Re-imagining The Resistor Color Code Cheat Sheet

May 7, 2022 by Donald Papp 108 Comments

Some people look at a venerable resource like resistor color code charts and see something tried and true, but to [Andrew Jeddeloh], there’s room for improvement. A search for a more intuitive way is what led to his alternate cheat sheet for resistor color codes.

Color code references typically have a reader think of a 560 kΩ resistor as 56 * 10 kΩ, but to [Andrew], that’s not as simple as it could be. He suggests that it makes more sense for a user to start with looking up the colors to make 5.6 (green-blue), then simply look up that a following yellow band means resistance in the 100 kΩ range (assuming a four-band resistor); therefore 560 kΩ is green-blue-yellow.

The big difference is that the user is asked to approach 560 kΩ not as 56 * 10 kΩ, but as 5.6 * 100 kΩ. [Andrew] shares a prototype of a new kind of chart in his post, so if you have a few minutes, take it for a spin and see what you think.

Is his proposed method more intuitive, or less? We think [Andrew] makes a pretty good case, but you be the judge. After all, just because something has always been so doesn’t mean there isn’t room for improvement. This happens to apply nicely to resistors themselves, in fact. It may seem like through-hole resistors have always had color bands, but that is not the case.

IBM PCjr Types Again, Thanks To KeybJr

April 24, 2022 by Donald Papp 6 Comments

Most of us think of keyboards — even vintage ones — as being fairly standardized and interchangeable, but that isn’t the case for the IBM PCjr. Its keyboard was quite unlike most others of its time, which means that a PCjr without an original keyboard is pretty much a dust collector. That’s what led [Jozef Bogin] to create the KeybJr, a piece of hardware that allows one to use any AT, XT, or PS/2 keyboard with the IBM PCjr.

The PCjr’s oddball keyboard can be a bit of a hassle for vintage computing enthusiasts.

What was strange about the PCjr’s keyboard? From the outside it looked pretty normal, but it definitely had its own thing going on. For one, the PCjr keyboard operated over a completely different protocol than the other keyboards of the time. In addition, its connection to the host was either by IR, or via its own wired cable adapter.

The KeybJr solves this by using an Arduino-based board to turn inputs from other keyboards of the time into something the PCjr expects. These signals are sent out and received either over infrared, or by the PCjr’s “K” port for a wired keyboard link.

Why bother with the IR functionality? Well, the connector and pins on the PCjr are not very rugged, and sometimes they are damaged. In those cases, it is nice to have the option of using a normal (for the time) keyboard over the IR link. Vintage hardware is not always in perfect shape, after all. That’s why things like ATX power supply adapters for the PCjr exist.

Want to give it a shot? There is a GitHub repository for the KeybJr, and you can see it in action in a brief video, embedded below.

Continue reading “IBM PCjr Types Again, Thanks To KeybJr” →

DIY Laptop Stand: Why Stop At One When You Can Slot Three?

April 24, 2022 by Donald Papp 15 Comments

We make the tools we need, and that’s definitely the case with [Marco Schulte]’s laptop stand. It slots not one, not two, but three laptops at once.

For all their portability, multiple laptops can be a bit clunky to manage on a desk, so [Marco]’s solution definitely saves space while keeping things accessible. The laptop in the front can be open for use and easy access, while the two in the back are held vertically and can be attached to external monitors or other peripherals.

Not only does it save space, but the stand provides ample spots to anchor cable ties for securing the inevitable mess of wires and cables that dealing with three laptops brings. It makes for a tidier desk, that’s for sure.

The stand was designed in Fusion 360 and was cut from plywood with a CNC router. Does this design give you any ideas, or would you like to make one for yourself? The design files are here.

No access to a CNC router? No problem if you have glue and some spare boxes laying around! You might be surprised at how sturdy a few layers of cardboard and glue can be.

A Universal, Non-planar Slicer For 3D Printing Is Worth Thinking About

April 23, 2022 by Donald Papp 28 Comments

One may think that when it comes to 3D printing, slicing software is pretty much a solved problem. Take a 3D model, slice it into flat layers equal to layer height, and make a toolpath so the nozzle can create those layers one at a time. However, as 3D printing becomes more complex and capable, this “flat planar slicing” approach will eventually become a limitation because a series of flat slices won’t necessarily the best way to treat all objects (nor all materials or toolheads, for that matter.)

How a 20 mm cube looks when sliced in a cone-shaped plane.

[René K. Müller] works to re-imagine slicing itself, and shows off the results of slicing 3D models using non-planar geometries. There are loads of pictures of a 20 mm cube being sliced with a variety of different geometries, so be sure to give it a look. There’s a video embedded below the page break that covers the main points.

It’s all forward-thinking stuff, and [René] certainly makes some compelling points in favor of a need for universal slicing; a system capable of handling any geometry, with the freedom to process along any path or direction. This is a concept that raises other interesting questions, too. For example, when slicing a 20 mm cube with non-planar geometries, the resulting slices often look strange. What’s the best way to create a toolpath for such a slice? After all, some slicing geometries are clearly better for the object, but can’t be accommodated by normal hot ends (that’s where a rotating, tilted nozzle comes in.)

Such worries may not be an issue for most users at the moment, but it’s worth trying to get ahead of the curve on something like this. And lest anyone think that non-planar slicing has no practical purpose, we previously covered [René]’s demonstration of how non-planar slicing can reliably create 90° overhangs with no supports.

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SMT Part Counter Aims To Ease Taking Inventory

April 20, 2022 by Donald Papp 16 Comments

[Nick Poole] has an interesting idea for a new tool, one that has the simple goal of making accurate part counts of SMT reels as easy as pulling tape through a device. That device is the BeanCounter, an upcoming small handheld unit of his own design that counts parts as quickly as one can pull tape through a slot. The device is powered by a CR2032 cell and and works with 8 mm wide tapes up to 2 mm in height, which [Nick] says covers most 0805 or smaller sized parts, as well as things like SOT-23 transistors.

Why would one want to make such a task easier? Two compelling reasons for such a tool include: taking inventory of parts on partial reels or cut tape, and creating segments that contain a known number of parts.

The first is handy for obvious reasons, and the second is useful for things like creating kits. In fact, the usefulness of this tool for creating tape segments of fixed length is perhaps not obvious to anyone who hasn’t done it by hand. Sure, one can measure SMT tape with a ruler or a reference mark to yield a segment containing a fixed number of parts, but that involves a lot of handling and doesn’t scale up very well. In fact, the hassle of cutting tape segments accurately and repeatedly is a common pain point, so making the job easier has value.

If you looked at the photos and suspected that the big, 7-segment numeric display is done with clever PCB fabrication options (making segments by shining LEDs through PCB layers, a trick we always like to see) you’re not alone. After all, [Nick] has a lot of experience in getting clever with board fabrication, and eagle-eyed readers may even suspect that the reset and setup buttons on the edge of the tool are created by using flex PCB segments as switches. Want the nitty-gritty details? Visit the GitHub repository for the project and see it all for yourself at the CAD level.

Paper Tape Reader Self-calibrates, Speaks USB

April 16, 2022 by Donald Papp 22 Comments

Input devices consisting of optical readers for punched paper tape have been around since the earliest days of computing, so why stop now? [Jürgen]’s Paper Tape Reader project connects to any modern computer over USB, acting like a serial communications device. Thanks to the device’s automatic calibration, it works with a variety of paper materials. As for reading speed, it’s pretty much only limited to how fast one can pull tape through without damaging it.

Stacked 1.6 mm PCBs act as an enclosure, of sorts.

While [Jürgen]’s device uses LEDs and phototransistors to detect the presence or absence of punched holes, it doesn’t rely on hardware calibration. Instead, the device takes analog readings of each phototransistor, and uses software-adjusted thresholds to differentiate ones from zeros. This allows it to easily deal with a wide variety of tape types and colors, even working with translucent materials. Reading 500 characters per second isn’t a problem if the device has had a chance to calibrate.

Interested in making your own? The build section of the project has all the design files; it uses only through-hole components, and since the device is constructed from a stack of 1.6 mm thick PCBs, there’s no separate enclosure needed.

Paper tape and readers have a certain charm to them. Cyphercon 4.0 badges featured tape readers, and we’ve even seen the unusual approach of encoding an I²C byte stream directly onto tape.

This DIY UPDI Programmer Is Nice And Cheap

April 15, 2022 by Donald Papp 3 Comments

[Daumemo] likes experimenting with DIY electronics, and like many people, eventually ran across an AVR microcontroller with a Unified Program and Debug Interface (UPDI). One option is of course to purchase an UPDI programmer, but an even better solution was to make a DIY USB version from nice, cheap parts.

Programming an Attiny404 over the UPDI interface.

UPDI is an interface for external programming and on-chip debugging of microcontrollers, and [Daumemo]’s solution is based on the jtag2updi project. It combines an Arduino Nano (in this case, a clone) with a single resistor, a single capacitor, and a six pin angled header (with a cleverly bent pin) to enable programming UPDI devices over a USB connection. [Daumemo] is happy to report that the device works just fine in both Microchip Studio with AVRDUDE, or PlatformIO.

Is an Arduino Nano a bit overpowered in this role? Maybe, but the price is certainly right. There’s no need for a custom PCB either, since everything can be soldered direct to the Nano board. A matching 3D printed enclosure is about all that’s needed to make a robust and reliable DIY USB UPDI programmer out of a handful of parts, and that sounds good to us.

On the other hand, if you do find yourself making custom PCBs, you may be interested in another of [Daumemo]’s DIY projects: a printable structure to turn a rotary tool into a PCB drill press.