Spoofing An Analog Rotary Knob With An ATtiny, And Vampiric Power

July 14, 2020 by Donald Papp 22 Comments

[Mitxela]’s repair of a Roland JV-1080 (a rack-mounted 90s-era synthesizer) sounds simple: replace a broken rotary encoder on the front panel. It turned out to be anything but simple, since the part in question is not today’s idea of a standard rotary encoder at all. The JV-1080 uses some kind of rotary pulse switch, which has three outputs (one for each direction, and one for pushing the knob in like a button.) Turn the knob in one direction, and one of the output wires is briefly shorted to ground with every detent. Turn it the other way, and the same happens on the other output wire. This is the part that needed a replacement.

The finished unit uses a modern rotary encoder and microcontroller in place of the original part, and implements a few tricks to power it.

Rather than track down a source for the broken part, [Mitxela] opted to replace it with a modern rotary encoder combined with an ATtiny85 microcontroller to make it act like something the JV-1080 understands and expects. There was an additional wrinkle, however. The original rotary pulse switch is an entirely passive device, and lives at the end of a four-conductor cable with no power provided on it. How could the ATtiny85 be powered without resorting to running a wire to a DC voltage supply somewhere? Success was had, but it did take some finessing.

For the power, it turns out that the signal wires are weakly pulled up to +5 V and [Mitxela] used that for a power supply to the microcontroller. Still, by itself that wasn’t enough, because the ATtiny85 can easily consume more current than the weak pullups can source. We really recommend reading all the details in [Mitxela]’s writeup, but the short version is that the ATtiny85 does two things.

First, it minimizes its power usage by spending most of its time in sleep mode (consuming barely any power at all) and uses an interrupt to wake up just long enough to handle knob activity. Second, the trickle of power from the weak pullups doesn’t feed the ATtiny directly. It charges a 100 uF capacitor through a diode, and that is what keeps the microcontroller from browning out during its brief spurts of activity. Even better, after browsing the datasheet for the ATtiny, [Mitxela] saw it was possible to use the built-in ESD protection diodes for this purpose instead of adding a separate component.

It’s a neat trick and makes for a very compact package. Visit the project’s GitHub repository to dive into the nitty gritty. In the end, a single assembly at the end of a 4-wire connector acts just like the original passive component, no extra wires or hardware modifications needed.

When opening older hardware it’s never quite certain what will be found on the inside. But at least [Mitxela]’s repair duties on this synth didn’t end up with him tripping out on LSD.

Multi-Volume Knob Gives All Your Programs A Turn

July 6, 2020 by Kristina Panos 19 Comments

We’ve all been there. You’re manning the battle station, deep in the sim-racing or some other n00b-pwning zone and suddenly some loudmouth blows out your eardrums over Discord. It’s insulting to have to stop what you’re doing to find the right Windows volume slider. So why do that? Build [T3knomanzer]’s simple yet elegant multi-volume knob and stay zen in the zone.

It’s easy, just turn the knob to cycle through your programs until Discord comes up on the little screen, and then push down to change it into a volume knob. If you need to change another volume, just click it again. Since there’s no Alt+Tabbing out to the desktop, no checkered flags should ever slip through your fingers.

Inside the well-designed case you’ll find the usual suspects — Arduino Nano, rotary encoder, an OLED display, and an LED ring, each with their own place carved out.

This completely open-source knob looks great, and we love that it’s been made incredibly easy to replicate by standing up a site with foolproof, well-depicted, step-by-step instructions. Watch them take it for a spin after the break.

Want more than volume at your fingertips? Here’s a DIY USB knob that does shortcuts, too.

Continue reading “Multi-Volume Knob Gives All Your Programs A Turn” →

Software Shortcut Keyboard Registers Many Macros

April 16, 2020 by Kristina Panos 18 Comments

[FabroLabs Technologies] is an industrial designer who uses several creative-type software programs in a given day. Unfortunately, they all have slightly different shortcut schemes, and trying to remember all the different modifiers is a waste of time better spent elsewhere.

This lovely little macro keyboard is every bit as useful as it is cool looking. Spinning the rotary encoder cycles through a menu of programs on the 16×2 LCD, and the key map just updates automatically for the chosen program. At the heart of this build is an Arduino Pro Micro and 20 of the loudest key switches ever made — Cherry MX blues. We like that it manages to look like toy cash register and a serious peripheral all at once — it probably has something to do with those way-cool circular keycaps that were made on a resin printer.

We’re glad that [FabroLabs] laid down such a comprehensive and open build guide during the process of making this macro keyboard. The average hacker can learn a lot from industrial designers who show their work. Remember the time [Eric Strebel] showed us all how to improve our foam board design game?

From The MacGyver Files: Using A Stepper Motor As An Encoder

April 8, 2020 by Al Williams 27 Comments

It isn’t hard to imagine a scenario where you are stuck at home all day with nothing to do and certain items are in short supply. Sure, bathroom tissue gets all the press, but try buying some flour or a freezer and see how far you get. Plus online shopping has given up on next day delivery for the duration. Not hard to imagine at all. Now suppose your latest self-quarantine project needs a rotary shaft encoder. Not having one, what do you do? If you are [Tech Build] you go all MacGyver on an old printer and pull out a stepper motor.

How does a stepper motor turn into an encoder? Well, that’s the MacGyver part. We are not big fans of the physical circuit diagrams, but it looks like [Tech Build] borrowed (with credit) from an earlier post and that one has a proper schematic.

Continue reading “From The MacGyver Files: Using A Stepper Motor As An Encoder” →

Baby Keyboard Is Really Three Boards

March 19, 2020 by Kristina Panos No comments

Just when we think we’ve peeped all the cool baby keebs out there, another think comes along. This bad boy built by [andyclymer] can be configured three different ways, depending on what kind of control you’re after.

As designed, the PCB can be used as a six-switch macro keyboard, or a rotary encoder with two switches, or a pair of rotary encoders. It’s meant to be controlled with Trinket M0, which means it can be programmed with Arduino or CircuitPython.

This could really only be cooler if the key switch PCB holes had sockets for hot-swapping the switches, because then you could use this thing as a functional switch tester. But hey, you can always add those yourself.

If you’re in the market for purpose-built add-on input device, but either don’t have the purpose nailed down just yet, or aren’t sure you want to design the thing yourself, this board would be a great place to start. Usually, all it takes is using someone else’s design to get used to using such a thing, at which point it’s natural to start thinking of ways to customize it. [andyclymer] is selling these boards over on Tindie, or you can roll your own from the repo.

Need just a few more inputs? We’ve got you covered.

Sort The Rainbow With An Algorithm Machine

February 9, 2020 by Kristina Panos 12 Comments

When you’re trying to learn how an algorithm works, it’s not always easy to visualize what’s going on. Well, except for maybe binary sort, thanks to the phone book. Professor [thatguyer] is a computer science teacher who wanted a way to help his students visualize the process of algorithms and at the same time, get a grasp on their resource cost.

The Algorithm Machine can demonstrate 8 different search and sort algorithms using two 100-count strips of RGB LEDs — one to represent an array of integers, and one to create indicators pointing to the integers under scrutiny.

This functional beauty is totally interactive, too. Once the user chooses the values and the algorithm and starts the process, they can speed it up or slow it down with the rotary encoder, or pause to discuss and start again with that slick triangular play button. We particularly like the control button wiring harness [thatguyer] created to keep everything neat and hot-swappable.

This iteration uses 3D printed face plates to give the LEDs shape, but in an early version, [thatguyer] cut and sanded a ton of circles out of brass tubing, and folded as many triangles cut from disposable baking pans. The world could use more teachers as committed as [thatguyer]. This really seems like a handy teaching aid for these concepts, and we wish we’d had one in class to play around with. Here’s your algorithm for watching the demo: click break, press play, enjoy.

If you’re still confused, there are other ways to understand algorithms through visualization. Failing all that, just watch these Hungarian folk dancers work out various algo-rhythms.

Continue reading “Sort The Rainbow With An Algorithm Machine” →

Micro Macro Keyboard Makes A Major Difference

February 5, 2020 by Kristina Panos 10 Comments

Media keyboards are nice in theory. But in practice they never have all the keys you want, and they almost always have a few you don’t. Sure, you could maybe reassign the ones you don’t use, but then the caps are wrong, and it’s a whole thing. So really, the only winning move is to make a micro macro keyboard as [littleSilvr] did to make all your shortcuts one-button accessible.

This lovely input has an Arduino Pro Micro for a brain, and Gateron browns for brawn. That knob there is a rotary encoder, not a potentiometer, because endless volume knob twiddling is just so much nicer. In case you’re wondering, those shortcuts open Fusion 360 and Cura, but we’re still not sure what the hyphen does.

Can we talk about those keycaps, though? [littleSilvr] used [Make Anything]’s process of of printing in multi-color with a single extruder. The technique involves building a vector for each color, each of which gets its own STL file. Then you add retraction as you go up through the layers, slow the print speed, change filament colors while the nozzle and bed are still warm, and voila, a vibrant canvas of colors.

If you don’t have a printer and you don’t mind a bit of compromise on the number of inputs, try basing your build on an existing input, like an old rotary telephone dialer.

Via r/duino