When Life Gives You Lemons, Make a Crude Electrochemical Battery


Not quite the saying that we’re all familiar with, but it does add some flavor to it.

Here’s another Tuesday night project that I wound up immersed in: the lemon battery. I’ve seen this project posted in a multitude of places (along with the notorious potato battery), but I wasn’t quite sure how it worked. I knew that fruits are great conductors of electricity…but how? Naturally, when I encounter something I don’t quite understand, I obsess over it until I actually do.

[By the way, it takes a very special partner in crime to simply say, “Okay, honey,” when one spontaneously declares, “I want to build a lemon battery!” outside of any sensible context. Joe is clearly a winsome catch. And lab partner, to boot.]

Constructing the battery

Making the battery is pretty simple. First, squeeze the lemon to release the citric acid from the pulp — the juicier it is on the inside, the better. Then insert something made of mostly copper and something made of mostly zinc on opposite ends (I used a penny and a galvanized screw). Why these elements in particular? For one, they’re fairly easy to find in household items. Secondly, well, we’ll get to that in a little bit.

Hook up each end to some alligator clips if you have them, and connect those to a voltmeter or multimeter. (You can also do without the alligator clips and merely touch the tips of the voltmeter/multimeter wires to the copper and zinc ends.) Then, ta-da! You should see a charge! But…why?

What’s happening here?

The answer is an oxidation reduction reaction, or redox for short. Don’t be discouraged by how many syllables there are in that term!

As zinc enters citric acid (C6H8O7), it dissolves as positively charged ions (Zn2+); this is because it sheds the two electrons in its outer shell.

[Note: Because of the way electron valence shells are organized, zinc has 2 valence electrons in its outer shell, but it wants either 0 or 8 total to be more stable. So, it chooses the easier route — to shed 2 rather than gain 6.]

Typically, these shedded electrons will bond with hydrogen ions floating around in the citric acid to form H2, a gas that ends up bubbling off of the copper electrode.  This reaction is called oxidation (the giving of electrons):

Zn → Zn2+ + 2e-

2H++ 2e- → H2 (stable & gaseous)

Copper, which has one electron in its outer shell, will also give away its valence electron. However, because it has a greater potential for taking electrons, it will attract free electrons in the citric acid. The electrons in the citric acid lost to the copper are made up for by moving electrons from the zinc through the external wire, creating a current. This itself is called reduction (the taking of electrons).

Remember when I asked why copper and why zinc? This is why. We want one side to be more positive (cathode) and the other to be more negative (anode), just like in a real battery!

Since we’re dealing with electricity, we only care about electrons and how they move. As far as we’re concerned, electrons are negatively charged and are attracted to positive charge (opposites attract, no?). It’s this flow from negative toward positive that creates electricity.

As Bill Nye would say, “It’s not magic — it’s science!”

Next time life gives you lemons, don’t skip the lemonade, but don’t hesitate to think about batteries or electrons either!

Science, Sound, Tattoos


First tattoo, my design. Here’s the story behind it.

Tycho Brahe’s Universe

The main part of the design is the Tycho Brahe model of the universe, a compromise between the geocentric (Copernican) and heliocentric (Ptolemaic) models. Brahe believed the Earth was at the center of the universe and that the sun and moon orbited the earth, while the planets orbited the sun. As you may already have noted, this is inconsistent with what we observe of the universe today. However, it was a paradigm shift in thinking that nudged us — and our egos — from the center of the picture, building toward a more accurate model. In fact, one of Brahe’s apprentices was Johannes Kepler, who, in later years, used Brahe’s work as the basis for the laws of planetary movement.

Here’s where it gets a little weird.

While I was doing some more research about Brahe, I learned that he apparently wore a prosthetic nose, allegedly a result of a sword duel:

“Tycho had earlier quarrelled with Parsbjerg over the legitimacy of a mathematical formula, at a wedding dance at professor Lucas Bachmeister’s house on the 10th, and again on the 27th. Since neither had the resources to prove the other wrong, they ended up resolving the issue with a duel.”

I kind of dig the fact that the nature of drunken academic disputes has barely evolved in the last few centuries. (I’m smarter than you. No, I’m smarter that you!”) Not to mention, this wasn’t Brahe’s only memorable brawl. He also got into a feud with Galileo.

And then…there’s the bizarre story about his pet moose:

The hoofed critter would trot alongside Brahe’s carriage like a loyal dog and lived inside his castle. But, unfortunately, it also appears to have developed a regrettable taste for Danish beer […] A nearby nobleman had asked him to send the moose to his castle to entertain the guests at a party. As the dinner wore on, the creature grew increasingly tipsy until it eventually wound up roaring drunk. According to Brahe’s biographer Pierre Gassendi, shortly thereafter, “the moose had ascended the castle stairs and drunk of the beer in such amounts that it had fallen down [them]” to its eventual demise.

Voyager and the Golden Record

On the outermost ring of my tattoo is an aerial view of a record needle, a symbol etched on the Voyager spacecraft’s Golden Record:


Screen Shot 2014-05-19 at 2.22.13 PM

The Voyager space craft is best known for being the only man-made object to have exited the heliosphere, traveling farther than anything else humans have ever built. The Golden Record was a project (directed by Carl Sagan) to create an all-encompassing sonic record of life on Earth to send off into space. Think of it as an audio time capsule of our existence, meant for anyone or anything that may eventually find it.

The ethos of that project was this: “To the makers of music — all worlds, all times.”

On that record are sound samples of 55 languages, whale calls, folk songs, heartbeats, you name it. Listen to an excerpt of an ancient Chinese folk song on that record:

Not surprisingly, a radio piece made me fall in love with this project, the story of how Carl Sagan and Ann Druyan fell for each other:


On a macro level, the tattoo design also resembles a mandala, elaborate and artful circular symbols in Hinduism and Buddhism. The psychologist Carl Jung once wrote that mandalas are expressions of the “totality of the self.” They are also used as representations of the universe:

In common use, mandala has become a generic term for any plan, chart or geometric pattern that represents the cosmos metaphysically or symbolically; a microcosm of the universe.

Monks who are trained to create mandalas spend days, even months working on meticulous designs, only to destroy them after they are finished. They are reminders of the impermanence of life itself — how the things we build, no matter how beautiful nor coveted, will eventually give into entropy. This follows the Hindu cycle of the universe, a belief that things are created and destroyed repeatedly, which I believe to be true in science and in ourselves. Matter and energy within the universe combine in a multitude of permutations to give us elements, planets, stars, and life. Within us, the energy and matter that encompass us allow us to experience life through suffering, joy, and healing (forces of destruction and creation in their own right).

THE MANDALA (A Short Documentary of the The Celestial Palace)


I also have a penchant for circles.

Mathematically, circles incredibly intriguing. They have an infinite number of tangents, and all points in a circle are equidistant from a center point, giving it a unique symmetry. Then, there’s the infamous value of  π, taken from a circle’s circumference divided by its diameter (C/d), which has maddened mathematicians and mystics alike. The number continues without a sensible pattern into infinity; the fact that such an irrational number can be derived from such a symmetrical shape is simultaneously fascinating and perplexing.

In nature, circles occur almost everywhere you look: ripples, halos around the sun, craters, bubbles, hurricanes. They also occur in man-made objects, e.g. clocks, wheels, bowls, compasses, buttons. They have come to symbolize balance and perfection, despite the fact that perfect geometry only truly exists in abstraction.

…Which brings us to the whirling dervishes from the Mevlevi Order. You’ve probably seen movies or photographs of whirling dervishes: men dressed in white gowns and tall hats spinning continuously – as if in a trance– usually on a stage or in a large hall. This dance, called the Sema, originated in the 13th century:

The Sema represents a journey of man’s spiritual ascent through mind and love to the “Perfect.” Turning towards the truth, the follower grows through love, deserts his ego, finds the truth, and arrives at the “Perfect.” He then returns from this spiritual journey as a man who has reached maturity and a greater perfection, able to love and to be of service to the whole of creation. The Sema is a testament to the dizzying effects of attempting to reach perfection.

If you think about it, the earth spins on its axis; the planets rotate around the sun. The quantum particles around and in us vibrate and spin, though undetected by the naked eye. Because we are rooted on the earth and made up of these particles, we are all eternally spinning. We are all constantly attempting, reaching to be better than ourselves.

Whirling dervishes

In short, the synthesis of all these symbols is a reminder of our collective longing for perfection, the perpetual pursuit of knowledge, our impermanence in this world, and two things that have made a lasting impact in my life thus far: science and sound.

Ohm, I Can’t Resist: My Secret Life as a Circuit Bender

An inventory of electronics projects — past, present and future.

I’m not an engineer, nor am I a scientist (not by definition, at least). However, one thing is for sure: I can’t help myself when it comes to building things. I love it! Here are some projects I’ve built and am building.


My latest Tuesday night project was a theremin, built from a kit that Joe got me from Hacker Space Seoul, South Korea. (Granted, it’s been sitting in my bin of rogue electronics parts for two years, but better late than never, right?) This model uses photoresistors/photocells to sense light vs. shadow. You can change the pitch and wave shape of the sound by changing up your motions. If you’d like to build it yourself, here’s the schematic. 10341874_10102534470971711_4143363418536678271_n   And here’s a brief demo of what it sounded like:

FM Transmitter + AM Transmitter

For me, my love of electronics stems from radio. In 2012 at the Allied Media Projects Conference (AMP) in Detroit, Michigan, I went to a workshop that taught folks how to build low-power FM transmitters. I had no idea what I was doing — the solder points were messy and I had to ask for help multiple times. Yet, I ended up building something that worked! I still keep this janky project around as a reminder that 1) progress takes time and 2) everyone starts somewhere.

Then, of course, there’s the AM transmitter that Joe made for me to go along with the FM transmitter.


Ham Radio (in progress)

Speaking of radio, I got my ham radio license last year (CQ, CQ…KC1AJN!) and decided to fix up a vintage Heathkit ham radio that I bought from a yard sale. The parts are ancient and some aren’t even manufactured anymore, but I’m up for the challenge. (Joe even found the original owners’ manual on eBay and snagged it for me!)

TARDIS outfit

For my inner Whovian two Halloweens ago, I made a TARDIS dress and blue-lit headpiece that consisted of a simple LED and coin battery.

Kissing Robots

Nothing says “Happy Valentine’s Day” like some kissing robots, right? This was my gift to Joe back in February 2013. I used a basic reed switch to create a circuit actuated by magnets (on both ends) so that the robots would light up when they kissed. They had red LEDs to simulate a heart beating.



Here’s a video of how they work:


Admittedly, this is something I bought for Joe so that I could play with it myself. The MakeyMakey is a “musical invention kit” that I heard about at a music hack day at MIT and knew would be a lot of fun. With a simple circuit, you can turn anything into an instrument — including bananas, grapes, pencil lead…the list goes on. Here are our fruit bongos:

LED sound sensor

This was my first project on an actual circuit board! It came in a hobby kit from RadioShack, which is unfortunately no longer available. Basically, it’s a switch-operated circuit that uses a microphone to detect sound and causes the LEDs to blink along with the sound. 1496657_10102208226438371_120641353_n

Curiously Strong Altoids flashlight 

A rite of passage for electronics geeks. Using this as a bike light!

Sun Logger (in progress)

My goal this summer is to start an indoor garden. Our tiny Somerville abode doesn’t fit much beyond the bare necessities and could definitely use more windows, so Joe and I are coming up with some hacks to get around that. With a brand spankin’ new Arduino UNO, we’re hoping to build a sun logger that tells us how much sunlight we’re getting in certain parts of the apartment (and perhaps even text/tweet the data!) so we can optimize plant placement.

Wearable bike turn signal (in progress)

Eventually, when I graduate to the LilyPad Arduino, this is something I’m hoping to build for biking at night, which can be terrifying in Boston traffic.

Image: Instructables

One of the best musicians I know once told me he didn’t know how to read sheet music. It took me aback — not because I had any expectation that one should be able to read music to play music but rather because it had never occurred to me that you didn’t have to. I approach electronics in a similar way. I look at a schematic and I see sheet music that doesn’t completely make sense to me the same way it would to an engineer. However, that doesn’t stop me from extracting pure delight from engaging with projects like these (even the more challenging ones) and improvising along the way.

What’s more, I’m extremely interested in how low cost DIY sensors/electronics can be applied toward social good and increased civic engagement with science. These projects are a way of working on my chops so I can be better equipped and better poised to contribute to community-based sensor projects in a more meaningful way.

While I don’t have any aspirations of designing skyscrapers or inventing the next big gadget, I do plan to geek out and make things at every opportunity I get.