Imagine being in the middle of the rainforest and finding (almost) all the materials necessary for building some decent loudspeakers! During a two-week expedition into the jungles of Madagascar we did exactly this - Hacking the Wild!
These Jungle Speakers were first made during the Dissemination Lab expedition lead by Brian Fisher. During the expedition Andrew Quitmeyer and I collaborated on building and hacking tech in the wild. If you are interested in the details of this crazy adventure you can read our live field journal on Open Explorer or follow us through #WildHacks on Twitter!
Since one of the goals of the expedition was to explore making electronics in the wild, we set off into the jungle equipped with an assortment of electronics from the lab, but one of the most inspiring discoveries we made, once we set up our JungleLab at the first base-camp, was that the plants and animals growing and living around us were extremely useful building materials.
A video of me talking about making speakers in the jungle:
I describe a range of different techniques we tried for coiling a conductor attached to a leaf as membrane, and the last one I talk about is the design described in this Instructable.
A summary of how a speaker works and how the Jungle Speakers are made:
The leaf in the Jungle Speaker is the membrane of the speaker, the part that will vibrate to move the air. In order to cause it to vibrate a coil of enameled wire is wrapped tightly around the narrow end of the leaf cone. This coil acts as an electromagnet when the audio signal is played through it. Beeswax from locally harvested honey comb is melted and used to hold the coil in place. A permanent magnet is inserted into the cone and rests just inside the electromagnetic coil. The two ends of the coil are the leads of the speaker to which the audio signal is fed. When the audio signal is high, the coil becomes magnetized it repels/attracts (depending on the polarity of the signal attached tot he coil) itself from the magnets within and when the audio signal is low (0V) it relaxes. this constant repelling/attracting - relaxing is what cases the leaf to vibrate and translate the digital audio signal (high/low) into movement of air that we can hear. In this example an amplifier module is used to increase the current provided to the speaker to make it more powerful and louder.
Video of the speaker playing music during our lunch in the jungle:
Help identify the leaf!
These Jungle Speakers are made from the leaves of a tree growing in the jungle of south-eastern Madagascar (If you can identify the name of the plant/tree please let me know, I'd love to add this information to the Instructable). These particular leaves roll really nicely into a cone shape making efficient membranes for digital signals into audible movements of air. In choosing what leaf made the best speaker membrane, this one is stiff and waxy and does not become soft or floppy once picked from it's tree.
Step 1: Materials and Tools
* Leaf (speaker membrane)
* Enameled wire (can also be salvaged from another speaker, a solenoid, a motor, a transformer....)
* Sewing needle
* Small piece of thread, or natural fiber, or dental tape
* Wax for holding coil in place
* Lighter and/or candle for heating wax
* Magnets >> http://magnet-magnete.eu/
* Amplifier for speaker (make it louder) >> http://www.adafruit.com/product/2130
* Sound source (mp3 player or similar)
* Music >> http://ptarmigan.bandcamp.com/
Step 2: Selecting the Right Kind of Leaf
Once you start looking for a leaf for your speaker, you'll start noticing a whole lot of details about leaves that you probably never paid attention to before. This was one of the nicest experiences building electronics project in the jungle that incorporate the jungle materials surrounding you, one gets to know these materials from a whole new perspective. Looking at them for their material properties to fulfill a specific purpose, but also simply collecting different plants and insects and observing them for inspiration.
So, the good kind of leaf for making an efficient membrane is one that fulfills the following criteria:
- Stiffness/rigidity (not too soft or limp)
- Surface area (not too small)
- Ability to roll into coil (in this example the leaf is rolled into a coil, so the leaf needed to be able to flexible enough to manage this)
Step 3: Rolling and Sewing the Leaf Cone
The leaf is rolled into a cone shape and then stitched in place with a single stitch. Roll the leaf into a cone and look for the place where the main stem/vain of the leaf overlaps itself as shown in the photos. Stitching either side of the stem/vain will allow you to pull the stitch tight without the thread cutting through the leaf material. It is important that this stitch goes in and out either side of the main leaf stem/artary since this artery is robust to stop the thread from tearing it, sewing anywhere else on the leaf will cause the force of the coiled leaf to slowly pull at the thread and cut through the material of the leaf. After stitching, pull the thread/fiber tight and tie two knots in it.
Step 4: Wrapping the Coil Around the Leaf Cone
For the electromagnetic coil we want a thin, single core wire that is insulated so that we can wrap it tight and close together without causing it to contact itself electrically. We want to force the electricity to flow through the whole coil without taking any shortcuts. If you have enameled/magnet wire at hand, this is what you want to use. The thinner the wire, the better. If you don't have any at hand, you can salvage some from inside other components such as another speaker, a motor, a solenoid or a transformer. The enameled insulation coating on the wire is normally not visible as is the plastic insulation on other wires. You can use a multimeter set to measuring continuity to check if the wire you have is really insulated.
Begin by wrapping the coil around the narrow end of the leaf cone, about 1cm up from the bottom. After making a few coils I found it easier to remove the coils and continue wrapping them around the tip of one of my fingers - making sure to maintain the same diameter. Then placing the coil back on the cone.
This example used about 1-2 meters of wire, but generally the more turns you can get, the stronger your electromagnet will be and the louder your speaker will sound.
Step 5: Melting Wax and Attaching the Coil
In order to affix the coil to the leaf cone melted wax works great.
We were lucky that the day before our guides had gone off in search of a route up the mountain to our next base camp and had come back with bags dripping with honey and full of honeycomb. Of course our first thought was to eat as much honey as we could - a welcome change from our rice and meat diet. But the wax soon became part of our Jungle Lab materials collection. Here is a really nice video Andy edited together about the origins of the beeswax I used to make the Jungle Spekers:
Beeswax is nice because it smells so good, but really you can use candle-wax for this. Heat up the wax in a continuer using a lighter or even lighting a candle and using it's flame. Hold the coil in place while dripping the wax over it and making sure to get it on the leaf as well. You can go back with lighter to re-heat the wax on the coil to smooth it out and disperse it more.
Step 6: Exposing Speaker Leads and Inserting Magnets
The two ends of the coil are the leads of the speaker to which the audio signal is fed. Because the enameled wire is insulated these need to be exposed so that we can make electrical contact to them. Use a lighter to burn off the insulation and possibly also the blade of a sharp knife to scrape it off.
Now we have a membrane with an electromagnet attached to it. We still need a permanent magnetic field (provided by a permanent magnet) to insure our electromagnet will want to repel/attract itself away/twoards something and move. In this example the magnet(s) are simply dropped into the bottom of the coil and since they are wider than the narrow opening, they do not fall out. But this is one aspect of the speaker that could do with improvement - how to attach the magnet(s) and also how to mount the speaker so that it can attach to something or stand by itself?
Step 7: Playing Jungle Speaker Music!
Now the speaker is finished, it needs to be connected to an audio signal. You can connect it directly to two of the wires coming out of your headphone jack by chopping the wires of a pair of cheap (airplane) headphones. Or you can buy various amplifier modules that will allow you to boost the volume of your speaker by providing it with more current. For the Jungle Speakers I chose to amplify the audio using an Amp module from Adafruit. The resulting sound quality and volume were surprisingly good, even among all the other sounds of the jungle we could clearly enjoy the music by Ptarmigan >> http://ptarmigan.bandcamp.com/
Short video of bees attracted the the beeswax used to hold the electromagnetic coil in place: