Day: October 19, 2023

You’ve Got Mail: Grilled, Scrambled, And Other Delicious Stamps

October 19, 2023 by 8 Comments

Well, we’re just zipping right through this series, no? So far we’ve looked at various postal machines and how they work to flip mail around, cancel the postage, and sort it, all in a matter of seconds. We explored the first automated post office and found out why it was a failure, and we learned why it all depends on ZIP code. Now, it’s finally time for some really fun stuff: the stamp trivia.

Now I’m no philatelist by any standard, though I do have a few hundred stamps strewn about the house. The danger in philately is that you learn all sorts of cool things about stamps and their history, and you just want to buy more and more of them. So let’s go!

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A Typewriter For The Paperless Age

October 19, 2023 by 9 Comments

Writing is, as any of the Hackaday crew will tell you, a task which requires concentration. For your best work there’s a need to be in that elusive Zone, and for some that means making the experience as distraction free as possible. For them there’s an entire class of minimalist word-processors and text editors which reduce the UI to nothing more than the text. [Adam Blumenberg] has taken this a step beyond software with his digital typewriter, a single-purpose Raspberry Pi-based cyberdeck that serves only for distraction-free writing.

There’s not a lot in the way of descriptive text at the above link but in a way there doesn’t need to be as the photographs tell the story. A mechanical keyboard and a wide but not very tall display fit with the Pi in a fairly rudimentary wooden case, and running Focuswriter it leaves very little in the way of distraction. In that sense it’s not quite so much a cyberdeck in its application as something more like the smart digital typewriters from a few decades ago without the printer, but we can see that it makes for a very handy writing implement. Sadly the job of writing for Hackaday requires constant access to online sources on a larger screen, or we’d be tempted to try one ourselves.

The one-purpose writing computer is an idea we’ve seen before from time to time, for example in this one with an e-paper display.

Simple Circuit Keeps Process Control Loops In Tune

October 19, 2023 by 7 Comments

Spare a moment’s pity for the process engineer, whose job it is to keep industrial automation running no matter what. These poor souls seem to be forever on call, fielding panicked requests to come to the factory floor whenever the line goes down. Day or night, weekends, vacations, whatever — when it breaks, the process engineer jumps.

The pressures of such a gig can be enormous, and seem to have weighed on [Tom Goff] enough that he spent a weekend building a junk bin analog signal generator to replace a loop calibrator that he misplaced. Two process control signaling schemes were to be supported — the 0 to 10 VDC analog signal, and the venerable 4-20 mA current loop. All that’s needed for both outputs is an Arduino and an LM358 dual op-amp, plus a few support components. The 0-10 V signal starts as a PWM output from the Arduino, with its 0-5 V average amplified by one of the op-amps set up as a non-inverting amp with a gain of 2. With a little filtering, the voltage output is pretty stable, and swings nicely through the desired range — see the video below for that.

The current loop output is only slightly more complicated. An identical circuit on a separate Arduino output generates the same 10 V max output, but a code change limits the low end of the range to 1 V. This output of the op-amp is fed through a 500-Ω trimmer pot, and the magic of Ohm’s Law results in a 4-20 mA current. The circuit lives on a piece of perf board in a small enclosure and does the job it was built for — nothing fancy needed.

And spoiler alert: [Tom] found the missing loop calibrator — after he built this, of course. Isn’t that always the way?

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