Rotary Controller Dials In PC Volume

As wonderful as mechanical keyboards are, most of the pre-fab and group buy models out there have zero media controls. If you want rotary encoders and OLED screens to show what function layer you’re working in, you’ll probably have to build your own keyboard from the ground up.

Hackaday alum [Cameron Coward] got around this problem by building an electromechanical buddy for his keyboard that works as a volume control. Now that we don’t rely on them to make phone calls, rotary dials are a fun throwback to a time that seems simpler based on its robust and rudimentary technology. This one is from a lovely burnt orange Bell Trimline phone, which was peak rotary dial and one of the idea’s last gasps before tone dialing took over completely.

Operationally speaking, [Cameron] is reading in the dial’s pulses with an Arduino Nano and using a Python script to monitor the serial connection and translate the pulses to volume control. We like that this is isn’t a volume knob in the traditional sense — it’s a game of percentages. Dialing ‘2’ gives 20% volume across all programs, and ‘8’ raises it to 80% of maximum. Need to mute? Just dial ‘0’, and you’ll begin to understand why people wanted to move on from rotary dialing. It won’t take that long, but it’s not instant. Check out the demo after the break.

This isn’t the first time we’ve seen a rotary dial used to control volume, but that’s one of the minor selling points of this rotary cell phone.

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Pump Up The (Windows) Volume With Physical Sliders

For as long as we can remember, Windows has provided a mixer that breaks out the volume level of every applicable application into its own slider-controlled lane. But navigating to these controls is non-trivial, especially if you’re in a hurry to silence someone on team speak. You have to stop what you’re doing, click the speaker, go into the mixer, and then go find the appropriate slider. Windows won’t respect resizes between mixer visits, so you’ll almost always have some horizontal scrolling to do.

So why on Earth would you put yourself through all of this when you could be pushing physical sliders on the fly like a DJ? A slider is just a potentiometer in a straight line, after all.

These are wired up to an Arduino Nano, which sends the serial data to a Python script on the PC that changes the volume values accordingly for whatever five programs are in the config file. Thanks to a little bit of Visual Basic, the Python script can run in the background.

[Aithorn]’s got everything you need to replicate this, so slide on over and grab the STL files and code. If you get to point where these sliders are too small, just build some bigger ones.

This Chromecast Volume Knob Has A Certain ’70s Chic

Chromecast devices have become popular in homes around the world in the last few years. They make it easy to cast audio or video from a smartphone or laptop, to a set of speakers or a display connected to the same network. [Akos] wanted to control the volume on these devices with a single, simple piece of equipment, rather than always reaching for a smartphone. Thus was built the CastVolumeKnob.

The project began by using Wireshark to capture data sent by the pychromecast library. Once [Akos] understood the messaging format, this was implemented in MicroPython on an ESP8266. A rotary encoder is used as a volume knob, and a Neopixel ring is used for visual feedback as to the device being controlled and the current volume level.

Further work was done to improve usability, with an ATtiny85 microcontroller being used to monitor the encoder for button presses before waking up the ESP8266, greatly reducing power consumption. The device is also rechargeable, thanks to an 18650 lithium polymer battery, and charger and boost converter boards. It’s all wrapped up in a sleek 3D printed case, with a translucent bezel for the LEDs and a swanky machined aluminium knob as the cherry on top.

It’s a homemade device that nonetheless would be stylish and unobtrusive in the living room environment. We imagine it proves very useful when important phone calls come in and it’s necessary to cut the stereo down to a more appropriate volume.

For another take, check out this USB volume knob with a nice weighty feel, courtesy of lead shot.

USB Volume Control

If you buy expensive computer speakers, they often have a volume knob you can mount somewhere on your desk so you aren’t dependent on the onboard volume control. [Kris S] decided to build his own version of the remote volume control. Not surprisingly, it uses an Arduino-compatible Digispark board and a rotary controller. The Digispark (that [Kris S] bought for $2) is compatible with the Adafruit Trinket. This is key because the Trinket libraries are what make it easy to send media keys over the USB (using the HID interface) to control the volume.

Really, though, the best part of the build is the good looking knob made out of a pill bottle (see the video below). The micro Digispark is small enough to fit in the lid of the pill bottle, and some wax and pellets add some heft to the volume control. Continue reading “USB Volume Control”

Stereo Amplifier With Digital Volume Control

A regular Hack A Day reader sent in a tip about an LM386 stero amplifier with digital volume control. The resulting build is very professional and could easily be adapted into a slick iPod dock build.

We’ve seen a few LM386-based amplifiers over the years including one that fits inside a 9V battery, but this is the first implementation of digitally controlled volume we’ve seen. The volume control of this amp uses the DS1868 dual digital pot IC in place of the usual 10K pot providing 256 steps between zero and full volume. The DS1868 is controlled by a PIC μC with a 3-wire serial connection, although this could be implemented on any microcontroller.

Although the code provided with this build outputs volume as a linear function, it would be trivial to implement a logarithmic volume output. Because the ear perceives loudness on a logarithmic scale, this would be a great way to adjust audio volume and provide a more fine-grained control. Of course this could be implemented with a logarithmic pot, but where’s the fun in that?

Check out a video of the amp after the break.

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Resistive Ladder Volume Control


[jefffolly] published some straight forward plans for a passive volume control. It uses a resistive ladder built across the contacts of 12W rotary switches. Each resistor provides a 5dB difference, and he recommends using 0.1% tolerance resistors to maintain accuracy. The use of discrete resistors instead of volume pots means that the output is much more predictable. All of the RCA sockets were connected using oxygen-free copper wire.