In an effort listen to his music on shuffle without the need to touch the volume knob [Mike] build his own automatic volume leveling hardware. He knows what you’re thinking right now: there’s software to do that for you. But building the feature in hardware is a great stepping off point for a project.

He started the prototype using LabVIEW along with a Mobile Studio development board and a Bus Pirate. This project will be a mix of digital and analog components and it’s a bit easier starting off the exploration with these tools rather than jumping right into the AVR code.

The circuit will sample the incoming audio, modify it accordingly, and output the result. The output side is where the Bus Pirate really shines. He’s using some MCP42010 digital potentiometer chips to make the necessary changes to the levels. They communicate via SPI and it’s nice to have the Bus Pirate’s terminal to issue commands without the need to reflash a microcontroller.

[Mike] made a video showing an audio waveform with and without the hardware leveling. Sound quality is still great, and each clip is played at a reasonably comfortable listening level. We’ve embedded that demonstration after the break.

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A few years back [Evan] built a kegerator from a mini fridge and was quite happy with his new beer chiller. Like many of us do, he started thinking up ways in which he could improve the project as soon as it was completed. While it took a couple of years, he recently got around to adding the temperature and capacity gauges he always wanted.

He added a temperature probe to the refrigerator, and then constructed a pair of tools that he could use to measure how much beer was left in the keg. The volume monitors include a scale built using a pair of pressure sensors from SparkFun, and a flow sensor installed in the beer line.

[Evan] scored an old Chevy gauge cluster and cleaned it up before installing a pair of analog meters which he used to show the keg’s temperature and “fuel” level. Since he feels no project is complete without some LED love, he added a few of them to the display without hesitation. The LEDs calmly pulsate when the keg sits idle, but spring to life and begin flashing when the flow sensor is activated.

As evidenced by this pair of keg monitoring systems, we think that you can never have enough information when it comes to your beer stash, so we really like how this project came together.

Be sure to check out his kegerator’s gauge cluster in the video below.

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There are cars that increase the radio volume as you drive faster, and video games that ramp up the music as your gameplay improves (we’re looking at you SSX Tricky). Now you can add that feature to your workout with [Polymithic's] Motion Feedback MP3 Player. It uses a passive infrared sensor to detect motion so there’s no need to wear any electronics. But if you used some Bluetooth headphones you could bring the system with you to the gym, just don’t exercise so hard that you blow your eardrums out.

[via Hacked Gadgets]

[Jean-Michel] tipped us off about his beer keg monitoring setup. It can tell you how much beer is left in each keg, how much carbon dioxide remains in the canister, and it can monitor and regulate temperature.

An Arduino mega is the brain of the system. A shield was built to interface force sensors, measuring the weight of the keg to estimate how much beer remains. Analog temperature sensors allow for temperature monitoring and control of the compressor for regulation. Information can be displayed on a graphic LCD or a computer via XBee wireless communications.

This is along the lines of the SparkFun kegerator but we like the added functionality. Does this need to Twitter? Probably not but if you want that, it’s only a bit of a software hack away.

Dallas/Maxim’s DS1801 is an audio volume potentiometer with a simple SPI interface. This chip has two channels of volume control that might be useful in a DIY audio project. We previously looked at the DS1807, a similar part with an I2C interface. This week we’ll show you how to use the SPI version.

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The DS1807 contains two logarithmic digital potentiometers (pots) for audio volume adjustment. Each pot has 64 volume levels plus a mute setting. The volume level of each pot is set over a two-wire I2C serial interface. We’ll show you how to connect and interface the DS1807 below.

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[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.