Upgrading A Soviet Calculator With A Modern CPU

January 27, 2022 by Robin Kearey 17 Comments

Today’s supply chain issues can make it hard to buy microcontrollers, or really any kind of semiconductor. But for those keeping retrocomputers alive, this problem has always existed: ancient components might have been out of production for decades, with a dwindling supply of second-hand parts or “new old stock” as the only option. If a rare CPU breaks, you might have no option but to replace the entire computer.

[Piotr Patek] ran into this issue when he obtained an Elektronika MK-85 programmable calculator with a broken CPU. Unable to find a replacement, he decided instead to build a pin-compatible CPU unit based on an STM32 microcontroller. Of course no modern CPU is pin-compatible with a Soviet design from the 1980s, so [Piotr] had to design a small interposer PCB to match the original pinout. This also gave him enough space to add an efficient DC/DC converter chip that generates the 2.5 V supply for the STM32.

As for the software, [Piotr] managed to port the original BASIC interpreter, which was written in PDP-11 assembly, to a modern equivalent written in C. While he was at it, he fixed a few bugs that had been sitting there for about 35 years. The updated CPU also allows the MK-85 to run circles around its contemporary siblings: [Piotr] timed it to be about thirty times faster than the original chip, while using a comparable amount of power.

If you also happen to have an MK-85 with a dodgy CPU, you’ll be pleased to find that the schematics and source code to [Piotr]’s modification are all available on his blog. This is probably the first calculator CPU update we’ve seen, although we’ve featured other ancient calculators updated with new firmware, and some completely new calculator designs based on classic hardware.

Thanks for the tip, [cmholm]!

555 Teardown Isn’t Just A Good Time, It’s To Die For

January 25, 2022 by Ryan Flowers 10 Comments

It seems only appropriate that hot on the heels of the conclusion of Hackaday’s 555 Timer Contest that [Ken Shirriff] posts a silicon die teardown of an early version of a hacker’s favorite chip, the 555.

Starting with a mystery chip from January 1973, [Eric Schlaepfer] painstakingly sanded down the package to reveal the die, which he deemed to be a 555 timer. Why didn’t they know it was a 555 timer to start? Because the package was not marked with “555” but rather some other marks that you can see in the blog post.

In addition to a great explanation of how the 555 works in general, [Ken] has taken a microscopic look at the 555 die itself. The schematic of a 555 is easily available, and [Ken] identifies not just sections of the die but individual components. He goes further yet by explaining how the PNP and NPN resistors are constructed in silicon. There’s also a nice and juicy bit of insight into the resistors in the IC, but we won’t spoil it here.

Be sure to show your love for the winners of the 555 contest, or at the very least check out the project that took the stop spot: a giant sized 555 that you don’t need a microscope to see inside of.

Remoticon 2021 // Debra Ansell Connects PCB In Ways You Didn’t Expect

January 20, 2022 by Elliot Williams 21 Comments

“LEDs improve everything.” Words to live by. Most everything that Debra Ansell of [GeekMomProjects] makes is bright, bold, and blinky. But if you’re looking for a simple string of WS2812s, you’re barking up the wrong tree. In the last few years, Debra has been making larger and more complicated assemblies, and that has meant diving into the mechanical design of modular PCBs. In the process Debra has come up with some great techniques that you’ll be able to use in your own builds, which she shared with us in a presentation during the 2021 Hackaday Remoticon.

She starts off with a quick overview of the state of play in PCB art, specifically of the style that she’s into these days: three dimensional constructions where the physical PCB itself is a sculptural element of the project. She’s crossing that with the popular triangle-style wall hanging sculpture, and her own fascination with “inner glow” — side-illuminated acrylic diffusers. Then she starts taking us down the path of creating her own wall art in detail, and this is where you need to listen up. Continue reading “Remoticon 2021 // Debra Ansell Connects PCB In Ways You Didn’t Expect” →

Honda Ignition Coils Sing The Song Of Their People

January 11, 2022 by Tom Nardi 7 Comments

High-voltage experimenters have been using automotive ignition coils to generate impressive sparks in the home lab for decades, and why not? They’re cheap, easily obtainable, and at the end of the day, producing sparks is literally what they’re designed to do. But that doesn’t mean there isn’t room for improvement.

In his latest Plasma Channel video [Jay Bowles] revisits this classic experiment, bringing to bear the considerable high-voltage experience he’s gained over the last several years. Building on an earlier setup that used a single Honda ignition coil, this new dual-coil version can produce up to 60,000 volts and is driven by a cleaner and more reliable circuit based on the iconic 555 timer. A pair of potentiometers on the front of the driver can adjust its square wave output from 1 to 10 kilohertz manually, while a commercial Bluetooth audio receiver tied into the 555 circuit allows the output to be modulated by simply playing audio from a paired device.

Continue reading “Honda Ignition Coils Sing The Song Of Their People” →

LED Bubbles From The 1970s Tell The Time

January 11, 2022 by Al Williams 15 Comments

[CuriousMarc] is nothing if not curious. Finding some old TI timekeeping chips to reverse engineer, he set out to make a clock using old-fashioned “bubble LEDs.” You can see the result of his tinkering in the video below. For the uninitiated, bubble LEDs are 7-segment LEDs with magnifying bubbles over each digit. These were popular in calculators, watches, and other places that used LEDs before LCDs largely displaced them.

The history of these has to do with the power required to light an LED. You don’t technically need a magnifying lens, but larger LEDs take more power. These displays were relatively low power and used tiny LEDs with light pipes to make each dot a full segment. The lens made the segments larger and easier to see.

Beyond the TI chip and HP displays, there isn’t too much else needed. [Marc] just wired the whole thing using the IC as a substrate. Sort of dead bug construction using enameled wire. At first, it didn’t work but it turned out to be a battery issue. The device really wanted 2.5 V and not the 3 V provided by the battery. The solution required a little detective work.

We know this isn’t a very practical project, but we love seeing this old tech again and while the dead bug construction isn’t beautiful, there is something appealing about the look of it. Maybe one day people will build steampunk things and discopunk will be for the 1970s?

We’ve seen bubble LED projects before. If you want something more in a watch form factor, that exists, too.

Continue reading “LED Bubbles From The 1970s Tell The Time” →

New Part Day: The RISC-V Lichee-RV Module And Dock

January 6, 2022 by Dave Rowntree 47 Comments

Sipeed have been busy leveraging developments in the RISC-V arena, with an interesting, low-cost module they call the Lichee RV. It is based around the Aliwinner D1 SoC (which contains a Pingtou Xuantie C906 for those following Chinese RISC-V processor development) with support for an optional NAND filesystem. This little board uses a pair of edge connectors, similar to the Raspberry Pi CM3 form factor, except it’s based around a pair M.2 connectors instead. The module has USB-C, an SPI LCD interface, as well as a TF card socket on-board, with the remaining interfaces provided on the big edge connector.

The minimalist Allwinner D1-based Lichee RV

So that brings us onto the next Sipeed board, the Lichee RV Dock which is a tiny development board for the module. This breaks out the HDMI, adds USB, a WiFi/Bluetooth module, audio driver, microphone array interface and even a 40-way GPIO connector. Everything you need to build your own embedded cloud-connected device.

Early adopters beware, though, Linux support is still in the early stages of development, apparently with Debian currently the most usable. We’ve not tested one ourselves yet, but it does look like quite useful for those projects with a small budget and not requiring the power-hungry multi-core performance of a Raspberry Pi or equivalents.

We’ve seen the Sipeed MAix M1 AI Module hosted on a Pi Hat a couple of years ago, as well as a NES emulator running on the Sipeed K210. The future for RISC-V is looking pretty good if you ask us!

Thanks [Maarten] for the tip!

Planning Custom Aluminum Enclosures With OpenSCAD

December 26, 2021 by Tom Nardi 20 Comments

We’ve seen a number of projects over the years that let you create custom enclosures using OpenSCAD, and for good reason. The parametric CAD tool is ideal for generating 3D models based on user-adjustable variables, and if you leverage its integrated Customizer, producing a bespoke box is as easy as moving some sliders around. The resulting files get sent off to the 3D printer, and you’re set. But what if you’re looking for a custom enclosure that’s not so…plastic?

In that case, AlClosure by [0xPIT] might be the answer. Rather than generating STL files intended for your 3D printer, the code is written to help you design an enclosure made from aluminum sheets. The top and bottom panels are intended to be cut from 1.5 mm – 2.5 mm sheets, while the sides are made from thicker 5 mm – 8 mm stock to accept a machined pocket that holds the front and rear inserts.

Since it’s OpenSCAD, much of the design is governed by variables which you can tweak. Obviously the outside dimensions of the enclosure can be changed in a flash, but it’s just as easy to modify the thickness of the aluminum sheet being used, or the size of the screw holes. [0xPIT] has also done a great job of documenting the code itself, so you’ll know exactly what you’re modifying.

Obviously, you’ll need the ability to cut and machine aluminum to actually utilize this project. The code itself is really just a way to conceptualize the design and get your dimensions figured out ahead of time. But as we were recently reminded by the keynote presentation [Jeremy Fielding] gave at the 2021 Remoticon, this sort of early prototyping can often save you a lot of headaches down the line.