A 3D Printed, Open Source Lathe?

October 23, 2024 by Dave Rowntree 10 Comments

[Chris Borge] has spent the last few years creating some interesting 3D printed tools and recently has updated their 3D printable lathe design to make a few improvements. The idea was to 3D print the outer casing of the lathe in two parts, adding structural parts where needed to bolt on motors and tool holders, and then fill the whole thing with concrete for strength and rigidity.

The printed base is initially held together with two lengths of studding, and a pile of bolts are passed through from below, mating with t-nuts on the top. 2020 extrusion is used for the motor mount. The headstock is held on with four thread rods inserted into coupling nuts in the base. The headstock unit is assembled separately, but similarly; 3D printed outer shell and long lengths of studding and bolts to hold it together. Decent-sized tapered roller bearings make an appearance, as some areas of a machine tool really cannot be skrimped. [Chris] explains that the headstock is separate because this part is most likely to fail, so it is removable, allowing it to be replaced.

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Tridora: A Full-Custom CPU Designed For Pascal

October 23, 2024 by Dave Rowntree 10 Comments

[Sebastian Lederer] has created Tridora: an unusual stack-based CPU core intended for FPGA deployment, co-developed with its own Pascal compiler. The 32-bit word machine is unusual in that it has not one but three stacks, 16-bit instruction words, and a limited ISA, more like those of the 8-bit world. No multiply or divide instructions will be found in this CPU.

The design consists of about 500 lines of Verilog targeting the Digilent Arty-A7 FPGA board, which is based around the Xilinx Artix-7 FPGA line. [Sebastian] plans to support the Nexys A7 board, which boasts a larger FPGA array but has less RAM onboard. The CPU clocks in at 83 MHz with four clock cycles per instruction, so over 20 MIPS, which is not so shabby for a homebrew design. Wrapped around that core are a few simple peripherals, such as the all-important UART, an SD card controller and a VGA display driver. On the software side, the Pascal implementation is created from scratch with quite a few restrictions, but it can compile itself, so that’s a milestone achieved. [Sebastian] also says there is a rudimentary operating system, but at the moment, it’s a little more than a loader that’s bundled with the program image.

The Tridora Gitlab project hosts the Verilog source, an emulator (written in Golang, not Pascal) and a suite of example applications. We see quite a few custom CPUs, often using older or less popular programming languages. Here’s an FPGA-based Forth machine to get you started. Implementing programming languages from scratch is also a surprisingly common hack. Check out this from-scratch compiler for the Pretty Laughable Programming language.

Zero To Custom MacroPad In 37 Easy Steps

October 21, 2024 by Dave Rowntree 5 Comments

[Jeremy Weatherford] clearly has a knack for explaining projects well enough for easy reproduction but goes way further than most and has created a four-part YouTube series detailing every step from project inception to the final assembly, covering all aspects of 3D modelling and PCB design for a custom MacroPad design. Many tools are introduced along the way, all of which help reduce complexity and, by extension, the scope for errors. As every beginner hacker knows, early successes breed confidence and make for better and more ambitious projects.

Part 1 covers the project motivation and scope and introduces a keyboard layout editor tool. This tool allows one to take a layout idea and generate a JSON file, which is then used to drive keyboard tools. XYZ to produce a usable KiCAD project. The tool only generates a PCB project and an associated netlist file. No schematic is created; you don’t need one for a simple layout.

Part 2 is a walkthrough of the design process in KiCAD, culminating in ordering the PCB from JLCPCB and assembling the surface-mount parts. This particular design uses a controller based on the Sea-Picro RP2040 module, but there are many options if you have other preferences. [Jeremy] shows what’s possible with the selected suppliers, but you need not follow this step precisely if you have other ideas or want to use someone local.

Part 3 covers exporting the mechanical aspects of the PCB out of KiCAD and into a 3D CAD program, specifically OnShape. [Jeremy] covers some crucial details, such as how to read the mechanical drawing of the keys to work out where to place the top plate. It’s very easy to plough straight in at this stage and make a design which cannot be assembled! The plan is to use a simple laser-cut box with a bottom plate with mounting holes lining up with those on the PCB. A Top plate is created by taking the outline of the PCB and adding a little margin. An array of rectangular cutouts are designed for the keys to protrude, lining up perfectly with where the keys would be when mounted on the PCB below. The sides of the case are formed from laser-cut sections that lock into each other and the laser-cut base—using the laser joint feature-script addon tool from the OnShape community channel. A second feature script addon is used to auto-layout the laser-cut components onto a single sheet. A CAM application called Kiri Moto is used to export for laser cutting and is available on the OnShape store.

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The FNIRSI HRM-10 Internal Resistance Meter

October 17, 2024 by Dave Rowntree 13 Comments

Occasionally, we find fun new electronic instruments in the wild and can’t resist sharing them with our readers. The item in question is the FNIRSI HRM-10 Internal resistance meter, which we show here being reviewed by [JohnAudioTech].

So what does it do, and why would you want one? The device is designed to measure batteries so you can quickly determine their health. Its operating principle also allows it to do a decent job of measuring low-resistance parts, which is not necessarily as easy to achieve with the garden variety multimeter, especially the low-end ones. We reckon it would be useful in the field for checking the resistance of switches and relays, possibly in automotive or industrial applications. The four-pin connector is needed because there are two wires per probe, making a Kelvin (also known as four-wire) connection.

Likely, the operating principle is to apply a varying load to the battery under test and then measure the voltage drop. The slope of the voltage sag vs load is a reasonable estimate of the resistance of the source, at least for the applied voltage range. The Kelvin connection uses one pair of wires to apply the test current from a relatively low-impedance source and the second pair to measure the voltage with a high input impedance. That way, the resistance of the probe wires can be calibrated out, giving a much more accurate measurement. Many lab-grade measurement equipment works this way.

Circling back to the HRM-10, [John] notes that it also supports limit testing, making it a helpful gauging tool for the workbench when sorting through many batteries. Data logging and the ability to upload to a computer completes the feature set, which is quite typical for this level of product now. Gone are the days of keeping a manual logbook next to the instrument stack and writing everything down by hand!

We’ve touched on measuring battery internal resistance before, but it was a while ago. Regarding Kelvin connections, here’s a quick guide and a hack upgrading a cheap LCR to support 4-wire probes.

Continue reading “The FNIRSI HRM-10 Internal Resistance Meter” →

DIY Core Rope Memory Z80 Demonstrator Generating A Fibonacci Sequence

October 16, 2024 by Dave Rowntree 14 Comments

We’ve seen a few retro products using core rope memory, such as telephone autodiallers. Obviously, we’ve covered the Apollo program computers, but we don’t think we’ve seen a complete and functional DIY computer using core rope memory for program storage until now. [P-lab] presents their take on the technology using it to store the program for a Z80-based microprocessor demoboard, built entirely through-hole on a large chunk of veroboard.

For the uninitiated, core rope memory is a simple form of ROM where each core represents a bit in the data word. Each wire represents a single program location. Passing a wire through the core sets the corresponding bit to a logic 1, else 0. These wires are excited with an AC waveform, which is coupled to the cores that host a wire, passing along the signal to a pickup coil. This forms an array of rudimentary transformers. All that is needed is a rectifier/detector to create a stable logic signal to feed onto the data bus.

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Solve: An ESP32-Based Equation Solving Calculator

October 15, 2024 by Dave Rowntree 10 Comments

We’re suckers for good-looking old-school calculators, so this interesting numerical equation-solving calculator by [Peter Balch] caught our attention. Based around the ESP32-WROOM-32 module and an LCD, the build is quite straightforward from an electronics point of view, with the main work being on the software side of things.

A custom keyboard was constructed on Veroboard using a handful of tactile switches arranged in a charlieplexing array to minimize the number of IO pins consumed. For the display, an off-the-shelf 240×320 ILI9341-based module hooked up by SPI was used. A single lithium cell was used for the power supply, connected to a USB

You don’t need much to make a usable keyboard.

charger module, but you could just as easily substitute a 3 x AA battery box. The case was designed in DesignSpark mechanical and 3D printed. It’s unclear what keyboard version they settled on; there are options for one with keycaps and one without. Regardless, a 3D-printed frame sits atop the keyboard circuit, with the graphics printed on photo paper and a protective coversheet on top. Continue reading “Solve: An ESP32-Based Equation Solving Calculator” →

Your Battery Holder Is Also Your Power Switch With ToggleSlot

October 15, 2024 by Dave Rowntree 23 Comments

We really like PCB-level hacks, especially ones that show ingenuity in solving a real problem while being super cheap to implement. Hackaday.IO user [Steph] wanted a cheap way to switch a wearable on and off without having to keep popping out the battery, so they came up with a tweaked battery footprint, which is also a simple slide switch.

Most people making badges and wearables will follow the same well-trodden path of just yanking out the cell or placing some cheap switch down and swallowing the additional cost. For [Steph], the solution was obvious. By taking a standard surface-mount CR2032 button cell holder footprint, extending its courtyard vertically, and moving the negative pad up a smidge, the battery can be simply slid up to engage the pad and slid down to disengage and shut off the juice. The spring section of the positive terminal keeps enough pressure on the battery to prevent it from sliding out, but if you are worried, you can always add a dummy pad at the bottom, as well as a little solder bump to add a bit more security.

Now, why didn’t we think of this before? The KiCad footprint file can be downloaded from the project GitHub page, imported into your project and used straight away.

Many of our gadgets are powered by CR2032 cells—so many so that eliminating the need for them leads to interesting projects, like this sweet USB-powered CR2032 eliminator. But how far can you push the humble cell? Well, we held a contest a few years ago to find out!