Wherein The Mechanical Keyboard Community Discovers Motorized Linear Potentiometers

April 26, 2017 by Brian Benchoff 79 Comments

Deep in the bowels of the Digikey and Mouser databases, you’ll find the coolest component ever. Motorized linear potentiometers are a rare, exotic, and just plain neat input device most commonly found on gigantic audio mixing boards and other equipment that costs as much as a car. They’re slider potentiometers with a trick up their sleeve: there’s a motor inside that can set the slider to any position.

The mechanical keyboard community has been pushing the boundaries of input devices for the last few years, and it looks like they just discovered motorized linear pots. [Jack] created a motorized sliding keycap for his keyboard. It’s like a scroll wheel, but for a keyboard. It’s beautiful, functional, and awesome.

The hardware for this build is just about what you would expect. A 60 mm motorized linear pot for the side-mount, or 100 mm mounted to the top of the keyboard, is controlled by an Arduino clone and a small motor driver. That’s just the hardware; the real trick here is the software. So far, [Jack] has implemented a plugin system, configuration software, and force feedback. Now, messing with the timeline in any Adobe product is easy and intuitive. This device also has a ‘not quite vibration’ mode for whenever [Jack] gets a notification on his desktop.

Right now, [Jack] is running a group buy for this in a reddit thread, with the cost somewhere between $55 and $75, depending on how many people want one. This is a really awesome product, and we can’t wait for Corsair to come out with a version sporting innumerable RGB LEDs. Until then, we’ll just have to drool over the video [Jack] posted below.

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Hackaday Prize Entry: [Nardax] Shoots Fireballs

March 31, 2017 by Elliot Williams 3 Comments

If you’re looking for a high entertainment value per byte of code, [Nardax] has you covered with his wearable spellcasting controller. With not much effort, he has built a very fun looking device, proving what we’ve always known: a little interaction can go a long way.

[Nardax] originally intended his glorified elbow-mount potentiometer to be a fireworks controller. Ironically, he’s now using it to throw virtual fireballs instead. Depending on the angle at which he holds his elbow before releasing it, he can cast different spells in the game World of Warcraft. We’re not at all sure that it helps his gameplay, but we’re absolutely sure that it’s more fun that simply mashing different keys.

There’s a lot of room for expansion here, but the question is how far you push it. Sometimes the simplest ideas are the best. It looks like [Nardax] is enjoying his product-testing research, though, so we’ll keep our eyes out for the next iterations of this project.

We’ve seen a number of high-tech competitors to the good old power glove, and although some are a lot more sophisticated than a potentiometer strapped to the elbow, this project made us smile. Sometimes, it’s not just how much tech you’ve got, but how you use it. After all, a DDS pad is just a collection of switches under a rug.

Old Motor Donates Rotor For Coaxial Wind Vane And Anemometer

January 12, 2017 by Dan Maloney 9 Comments

Problem: build a combined anemometer and wind vane where the pivots for both sensors are coaxial. Solution: turn an old universal motor into a step-wise potentiometer for the wind vane, and then pull a few tricks to get the whole thing assembled.

We have to admit that when we first saw [Ajoy Raman]’s Instructables post, we figured that he used a universal motor to generate a voltage from the anemometer. But [Ajoy]’s solution to the coaxial shafts problem is far more interesting than that. A discarded universal motor donated its rotor and bearings. The windings were stripped off the assembly leaving nothing but the commutator. 1kΩ SMD resistors were soldered across adjacent commutator sections to form a series resistance of 22kΩ with taps every 1k, allowing 0 to 2.2V to be read to the ADC of a microcontroller depending on the angle of the vane.

As clever as that is, [Ajoy] still had to pull off the coaxial part, which he did by drilling out the old motor shaft from one end to the other using just a drill press. The anemometer shaft passes through the hole in the shaft and turns a small DC motor to sense wind speed.

There might have been other ways to accomplish this, but given the constraints and the low cost of this solution, our hats are off to [Ajoy]. We’re a little concerned with that motor used for the anemometer, though. It could result in drag when used as a generator. Maybe a better solution would be a Hall-effect sensor to count rotations of a hard drive rotor.

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A Ten Turn Pot, For Not A Lot

January 3, 2017 by Jenny List 39 Comments

If you have a traditional regulated power supply that you want to make adjustable, you’ll have somewhere in the circuit a feedback line driven by a potential divider across the output. That divider will probably incorporate a variable resistor, which you’ll adjust to select your desired voltage.

The problem with using a standard pot to adjust something like a power supply is that a large voltage range is spread across a relatively small angle. The tiniest movement of the shaft results in too large a voltage change for real fine-tuning, so clearly a better means of adjustment is called for. And in many cases that need is satisfied with a ten-turn potentiometer, simply a pot with a 10 to 1 reduction drive built-in.

[Dardo] had just this problem, and since 10-turn pots are expensive to buy and expensive to ship to his part of the world he built his own instead of buying one.

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Crossing Wheatstone Bridges

November 8, 2016 by Steven Dufresne 18 Comments

The Wheatstone bridge is a way of measuring resistance with great accuracy and despite having been invented over 150 years ago, it still finds plenty of use today. Even searching for it on Hackaday brings up its use in a number of hacks. It’s a fundamental experimental device, and you should know about it.

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Resistance In Motion: What You Should Know About Variable Resistors

September 16, 2016 by Steven Dufresne 42 Comments

Adjusting the volume dial on a sound system, sensing your finger position on a touch screen, and knowing when someone’s in the car are just a few examples of where you encounter variable resistors in everyday life. The ability to change resistance means the ability to interact, and that’s why variable resistance devices are found in so many things.

The principles are the same, but there are so many ways to split a volt. Let’s take a look at what goes into rotary pots, rheostats, membrane potentiometers, resistive touchscreens, force sensitive resistors, as well as flex and stretch sensors.

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Joysix, Six Degree Of Freedom Mouse Made From Retractable Key Rings

February 2, 2016 by Gerrit Coetzee 24 Comments

[Nicolas Berger] submits his six degree of freedom mouse project. He hopes to do things like control a robot arm or fly an alien mothership.

We thought the construction was really neat; suspending a wooden ball in the middle of three retractable key rings. By moving the ball around you can control the motion of a cube displayed on the computer. We first thought this was done by encoders or potentiometers measuring the amount of string coming out of the key fobs. However, what’s actually happening is a little bit cleverer.

[Nicolas] has joined each string with its own 2 axis joystick from Adafruit. He had some issues with these at first because the potentiometers in the joysticks weren’t linear, but he replaced them with a different module and got the expected output. He takes the angle values from each string, and a Python program numerically translates the output from the mouse into something the computer likes. The code is available on his GitHub. A video of the completed mouse is after the break.

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