Hi - I'm Jack, a researcher with the US National Cancer Institute. I am based in Antananarivo, Madagascar. This blog is devoted to hobby items like amateur radio (my call sign: 5R8SV), electronics, computers and interactive fiction.

Solar CDX

Three Time Zone Arduino-based Clock

I’ve been meaning to add a clock with multiple time zone display to my radio operating position for a while. The time in UTC is displayed on my computer when I’m logging, but it’s small and it disappears when the screen sleeps. Also, I use the same room to take work-related conference calls, and it […]

Variable Power Supply from Targus PA350

Continuing on the theme of power supplies and related, I thought I would try my hand at making a bench top variable power supply based on a universal laptop adapter. My rationale is that these adapters are made to run on 11-16V, so I could run it off whatever power is available (the 12V bus […]

Electronic Load

It’s been a chicken and egg race for the last couple months – I was working on power supply projects, but at the same time needed an electronic load so I could test the supplies at known current draws. I have had a working electronic load for a few months, but only got around to […]

Fox and Hound

No, not an article on QRP fox hunts (which I miss, being a bit out of range), but a construction project to make a pair of devices for tracing down wiring. The fox sends a tone down a wire and the hound sniffs around until it finds the right wire by detecting the tone. I […]

Variable Power Supply

I’ve been focusing on power supplies and related equipment lately because I don’t have a lot of bench gear. On one hand, I would like to build equipment from scratch, but on the other, it would be crazy not to look at some of the building block modules available on eBay and other outlets. I […]

ATX Supply

Remember that ATX power supply that I fried last year? I replaced it with another mail-ordered supply and then it sat on the shelf long enough for me to get around to fixing it: a new regulator, some MOVs, a cap and the fuse, and it was ready for action — except I had no […]

Soft latch

I liked the circuit so much I made two of them. Here’s front and back. The one on the left has an extra electrolytic cap; its addition did not affect the switching circuit at all.

Catching up on the bench back catalog: here’s a useful little module – a soft latch that isn’t finicky, […]

Back to the bench: 7 segment display

Three 4-digit displays: red, yellow, and green. Ew, shiny pads!

Since the SOTA genie escaped the bottle, the blog has leaned towards operation rather than bench work, but rest assured that projects have been percolating in the background. Here’s an update on a few of them: a custom LED display, a soft latch circuit, […]

Weller: The Final Chapter

Well, I hope it is the final chapter. I’ve written before about fixing and then learning that I hadn’t quite fixed my Weller WESD51 digital soldering iron. After much manipulation, I think I ended up cooking the PIC chip on the PC board, so I just ordered another board. Long story short: replacing the old […]

The Ginger Polygraph

The frequently lit red light indicates that our dog is lying.

My dog Ginger has a problem: she really likes food. That, coupled with her uncanny ability to convince family members that she has not been fed adds up to an overweight dog. She is not particularly sensitive about the subject and besides, she […]