Blog/July 2025/Jul 25th

July 25th

And now, for a meander down Geekdom Lane:

The “high intensity lamp” at my workbench is pathetic, so I decided to build myself a better one, using LEDs. Among my other questionable purchases, I had got a bunch of bright-white LEDs, and I already had the usual collection of old laptop power bricks and other assorted electronic bits. The original plan was for a 5 by 5 array of LEDs powered by a 19V laptop power-brick. But when I did the calculations, the current through the limiting resistors would require ones of a higher power-capacity than I had. So I settled on 6 by 6 array of LEDs with smaller resistors. So far, so good.

Then I decided I wanted to be able to adjust the brightness of the lamp, which could be done with a “variable resistor” – you know, one of those dial things? But again, the ones I have wouldn’t be able to handle the load… and controlling brightness via resistors wastes power.

So after some research, I settled on a PWM scheme using a 555 chip. Since my power brick supplies a bit more than 19V, and the 555 can't handle that, I needed to add a voltage regulator.

So I added a LM317L &c. After looking at what I managed to cobble together in KiCad, I decided to test each subsystem. First the voltage regulator: 19V in, 5V out, perfect! Hooked that up to the 555 PCM system with a test LED and resistor, and it worked great! Relatively efficient brightness control, with only a few components.

I plan on arranging the 36 LEDs in a circle, on a salvaged hard-disk platter (because it's very shiny aluminum), but I haven’t yet figured out the housing. Next week, hopefully, I'll have done that. Here's the schematic, and the working circuit on a breadboard. Messy, right? Well, next week B”H I’ll have properly arranged the components on a board, and emplaced the LEDs on the platter. Hopefully.

Seen in passing:

Unexpected results of NASA’s asteroid deflection test.
An absolutely massive Iranian shipment of arms to the Houthis was intercepted…
… and a Russian drone factory pumping out many hundreds of drones a day. What, me worry?
About the Druze resistance in Suwayda.
A long and interesting thread: I Spy with my Little Eye something beginning with… Nazi?
One reason to avoid using AI for coding: it deleted the dev’s entire database because “it panicked” and “ignored restrictions”. SkyNet anyone?
Random foodies: did barbecue exist in early America?

Apart from geeky endeavors, I spent around 5 hours through the week in gardening adventures: replacing all the irrigation lines and replanting some things. It was more work than I had bargained on.

We had a pleasant Jerusalem outing, visiting cousins of mine at “Piccolino” – a restaurant which is consistently good. The live music started out nice enough, but it became loud enough we had to shout at each other; apart from that, a very pleasant evening.

N.B.: Esther’s iPad has not yet arrived, she’s getting testy…

It’s gonna be a hot one this shabbat, highs around 38C or more. The heat-wave is supposed to break Tue-Wed next week, which is just too long. We’ll make sure to have cold drinks available!

This shabbat, we’ve got:
homemade ḥalla, stuffed vegetables, chicken schnitzel, okra winfrey, coleslaw, various salatim, and fruit.

Until next time,
shabbat shalom and ḥodesh ṭov!

To subscribe to this blog via email, click here; or, alternatively, unsubscribe.

Top: Blog

Prev: Jul 18th

Blog/July 2025/Jul 25th

From RonWareWiki