We’re not sure, but the number of recognizable alphanumeric characters that a seven-segment display can manage seems to have more to do with human pattern recognition than engineering. It takes some imagination, and perhaps a little squinting, to discern some characters, though. Arguably better is the fourteen-segment display, which has been pressed into service in this just-for-funsies IOT message board.
As [Steve] tells the story, this is one of those “boredom-buster” projects that start with a look through the junk bin to see what presents itself. In his case, some fourteen-segment common-cathode LEDs presented themselves, and the result was a simple but fun build. [Steve] used some clever methods to get the display stuffed onto two protoboards, including mounting the current-limiting resistors cordwood-style between the boards. A Raspberry Pi drives the display through a very neatly routed ribbon cable, and the whole thing lives in a tidy wooden box.
The IOT part of the build allows the display to show messages entered on [Steve]’s web page, with a webcam live stream to close the loop. Strangely, the display seems stuck on the “HI HACKADAY!” we entered as a test after [Steve] tipped us off, so we’re not sure if we busted it or what. Apologies if we did, [Steve]. And by the way, if your cats are named [Nibble] and [Pixel], well done!
Around the back of the unit is a card cage that accepts up to five option cards providing
4×4 matrix switching
on/off SPST switching
switching signals to a common bus
Digital I/O signalling
The teardown is an interesting glimpse into the solid engineering design of 1980s HP test equipment. The option cards are well shielded, and have an interesting back panel connector that breaks out the signals to screw terminals and provides strain relief. The brains of switcher was a Motorola 6809 and connectivity was provided by an Intel 8291A GPIB interface chip. The power supply is solid, and many of its parts can be reused on other projects, such as the transformer and a beefy 20W DC-DC converter by ST. [IMSAI Guy] also scores a bunch of latching relays from the option cards which will no doubt come in handy on future projects.
These kinds of programmable relays can be very useful when building automated test fixtures. There were other solutions for this as well, back in the day. Metrabyte ( bought by Keithley, bought by Tektronix ) was one company that made a whole line of switching interface modules that hooked up to your PC’s ISA bus. Omron also offered similar products. Have you ever needed banks of programmable relays for your projects? If so, let us know your solution in the comments below.
For a device advertised as the “Multi-tool Device for Hackers”, the Flipper Zero already offers a considerable list of onboard capabilities. But some hard decisions had to be made to get the retail price down, so features like WiFi and Bluetooth had to be left off. Luckily, there’s an expansion interface along the top of the device which makes it possible to plug in additional hardware.
One of those expansions is the “Mayhem Hat” from [Erwin Ried]. This board adds many requested features to the Flipper Zero, as well as some that might not seem as obvious. The addition of an ESP32-CAM brings WiFi and Bluetooth to the party, while also unlocking access to the highly-capable ESP32Marauder firmware and the plethora of security research tools therein.
But the camera also enables some interesting features, such as motion detection and the ability to read QR codes. It even lets you use the Flipper as an impromptu digital camera, complete with an onscreen viewfinder reminiscent of the Game Boy Camera.
What’s more, the Mayhem Hat features its own expansion capabilities. There’s a spot to plug in either a CC1101 or NRF24l01 radio module, both of which are supported by community developed plugins that allow the user to sniff out and hijack signals. There are also extra pins for connecting your own sensors or hardware. In the demo video below you can see the device automatically detect the popular DHT11 environmental sensor and display the current temperature and humidity readings.
What is it about pi that we humans — at least some of us — find so endlessly fascinating? Maybe that’s just it — it’s endless, an eternal march of digits that tempts us with the thought that if we just calculate one more digit, something interesting will happen. Spoiler alert: it never does.
That doesn’t stop people from trying, of course, especially when “Pi Day” rolls around on March 14 every day — with apologies to the DD/MM set, of course. This year, [Cristiano Monteiro] commemorated the day with this Pi-based eternal pi calculator. The heart of the build is a Raspberry Pi Pico board, which does double duty thanks to its two cores. One core is devoted to running the pi calculation routine, while the other takes care of updating the seven-segment LED display with the last eight calculated digits. Since the calculation takes increasingly more time the farther into pi it gets, [Cristiano] thoughtfully included a 1-Hz heartbeat indicator, to assure users that the display isn’t frozen; the video below shows how slow the display gets even just a few seconds after starting up, so it’s a welcome addition.
This is actually [Cristiano]’s second go at a Pi Day pi calculator; last year’s effort was a decidedly tactical breadboard build, and only supported a four-digit display. We applaud the upgrades, and if anyone wants to replicate the build, [Cristiano] has posted his code.
While you might think the military doesn’t have a sense of humor with names. Take the AN/MSQ-19 “automated tactical operations central” for example. (Video, embedded below.) But then, when you find out that the truck-sized computer at the heart of it was MOBIDIC — yes, that’s pronounced Moby Dick — you know someone had a good chuckle somewhere. The video below was a promotional video from the early 1960s, and although it shows the unit in operation, it was most likely a mockup and not fully functional.
The MOBIDIC program ran from 1960-1964 and cost a whopping $25 million in 1960-era money. In 1964, testing revealed the system was too unwieldy, requiring at least five tractor-trailers, eight generators, portable buildings, and several large trucks to move around.
We doubt the system could have been very reliable, either. It relied on a Rube Golbergesque system to record and file transparencies that were projected on maps. These transparencies were stored in some sort of automatic filing system and carried around in pneumatic tubes. No kidding, watch the video. You can’t make this stuff up.
A 1966 report from an Army research lab discusses using parts of AN/MSQ-19 in a laboratory, so at least some of the high-tech equipment did find a home. The designers of the system weren’t wrong, they were just a little early and needed better graphics capabilities along with smaller computers. The MOBIDIC weighed about 12,000 pounds, although at least the “B” version used by this project did have dual CPUs! There was a unique input device called a Grafton which was sort of like a modern digitizer. Sort of.
The MOBIDIC was built late in the 1950s as part of a larger Army strategy to computerize. You can watch a video about the solid-state computer in the second video below. It even includes a contemporary film about the computer. The base machine had 32,000 transistors, 6,000 diodes, and 311,200 bits of magnetic core. That’s less than 40 kB, to save you the math, and the narrator on the Army’s film calls that a “huge memory.” Perhaps he was really referring to the giant tape drives, which could hold about 10 MB. Not huge by today’s standards, of course, but still.
The trailer/computer had six tape drives, several cabinets for memory with space reserved for future upgrades, and an air conditioner. With power and extra equipment, there were actually four trailers together. There were several variants of these computers produced, and some saw actual use, particularly in Germany. The National Bureau of Standards bought the MOBIDIC-B used in this system and you can read about its retirement in 1973.
They Simply Fade Away
Sylvania, the MOBIDIC’s developer, also produced the 9400, a commercial variant of the machine. What was it like to program? Well, you used BASICPAC, which didn’t look at all like BASIC, if you were wondering.
Looking back over the 60-some-odd years between this system and our modern computers, you could choose to be amused at how primitive the systems were. Or, you can stand in awe that people could look at this new technology and see what could be possible, even if they weren’t quite able to get there right away.
The Xerox Alto, which debuted in the early spring of 1973 at the photocopying giant’s newly established R&D laboratory, the Palo Alto Research Center (PARC). It seems so uncannily familiar today for one reason: We are now living in a world of computing that the Alto created.
The Alto was a wild departure from the computers that preceded it. It was built to tuck under a desk, with its monitor, keyboard, and mouse on top. It was totally interactive, responding directly to its single user.
In contrast, the dominant mainframe at the time—IBM’s hugely popular System 360, heavily used by big organizations, and the Digital Equipment Corp.’s PDP-10, the darling of computing researchers—were nothing like the Alto. These and the other mainframes and minicomputers of the era were room-size affairs, almost always located somewhere away from the user and almost always under the control of someone else. The many simultaneous users of one such computer shared the system as a common resource.
Steve Jobs and a whole team from Apple toured PARC in 1979. The visit was arranged as a quid pro quo for allowing Xerox to invest in Jobs’s exciting new personal-computer company. Viewing Alto’s graphical user interface, Jobs had what he later described as an epiphany, one that reoriented his efforts at Apple forever after.