Articles by Big Mess o' Wires

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 row can be turned on or off using six microcontroller outputs. At

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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 pins are rotated 180 degrees from the standard, as if the cable were plugged in backwards. Incredibly, it

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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 one pictured above. 110V 0.8A input – that’s 88 watts. 5V 4A output – that’s 20

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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 that’s already powered on, a large amount of current will flow briefly, as the

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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 current using PWM?

Normally a resistor is always needed in series with an

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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 use of general-purpose IO pins. That’s too bad, because with a little bit of work, the Raspberry

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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 purchased on eBay for $26. Each point in the matrix

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Version 2 of the Apple IIc Internal/External Drive Switcher is here, and is working nicely. It’s mostly the same as version 1, except for a few tweaks to the piece that goes inside the IIc case. Although the inside fit is still very tight, with this new version it’s

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I finished the redesign for my Apple IIc Drive Switcher PCB on Monday morning, and submitted the Gerber files to Elecrow on Monday at 11:25 am. Friday at 5:20 pm I held the finished PCBs in my hands. Only 4 days for manufacturing and delivery. From China. According to

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Oops, I did it again: another 10000 DB-19 connectors fresh from the factory! After helping to resurrect this rare retro-connector from the dead in 2016, and organizing a group of people to share the cost of creating new molds for manufacturing, I had some of the 21st century’s first

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