.net/esp8266-on-battery/ ESP8266 draws ~80 mA active and as little as 20 µA in deep sleep. Full breakdown by mode, GPIO16 wake wiring, and formulas to estimate real battery runtime. Mon, 09 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/auxetic-material/ https://blog.hirnschall.net/auxetic-material/ Auxetic materials expand when stretched. We design a re-entrant structure, simulate it with FEM, and 3D print it in TPU. Sat, 21 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/diy-video-light-stand/ https://blog.hirnschall.net/diy-video-light-stand/ Print a stable, height-adjustable video light stand for standard LED panels — total cost under $4. Print files and assembly instructions included. Sat, 22 Jan 2022 00:00:00 +0000 https://blog.hirnschall.net/rubber-band-gun/ https://blog.hirnschall.net/rubber-band-gun/ DIY 3D printed rubber band pistol with a 6-shot rotating drum mechanism. Covers the design, print settings, and assembly. Free STL download included. Sun, 12 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/esp8266-eeprom/ https://blog.hirnschall.net/esp8266-eeprom/ Store data across reboots on ESP8266 using EEPROM emulation. Arduino EEPROM library usage including the commit call that catches most people out. Mon, 09 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/tools/capacitors-in-parallel/ https://blog.hirnschall.net/tools/capacitors-in-parallel/ Calculate the total capacitance of capacitors in parallel. Add as many capacitors as needed. Includes formula explanation and practical use cases. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/tools/battery-runtime/ https://blog.hirnschall.net/tools/battery-runtime/ Calculate battery runtime from capacity and current draw. Supports power-based loads, converter efficiency, and depth of discharge. Solves for runtime, capacity, or current. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/capacitor-discharge/ https://blog.hirnschall.net/tools/capacitor-discharge/ Calculate capacitor discharge time, voltage, current, and charge over time. Supports RC exponential discharge and constant current discharge. Solve for time or voltage. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/tools/maxwell-bridge/ https://blog.hirnschall.net/tools/maxwell-bridge/ Calculate unknown inductance and series resistance from a balanced Maxwell-Wien bridge. Enter R2, R3, R4, C4 at null; L_x, R_x, and Q are computed. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/voltage-divider/ https://blog.hirnschall.net/tools/voltage-divider/ Calculate voltage divider output. Solve for V_out, V_in, R1, or R2 given any three. Divider ratio, current, power, and optional load effect included. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/capacitor-impedance/ https://blog.hirnschall.net/tools/capacitor-impedance/ Calculate capacitive reactance, impedance magnitude, and phase angle. Solve for X_C, capacitance, or frequency given the other two. Optional series resistance. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/tools/inductors-in-parallel/ https://blog.hirnschall.net/tools/inductors-in-parallel/ Calculate the equivalent inductance of inductors in parallel. Enter any number of values; result is always less than the smallest individual inductor. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/inductors-in-series/ https://blog.hirnschall.net/tools/inductors-in-series/ Calculate the equivalent inductance of inductors in series. Values add directly; total L is always greater than any individual inductor. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/capacitor-stored-energy/ https://blog.hirnschall.net/tools/capacitor-stored-energy/ Calculate the energy stored in a capacitor. Solve for energy, capacitance, or voltage given the other two. Stored charge shown as additional output. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/tools/rc-time-constant/ https://blog.hirnschall.net/tools/rc-time-constant/ Calculate the RC time constant. Solve for τ, resistance, or capacitance given the other two. Optionally calculate charging or discharging voltage at any time t. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/tools/rl-time-constant/ https://blog.hirnschall.net/tools/rl-time-constant/ Calculate the RL time constant τ = L/R. Solve for time constant, inductance, or resistance. Optionally compute energizing or de-energizing current at a given time. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/wheatstone-bridge/ https://blog.hirnschall.net/tools/wheatstone-bridge/ Calculate the Wheatstone bridge balance condition or output voltage. Solve for any unknown resistor or compute V_out for an unbalanced bridge. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/tools/capacitors-in-series/ https://blog.hirnschall.net/tools/capacitors-in-series/ Calculate the total capacitance of capacitors in series. Add as many capacitors as needed. Includes formula explanation and special cases. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/tools/inductor-impedance/ https://blog.hirnschall.net/tools/inductor-impedance/ Calculate inductive reactance, impedance magnitude, and phase angle. Solve for X_L, inductance, or frequency given the other two. Optional series resistance. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/parallel-plate-capacitor/ https://blog.hirnschall.net/tools/parallel-plate-capacitor/ Solve for capacitance, plate area, separation, or permittivity given the other three. Online calculator with formula explanation for each variable. Sat, 23 Nov 2024 00:00:00 +0000 https://blog.hirnschall.net/tools/inductor-stored-energy/ https://blog.hirnschall.net/tools/inductor-stored-energy/ Calculate the energy stored in an inductor. Solve for energy, inductance, or current given the other two. Flux linkage shown as additional output. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/schering-bridge/ https://blog.hirnschall.net/tools/schering-bridge/ Calculate unknown capacitance and ESR from a balanced Schering bridge. Enter C2, R3, R4, C4 at null; C_x, R_x, dissipation factor, and loss angle are computed. Mon, 11 May 2026 00:00:00 +0000 https://blog.hirnschall.net/tools/lc-resonance-frequency/ https://blog.hirnschall.net/tools/lc-resonance-frequency/ Calculate the resonant frequency of an LC circuit. Solve for frequency, inductance, or capacitance given the other two. Angular frequency shown as additional output. Tue, 01 Apr 2025 00:00:00 +0000 https://blog.hirnschall.net/esp32-iot-wifi-provisioning/ https://blog.hirnschall.net/esp32-iot-wifi-provisioning/ To avoid hardcoding credentials, the ESP starts in AP mode and hosts a site where we can enter the WiFi credentials. Once done, it connects to the WiFi. Mon, 27 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/force-moment-equilibrium/ https://blog.hirnschall.net/force-moment-equilibrium/ Symbolic calculator for 2D static equilibrium problems (FSAE-friendly). Enter points with coordinates and known forces, get all unknown reactions solved in the browser. Thu, 14 May 2026 00:00:00 +0000 https://blog.hirnschall.net/same-domain-analytics/ https://blog.hirnschall.net/same-domain-analytics/ Hosting on GitHub Pages with Cloudflare Worker + D1 for same-domain analytics, llms.txt and per-page markdown for LLMs. No cookies, no third parties. Wed, 22 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/flow-simulation-js/ https://blog.hirnschall.net/flow-simulation-js/ Simulate particle flow fields in JavaScript using Perlin noise to drive particle direction. Annotated p5.js source to build visualizations like this one. Fri, 24 Jul 2020 00:00:00 +0000 https://blog.hirnschall.net/esp32-http-request-influxdb/ https://blog.hirnschall.net/esp32-http-request-influxdb/ Make HTTP GET and POST requests from an ESP32 with HTTPClient.h. Response codes, connection reuse, and logging sensor data to InfluxDB. Tue, 14 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/everything-aero-concept/ https://blog.hirnschall.net/everything-aero-concept/ Define equation templates, provide knowns, let the solver derive the unknowns. Vehicle dynamics and aero built-in, applicable to any physics system. Sat, 07 Mar 2026 00:00:00 +0000 https://blog.hirnschall.net/perlin-noise/ https://blog.hirnschall.net/perlin-noise/ How Perlin noise generates smooth randomness — gradient noise vs value noise, computational cost, and practical use in terrain generation and animation. Thu, 27 Aug 2020 00:00:00 +0000 https://blog.hirnschall.net/programming-an-advanced-cpp-calculator/ https://blog.hirnschall.net/programming-an-advanced-cpp-calculator/ Build a C++ calculator that parses variables, parentheses, unary operators, and mathematical constants — full recursive descent parser with source code. Wed, 04 Sep 2024 00:00:00 +0000 https://blog.hirnschall.net/esp8266-reference/ https://blog.hirnschall.net/esp8266-reference/ ESP8266 pinout for ESP-01, ESP-01S, ESP-07, and ESP-12E/F. Boot mode pins (GPIO0, GPIO2, GPIO15), reset circuit, and minimal wiring for each. Mon, 09 Jan 2023 00:00:00 +0000 https://blog.hirnschall.net/esp32-ota-update/ https://blog.hirnschall.net/esp32-ota-update/ Flash new firmware over WiFi from the Arduino IDE using ArduinoOTA.h library. This setup allows us to easily update deployed or hard to reach ESPs. Mon, 27 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/gas-cycle-calculator/ https://blog.hirnschall.net/gas-cycle-calculator/ Symbolic calculator for ideal gas cycle problems (FSAE-friendly). Enter state-change types and knowns, get solved P-V and T-V diagrams in the browser. Wed, 13 May 2026 00:00:00 +0000 https://blog.hirnschall.net/silent-home-server/ https://blog.hirnschall.net/silent-home-server/ A silent home server case from aluminium sheets and extrusions — 8 hot-swap drives, automotive sound damping, rubber-isolated mounts, forced airflow. Wed, 15 Apr 2026 00:00:00 +0000 https://blog.hirnschall.net/everything-aero/ https://blog.hirnschall.net/everything-aero/ Open-source symbolic physics calculator for aero and vehicle dynamics (FSAE). Enter knowns and assumptions, let the solver do the rest! Wed, 13 May 2026 00:00:00 +0000 https://blog.hirnschall.net/esp32-w5500-ethernet/ https://blog.hirnschall.net/esp32-w5500-ethernet/ Add wired Ethernet to an ESP32 with a W5500 module — using ETH.h (not Ethernet.h, which silently breaks on ESP32), DHCP, and mDNS. Sat, 11 Apr 2026 00:00:00 +0000