Microcontroller-Based Air Quality Mapper

The webpage displaying CO2 measurements acquired in a session

Raul Alvarez Torrico’s Air Quality Mapper is a portable device designed to track levels of CO2 and CO gasses for constructing “Smog Maps” to determine the healthiest routes. Featuring a Renesas RDKRL78G13 development board, the Mapper receives location data from … Continue reading


2014 Year-End Notes

Steve Ciarcia

In every December issue, we like to take a look at where we’ve been and where we’re going. Since this is the final issue of the year, let’s review a few important notes about 2014 and the 2015 editorial schedule. CIARCIA … Continue reading


Electronica in Images


Joao Martins, editor in chief of Circuit Cellar‘s sister publication, audioXpress, attended the 2014 Electronica show in Munich from November 11 to 14, 2014. Here we provide some of the photos he took from the floor. 


Budgeting Power in Data Centers

Figure 1: The plot demonstrates billion of instructions per second (BIPS) versus server power consumption as measured on an Oracle enterprise server including two SPARC T3 processors.

In my May 2014 Circuit Cellar article, “Data Centers in the Smart Grid” (Issue 286), I discussed the growing data center energy challenge and a novel potential solution that modulates data center power consumption based on the requests from the … Continue reading


Embedded Chip = Subdermal Chip?

Circuit technology  human palm.

Forget stashing your cash under your mattress. Now you can stash it under your skin. Sort of. The Telegraph reported Tuesday that Martijn Wismeijer, a Dutch innovator, recently implanted a 12-mm xNTi NFC chip in his body to store Bitcoin. The … Continue reading


WIZnet Distinctive Excellence IoT Projects

WZ1327 - Iot Gateway

The Circuit Cellar team felt strongly that there were considerably more first-rate projects entered in WIZnet Connect the Magic 2014 Design Challenge than could be satisfied with the available prizes. Thus, it designated a special category called “Distinctive Excellence” for … Continue reading


Twin-T Oscillator Configuration

The front panel of the oscillator/volume unit (VU) meter contains all the necessary controls. (Source: L. Cicchinelli)

Since retiring in 2013, electrical engineer Larry Cicchinelli has provided technical support at an educational radio station. For audio circuit debugging and testing, he uses a DIY battery-powered oscillator/volume unit (VU) meter. Details follow. Originally, I was only going to build … Continue reading


Arduino-Based Tube Stereo Preamp Project

Budgie preamp (Source: S. Parks)

If you happen to be electrical engineer as well as an audiophile, you’re in luck. With an Arduino, some typical components, and a little knowhow, you can build DIY tube stereo preamplifier design. Shannon Parks—owner of Mahomet, IL-based Parks Audio—designed … Continue reading


Issue 290: EQ Answers


Problem 1—What is an R-C snubber, and what is a typical application for one? Answer 1—An R-C snubber is the series combination of a resistor and a capacitor that is placed in parallel with a switching element that controls the … Continue reading


Issue 288: EQ Answers


Problem 1—When designing a pair of band-splitting filters (for, say, an audio crossover), why is it important to match frequencies of the –3-dB points of the low-pass and high-pass responses? Answer 1—The cutoff frequencies of the two filters should be … Continue reading


DIY Network-Ready Polyphonic Music Controller

Portner's Chimaera project

Hans Peter Portner’s Chimaera project is a touch-less, expressive, network-ready, polyphonic music controller released as open source hardware. It is a mixed analog/digital offspring of the Theremin. An array of analog, linear Hall effect sensors make up a continuous 2-D … Continue reading


WIZnet Design Challenge Winners (Sponsored)

First Prize — Chimaera: The Poly-Magneto-Phonic Theremin, Hans Peter Portner (Switzerland)

WIZnet’s Connect the Magic 2014 Design Challenge provided electronics enthusiasts with the opportunity to use WIZnet’s WIZ550io Ethernet module in a project for a chance to win a share of $15,000 in prizes. The submission deadline was August 3, 2014, and soon … Continue reading


Data Acquisition Issues (2 Free Downloads)


As Maurizio Di Paolo Emilio noted in his essay “The Future of Data Acquisition,” data acquisition “is a necessity, which is why data acquisition systems and software applications are essential tools in a variety of fields.” For a limited time, … Continue reading


DIY Dead Man’s Switch (No Microcontrollers)

Figure 1: This is the timer schematic. The Reset button S1 is optional.

A “dead man’s switch” (abbreviated here as DMS) is a very useful device for applications where the effect of forgetting to turn something off ranges from a mild annoyance to costly or dangerous consequences. We first learned about the DMS … Continue reading


Solar-Power the Circuit Cellar (Free Download)

Team installing solar panels on Steve Ciarcia's roof

In the spirit of DIY engineering and solar power innovation, we’re re-releasing Circuit Cellar founder Steve Ciaria’s three-part series, “Solar-Powering the Circuit Cellar.” An excerpt from the first article in the series appears below. And for a limited time, you … Continue reading