Technical articles
Technical notes, repairs, solutions and practical experiences from electronics, embedded systems, servers and other engineering projects.
Toyota RAV4 Front USB Error When Connecting a Phone
6 August 2025
A practical workaround for repeated "USB Error" or "USB device not recognized" messages when connecting certain phones to a Toyota RAV4.
Off-grid Solar Inverter as UPS
19 October 2023
Using off-grid and hybrid solar inverters as high-power UPS systems, including serial monitoring, transfer measurements and battery discharge tests.
Retrofitting a Laser to an LPKF PCB Milling Machine
23 September 2022
Converting an old LPKF ProMat PCB milling machine to a diode-laser engraver for making solder-paste stencils, engraving wood and other prototype work.
Installing Pi-hole as a Linux-VServer Guest on Debian 10
14 October 2022
Running Pi-hole DNS and DHCP services inside a Debian Buster Linux-VServer guest, including network capabilities, systemd-related installation issues and configuration notes.
Installing Linux-VServer on Debian Buster
8 February 2020
Installing a Linux-VServer-enabled kernel on Debian Buster, fixing util-vserver compatibility problems and creating and running Debian guest systems.
Linux-VServer Errors and Solutions
8 February 2020
Troubleshooting Linux-VServer problems including lost connectivity, XFS inode issues with 32-bit guests, Subversion errors and the particularly nasty case where starting a guest unmounts /proc on the host.
Saving Electricity by Planning AC in a Server Room
16 September 2022
Using cold outside air, temperature sensors and a controlled exhaust fan to reduce the energy required for cooling a small server room.
Read articleMCU Coding
23 February 2022
Practical microcontroller programming notes covering integer types and optimization, I²C EEPROM page writes, bit-banged UART debugging and two's-complement sensor data.
Read articleMigrating from Certbot to acme.sh on an Old Zimbra Server
8 February 2020
A historical solution for renewing Let's Encrypt certificates on a legacy CentOS 6 Zimbra server after certbot-auto stopped supporting the operating system.
Read articleBiltema Power Drill Charger 17-277 Repair
8 February 2020
A short repair note for a dead Biltema 17-277 battery charger, including the fuse, mains rectifier and ZD2 gate-protection Zener.
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