The SInclair ZX 8-bit computers of the early 1980s were masterpieces of economy, getting the most out of minimal hardware. The cassette tape interface was a one-bit port, the video was (on the first two models anyway) created by the processor itself rather than a CRT controller, and the keyboard? No fancy keyboard controllers here, just a key matrix and some diodes between a set of address lines and some data lines. The ZX80 and ZX81 were not very fast as a result of their processors being tied up with all this work, but it ensured that their retail price could break the magic £100 barrier in the British market, something of a feat in 1980.
A host of hackers still devote their time to these machines, and among them [Danjovic] has updated that ZX keyboard by producing an interface between that matrix and a PS/2 keyboard. As you might expect it uses a modern microcontroller board, in this case an Arduino Nano but it doesn’t stretch the imagination to think that a USB equipped board might perform the same task. It sits upon the relevant lines, and performs the necessary logical connection between them depending upon the serial input from an attached PS/2 keyboard. The project goes into some detail on PS/2 to ZX mappings, but perhaps of most interest is its explanation of the bus timings involved. The Arduino makes use of the ZX WAIT line to hold the Z80 and ensure that there is enough time for it to perform its task, it would be interesting to note whether or not this has a visible impact on BASIC program timing.
We are more used to seeing ZX keyboards being attached to PCs, rather than this way round.
ZX Spectrum image: Bill Bertram [CC BY-SA 2.5].
Researchers from the University of Sussex used 3D printing for a modular approach to acoustic lens design. 16 different pre-printed “bricks” (shown here) can be assembled in various combinations to get different results. There are limitations, however. The demonstration lenses only work in a narrow bandwidth, meaning that the sound they work with is limited to about an octave at best. That’s enough for a simple melody, but not nearly enough to cover a human’s full audible range. 
The payload container is a hollow tube with a 3D printed threaded adaptor attached to one end. Payload goes into the tube, and the tube inserts into a hole in the bulkhead, screwing down securely. The result is an easy way to send up something like a GPS tracker, possibly with a LoRa module attached to it. That combination is a popular one with high-altitude balloons, which, like rockets, also require people to retrieve them after not-entirely-predictable landings. LoRa wireless communications have very long range, but that doesn’t help if there’s an obstruction like a hill between you and the transmitter. In those cases, 
