Electromagnetic Speaker Review


(Image taken from the Otona no Kagaku site for review purposes only.)

Otona no Kagaku Plus, Electromagnetic Speaker, 2950 yen, Nov. 28
This kit has “Plus” in the name to set it apart from the regular Adult Science series, in that it’s also aimed at kids. The motto is “Let’s have fun with experimenting!” The kit itself is an external pair of speakers for your MP3 player. There’s a coil that creates a varying electromagnetic field, so that the little LED units will pulse in time with the music as a demonstration of the wireless transmission of energy. Actually, there are little coils in the capsules with the LED units, and the entire thing works as a transformer with an air core. One of the units is in the shape of a fish, and a magnet in the rear end causes the tail assembly to move, to propel the fish if you put it in water. The kit comes with a plastic tray that you can fill with water if you want, and all of the LED units are water tight.


(Front view.)

The kit has a suggested assembly time of 60 minutes, and it took me a little more than that to finish, because I had to spend 20 minutes unraveling the wire coil. The mook suggests wrapping the wire around a piece of cardboard, first, to make it easier to handle. I opted to not do that, which resulted in my having to unknot the wire after it unlooped and twisted itself up. There aren’t any really tricky parts to the assembly this time. Just leave 12 cm of one end of the wire floating, and hold it in place on the case body with cellophane tape. Wrap the wire around the circular shape of the case like you would for an antenna coil. When you finish, use more tape to keep everything neat, and wrap the excess wire around the three pegs near the circuit board. Put in the speakers, using the big flat-washer screws to hold them in place. Add the battery holder parts, making sure that the springs and leads match the pictures in the instructions. Plug the speaker and battery connectors to the circuit board and route the wires so they don’t get pinched. Put in the two normal screws at the center of the board and wrap the coil ends around them as shown in the instructions. There’s a clear plastic sheet that gets placed over the circuit board and held down by the remaining 2 screws at the corners of the board. Finally, put in 4 AA batteries and mount the control knobs on the potentiometer shafts at the front of the unit. (Note that there was a big solder splash on one of the coil mounting pads on the circuit board that I had to pry off with a screwdriver. It didn’t affect the operations of the circuit board, anyway.) The kit measures 24cm x 15cm x 3cm.


(Rear view.)

The power switch has 3 settings: Off, Internal lighting, External input. With Internal lighting, the 3 controls adjust the intensity of the light from the LEDs. With External input, plug the mini phono jack into your MP3 player and turn it on. Volume control will be from your player; the knobs just adjust LED light intensity and disco action sensitivity. The regular usage of the kit is to place it flat face up on a table, and put the clear plastic tray into the opening inside the coil area. Fill the tray with water and put the four LED units in the tray. Technically, the fish unit (you have to attach the white tail fin to the fin holder) should move around in the water by itself, but the water surface tension kind of overpowered the magnet in the tail and it wouldn’t flip for me.


(Close-up of the excess wire take-up pegs.)

The mook starts out with mod suggestions, including making cloth octopi to place inside a gold fish bowl on top of the coil; and a kind of merry-go-round structure, also set on top of the coil. There are instructions for making more small coils and soldering them to regular LEDs for additional lighting. A third mod is to drill small holes into the LED ball units and turn them into battle tops. Other articles discuss wireless power, including wireless smartphone chargers; the principle behind the speaker kit; and experiments you can try with the LED units (turning them at different angles to the coil, or putting different materials between the units and the coil). There’s a discussion of electromagnets and circuits using your own hand-made coils. The 8-page “Wireless Communications Chronicle” is a brief history of electromagnetism, running from 1887 with Heinrich Hertz, through the telegraph, radio and television, up to satellites, smart phones and rail pass cards. 9 pages on the assembly and operation of the kit, and then 10 pages on Tesla and his dream of beamed power. The rest of the mook is advertising for other Gakken kits and publications.


(Night view.)

I don’t really like having the kit main unit lying down on the table, because you can’t see the LEDs from a distance that way. But, when you stand the main unit upright, it’s resting on the power switch, which makes it unstable. I taped 2 toothpicks to the bottom as feet and to raise the power switch off the table. Then I used thread and part of a wooden chopstick as a hanger for the LED units. Unfortunately, the thread is twisted enough so that the LEDs face the rear of the kit, so I’m thinking of putting a mirror at the back as a reflector, maybe to get a kind of kaleidoscope effect. I don’t have any other mods in mind, yet, but the obvious ones are to add a 6 volt adapter jack and to move the power switch to another part of the case. And maybe to put rubber feet on the “bottom” so it will stand up better.

Overall, it is a nice kit, and fun to play with at night when the house is dark. Recommended if you want to teach kids about wireless power.

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