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How to Clean a PCB
Lately I’ve been assembling a lot of Retro USB boards, and that’s got me thinking about the best way to clean them after assembly. I use a “no clean” flux for my assembly work, so in theory I don’t...
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Build an Electric Scribble Machine
Looking for a creative project for kids to build? The Electric Scribble Machine is an entertaining device that’s easy to build from common parts – great for a scout troop project, school science fair,...
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Future Hardware with Animal Names
Yesterday’s post mentioned some hypothetical marsupial-themed hardware: WiFi Wallaby, Video Platypus, and others. While these were meant as a joke, they got me thinking about what exactly a “Video...
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Custom Mini Case for Macintosh LC, P475, Q605
Here’s a custom laser-cut case for the Macintosh LC family, Performa 400 series, and Quadra 605. By removing the internal floppy drive and fan, and replacing the internal SCSI drive with a SCSI2SD...
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Meltdown and Spectre Vulnerabilities Explained
This week brought some fascinating news for CPU nerds: the revelation of security vulnerabilities in the basic hardware architecture of many modern processors. The Meltdown and Spectre vulnerabilities...
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What’s on the BMOW Bookshelf
Over the decades, I’ve pared my collection of books down to just four shelves – only about 100 volumes from a lifetime of reading and studying. Because who needs physical books in an age where...
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Thoughts on Low Latency Interrupt Handling
How quickly can a modern microcontroller respond to an external interrupt? Is it possible to achieve consistent sub-microsecond response times, so that external glue logic like muxes could be replaced...
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Star Ring: Abusing the PCB Fab
Why use a PCB silkscreen when you could showcase the shiny gold metal layer? Why build a rectangular board when you could have strange and wonderful shapes? And why settle for a dull LED flasher when...
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More on Fast Interrupt Handling with Cortex M4
Can a fast microcontroller replace external glue logic, while also continuing to run application code? This is the third in a series of posts considering the question. It’s part of a potential...
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Star Ring Version 2
Version 2 of my PCB-abusing LED blinky is here! It’s the same odd shape as Star Ring version 1, with the same abuse of the metal layer to make shiny stars and planets, and the same low power usage and...
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64 x 32 LED Matrix Programming
Everybody loves a big bright panel of LEDs. Way back in 2011, my daughter and I hand-built an 8 x 8 LED matrix Halloween display. More recently I’ve been playing with a 64 x 32 RGB matrix that I...
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Raspberry Pi GPIO Programming in C
The Raspberry Pi’s 40-pin GPIO connector often gets overlooked. Typical Pi projects use the hardware as a very small desktop PC (RetroPie, Pi-hole, media center, print server, etc), and don’t make any...
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What’s on the BMOW Bookshelf
Over the decades, I’ve pared my collection of books down to just four shelves – only about 100 volumes from a lifetime of reading and studying. Because who needs physical books in an age where...
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LED PWM Without Resistors
I’ve been working on version 3 of Star Ring, my fun but useless circular LED blinker, and I had an idea. Do I really need current-limiting resistors for the LEDs? Or can I effectively control the LED...
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Limiting SD Card Inrush Current
I’m experimenting with methods to limit the inrush current when an SD card is inserted, and beginning to wonder whether my solutions are worse than nothing. When an SD card is inserted into a board...
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Where Did All The Watts Go?
How efficient is a typical 5V AC-to-DC power supply? I’m digging through my box of assorted power supplies from past projects, looking for something appropriate for a large LED matrix, and noticed the...
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Atmel ICE Wiring Horror
The Atmel ICE programmer/debugger has its SWD connector pins reversed from the standard ARM Cortex debug connector. Arghh… why? It’s the same physical connector (5×2 0.05 inch polarized male), but the...
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Spot The Design Error
A prototype for the latest Star Ring. Q1, Q2, and Q3 use this N-channel MOSFET. The circuit runs from a 3V battery. When one of the transistors is turned on, the six red/green LEDs in the associated...
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Cortex M4 Interrupt Speed Test
How quickly can a microcontroller detect and respond to changing inputs? Fast enough to replace a dedicated combinatorial logic chip, like a mux? I finally have some test results to begin answering...
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Halloween LED Matrix and PSU Death
In preparation for Halloween this year, I built a large and colorful LED matrix. After programming it with monster-themed animations, it looked fantastic! Months passed, and when October 31st finally...
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