We’re now all used to near-limitless storage on flash and other semiconductor technologies, but there was a time when persistent storage was considerably less easy to achieve. A 1970s programmable calculator from Sharp approached the problem with magnetic strips on special cards, and since [Menadue] has one with no cards, he set about making his own.
These cards are a little different to the credit-card-style cards we might expect, instead they’re a narrow strip with a magnetic stripe down their centre. The unusual feature can be found at the edge, where a row of perforations provide the equivalent of a clock line.
The newly manufactured cards have the clock slots machined along their edges, and then the magnetic part formed from self-adhesive magnetic strip. This last thing is a product we were not aware existed, and can think of plenty of possible applications.
The result as you can see in the video below the break are some cards with variable reliability. There’s a suggestion that white cards might work less well with the infrared light used in the clock detector, also a suspicion the low batteries make reading less easy, but still he’s able to retrieve a stored program. An extinct medium is revived.
The interesting thing about the SX-70 camera design is that its shutter speed and aperture setting are essentially linked together as the aperture and shutter assembly are combined into one unit with a variable tear-drop shaped opening. Thus, the timing of the shutter opening and closing and the extent to which it opens are what determines exposure and aperture.
Thankfully, [Jake Bright] has learned a lot about these unique cameras and exactly how this complex system operates. He shares his tips on firstly restoring the camera to factory-grade operation, and then the methods in which they may be converted to work with modern film. Fundamentally, it’s about changing capacitors or resistors to change the shutter/aperture timing. However, do it blindly and you’ll have little success. You first need to understand the camera’s mechanics, pneumatics, and its “Electric Eye” control system before you can get things dialed in just so.
For all that modern washers and dryers do, they don’t let you know when they’re finished. Or they do, but it’s only a short victory song that plays once and can be easy to miss. What most of us need is a gentle reminder that there’s damp laundry festering in the washer, or fresh laundry in the dryer getting wrinkly.
This laundry monitor from [Sparks and Code] is version 2.0. The first version was working fine, but it was based on vibration (or lack thereof). Fast forward a few years, and [Sparks and Code] got a modern pair that’s so finely tuned, it doesn’t produce enough vibration to register. Back to the drawing board [Sparks and Code] went, and eventually came up with version 2.0.
Now, [Sparks and Code] is detecting whether the machines are on using a pair of split-core transformers to monitor power at the breaker box. With these, you just run the wire through the hole, and it gives the relative mV value going through the wire on a 3.5mm cable. Those cables are connected to an ESP32 inside the 3D-printed box, which is mounted above the cabinet door. Since [Sparks and Code] already has home assistants all over the house, it was easy to integrate and have them all play the message ‘please flip the laundry’.
Once this project was all buttoned up, they thought of one issue — the self-cleaning cycle. Since it takes about four hours, they like to run it overnight. You can see the problem here — no one wants to hear Alexa at 3AM. Fortunately, [Sparks and Code] was able to adjust the Python script to ignore these events. Be sure to check out the build video after the break.
If you solder (and we know you do), you absolutely need ventilation, even for that lead-free stuff. Fortunately, [tinyboatproductions] has gotten into air quality lately and is here to help you with their snappy 3D printed air-filtering design.
At the heart of this build is a 120 mm notoriously-quiet Noctua fan coupled with a carbon filter. It does what you’d think — position the fan the right way and it sucks the air through the filter, which catches all those nasty particles.
The only problem is that the Noctua uses PWM, so there’s no governing it with a just potentiometer. To get around this, [tinyboatproductions] introduced an Arduino Nano and a buck converter, both of which were admittedly a bit overkill. Now the speed can be controlled with a pot.
Once control of the fan was sorted, [tinyboatproductions] decide to add an OLED display to show the fan speed and power condition, which is a nice touch. Be sure to check out the build video after the break.
Over the years we’ve reported on the passing of a few of the broadcasting technologies of yesteryear, such as analogue TV in America, or AM radio in Europe. Now it’s the turn of an early digital contender, as one of the few remaining holdouts of old-style teletext is to shut down its service. The Irish broadcaster RTÉ is to turn off its teletext service Aertel, which has been live in some form continuously since 1986.
Like all European countries, Ireland has had only digital TV for quite a few years now. The linked RTÉ piece implies that the Aertel service has been carried as the old-style data in the frame blanking period even when part of a digital multiplex rather than the newer digital teletext system, so we’d be really grateful if some of our Irish readers could flick on their TVs and confirm that.
In an internet-connected world it seems quaint that a limited set of curated pages could once have been such a big deal, but it’s easy to forget that for many the teletext system provided their first ever taste of online information. As it shuffles away almost unnoticed we won’t miss counting through the page numbers cycling by in the top corner as we waited for our page to load, but it’s worth marking its final passing from one of the few places it could still be found.
If you want to add sound to something these days, you usually store it digitally. Microcontrollers are cheap and fast, and you can hold a lot of audio on a small flash card or in a ROM. But back “in the day,” storing audio was often done with tape. If you wanted something you could automate, you often turned to an endless loop tape. They had the advantage of not needing rewinding and had a way to sense spots on the tape (usually the start). The 8-track, for example, was an endless loop tape, and radio stations used “carts” (technically Fedelipak cartridges). But what if you wanted to build something tiny? Bandai had the answer, and [Tech Moan] shows the 1986-era tiny carts.
In the US, these appear to be mainly in the realm of novelty items. [Tech Moan] has an Elvis figurine that sings thanks to the tape and a diminutive jukebox. He suspects these must have been used in something else, perhaps in the Japanese market.
When you’ve been a fact-sponge for electronics trivia for over four decades, it’s not often that an entire class of parts escapes your attention. But have you seen the Skiatron? It’s a CRT that looks like a normal mid-20th-century tube, until it’s switched on. Then its secret is revealed; instead of the glowing phosphor trace we’d expect, the paper-white screen displays a daylight-readable and persistent black trace. They’re invariably seen in videos of radar installations, with the 360 degree scans projected onto large table-top screens which show the action like a map. It’s like e-ink, but from the 1940s. What’s going on?
The tenebrescent mineral Hackmanite, before and after UV exposure. Leland Green…, CC BY-SA 2.0 and CC BY-SA 2.0.
The phosphor coating on a traditional CRT screen is replaced by a halide salt, and the property on which the display relies is called tenebrescence, changing colour under the influence of radiation. This seems most associated online with UV treatment of some minerals and gemstones to give them a prettier look, and its use a s a display technology is sadly forgotten.
A high-school physics understanding of the phenomenon is that energy from the UV light or the electron beam in the case of the tube, places some electrons in the crystal into higher energy levels, at which they absorb some visible light wavelengths. This is reversible through heat, in some substances requiring the application of heat while in others the heat of room temperature being enough. Of course here at Hackaday we’re hands-on people, so into the EPROM eraser went a small amount of table salt in a makeshift dish made of paper, but sadly not to be rewarded by a colour change.
On a real dark-trace CRT the dark trace would be illuminated from behind by a ring light round the glass neck of the tube. An interesting aside is that, unlike phosphor CRTs, they were more suitable for vertical mounting. It seems that small amounts of phosphor could detach themselves from a vertically mounted screen and drop into the electron gun, something that wasn’t a problem for tenebrescent coatings.
This display tech has shuffled off into the graveyard of obsolescence, we’re guessing because CRT technology became a lot better over the 1950s, and radar technologies moved towards a computerised future in which the persistence of the display wasn’t the only thing keeping the information on the screen. It seems at first sight to be a surprise that tenebrescent coatings have never resurfaced in other displays for their persistence, but perhaps there was always a better alternative whether it was ultra-low-power LCDs or more recently e-ink style devices.
For more bleeding-edge 1950s radar displays, we’ve previously brought you Volscan, a radar with an early form of GUI, which no doubt was one of those which consigned dark-trace CRTs to history.
