February 9th, 2010 by admin

Cigar boxes are great containers for loads of things. I had a bunch on hand after going to the local wine shops and asking for donated cigar boxes. Inspired by the Rock and Roll Speakers project in Fashioning Technology, it seemed like a good idea to have my students build their own music player embedded in a cigar box. This is a major project, taking several weeks, though it probably could be done by an individual in an afternoon without introducing many of the concepts we’ve worked on.

Box preparation
The boxes are pretty well made, and we found that we could sand them and coat them with spray paint. Boxes with colorful printed designs can be left unpainted. We have a vinyl cutter, so a lot of class time has gone into making custom multicolor stickers from photos. We’re using the Threshold tool in Gimp to convert the image to a high contrast black and white, and then importing it to Open Office Draw to add a border. Having a border makes the sticker weeding process much easier.

Speaker insert
Using some scrap cardboard a metal ruler, utility knife, and careful measurement, we made an insert to hold the speakers and cover up the electronics. The speakers sound much better when enclosed. Just putting them inside the box improves their sound even without the cardboard insert. The speakers are secured to the cardboard with hot melt glue, and some students are making speaker grilles for further protection.

Speaker preparation
Our speakers came from leftover parts scavenged from the 80 Pentium IIIs project. A parent helped cause a donation of a couple of pallets worth of aging corporate computers. We got a lot of mileage out of those relics, and some of the last traces are the front panels which each have a speaker, two switches, three LEDs and a 12 volt fan. The speakers look cool when painted as described in the Fashioning Technology article. Each speaker box gets two speakers, the negatives are soldered together and covered with a bit of heat shrink. The positives then go to the amplifier right and left connections.

Amplifiers
Originally, the plan was to build a circuit using an LM386 op amp. We would fabricate our own circuit boards from a vinyl clad etch and populate the boards with the components. This chip by itself will give only a mono output, and the circuit debugging process was taking too long, so we went to Plan B. A sizeable pile of computer speakers was gathering dust in the storage loft, and it was time to mine them for some goodies. Inside many of them, we found some very useful amps. Also inside were examples of manufacturing technology, speaker design and a bunch of 1/8″ stereo audio jacks.

Power supplies
The speakers we most desire have battery holders inside the speakers already. This is a good indicator, since those are likely to be designed for low power usage. The battery enclosures can be used to hold cells inside the case if there is enough room. Some have AC in, others have huge heat sinks. The AC powered ones could be good, but will require access to the electric grid to work. Tapping in to the circuit board with a battery pack will add portability to the design. The ones with big amplifiers and heat sinks may prove useful on some other project.

On off switching
By placing a switch between the power supply and the circuit, we’re be able to shut the box off. A slider or toggle switch will do the trick. One neat feature is using a leaf switch from the computer panel. Wiring the switch with the common and Normally Open leads allows the top of the box to serve as the shutoff device. When the box is closed, the amp loses its’ connection to the battery.

Process and progress
The cigar box music players are coming along nicely. Students are pretty engaged with the various aspects of custom designing and manufacturing their own entertainment devices, despite the long time frame of the project. These will be complete in a short time, so watch for updates.