Keeping Track Of The Night Sky With Discrete Logic Chips

February 9, 2024 by Dan Maloney 11 Comments

As hobbies go, stargazing has a pretty low barrier to entry. All you really need is a pair of Mark 1 eyeballs and maybe a little caffeine to help you stay up late enough. Astronomy, on the other hand, takes quite a bit more equipment, not least of which is a telescope and a way to get it pointed in the right direction at the right time, and to make up for the pesky fact that we’re on a moving, spinning ball of rock.

Yes, most of the equipment needed for real astronomy is commercially available, but [Mitsuru Yamada] decided to go his own way with this homebrew retro-style telescope motor controller. Dubbed MCT-6, the controller teams up with his dual-6502 PERSEUS-9 computer to keep his scope on target. There are a lot of literally moving parts to this build, including the equatorial mount which is made from machined aluminum and powered by a pair of off-the-shelf stepper-powered rotary stages for declination and right ascension. The controller that runs the motors is built completely from discrete 74HCxx logic chips that divide down a 7.0097-MHz crystal oscillator signal to drive the steppers precisely at one revolution per diurnal day. The pulse stream can also be sped up for rapid slewing, to aim the telescope at new targets using a hand controller.

As impressive as all this is, the real star (sorry) of the show here is the fit and finish. In typical [Yamada-san] fashion, the impeccably wire-wrapped mainboard fits in a robust die-cast aluminum case that fits the retro aesthetic of the whole project. The PERSEUS-9 is used mainly as a display and control terminal, running custom software to show where the telescope is pointed and calculate the coordinates of various heavenly bodies. As a bonus, the 40×7 alphanumeric red LED display should be easy on dark-adapted eyes.

Hats off to [Mitsuru Yamada] on another fabulous build. If you haven’t had enough of his build style yet, be sure to check out his PERSEUS-8 or even his foray into the analog world.

Continue reading “Keeping Track Of The Night Sky With Discrete Logic Chips” →

Wiring Harness? That’s A Wrap!

January 12, 2024 by Al Williams 22 Comments

[Mr Innovative] likes to keep his wire harnesses tidy, but it is a pain to neatly wrap cables. So, he automated the process using a combination of milled acrylic and 3D printing. We hope the design files will be up on his website soon, although the mechanism is similar to another wrapping machine he made a few years ago. However, it can still be a source of inspiration if you want to do a unique take on it.

To use the machine, you feed the wires through the center hole and mount tape on the spool. A motor spins the spool and you only need to slowly advance the tool to get a nice close wrap. Naturally, you can wrap tape around wires by hand, so this is a bit of a luxury item. However, we could see modifying it to move the cable through at a constant rate with another motor, which might do a better job than you can do by hand.

We couldn’t help but wonder if you could start with a ping pong paddle instead of cutting the frame out of acrylic.

Continue reading “Wiring Harness? That’s A Wrap!” →

Retrotechtacular: Building The First Computers For Banking

August 11, 2023 by Dan Maloney 26 Comments

If you’ve ever wondered where the term “banker’s hours” came from, look back to the booming post-war economy of 1950s America. That’s when banks were deluged with so many checks, each of which had to be reconciled by hand, that they had to shut their doors at 2:00 or 3:00 in the afternoon, just to have a hope of getting all the work done at a reasonable time. It was time-consuming, laborious, error-prone work that didn’t scale well, and something had to be done about it.

The short film below, “Manufacturing Competence,” details the building of ERMA, the Electronic Recording Machine, Accounting. ERMA was the result of years of R&D work, and by the early 1960s, General Electric was gearing up production at its new Phoenix, Arizona plant. The process goes from bare metal racks and proceeds through to manufacturing the many modules needed for these specialized machines, which were perhaps the first commercial use of computers outside of universities and the military.

The sheer number of workers involved is astonishing, especially in backplane assembly, with long lines of women wielding wire-wrapping guns and following punch-tape instructions for the point-to-point connections. PCB stuffing was equally labor-intensive, with women stuffing boards from a handful of seemingly random components. And the precision needed for some of the steps, like weaving the ferrite core memory, was breathtaking. We really enjoyed the bit where the tiny toroids were bounced into place with a vibrating jig.

The hybrid nature of ERMA, and the assembly methods needed to produce it, are what strike us most about this film. The backplanes were wire-wrapped, but the modules were wave-soldered PCBs. Component leads were automatically formed and trimmed, but inserted by hand. Assembly and testing were directed by punched tape, but results were assessed by eye. Even ERMA itself was prototyped with vacuum tubes, but switched to transistors for production. The transitional nature of electronics in the early 1960s is on full display here, and it offers an interesting perspective on how change in this field can be simultaneously rapid and glacial.

Continue reading “Retrotechtacular: Building The First Computers For Banking” →

PERSEUS-9, The Dual-6502 Portable Machine That Should Have Been

July 29, 2022 by Dan Maloney 53 Comments

A question: does anyone who was around in the early days of the 8-bit computer revolution remember a dual-CPU 6502 portable machine like this one? Or just a dual-CPU machine? Or even just a reasonably portable computer? We don’t, but that begs a further question: if [Mitsuru Yamada] can build such a machine today with parts that were available in the era, why weren’t these a thing back then?

We’re not sure we have an answer to that question, but it just may be that nobody thought of it. Or, if they did, the idea of putting two expensive CPUs into a single machine was perhaps too exorbitant to take seriously. Regardless, the homemade mobile is another in a growing line of beautifully crafted machines in the PERSEUS line, all of which have a wonderfully similar look and feel.

For the PERSEUS-9, [Yamada-san] chose a weatherproof aluminum enclosure with just the right form-factor for a mobile computer, as well as a sturdy industrial look. Under the hood, there are two gorgeous wire-wrap boards, one of which is home to the 48-key keyboard and the 40×7 alphanumeric LED matrix display, while the other is a densely packed work of art holding the two 6502s and a host of other DIPs.

The machine is a combination of his PERSEUS-8 computer, his 6802 serial terminal, and the CI-2 floating point interpreter he built for the PERSEUS-8. A brief video of the assembly of this delightful machine is below. One of the many things about these builds that impress us is the precision with which the case is machined, apparently all by hand. How he managed to drill out all those holes for the keyboard without having one even slightly out of alignment without the aid of CNC is beyond us.

Continue reading “PERSEUS-9, The Dual-6502 Portable Machine That Should Have Been” →

Ironclad Tips For Copper-Clad Prototyping

May 24, 2020 by Kristina Panos 25 Comments

The idea of trying to prototype with SMD parts on the fly sounds like insanity, right? But then we watched [Leo Fernekes] walk calmly and carefully through his process (video, embedded below). Suddenly, SMD prototyping jumped onto our list of things to try soon.

[Leo] speaks from a lot of experience and tight client timelines, so this video is a fourteen-minute masterclass in using copper-clad board as a Manhattan-style scratch pad. He starts by making a renewable tool for scraping away copper by grinding down and shaping an old X-Acto blade into a kind of sharpened Swiss Army knife bottle opener shape. That alone is mind-blowing, but [Leo] keeps on going.

In these prototypes, he uses the through-hole version of whatever microcontroller is in the design. For everything else, he uses the exact SMT part that will end up on the PCB that someone else is busy designing in the meantime.

After laying the board out on paper, [Leo] carves out the islands of conductivity, beep-checks them for shorts, shines the whole thing with steel wool, and goes to town.

The tips and tricks keep coming as he makes jumps and joins ground planes with bare copper wire insulated with heat-proof Teflon tubing, and lays out the benefits of building up a stash of connectors and shelling out the money for a good crimp tool.

And why do you need a good crimp tool? Because when they’re done properly, crimped connections are stronger and more reliable than solder. There’s a lot more to them than you might think.

Continue reading “Ironclad Tips For Copper-Clad Prototyping” →

Grace Under Pressure: Shelley Green Celebrates Crimped Connections

April 27, 2020 by Kristina Panos 18 Comments

We think it’s pretty safe to assume that most of the electrical connections our readers are making out there involve solder or solder paste. But we’ve all made a crimp connection or two in our lifetimes. Maybe you’ve squeezed a butt connector here and there, or made an Ethernet cable. Beyond getting the wiring order right in the Ethernet cable, how much did you wonder about what was happening inside the connector?

It may seem like solder is the superior option for making a low-resistance electrical connection. After all, you’re welding metals together with another metal. And this is usually all fine and good for circuit boards with sedentary indoor lives. But if a joint needs to be mechanically stable and survive in potentially harsh environments, you don’t want an alloy holding things together. You want metal to metal contact, and crimping is where it’s at.

A well-made crimp should last for several decades, but as Shelley Green explained in her talk at the 2019 Hackaday Superconference, good quality crimps don’t happen by accident. Good crimps are meticulously designed, and carefully executed from start to finish.

Continue reading “Grace Under Pressure: Shelley Green Celebrates Crimped Connections” →

Drill Thrice, Solder Once

December 27, 2019 by Brian McEvoy 28 Comments

If you design printed circuit boards, then you will have also redesigned printed circuit boards. Nobody gets it right the first time, every time. Sometimes you can solder a scrap of 30gauge wire, flip a component 180°, or make a TO-92 transistor do that little pirouette thing where the legs go every-which-way. If you angered the PCB deities, you may have to access a component pad far from an edge. [Nathan Seidle], the founder of Sparkfun, finds himself in this situation, but all hope is not lost.

Our first thought is to desolder everything, then take a hot iron and tiny wires to each pad. Of course, this opens up a lot of potential for damage to the chip, cold joints, and radio interference. Accessing the pin in vivo has risks, but they are calculated. The idea is to locate the pin, then systematically drill from the backside and expose the copper. [Nate] also discovers that alcohol will make the PCB transparent so you can peer at the underside to confirm you have found your mark.

In a real, “fight fire with fire” idea, you can rework with flex PCBs or push your PCB Fu to the next level and use PCBs as your enclosure.