Pimp My Pot Redux, Now Cheaper And Even Better

If there’s one thing we like around here more than seeing an improved version of a project we’ve already covered, it’s when the improvements make the original project cheaper. In the case of this LED ring light for pots and encoders, not only is it cheaper than its predecessors, it’s better looking and easier to integrate into your projects.

Right from its start, [upir]’s “Pimp My Pot” project has been all about bringing some zazzle to rotary controls. Knobs with a pointer and a scale on the panel are okay — especially when they go to eleven — but more lights mean more fun. The fun comes at a price, though; the previous version of “PMP” used an off-the-shelf LED ring light with a unit cost of about $10. Not the end of the world, perhaps, but prohibitive, and besides, where’s the fun in just buying a component specifically made for rotary control indication?

The new version shown in the video below is pin-compatible with the driver board [upir] used for the previous version, which is based on the MAX7219 display driver. Modifying the previous board to accommodate 32 white 0402 LEDs over a 270° arc was no mean feat. [upir] covers both creating the schematic and the PCB layout in some detail, providing his usual trove of tool-chain tips for minimizing the amount of manual work needed.

Wisely, [upir] chose to get his boards assembled by the vendor; getting all those LEDs to line up perfectly is a job best left to the robots. While the board is designed for use with pots that mount on either side, we much prefer mounting the pot’s shaft through the board, as it keeps the LEDs closer to the knob. The final price per board works out to about $6.30 in quantities of ten and falls to a trivial $1.70 each for lots of 1,000. Pretty sweet savings on a pretty sweet-looking build.

This is a cool use of a ring of LEDs, but if you prefer the finger kind, you can make that, too. You can do it the easy way or the hard way.

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Roll Your Own Servo

Usually, when you want a servo motor, you simply buy one already made. But if you need something unusual, you can turn any DC motor into a custom servo you can control just like [Dejan] did. You can watch a video of the process below.

The custom servo can tune the endpoints, the center point, and the sensitivity. It also can be set to handle continuous rotation. A 12-bit encoder tells the microcontroller where the motor is and the output drivers can handle over 3 A of motor current. The microprocessor is a tried-and-true ATmega328. [Dejan] wanted to make the board as small as possible, and we think 40 mm square isn’t bad at all. There is also a 3D printed gearbox and housing. Overall, a very well-done project.

The motor control uses a PID algorithm. Potentiometers set the end range and sensitivity. A push button allows resetting the center position. DIP switches control the mode. The video shows a computer and an RC controller setting the position of the motors.

We have, of course, seen many variations on this idea. We’ve also seen servos rebuilt for better performance.

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Kino Wheels Gives You A Hand Learning Camera Operation

Have you ever watched a movie or a video and really noticed the quality of the camera work? If you have, chances are the camera operator wasn’t very skilled, since the whole point of the job is to not be noticed. And getting to that point requires a lot of practice, especially since the handwheel controls for professional cameras can be a little tricky to master.

Getting the hang of camera controls is the idea behind [Cadrage]’s Kino Wheels open-source handwheels. The business end of Kino Wheels is a pair of DIN 950 140mm spoked handwheels — because of course there’s a DIN standard for handwheels. The handwheels are supported by sturdy pillow block bearings and attached to 600 pulse/rev rotary encoders, which are read by an Arduino Mega 2560. The handwheels are mounted orthogonal to each other in a suitable enclosure; the Pelican-style case shown in the build instructions seems like a perfect choice, but it really could be just about anything.

To use Kino Wheels, [Cadrage] offers a free camera simulator for Windows. Connected over USB, the wheels control the pan and tilt axes of a simulated camera in an animated scene. The operator-in-training uses the wheels to keep the scene composed properly while following the action. A little bit of the simulation is shown in the brief video below, along with some of the build details.

While getting camera practice is the point of the project, that’s not to say Kino Wheels couldn’t be retasked. With a little work, these could be used to actually control at least a couple of axes of a motion control rig, or maybe even to play Quake.

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Not A Pot, Not An Encoder: Exploring Synchros For Rotational Sensing

We’re all familiar with getting feedback from a rotating shaft, for which we usually employ a potentiometer or encoder. But there’s another device that, while less well-known, has some advantages that just might make it worth figuring out how to include it in hobbyist projects: the synchro.

If you’ve never heard of a synchro, don’t feel bad; as [Glen Akins] explains, it’s an expensive bit of kit most commonly found in avionics gear. It’s in effect a set of coaxial transformers with a three-phase stator coil and a single-phase rotor. When excited by an AC reference voltage, the voltage induced on the rotor coil is proportional to the cosine of the angle between the rotor and stator. It seems simple enough, but the reality is that synchros present some interfacing challenges.

[Glen] chose a surplus altitude alert indicator for his experiments, a formidable-looking piece of avionics. Also formidable was the bench full of electronics needed to drive and decode the synchro inside it — a 26-volt 400-Hz AC reference voltage generator, an industrial data acquisition module to digitize the synchro output, and an ESP32 dev board with a little OLED display to show the results. And those are impressive; as seen in the video below, the whole setup is capable of detecting tenth-of-a-degree differences in rotation.

The blog post has a wealth of detail on using synchros, as does this Retrotechtacular piece from our own [Al Williams]. Are they practical for general hobbyist use? Probably not, but it’s still cool to see them put to use.

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Make Your Own Pot And Encoder Knobs, Without Reinventing Them

Rotary potentiometers, switches, and encoders all share a basic design: adjustment is done via a shaft onto which a knob is attached, and knobs are sold separately. That doesn’t mean one knob fits all; there are actually a few different standards. But just because knobs are inexpensive and easily obtained doesn’t mean it’s not worth making your own.

A simple and effective indicator can be easily printed in a contrasting color.

Why bother 3D printing your own knobs instead of buying them? For one thing, making them means one can rest assured that every knob matches aesthetically. The ability to add custom or nonstandard markings are another bonus. Finally, there’s no need to re-invent the wheel, because [Tommy]’s guide to making your own knobs has it all figured out, with the OpenSCAD script to match.

By default, [Tommy]’s script will generate a knob with three shims (for interfacing to a splined shaft) when pot_knob(); is called. The number of shims can be adjusted by modifying potKnobDefaultShimCount. To give the knob a flat side (to interface with D-shafts), change flatted = false to flatted = true. And for adding a screw insert suitable for a set screw? Change tightenerDiameter = 0 from zero to the diameter desired.

The script is quite comprehensive and has sensible defaults, but it does require a bit of knowledge about OpenSCAD itself to use effectively. We have covered the basics of OpenSCAD in the past, and if you’re ready for a resource that will help you truly master it, here’s where to look.

Odd Inputs And Peculiar Peripherals: RoenDi Smart Knob Thinks Outside The Box

When it comes to design decisions, we’re often advised to “think outside the box.” It’s generally good advice, if a bit abstract — it could really mean anything. But it appears that someone took it quite literally with this nifty little smart knob display and input device.

[Dimitar]’s inspiration for RoenDi — for “rotary encoder and display” — came from an unusual source: a car dashboard, and specifically, the multipurpose knobs that often crop up in a car’s climate control cluster. Designed for ease of use while driving while causing as little distraction as possible, such knobs often combine a rotary encoder with one or more indicators or buttons. RoenDi builds on that theme by putting a 1.7″ round LCD display in the middle of a ring attached to an Alps rotary encoder, allowing the knob to be customized for whatever you want it to represent. The backplane sports a powerful STM32 microcontroller with a lot of the GPIO pins broken out, so customization and interfacing are limited only by your imagination. The design is open source, so you can either build your own or support the project via Crowd Supply.

Unlike the haptic smart knob we’ve been seeing a bit about lately, which also features a round LCD at its center, RoenDi’s feedback is via the physical detents on the encoder. We think both devices are great, and they fill different niches in the novel input ecosystem.

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Abacus Synthesizer Really Adds Up

The abacus has been around since antiquity, and takes similar forms over the hundreds of cultures that have embraced it. It may be one of the first devices to be considered as having a “user interface” in the modern context — at least for simple arithmetic calculations. But using an abacus as the UI for a music synthesizer seems like something entirely new.

Part art concept project and part musical instrument, the “Abacusynth” by [Elias Jarzombek] is a way to bring a more visual and tactile experience to controlling a synth, as opposed to the usual knobs and switches. The control portion of the synth consists of four horizontal rods spanning two plywood uprights. Each rod corresponds to a voice of the polyphonic synth, and holds a lozenge-shaped spinner mounted on a low-friction bearing. Each spinner can be moved left and right on its rod, which controls the presence of that voice; spinning the slotted knob controls the modulation of the channel via photosensors in the uprights. Each rod has a knob on one side that activates an encoder to control each voice’s waveform and its harmonics.

In use, the synthesizer is a nice blend of electronic music and kinetic sculpture. The knobs seem to spin forever, so Abacusynth combines a little of the fidget spinner experience with the exploration of new sounds from the built-in speaker. The synth also has a MIDI interface, so it works and plays well with other instruments. The video below shows the hardware version of Abacusynth in action; there’s also a web-based emulation to try before you build.

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