A Wheatstone Bridge Matches Your Pots

December 7, 2022 by Jenny List 15 Comments

Sometimes the simplest hacks can be the most useful or ingenious, and such is the case with [Keri Szafir]’s method of ensuring that potentiometers used in audio devices are matched. If you consider a typical stereo amplifier for a moment, you’ll see two amplifiers in one box with a single volume control. Two channels, one knob? Volume knobs are ganged stereo potentiometers.

All potentiometers are not created equal, and particularly in the cheaper devices they may not have a consistently matched resistance across both pots and across their travel. This messes up the stereo balance, so naturally it’s worth selecting a part with good matching. [Keri] selects them not with his golden ears, but by wiring both pots together as a Wheatstone bridge. A meter between the two wipers would detect any current due to a mismatch.

A Wheatstone bridge is one of those handy circuits that has plenty of uses in both AC and DC measurements. We probably see them most often in a strain gauge.

Giving Vintage Synths New Life In A Potentiometer Cleaning Showdown

January 19, 2022 by Maya Posch 24 Comments

As anyone who has ever owned a piece of older equipment that has a potentiometer in it can attest to, these mechanical components do need their regular cleaning ritual. Whether it’s volume knobs on a receiver or faders on a mixer, over time they get crackly, scratchy and generally imprecise due to the oxidation and gunk that tends to gather inside them.

This is your potentiometer caked with gunk.

In this blast from the past, [Keith Murray] shows a few ways in which fader-style potentiometers can be cleaned, and how well each cleaning method works by testing the smoothness of the transition over time with an oscilloscope. It’s enlightening to see just how terrible the performance of a grimed-up fader is, and how little a blast of compressed air helped. Contact cleaner works much better, but it’s essential to get all of the loosened bits of gunk out of the fader regardless.

In the end, a soak in isopropyl alcohol (IPA), as well as a full disassembly followed by manual cleaning were the only ones to get the fader performance back to that of a new one. Using contact cleaner followed by blasting the fader out with compressed air seems to be an acceptable trade-off to avoid disassembly, however.

What is your preferred way to clean potentiometers to keep that vintage (audio) gear in peak condition? Let us know in the comments below.

Thanks, [Grant Freese], for the tip!

Xbox Controller Mod Gets Serious About Stick Drift

January 5, 2021 by Tom Nardi 47 Comments

Many a gamer has found that after a few years of racing around the track or sending demons back from whence they came, the analog sticks on their trusty controller can start to drift around. Many times it’s a fairly minor problem, something you might only notice if you were really keeping an eye out for it, but it can definitely be annoying. Those handy with a soldering iron might just swap out the sticks for replacements once it gets to that point, but [Taylor Burley] wondered how difficult it would be to recalibrate the ailing sticks instead.

To be clear, [Taylor] acknowledges this approach is overkill. It would be cheaper and easier to just replace the drifting stick with a new one. Even if you take into account that new sticks might not be as high quality as the originals and could give up the ghost faster, this probably isn’t worth the effort. But that doesn’t mean it’s not an interesting hack.

In the video after the break, [Taylor] starts by explaining how stick drift occurs in the first place. Each axis of the stick is physically connected to the wiper of a potentiometer, so for 10K pots, the stick’s center point should correspond to a resistance of 5K. He then goes on to measure the resistance in a bad joystick, and sure enough, the center resistance is off by several hundred Ohms.

To fix this, he comes up with a simple circuit that places additional potentiometers between the wipers. With two joysticks and two adjustment pots per axis, that makes eight little adjustment wheels that need to be fiddled with to get the center points calibrated properly. In this case [Taylor] uses a controller diagnostic tool for the Xbox to quantify the impact his adjustments are making so he can dial it in perfectly, but the idea is the same no matter who’s logo is on the box.

We’d say this is the most overkill attempt at addressing the issue of stick drift on gaming controllers we’ve ever seen, but that title has to go to [Matteo Pisani], who replaced the analog stick on his Switch Joy-Con with a custom circular touchpad.

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Cassette Synth Plays With Speed Control

December 7, 2020 by Kristina Panos 10 Comments

Tape may not sound that great compared to vinyl, but cassette players can be tons of fun when it comes to making your own music. See for instance the Mellotron, or this relatively easy DIY alternative, [Rich Bernett]’s Cassettone cassette player synth.

The Cassettone works by substituting the trim pot that controls the speed of the tape player’s motor with a handful of potentiometers. These are each activated with momentary buttons located underneath the wooden keys. In the video after the break, [Rich] gives a complete and detailed guide to building your own. There’s also a polished Google doc that includes a schematic and the pattern pieces for making the cabinet.

Speaking of which, isn’t the case design nice? It’s built out of craft plywood but aged with varnish and Mod-Podged bits and bobs from vintage electronics magazines. This really looks like a fun little instrument to play.

Would you rather control your tape synth with a MIDI keyboard? Just add Arduino.

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Mix It Up With A Multi-Volume Controller

November 6, 2020 by Kristina Panos 2 Comments

What’s the use of waiting around for something to break in order to hack into something else? As long as it’s just sitting around not being used, who cares? [OmniSaiRen] had a Behringer MIDI controller just taking up space. Instead of selling it, they decided to build it into something they would definitely use — a multi-volume controller with mute keys and other useful macros.

After gutting the case, [OmniSaiRen] gave it a couple coats of glossy white paint that looks really nice with the black keycaps and knobs. The plan was to use the original encoders, but [OmniSaiRen] replaced them with potentiometers when they couldn’t get the encoders working with the Arduino Nano. We are sad to report that Cherry Blues only made it to the build because they have all black housings and were also lying around taking up space, but maybe [OmniSaiRen] will grow to love them.

If you’re tired of all the mousing and clicking it takes to turn down this or that volume, you need to build one of these things. It runs on deej, an open source volume mixer that works with Linux and Windows, so what are you waiting for? If you only want a single hardware volume knob, you can’t go wrong dialing it in rotary style.

Via r/duino

Axe Hacks: Spinning Knobs And Flipping Switches

October 15, 2020 by Sven Gregori 15 Comments

From a guitar hacking point of view, the two major parts that are interesting to us are the pickups and the volume/tone control circuit that lets you adjust the sound while playing. Today, I’ll get into the latter part and take a close look at the components involved — potentiometers, switches, and a few other passive components — and show how they function, what alternative options we have, and how we can re-purpose them altogether.

In that sense, it’s time to heat up the soldering iron, get out the screwdriver, and take off that pick guard / open up that back cover and continue our quest for new electric guitar sounds. And if the thought of that sounds uncomfortable, skip the soldering iron and grab some alligator clips and a breadboard. It may not be the ideal environment, but it’ll work.

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DIY Ribbon Controller For A DIY Synth

May 3, 2020 by Kristina Panos 13 Comments

There’s kind of a special joy in making instruments, no matter how simple or complex they are. Even if it’s a straight-up noisemaker, that’s noise you can be proud of. And besides, noise plus rhythm equals music.

Whenever you’re ready to have some next-level fun, try making controllers for your DIY instruments. Synthesizers of all stripes are often controlled with various types of potentiometers. While it would definitely be an interesting exercise to make your own standard twist-style potentiometer, [lonesoulsurfer] shows that making a ribbon controller is relatively easy.

A ribbon controller is essentially a deconstructed potentiometer that uses your finger to actuate the wiper. Here the wiper is made from Velostat, a fun, low-cost conductive material that’s also pressure-sensitive. The rest of the ribbon controller is a sandwich of thin copper plates and non-conductive plastic mounted on a wood base.

But what’s a fun controller without a fun instrument to control? As a special bonus, [lonesoulsurfer] made a little square wave-squirting synth based on the 4046 hex inverter and included the schematic for it. Slide your finger past the break to check ’em both out.

Depending on what you have lying around, it may be easier to make analog instruments like this rubber band boinger or its country cousin, the wheelbarrow bass.

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