1-Vacuum Tube Radio

Gakken likes radios. They’ve published at least 4 such kits so far. And I know that I said I was only going to buy the numbered mook kits, but I was feeling withdrawal and had to buy something to build, since the 8-bit microprocessor kit wasn’t coming out for at least another 4 weeks. The 1 vacuum tube radio costs 3150 yen (approx. $36 USD).

AM radio transmissions consist of using a transmitter broadcasting at a specific frequency and varying the strength of the signal based on what you want to send (voice or music). The easiest method is to just hook up a microphone to the volume control of the transmitter and send your voice that way. Receiving the transmission then requires using some kind of circuit tuned to the desired frequency, and stripping that base frequency out to just leave the amplitude variations in place. This means that the receiver will have an antenna, a tuner circuit and an amplifier. While there can be many radio broadcasts simultaneously, only the broadcast on the frequency the tuner is set at will be strong enough to hear at that moment. Even so, the audio portion may still be too weak to hear as-is, which is why we need the amplifier.

This kit uses a special twist on the tuner circuit – the antenna is also part of the tuner. It’s made up of two coils, and turning the inner coil acts as a fine tuning control. The rough control comes from a variable capacitor, and the high/low frequency switch throws in a parallel capacitor to select between the 500-900KHz and 900-1600 KHz bands.

(The back.)

If you’re not familiar with vacuum tubes, you can imagine them as a really big, early version of a transistor. In order for a vacuum tube to work, it needs two power supplies – one for the primary signal power and the other for the heater filament. This kit uses three 9-volt batteries for the main power, and a 1.5V C cell for the heater. Rotating the C cell battery housing acts as the radio’s on-off switch. Kind of clunky, but elegantly simple. Audio out is just a mono earplug. (Fortunately, because we’re just using 1.5 V on the heater, the tube never gets hot enough to be a burn hazard, unlike with older-style tubes.)

The kit has less than 15 pieces, and the circuit board is preassembled in the base housing so you don’t even need to mess with it. Suggested assembly time is 60 minutes. I took my time, rereading the instructions to make sure I got them right, and being careful while wrapping the antenna coils to avoid kinks – which is what took up all the time. You need to pull the wire a little tight – otherwise the wrappings will get too close to the edge of the form at the end and will unwrap on you – but not so tight as to snap the wire. The form is designed for an interleaved, alternating wrapping. If two consecutive wraps are on the same side of the tabs, you missed alternating on one of the tabs somewhere. The book says to start out with a 15 cm loose end, but that leaves a lot of slack on one end and not the other. Ideally, it’d be better to trim both ends of the coil to be about 4-6 cm when you’re done, but the insulation on this wire isn’t easy to remove, so I just balled up the slack to hide it at the back of the radio. Final assembly time was about 1 hour and 40 minutes.

You want to be a little careful in the handling of the vacuum tube, since strain at the base of the pins can crack the glass and let the vacuum out. There’s a set of holes on the base of the kit for straightening out the pins before putting the tube in the socket.

(Interwoven antenna.)

The kit works fairly well, but there’s no volume control on it and the sound level was pretty weak. You may want to add an audio jack to plug in a powered speaker. To operate the radio, rotate the C cell housing to the “on” position (the LED will light), then adjust the VC knob until you get some kind of voice, music or squealing. Slowly rotate the inner antenna coil (clockwise or counter-clockwise, doesn’t matter) to fine tune the signal. The radio is directional, so you’ll need to rotate the entire kit to obtain the optimal signal strength. In fact, the mook offers a suggestion to use a map for triangulating on the transmitter. Get a city map and a compass. Lay the map down pointing north and mark where your house is on it. Tune the radio and rotate it to get the strongest signal, then use a ruler to draw a line through your house in the direction indicated by the outer antenna. Next, go somewhere perpendicular to that line, about 1.5 or 2 km, and repeat the process. The transmitter then will be in the approximate area of where the lines cross.

The unnumbered mooks only discuss subjects directly related to the kits, so they’re about half the pages of the numbered kits. This mook discusses the history of radio, talks about de Forest and Fleming, gives the theory of vacuum tube operations, and shows photos of various types of antique radios. The suggested mods are to add a bigger antenna, wrapping the antenna coil around an umbrella, and to use a telegraph key to send morse code to a second radio (requires cutting up the circuit board and adding a few extra parts).

Overall, the cheaper Gakken kits tend to be hit or miss. When they work well, they’re really fun and offer lots of replay value. Otherwise, they just become something different to be placed on a bookshelf and forgotten. If you want a good, working AM radio, go to Radio Shack and plop down $10. If you like wrapping coils and learning how radios work, this is a good kit to pick up.


Aurorarium 2200 yen ($24 USD).

The Aurorarium is an attempt to imitate the northern lights, hence “aurora-rium”. The kit consists of a pre-assembled base plate – with the motor, power switch, and circuit board already built – two small plastic “chips”, the fogged plastic cone sheet, the plastic cone tip, the reflecting tray, and two thin mylar disks. Assembly takes no more than 5-10 minutes, and most of that is for making sure that the cone is taped together right. You can choose whether to put the chips in place or not. There are four sawtooth-like teeth on the bottom of the reflector dish, and as the dish turns, the teeth press against the raised chips, causing the dish to tilt and change the angle of the reflected light a bit. Putting in one chip will make the disk tilt 4 times per rotation, and 2 chips makes it tilt 8 times. Of course, there’s no tilting if you don’t use either chip. Assembly consists of mounting the LED projector arm in the base, putting in the desired chips, making the cone using double-sided tape, putting the reflecting dish on the base, putting the plastic tip on the cone, and then putting the cone in place. The kit also requires 4 AA batteries (not included).

You can mod the kit a couple of ways. First, take one of the mylar disks and draw lightly on it on one side using a pen on a soft surface. It doesn’t take much to affect the surface on the other side. Then put the disk in the reflecting tray, put the cone on, and push the switch. A second mod is to put a little water in the tray. A third is to put plastic crystals in the tray. You can also choose to leave the cone off, which lets the light reach the ceiling and walls. (Naturally, you can also put in a 6V adapter jack.)

There are three small LEDs in the projector head – one each red, blue and green. As the disk rotates (it is really geared down and takes 2-3 minutes to turn once), the LEDs fade in and out, going from red, to blue to green to yellow to white, etc. The actual pattern for the fades is based on the switch. Pushing it once gives it a red-dominated pattern; twice includes purple and yellow colors; 3 times is primarily blue, purple and white; 4 is mostly purple/white; and pushing the button 5 times turns the kit off.

As with all of the other unnumbered mook kits, the mook for the Aurorarium concentrates solely on the properties of light, with an explanation of how prisms and rainbows work; a suggestion to put a flashlight in a liter soda bottle to see a prism effect; photos of auroras; photos of strange effects from the sun, including the green flash and sun dogs; and some pictures of sea life and fireflies that can make their own light. It’s a thin mook, at only 18 pages, but the pictures are nice. Not a lot of alternative suggestions for mods, though. After using up the 2 mylar sheets, you can try using reflective wrapping paper, or aluminum foil.

(The mylar disk really doesn’t look brown like this. It’s silver and highly reflective, which is why it looks so weird here in the photo. The little black arm and cylinder over the base unit is the projector arm and head. The projector head contains the three (red, blue and green) LEDs, which are aimed down at the mylar sheet.)

One thing I need to clear up – the aurorarium is not actually part of the Otona no Kagaku (adult science) series. Instead, it’s part of Kagaku no Tamago (science egg), which are build-it-yourself kits for kids. But, it’s generally included in with the adult kits at bookstores like Kinokuniya. This kit originally came out in 2008, so I’m a little late in reviewing it, comparatively.

Basically, this is a high-tech lava lamp, but without the endlessly changing shapes. The motor is kind of noisy, which can be a distraction. If you leave it on, it’ll turn off by itself after 10 minutes. At $24 USD in Japan, it’s probably not worth buying at the expected import prices of $40-$50. You can easily make your own aurorarium with some colored Christmas light strings and a geared-down 1.5V motor connected to a CD. But, the Gakken kit will probably look better on your bookshelf.

SX-150 Mark II

I’ve been getting antsy lately, because I haven’t been able to build anything serious since leaving Tokyo. I miss having easy access to Akihabara and being able to pick up a handful of parts to wire into the Japanino whenever I want. So, when Gakken came out with the Rhino kit at the end of July, I became very interested in something that had been printed in the mook – a 1/2-page ad for their new “Sound Gadget Series”, with pictures of the SX-150 Mark II and the Udar. The ad gave a tentative start date of “this Fall” (2011), so I’ve been visiting the Otona no Kagaku site pretty much daily looking for news.

(Image of Mark II from the Gakken site, used for review purposes only.)

Finally (Oct. 8, 2011) they have the announcement up for the first kit in the series – the SX-150 Mark II synthesizer. It looks very similar to the Mark I, with the stylus and ribbon controller, but in a red case. The Resonance switch has been replaced with a variable control, and there’s a new LFO Depth control. The two buttons to the left switch the controls between LFO and VCF modes. Just about everything else is the same. The price is almost 50% higher though, at 7350 yen (close to $90 USD), making it fairly pricey. (I’m currently thinking about getting a Casio CTK-4000 at 12,900 yen, and it has an actual keyboard).

(Image of Mark I from amazon, used for review purposes only.)

Right now, the Mark II webpage is limited to just the ad photo, some minor statistics, and a link to the Highlights page. (which has 5 pages of background on the synth, and videos demonstrating different sound settings).  If you’ve got the Mark I, you may just want to hack it to add the two new controls and the switches. Otherwise, the Mark II (there is no mook) will be useful primarily as an introduction to analog synth music. If you just want to play music on something similar cheaper get the KORG monotron off of amazon.

SX-150 Mark I Synth

SX-150 Synthesizer (3300 yen): Ok, I finally broke down and bought the synth. Actually, I’ve been wanting to get this kit for weeks, I was just waiting to reduce my “snack money for kits” debt, while also squeezing out as much remaining entertainment value as I could get from the other kits I already own. However, that opened me up to a rather rude shock. One Sunday, I’m in two different bookstores in Akihabara, looking at the synth kit mook to see what’s required to add a 6V power adapter jack. The following Tuesday afternoon, the synth is sold out from both stores. Since I work Tuesday evenings, I didn’t have time to try looking anywhere else, so I had to sit and wait. The next day, I go to another shop – also sold out. This place had an entire stack of the kits a few weeks earlier, and now, nothing. Which is a little strange, since the synth had only come out last August and it’s going out of stock so quickly. But understandable since the smaller stores want to free up shelf space for selling the newest products. Anyway, I went into Kinokuniya in east Shinjuku, and they had two kits there – I bought both since my current plans are for using up to 3 kits on my homemade keyboard. Moral – buy what you need when you can (I’ll get the third later if my plans work out).

(The kit, once it’s assembled.)

The SX-150 is very similar to an analog synthesizer that PAiA Co. used to sell back in the 1980’s (PAiA’s still in business selling synth kits, but this one’s not in their catalog anymore). It has a simple triangle wave/square wave generator, controls for Attack, Decay, Pitch and Cutoff, plus a reverb switch. There’s an on-off switch, ext. source input and headphones output. The “keyboard” is a ceramic-like resistive strip and stylus. Where you put the stylus on the strip changes the output sound frequency. The case is heavy plastic, but the bottom plate is just a pre-punched piece of cardboard from the box the kit came in. The synth output is fairly limited as-is, being able to come close to a violin or a bass guitar, but mostly producing only sound effects suitable for 8-bit video games. The knobs and controls are flimsy, and the screw for holding on the bottom plate is too short to hold the plate in place (one of the knobs fell off when I was taking the kit apart, and it rolled somewhere so remote that I can no longer find it).

It’s a very simple kit, compared to the rest of the Otona no Kagaku series – the case, 5 knobs, the resistive strip, the stylus, the circuit board with speaker pre-wired, and 8 screws. There’s also a sheet of stickers if you want to fancy up the knobs and case. Even if you take your time and read the instructions carefully to ensure that you do everything right, it’ll take less than 15 minutes to assemble it.

(I’ve got the 6V DC adapter jack added already. Next is the jack for the noise generator input.)

My first mod was to add a jack for an external 6V DC power adapter. The second was my keyboard, and the third is a simple resistor string. The mook describes a mechanical sequencer (a hand-cranked drum with contacts to various resistive strips), a MIDI converter circuit, tactile bumps for use by the visually impaired, and how to make a wooden case and stylus. Youtube has a number of videos showing additional mods, like adding a piano-type keyboard, a push button bank, a larger resistive strip, a trill function and a noise generator. There’s one video showing a variety of enhancements to the waveform circuits themselves. What I haven’t seen yet, though, is a PC-driven digital controller to replace the ADSR volume controls. I’ve already built the fingertip keyboard circuit.

(From the bottom, minus the cardboard cover plate.

The Ext. Source jack feeds an F/V circuit (which I’m assuming means Frequency to Voltage), so any input source that has a changing frequency can replace the resistive strip. The mook suggests connecting up the Theremin for this, but it’s just as easy to plug in an MP3 player headphone jack (mono plug only), or to use Gakken’s Poulson Wire Recorder. The point is that there’s a lot of unexplored ideas for modding up the other Gakken kits to work in combination with the SX-150 (which I’ve already done for the Theremin).

(The full set-up (so far) – 2 synths, the keyboard, the relay and pots bank, and the theremin hooked up as an external input source. I’ve turned two pencils into fake drum sticks.)

The mook is a wonderful look into the history of synthesizers and the musicians that love them. There are various products from Moog, Roland, etc.; looks at Keith Emerson, Kraftwerk and Devo; and interviews with many Japanese musicians and engineers, including YMO (Yellow Magic Orchestra). There’s a comparison between physical synthesizers and software versions. And, there’s a description of a demo version of a software synth program called MT-1 (Music Track 1). (musictrack.jp) And, if you needed suggestions, YMO offers settings for specific sounds for the SX-150 (electric guitar, ambulance siren, cat voice, and synth drums).

One of the guys mentioned in the mook has a few additional mods explained on his website. They include a couple variations on the ribbon controller, some changes to the waveform circuits, and an analog sequencer (same one shown in the mook).

(It’s a little “rats-nesty”, but I’ll get some tie wraps for that later.)

Summary: Of all the Gakken Otona no Kagaku (Adult Science) kits, the SX-150 is the one most amenable to being modded. Out of the box, the sound range is very limited, thin and unsophisticated. There’s no force control, so how hard you tap the resistive strip doesn’t affect the sound out (unlike a piano key). But you can’t expect much for 3000 yen (3300 including tax = $33 USD). Then again, with all of the mod suggestions, and possible sounds you can get when you’re done, $33 is an incredible deal, even if you just look at the entertainment value for reading the mook and the time spent on experimenting with the kit. Sure, you can get better synths for just a few hundred dollars, but the little SX-150 is still a fun toy to play with. Get 3 – they’re small. But only while supplies last.


Of all the Gakken kits I know of, the SX-150 analog synthesizer is the only one that really lets you modify it even before you have the kit in your hands. Because people have been using synths in a hobbyist capacity for well over 20 years, most of the standard circuits and sound modules have long been available on the market, and it’s a simple matter to determine what the SX-150 is missing, and how to add it. A case in point is the MIDI controller. One person posted a home-made controller video on youtube before the SX-150 even hit the shelves back last August.

After going through all of the youtube videos featuring the SX-150 that I could find, I decided that I’d make the fingertip keyboard in advance of buying the synth itself. This was both a good and a bad idea. First, it gave me something to keep busy with for over a week, from sketching up the initial layout to trying to find which parts were available where, to actually building it. Secondly, it broke the bank. I’ve been foregoing snacks and Tully’s coffee in order to redirect the money into buying the Gakken kits. I can generally scrape up $25 a week this way, but I’ve been getting really sleepy during the day, and hungry before I finish work at night. Normally, I’d just buy 1 Gakken kit a month, and the remaining money would go to paying off the “debt” I’d accumulated when buying all of the older Gakken kits prior to them going out of print. I’d gotten my debt down to $90, and then the keyboard circuit single-handedly more than doubled that.

The single biggest cost were the relays. I wanted 12 switches, and I wanted each switch to turn LEDs on and off along with making sounds from the synth. I tried going with a mini 3V relay, but the shops only had 1-pole 3V relays, meaning that I couldn’t use the LEDs with it. The next higher voltage relay I could find was 5V, and there were double-pole double-throw relays in this range, but they cost about $1 more. 12 relays at $3.80 each ran me almost $48 right there. The circuit board was $6, and the 2 terminal blocks were $7 each. All of the other hardware, resistors, and LEDs totaled about $30 all together. At least two of the LEDs burned out for some reason and needed replacing, but at 30 cents each, that’s the least of my worries. The LEDs are only cosmetic, anyway. The potentiometers are what actually drive the synth.

The next biggest expense was the 50 K ohm potentiometers, since I needed 12 of them, and they’re about $2.50 apiece, and the plastic knobs will be another $1.50 each. So that’s another $45-$50 right there. Anyway, I now have a working keyboard and relay bank, sans the synth.

Then again, one of the interesting things about this entire set-up is that I could use the keyboard to drive multiple synths. Program 3 synths to three different sounds, then wire them to 4 each of the pads on the keyboard and route the outputs through a mixer to a single amp. This makes for a decent little drum kit. Unfortunately, the SX-150s are $35 each ($28 from a used book shop via Amazon + $3 for shipping). So, getting 3 of them would put me another 3 weeks into “the hole of no snacks, no lunch and no breakfast on weekends”. Not to mention that the little mixer I’ve been eying is $75 to $98…

Kit 32: Denshi Mini Block

Gakken has been moving steadily into the electronics realm over the last 1-2 years, starting with the DC motor car, then the theremin, Poulson recorder, guitar and the Japanino. Kit #32, the latest one out, is the first real step into electronics design. With the previous kits, the electronics concepts were still masked by the surface application (i.e. – producing music, or writing software). But, the 25 block mini Denshi kit actually requires you to learn how transistors work and to calculate current flow in order to avoid blowing out the more sensitive parts.

Kit #32, Mini Denshi Block, released Nov. 30, 2011, 4000 yen ($50 USD).
Includes suggestions for 50 different experiments.

(The kit is about 4″ x 6″. Shown here with the earphone, microphone cup, and two jumper wires (used as contacts, sensors, switch plates and jumpers.) You can remove the ear piece from the earphone and replace it with the cup to turn the earphone into a microphone for the amplifier speaker and PA circuits. The decal at the top left corner refers to the wiring of the contacts running along the left side of the case. Primarily, the left side contacts are for the radio tuning coil.)

The mini Denshi (“electronics”) set is a scaled-down version of the EX-150, but the principles are the same. You start out with a plastic holding case, and 25 plastic cubes. Each cube contains one part – a wire, resistor, transistor, diode, LED, capacitor, etc. The holding case has fingers at the bottom to allow you to snap in each of the components as you like. Contacts on the inside of the case touch the contacts on the sides of the cubes to form the circuit. The holding case also contains the battery pack (3 AAA’s), a power switch, an adjustable coil and a speaker. Actually, building the suggested circuits is pretty simple, since the cubes are all clearly marked and you just have to follow the pictures. The case itself requires assembly (mounting the speaker, switch, decals, battery holder, etc. The suggested time is 20 minutes, and it took me about 15. The main challenge is in routing the wires to avoid having them float or get pinched.) If you want to have a bottom cover over the wires and circuit board, you’re encouraged to punch out the plate from the main box and stick it in place using double-sided tape. I didn’t bother with it because the plate is just cheap cardboard.

(Back view. Cardboard backplate not included. You can see the speaker, speaker driver board, batteries, and radio tuning coil at the top of the case.)

Now, as for the theory behind the kit… Well, I went to a technical school for 2 years for an associate’s degree, and then a university for another 4 to get my BSEE. This is not something you’ll pick up after reading a blog entry for 5 minutes. Suffice it to say that you can get some information from wikipedia, and the Gakken site will probably have English instructions by the time the kit makes its way to the U.S.

Some highlights – current flows from positive to negative. By convention, “ground” is 0V. With the 3 AAA batteries, the power pin will be around +4.5V. It doesn’t take much to destroy a transistor or a diode, so if you don’t know what you’re doing, just be real sure to closely follow the pictures in the mook.

There is a relationship between voltage, current and resistance. It’s called Ohm’s Law, and it looks like:
Voltage = current * resistance. or,
V = I * R

If you have a 10 milliamp fuse, you need at least:
R = 4.5V / 0.01A = a 450 ohm resistor or bigger

in series (in line) with the fuse to avoid burning it out. Since LEDs are like 40 or 50 mA fuses, you should put a 220 ohm resistor in series with an LED to protect it as a general rule. Fortunately, the 2 LED blocks (1 red LED, the other green) both have the resistors already wired in for you.

If a diode, LED or transistor is damaged, it usually dies right there. If it’s dead, forget about the circuit working any more. So, BE CAREFUL.

It’s hard to draw an electrical circuit to look like something in the real world. Instead, we use special symbols to represent the individual components of a circuit. The total circuit picture is called a “schematic diagram” (or “circuit schematic”). When you look at the cubes of the kit, you’ll see these schematic symbols stenciled on the top of each one.

Another thing to keep in mind is that the direction of the component matters for diodes, LEDs and transistors. If you put the part in backwards, the circuit won’t work. You may not damage the component, but the thing you’re trying to build won’t do anything, or, at least, won’t do it right. Additionally, certain kinds of capacitors do care which direction they’re facing, and can suffer physical damage if plugged in the wrong way. So, again, be sure to have the blocks in the circuit look exactly like they are in the pictures in the mook.

Regarding the mook – it’s 124 pages this time, roughly 2/3’s of which is dedicated to the assembly of the kit, and the descriptions of the 50 circuits you can build. There’s another 6 circuits identified as “Denchi mini 120%”, which can only be built if you have 2 kits. Many of the circuits are kind of silly, such as making variations on the “turn on the LED with 1, 2, or 3 switches” – these are essentially the same circuit but using extra wires. Some of the circuits attempt to teach how AND, NOR and XOR gates work, but again, it’s just one transistor with different switch wiring configurations. The Lie Detector and the Love Compatibility circuits are also very similar. Probably the more interesting projects are the crystal radio with 1-transistor amplifier, and the analog synthesizer. If you’ve got 2 kits, then you can make the wireless transmitter and receiver.

Articles in the mook include artistic photos of old circuit boards (including a Korg 800DV synth, and a Hitac-10 mainframe computer), art projects using the denchi blocks to make running figures, a story on the history of the denchi block product dating back to 1966, and a study in optical illusions and how the wiring of the human eye and brain allow illusions to work. No real theory of electronics, history of the science, or biographies of the scientists involved in it this time. The manga at the back of the mook talks about animal sex.

Suggestions for modding the kit include: putting it in a rabbit pouch to turn it into a purse; driving LEDs to make an illuminated photo of the Big Dipper; driving larger circuits for a synth and a rhythm box; making a Geiger counter; and wiring up to a Japanino to make an LED bar volume level display. I would argue that if you’re going to build the rest of the support circuitry for a Geiger counter, that there’s no real need to put the denchi block kit in the circuit because it’s so bulky compared to the rest of the assembly. But, if you have the denchi block kit, I guess you’re going to want to make the most use of it.

The kit works fine for making the various suggested circuits, and it is very well-constructed. The spring contacts do push the blocks apart a bit so you’ll need to keep pushing them down into place as you assemble the experiment to ensure electrical contact. But, on the whole it is a good introduction to simple electronic design, without requiring the use of solder and an iron. Meaning that it’s good for kids to play with (under adult supervision, of course). My only complaint is that there’s no direct source for cheap blank blocks for adding in more components later (I’d like some more capacitors, other colors of LEDs, and at least one trim pot.) That, and if you get this as an import it’s going to be at least $65 USD, which places it on the low side of the bang for the buck scale. It would have been nice to have this kit when I was in tech school.

Kit 31: Ornithopter and Entomopter

Gakken Kit #31: The ornithopter and the entomopter, 2400 yen.
Ever since mankind has wished to fly, we’ve been using birds as the starting point, generally basing the designs on wings that flap rather than the more modern fixed-wing concept. These kinds of aircraft are called “ornithopters”, from the Greek “ornithos” (bird) and “pteron” (wing). If you’re under age 30, there’s a good chance that you may have been exposed to ornithopters either in school science classes or as a toy at home. The Ornithopter Zone is a good resource for building your own and entering them into competitions.

On the other hand, insects haven’t been as popular a research subject for artificial flight. The “entomopter” (which gets its name from the Greek “entomo” (insect) and “pteron” again) is, as defined by wikipedia, a “multimode (flying/crawling) insect-like robot developed by Prof. Robert C. Michelson and his design team from the Georgia Tech Research Institute (GTRI)”. It is classed as a subset of the ornithopter. According to Michelson’s own official Entomopter Project website, DARPA funding for a new kind of powered-flight craft was provided in 1998, and the first patent on one of the moving components of the craft was granted in 2002. While some of the applications are for the military, there’s interest in using the entomopter for Mars surface exploration.

(Ornithopter on the launcher stand.)

Because both the ornithopter and the entomopter are so well documented on wikipedia, there’s no point in my talking about the mechanics or physics here. The important thing is that kit #31 allows you to build rubber band-driven versions of both and compare them in terms of motion and flight effectiveness. (For motive power, the ornithopter front wings flap; the tail is just used for changing attack angles. For the entomopter, the front wing is one unit that wags up and down, and the stationary tail just acts as a stabilizer.)

#31 has roughly 40 parts. Gakken recommends 90 minutes for assembling both kits. It took me closer to 2.5 hours, partly because I was having trouble figuring out the instructions, and the fact that I kept using the entomopter parts for the ornithopter (which is the first one you build according to the instructions). If you buy kit #31 as an import, odds are that the English instructions will be posted to the Gakken site by the time you get it in your hands. This is very important, because there are a couple easy mistakes to make which can ruin the kit. First and foremost is the fact that the plastic sheet for the wing material is in fact two sheets that you start out cutting at the same time. You only need one sheet, so separate them before cutting the wings out, or you may end up mangling your back-up material. Second is that the entomopter front and back wings look very similar, but the front wing needs to be the wider of the two. Third, when you’re applying the wings to the double-sided tape, it helps to have someone assisting you. The film is drawn to the tape, making it hard to apply correctly. For the ornithopter, there’s a notch in the film that goes at the front of the front wing. You want to center this notch around the “shoulder” of the wing, and avoid having too much slack around the joint before the wing touches the tape. Unlike the mess that I created of things. Fourth, the shoulder action of the entomopter can be a little confusing when it comes to centering the carbon rod and affixing the wing material. It may be obvious to most people (apparently not to me, though) that the center point is the back spine. You want the arms to extend 10 cm either side of the spine, and the dotted line of the wing to sit atop the spine. The entomopter will still fly regardless, but it won’t look as cool otherwise.

(Launcher stand, cocked.)

Also, some of the thinner pieces can be very brittle and will snap in two while you’re removing the flash from the parts. This may be one good reason for not bothering trimming the flash off to pretty up the final assembly. I snapped the back spine of the entomopter, and gluing the pieces together added to my total assembly time. (I should mention that the pieces come still attached to the molding frame and need an x-acto knife to be cut apart. If you build the launcher you’ll also need a small Phillips driver for the 3 screws.)

As for flying the kits – there’s a little rubber band-driven launcher that holds the wing drive rod in place as you wind the main rubber band for either the entomopter or the ornithopter. The launcher will fire the kit into the air for those people too skittish to hold it in their hands before letting go. Again, it helps to have two people – one to hold the prop in place and the other to wind the rubber band using the crank in the back. Because of the torque involved, if you try to do it yourself holding only the front and back of the kit, you can damage the balsa wood body piece if you do it wrong. I found that I could wind the rubber band better without the launcher and I got better results just by throwing the kits into the air by hand. Even fully wound, the ornithopter only flapped for 5 seconds, and the entomopter for 3. If the wind is right, the ornithopter will get another 3-5 seconds of glide time. The entomopter isn’t designed for gliding and will land within a couple of seconds. Your results will vary depending on how far off the ground you throw the kits (obviously, starting at the top of an apartment building will get more glide time).

The mook includes articles that talk about how both birds and insects fly, as well as getting into the specifics of both plastic models. There’s a speculative piece on bio-mecha for exploring Mars in the year 2040, and a pictorial on the construction of a 787 jet aircraft. Additional articles include the inevitable history of failed man-powered craft; different kinds of home-made flying models; pictures of birds, insects and mammals in flight; mods to the two kits (basically different patterns for the wing materials); and some alternative power sources. The latter article ties in with the entomopter, because the original design includes an anaerobic chemical engine applicable for use in Mars’ atmosphere. The remaining articles are about the possible evolution of dinosaurs into birds; a paper punch-out zoetrope of a bird in flight; a manga on how the human tongue detects flavor; and home-made projects such as a cardboard box Gundam model, and a bicycle made mostly out of wood. I should also mention that there’s a Japanino project for syncing up a digicam with the entomopter as it comes off the launcher.

As for the zoetrope – it’s a small strip of magazine bond paper placed on a disk in a circle, with notches and pictures on either side, rotating on a toothpick. One side is a bird in flight, the other is the ornithopter. The effect doesn’t work well unless you tape the pieces together, making it more difficult to flip the strip over to see the second animation. And the slots in the sides are too narrow to let you see the pictures on the strips clearly. A nice idea but not very successful. However, it should give you some ideas if you choose to make your own zoetrope. One mod that would help would be to take a 3″ 6×32 bolt, a nut and some washers, and use that to make a more stable axis. This could then be mounted to a turntable to facilitate the rotation.

Links given in the mook:
Smart Bird
Butterfly Robot

More ornithopter designs
Mars drone plane
Sano Magic’s Wooden Bikes
Otto Lilienthal Museum

Note: Otto Lilienthal was a German inventor who pioneered glider flight. His research was used by the Wright Brothers for their own powered airplane designs. Otto was known as “the Glider King”.

In the last entry, I posted a rant on how the increased prices were threatening to make the Otona no Kagaku kits a bad deal if you buy them as imports in the U.S. at roughly a 2x mark-up. Kit #31 is cheaper, at 2400 yen ($28 USD). Is it worth buying as an import? Unless you’re a science teacher, probably not. This kit IS a great introduction to artificial flight, and it could be a good way to take up making your own craft, if you go to the Ornithopter Zone site for more blueprints and suggestions on getting into competitions. So, in that sense, money is probably not an obstacle. But, if you just want to have something to build and play with, you may be happier getting an RC kit from a local store for the same amount.

Theo Jansen Rhino

[Note: The Rhino was released between kits #31 and #32, but I’m including it now to keep it with the first Jansen kit.]

Otona no Kagaku – Mini-Rhinoceros, 3500 yen. The Animaris Rhinoceros is referred to as a “transport-style” beest, and the youtube video shows someone pulling it while a second could be riding inside. It’s one of the few of Theo Jansen’s beests that isn’t wind-powered. But it’s also one that actually has a practical purpose. The Rhino-Mini kit is a scaled-down version of the Rhino, measuring about 18 cm x 16 cm x 14 cm (7.1″ x 6.3″ x 5.5″). It’s made of light-weight plastic, but uses 2 small steel rods for holding the assembly together. The kit itself is wind-powered, with a little squirrel cage-style fan on top, but several of the suggested mods include replacing the fan with an electric fan or motor. My thought is that the life-sized version should be propelled by walking on a stairmaster in the main cab.

The only real mechanical difference between the mini-Strandbeest and the mini-Rhino is in the design of the legs. The theory behind the mechanics of the Jansen linkage is the same in both cases. The mini-Rhino has over 80 parts, and a recommended assembly time of 90 minutes. It took me a little longer than that because I wanted to remove the flash from the parts with a knife. All the pieces snap together so there’s no need for other tools. However, flash could conceivably rub against other moving parts, and I didn’t want to run the risk of having to disassemble the thing if it didn’t move smoothly (which was the problem I had with kit #30). The plastic is soft enough to be trimmed easily, but it’s still not something you want kids to do themselves. The instructions are pretty clear this time, and it’s pretty obvious what the order is for snapping the control rods to the crankshaft. Unlike with kit #30, the mini-Rhino walks unencumbered, although if you’re using a fan to spin the squirrel cage, there is an ideal attack angle involved. There’s also a separate drive rod for hand-powering the kit . The finished pieces don’t really fit together tightly, so you have to be careful about stripping the gears, or having the squirrel cage fan derail.

If you have some of the previous mooks, then the special mook is a little redundant, even though the material is all new. The first 16 pages are studies of the rhino animaris, the strandebeest and one or two of Theo’s latest concepts. This is followed by variations of the Rhino and examples of how the Jansen linkage can be put to use for artificial limbs. The next 8 pages are attempts at making robots based on snakes, tadpoles, lizards, cats and dogs. The Otaku Club section takes a look at Project Skeletonics, a group working on an exoskeleton; and a guy that makes robotic fish (more photos at hayashi). The suggested mods for the mini-rhino are to decorate it with fake barnacles, turn it into a horse-drawn cart, to make a mechanical wind-up crab with two of the legs, and to build an 8-arm cymbal-playing machine. The final article is the study of the movement of fossil creatures, and there’s a manga on the life of cockroaches (drawn by former Tezuka assistant and current director of the Suginami Animation Museum, Shinichi Suzuki). There’s also a one-page ad for a new “Sound Gadget” series of kits to come out from Gakken this Fall. Scheduled kits include the Udar, and the SX-150 Mark II (no prices, though. I’m assuming that the dedicated sound gadget series will allow Gakken to charge more, as with the premium theremin and the SX-150 synth.)

As always, the mook has a lot of nice pictures and some articles that introduce actual science concepts. However, this one does seem a little rushed, and a little lacking in historical content. At 3500 yen ($42 USD), it’s also at the top end of what I consider affordable. The mini-rhino is fun to watch, but just standing there waving a fan at it to make it go gets old fast. The ideal would be to put in a solar-powered motor and a couple switches and allow it to wander around the yard on its own. You can put it out in a parking lot on a windy day and scare the dogs, too, which is always good clean fun. But, I think it is a little lacking in replay value as-is.


One of the interesting things about the Gakken Otona no Kagaku “beest” kits is that with the Strandebeest, which is normally wind-driven, one of the suggested mods is to add a Japanino-driven motor to make it remote-controlled. While with the Rhinoceros, which is man-powered, the Gakken version uses a fan and there’s no suggestion in the attached mook for adding a motor. When I had my mini-Strandebeest, I tried adding a motor, but the movement of the legs was so stiff that the motor wouldn’t spin and the wires overheated. So, I was a little hesitant to buy the mini-rhino. Fortunately, the legs are geared down so much that the fan propels it with just a moderate breeze. Naturally, the next step was to figure out how to automate it.

I was able to find a small electric fan for 100 yen ($1.20 USD), which runs on 2 AA batteries. After a little experimenting, I came up with a mounting for it that consists of 4 thin sheets of cardboard glued together. If I was still in Akihabara I’d just get a sheet of perf board, but the cardboard, at least, is free. Also at the 100 Yen shop, I got a small package of nuts and bolts, and some tie-wraps. I hand-bored holes in the body of the kit for mounting the cardboard panel, and just tie-wrapped the fan battery casing and the motor in place. Luckily, the little white gear on the squirrel cage fan spindle turns out to fit on the motor spindle perfectly. One reason for mounting the motor on the panel, instead of hot gluing everything to the kit body is that it lets me switch between the motor and the squirrel fan as I like.

Initially, I wanted to mount the panel so that it brought both arms of the kit together a bit for added structural integrity, but this caused the gear threads to pull apart from each other and disengage. Seems that the kit was designed for the arms to be pushed apart instead. But, at that point I’d already drilled the holes on one side of the panel too close to the edge and the corners tore off. If I were to do this again, I’d go with the perf board and just slot the two far-end holes to make adjusting the arm tension (and gear spacing) easier. Another issue was that even with the gearing ratio as it is, the motor ran so fast that the legs thrashed about extremely hard and threatened to self-destruct. Because I don’t have access to a 1-battery holder, a soldering iron, or a potentiometer right now, I pulled out a good battery and replaced it with one that was nearly dead. Coupled with the extra workload associated with having to carry the motor, plastic case and batteries, the resulting walking speed is much more sedate and acceptable.

Link to Youtube video

In summary, I give myself a B for the final product. It make not look all that great, but it works as well as I could hope for. If I had my Japanino, I’d get a second motor, split the mini-rhino in two, and turn it into a proper self-sufficient programmable robot. Maybe another day.

Kit 30: Animaris Ordis Parvus

Gakken Otona no Kagaku Kit #30 – the Animaris Ordis Parvus, 3500 yen (approx. $45 USD). This kit is a miniature version of one made by the Dutch physicist-turned-artist Theo Jansen. You can see more of his work at his website.

The key element of Theo’s creations is a linkage mechanism, called the Jansen Linkage. According to Jansen himself, this mechanism has 11 dimensions, based on rod length and pivot point positions, that can be calculated to create a specific foot path. By placing several of these feet side-by-side in a phased stepping pattern, you can get a very smooth horizontal movement, similar to what you get with a car tire with a shock absorber. The difference is that by having feet instead of wheels, a mechanism can move more easily across sand.

Jansen’s concept is to have a series of machines using the Jansen linkage roaming along the beaches near his home. The machines are powered by wind pushing against the banners making up the “spine” of the “beests”, and they’re generally built out of PVC tubing, although there are some “species” using other materials. The beests can “think” in a fashion. A hose attached to the nose of one beest can sense when it gets too close to the water, alerting it to turn around and go the other way. Energy from the wind can be stored in the form of pressurized soda bottles to allow the beests to keep moving when the wind dies down. Another set of soda bottles interconnected with hoses forms a 6-8 bit “brain” to allow the beest to make simple decisions, and a mechanism that pounds a stake into the ground lets the beest anchor itself during a heavy storm. Overall, “beests” are powered by mechanical forces, and use mechanical systems for decision-making and situation analysis.

The release of the Gakken kit coincided with the exhibit on Theo Jansen that was held at the Tokyo Miraikan (“Future Museum”) in Odaiba, until Feb. 14, 2011. Admission was 1800 yen ($24 USD) for adults.

(Putting in the feet)

This kit has close to 100 pieces, and a recommended construction time of 90 minutes. For me, the most time-consuming part was in removing the extra plastic from the pieces with a cutter, and putting the feet on the legs. Most of the instructions are all pretty self-explanatory and you can follow them just from the pictures. The most difficult thing for me was in trying to figure out the first step. This is where you’re being told to put the feet on the legs, but the picture is confusing. There’s a strip of 13 little rubber feet. You tear one off and push it into place in the holder gap of one of the 12 legs (this will leave one foot left over). There’s an easy way for the foot to slide into place, and a hard way. You can figure out which is which pretty quickly.

(Leg assemblies)

Once the feet are in place, build up the leg assemblies. When you have all 12 legs, start building the frame. You take a frame piece and connect it to one of the two crankshafts. Then, use the connector rods to attach one leg on each side of the crankshaft, attached to one crank rod. When the first two legs are attached, put on the second frame piece and go to the next 2 legs. When all 6 legs are attached, add the last frame piece, and then do the second half of the beest.

(If the frame looks like this, you did it wrong. You have to build up the frame as you put each pair of legs on.)

If you look at the finished assembly detail you can see that the connector rods from the legs to the crankshaft have a specific location order. The connecting rods do naturally want to attach in this order, so it’s not too difficult to get this right. Basically, you’re just trying to avoid the feet from hitting each other. Note that you don’t need any special tools for this kit – just the exacto knife if you want to remove excess plastic from the frame joints. The final product is about 4″ tall and 6″ long.

There are a lot of different mods suggested in the mook. The first and foremost is motive power. The normal power source is wind against the fan blades. But, unless you have a really strong wind, it’s not going to move. The second alternative normal source is to connect a plastic rod to the drive shaft using a rubber tube connector and turn the rod by hand. But, the connector piece may be too elastic and may just twist around itself instead of turning the crankshaft. The first real mod is to take a piece of one of the frames, trim it, and use it to wind up a rubber band to turn the crankshaft. This works, but you need a drill if you want to put a hole in the frame piece (otherwise, no other tools needed). After this, other mods include connecting two beests in series or parallel, running them with a solar-panel driven motor, or using two 3V motors to run 2 beests driven by a Japanino.

(Correctly assembled frame with legs.)

My beest has a problem with relatively high torque on the drive shaft, probably caused by the legs rubbing against each other. This makes playing with it in the wind troublesome. Putting a weight on top makes the beest move more smoothly along the floor, but doesn’t address the torque issue. I think that using the wind-up rubber band, or a 3V motor with a connecting gear, is the best way to go. Please note, though, that the Otona no Kagaku troubleshooting page states that this problem is caused by connecting the legs in the wrong order to the crankshaft, so it may be fixable in most cases.

The mook consists largely of articles on Theo Jansen and his creations. There’s no real “history of the main topic” section this time, since nothing like the beests pre-dates 1990. There is one article on modern kinetic sculptures, a good 10 pages on mods to the Animaris and variations on Theo’s beests, and 10 pages on making the Japanino-driven bluetooth-enabled RC duo-Animarus. The hobbyist highlight corner has sculptures carved from toothpicks, a worm mechanism, and ships made out of recycled paper. There is one article on the mechanics and motion path of a Jansen linkage, and comparisons to how flesh-and-blood muscles move. Finally, there’s a 12-page manga on products that cause hair regrowth in balding men.

Links from the mook:

Steel beest
Lego Beest
RC Walking Robot
Steam Spider
Strandbeest Desktop
Street Beest
Theo Jansen Walker
Schnee Beast
Straw Jansen
Papercraft Theo Jansen’s Mechanism


An unfortunate side effect of time is that after a while prices go up. When the putt put boat first came out in 2003, the Gakken kits ran around 1600 yen apiece. The first price bump occurred 18 months later, and by 2006 the kits were 2100 or 2200 each. The really big jump came on Dec., 2009, with the electric guitar, at 3675 yen, but the prices dropped a bit to between 3300 and 2950 since then. Because the kits have been fairly complex lately, the increased prices haven’t been that distracting. The Animaris Ordis Parvis, though, is 3500 yen and if you get it as an import in the U.S., it will probably be between $70 and $90. Are the Gakken kits worth this much money now?

For the Animaris Ordis Parvis, the answer is “maybe”. If you have the Japanino, you can connect up a motor, solder in a bluetooth module on the Japanino, and play with the Animaris as an RC car.

But, for me, the kits are getting a little too expensive for what they include. The electric guitar suffers from an inability to stay in tune because the strings get stretched out of shape too quickly, so I can’t really play it much. The Edo Clock is noisy, with the ticking being really loud late at night, plus it needs to be readjusted to correct for the changes in daylight all the time. The origami lantern is nice, once you decide on the lantern cover to put on it, but if you have the Japanino, you can make the lantern yourself just by buying a $2-$3 tri-color LED. The Japanino is the only kit that I’m still using 8 months later. Bottom line is I think that it’s becoming more important now to decide in advance just what you want out of these kits. If you like learning about the science behind a specific kind of technology, and you like building stuff, these kits are still worth the price. If you’re looking for toys to play with, and things to kill time with, you’re better off just buying commercial products designed for specific tasks – such as a digital clock, a lava lamp, or a Gibson Stratocaster. What this means is that I’m buying the Animaris to be able to review it here. A few weeks from now, I’ll be trying to find a good home for it to make room on my shelves for things I really want to keep long-term.

On the other hand, the kits seem to be coming out less frequently. Originally it was 4 kits a year, at roughly 3-month intervals. But, it looks like there’s going to be a 6-month gap between kits 30 and 31. I don’t know what Gakken’s strategy is, but it may be one of fewer kits per year, with higher-quality, more expensive kits.

Kit 29: Akari Origami

One of the interesting things about the publishing world is that a publisher has to announce some time in advance what their next book or magazine is going to be. In the case of Gakken, it’s when the next kit is coming out. When things become more amusing is at the point where one kit hasn’t hit the shelves yet, but the Gakken website has to announce the contents of the subsequent kit. What I mean is that kit #29, the Akari, had a Nov. 5 release. On Oct. 30, the official artwork was placed on the website. That meant that kit #30 also had to be placed on the website for the “Next Up” page. So, I can write up a short comment on kit #30 a week before I can get my hands on #29. It also means that I can pull up the PDF for #29 and see how difficult the assembly is going to be (short answer – there’s two parts: the stand and the lamp shade. The stand is about 10 parts and can be put together in a minute or two. The lamp shade is paper folded in any shape you want, so it can be as easy as a cylinder held in place with tape, or something that looks like the faces of Mount Rushmore. You can finish this kit in under 5 minutes, or over 5 days.)


Kit #29, Akari Origami, 3000 yen. Akari means “light”; origami is the Japanese art of paper folding. The kit itself is a circuit board driving a small holder containing a tricolor LED (red, blue and green). The board is in the base of the stand, and has connectors for wiring to the Japanino. This lets you set up any series of patterns for the LEDs that you like, if you also own the Japanino.

Now that I have the kit in my hands, I can say that there are 10 pieces, not including screws, plus sets of sheets of white paper for making the square-fold lamp cover (the Checker) and the curly polygon (the Celes). The suggested assembly time is 30 minutes. I completed the base in about 10 minutes. I’ll talk about the covers later. The only bit that’s even slightly tricky about the case is when you put the circuit boards into the base piece – it may not look like it but there is an orientation to the base. The small circular hole part at one side of the base needs to line up with the push button on the bigger half of the circuit board. You’ll probably have 2 or 3 of the screws in place before you discover that you did it wrong and have to start over again.

(Close-up of the LED.)

The Akari is very similar to the Aurorarium in that they both have switch-selectable display modes (single-color shades, or fading in and out pseudo-randomly) and the 3-color LEDS. The differences are that the Aurorarium bounces the light down on a motor-driven mylar sheet, and the Akari has 3 volume controls for individually making the LEDs brighter or dimmer. They’re both about as bulky, although the Akari is has a more stable base for holding lamp shades of various sizes. The base and light stem are 6″ tall, total. The base is about 3″ across. If you’ve got the Aurorarium, I’d suggest disconnecting the motor, and redirecting the LEDs upward and putting a lamp shade on that – it’d be cheaper because the Aurorarium is only 2200 yen (about $26 USD).

(Checker cover.)

Origami is the art of folding paper. Kirigami is the art of cutting paper. Amigami is the art of paper weaving. The mook suggests using any or all of the 3 arts for making the lamp shade. Some of the suggestions are a fish, a duck and a flower. The mook goes into a lot of detail regarding how to make single “units” – paper folded into specific shapes with pockets on each of the faces. By interlocking the pointy sections into the matching pockets, you can make polygons with 5, 6 or 30 “units”. This allows you to make lamp shades as simple and small, or as large and complex as you like. Or, you can just roll the paper into a cylinder and put that on the lamp.

(Celes cover.)

The mook starts out with photos of an art installation, where a number of Akari lamps are set up inside a cave. After this are several pages of lamp shade suggestions, examples of silhouettes in ukiyo-e and European artwork, examples of lighting used in different ways in modern architecture – including the LED illuminations on Tokyo Tower and the new Sky Tree. There are examples of polyhedrons in nature, and paper masks from a modern Japanese artist. There’s the requisite display of antique forms of lighting (from oil lamps up through carbon arcs and the incandescent bulb). Plus the theory of operation for LEDs.

Oddly enough, there’s a two page spread on the kinetic sculptures by Theo Jansen (see below) which are the featured project for Gakken kit #30. There’s also some examples of personal projects, including a racing bike that has solar-powered electronics mounted on it, a windbreaker with an 8×8 LED matrix on the back, and a Lego robot made for playing Othello.

The Akari has a 4-pin connector for running wires to the digital I/O pins of the Japanino (D9-11 and gnd). This connects the Japanino directly to the Akari’s LEDs. One sketch is to just write random values (0-255) to the PWM pins and pause a quarter-second, in a loop. Mio Izawa put a clear plastic globe around the LED portion and then spun little plastic balls around while the Japanino strobed the LEDs on and off rapidly, making for a “psychedelic worm” effect. Artist Julie Watai removed the LEDs from the Akari, connected them directly to the Japanino, and put everything into a clear housing for a “magic crystal therapy” effect. Finally, there’s a sketch for getting weather information from your Mac over the USB port in serial data form, and using that for changing the color patterns based on whether the weather is fair, cloudy or rainy.

Last, the mook has a manga describing the making of alcohol, and its affects on the brain. (“Everything in moderation.”)

About making the paper lamp covers: As mentioned above, the kit includes sheets for the square-fold (checker) and curly polygon (Celes) covers. The Checker consists of 6 sheets of pre-scored bond paper. The idea is that you fold each sheet into a “unit”, then interlock the units together to make the finished cube. I spent a lot of time double-checking my work, so it took me about 20-30 minutes. Having the paper pre-scored makes folding it a whole lot easier; if you drew out, cut and folded the units from scratch it could take at least an hour to make this one. You want to use heavy bond paper; anything lighter will rip or deform. Anything heavier will be too thick and and bulky when folded into units.

Naturally, after buying the kit, I had to make a visit to the Origami Center (Origami Kaikan) in Ochanomizu, a 20-minute walk from my office in Akihabara. I showed the kit to the people there, and they were surprised that it existed since Gakken apparently never contacted them during the research phase. The chairman of the Center was in the building, making origami rabbits for the customers in the gift shop, and I showed him the mook. He said he knew several of the artists featured, and was surprised by the complexity of some of the computer-designed shapes. At one point, he said that someone in New York had made the Checker using metal sheets, and he brought over one that the shop has available for sale. So, it looks like the Checker is a well-known pattern in origami circles.

The Celes (derived from “celestial” because of the star shapes) was packaged as 3 strips of pre-scored units per sheet, 10 sheets. It’s a deceptively easy shape to start assembling – you just pre-fold the 30 units and then unfold them to make “j” shapes. The “j” shapes interlock, and you fold the “pocket” tabs to lock the units together. However, when I got about halfway through, all of the loose ends got in the way of each other and I couldn’t tell where I was in the project. Near the end, the units were pushing away from each other, making it hard to pull them into a ball shape. The paper was getting damp from all of the handling with my hands, and the tension against the paper was making the units unfold. At one point, I got a glue stick out and was about to cheat and glue the pieces together, but I couldn’t figure out how to do the gluing without making things worse, so I started looking for my stapler. Finally, I tried approaching the assembly as two halves of a ball and stitching the halves together in the middle. That worked, and suddenly the tension of the two halves balanced out and the assembly took on a rounded ball shape all on its own. In the process, I had to completely disassemble everything 3 times, and had to unravel the ball halfway to backtrack another 5-6 times. In all, this one lamp cover took over 4 hours to make, and I finished at 4 AM. It looks way-cool with the Akari turned on, so it was worth all of the frustration. But I don’t think I want to do something this complicated again any time soon. The Celes was probably one of the hardest things I’ve ever tried to make in my life. (Note: I’ve since made over 30 of these Celes balls, and it does get easier with practice.)

Here are the URL links from the mook, if you want to check them out.
Byodin Temple
Japanese cave
Paper crafts 1
Paper crafts 2
Wood materials
Paper crafts 3
Paper crafts 4
Lego Robot plays Othello
Make Club in Japan

Summary: In short, if you have the Japanino, and can get your hands on a red, a green and a blue LED, you can easily make the Akari yourself. And you can find lots of origami patterns on the net. But, you’d be missing out on the fun of assembling the Akari kit, and all of the theories behind the creation of geometric shapes that are featured in the mook. If you don’t have the Japanino, then the Akari is a fun way of making a paper and LED lamp. Recommended.


As I mentioned above, as soon as I saw all of the origami projects in the mook, I decided that I’d go to the Origami Kaikan (Origami Center) about 1 mile from my office. Part of the idea was just to see if the people there had known of the kit in advance, and if not to tell them about it. Another part was to see if I could meet the chairman (who is generally in the third floor gift shop giving demonstrations to visitors) and ask him for suggestions for a project of my own.

While the chairman did act impressed with the mook, I found it hard to get him to give me ideas. But, as I was talking I noticed a box of key chains on one shelf, and one of them was a small wood and paper lantern shape. I was also trying to find good quality paper that wouldn’t collapse under its own weight, and the chairman commented that most of the paper is lighter to be easier to fold, and therefore not all that structurally strong. The more I thought about it, the more I liked the idea of making a lantern. Finally, I noticed some paper that had rabbits on it (2011 was the Year of the Rabbit, so rabbit origami and rabbit-patterned paper were big then). I asked where the paper was, and was taken over to some other shelves where the Kaikan was selling its own washi (handmade rice paper) for 1600 yen for a square meter.

Back home, I grabbed some construction paper that I had left over from a previous art project, and experimented with making a box 4″x4″x6″. The result was strong enough to justify moving forward with the idea. By accident, I chose to use 1 cm-thick borders, which turned out to be a good choice, because the sticky-back tape I had was 1 cm wide. I tried looking for lantern frame patterns on the net, but nothing useful popped up right away, so I just tried some ideas that were more-or-less asymmetrical. After cutting out the frame pieces, I tried finding patterns on the rabbit washi paper that fit well inside the frames. Unfortunately, the washi seems to be designed more for wrapping paper, and most of the patterns are fairly spread out. But, I did get a couple pieces that worked out.

The final project took 2 hours to complete, and I think that it looks pretty good sitting on the Akari. I just wish that I hadn’t been told at the end that these lanterns are used primarily for Obon (the 1-week period in August when the Japanese set out to visit with the spirits of their ancestors).

Kit 28: Edo-era Lunar Clock

Gakken kit #28 – the Edo-era lunar clock (2900 yen). The clock face represents the 12 animals from the old Edo-era timekeeping system (i.e. – “hour of the snake”, “hour of the rabbit” and so on). Recommended construction time is 90 minutes, and it took me about that long to put it together, including the time needed to mess with the threads, and to take the face back off to put the leaf switch in.

If you built the Slow Clock (kit #8), then you know roughly what to expect. A clock like this has a drive shaft that is connected to a series of gears that ultimately cause the clock’s hands to sweep around the clock face. For both #8 and #28, there is only one hand (an hour hand for the Slow Clock), which keeps the gearing system simple, but does make the fully constructed kit kind of boring. There has to be a way to control the timing of the gears, and this is where the pendulum comes in.

Both clocks have a rotating pendulum connected to the escapement – a sawtooth gear that advances the rest of the clock. Two plates on the pendulum shaft press against the sawtooth gear and only allow the sawtooth to advance once the pendulum swings far enough to one side or the other. The rotating speed of the pendulum can be adjusted by two threaded weights on the arms, which then fine tunes the timing of the clock.

What sets kit #28 apart from the Slow Clock is that while the Slow Clock got its energy from a hanging weight attached to a string wound around the drive shaft, #28 uses a wind-up spring. Depending on how high up from the floor the Slow Clock was, it would run maybe 8 hours until needing rewinding. The wind-up spring can run up to 2 or 3 days. What this means is that #28 doesn’t need to be hung from a wall – you can set it on a table or on the floor if you like. Second, #28 has two rotating pendulum arms, but only 1 runs at a time. Inside the gear mechanism itself is a cam shaft. This cam shaft raises and lowers the pendulum arms so that only one arm is in line with the sawtooth gear at a time.

There really aren’t that many pieces to the clock, maybe 8 parts making up the main body, 5-6 gears and shafts, and another 10 pieces acting as holder plates and stuff. The spring mechanism, and a couple of the gears arrive fully assembled, simplifying assembly even further. Even so, there are a couple places where assembly is kind of tricky and if you’re not paying close attention you may have to take things apart and start over. One such section is the central pendulum arm assembly. There are two plastic plates that hold the 2 pendulum arms. One pendulum arm is longer than the other, and each plate is mated to the appropriate arm. That is, the pendulum arm with the long metal rod goes in front of the clock, and is mounted on the longer plate. The pendulum arm with the short rod goes to the shorter plate at the back of the clock. Then, when you attach the threads to suspend the arms from the mounting plates, you need to have just enough slack to let you move the mounting plates both up and down in order to adjust the arms so that the jamming plates on the rods align with the teeth of the sawtooth gear. Keeping in mind that the cams on the cam shaft need to be moved so you can check the alignment of both pendulum arms. (You’ll know what I’m talking about when you build the clock).

If you do have to take things apart to do troubleshooting, be careful. The plastic the screws bolt into has a tendency to strip. Don’t remove the screws more than you have to.

The fully assembled kit is about 6″ tall, and with a 3″ x 3″ foot print. And it weighs a little less than a pound. The ticking is a bit noisy, so you probably won’t want this in your room when you’re trying to sleep. Still, it is cool that a clock like this that I’ve built does run right “out of the box”, so to speak.

This brings me to the leaf switch. One of the advertising points for kit #28 is that there’s a leaf switch that allows you to connect the Japanino microcontroller to the clock. Don’t worry if you don’t have the Japanino, this clock will work just fine without it. And, you don’t need to screw in the leaf switch if you don’t want it. Basically, the leaf switch is just two pieces of metal screwed onto a plastic mounting block, which is in turn screwed down to the inner body of the clock (you can attach the switch to the body at any time, although the mook suggests doing it right away when you start out). One of the gears has a little plastic tooth sticking up inside it that presses against the switch momentarily once per rotation. You can then use this change in switch status to tell the Japanino to do something (see below).

As always, the mook contains suggestions for modifying the kit. This time, one such mod is to mount a steel bell to the top of the clock, and to connect the Japanino to the leaf switch and to a small servo motor. The servo can drive a small metal bolt to hit the bell to make it chime once a day, or whatever you prefer. Other mods include using the clock to control a motor-driven car, and to put stickers on the face of the clock.

There’s a strong nostalgia element to this mook. The first few pages are pictures from around Japan, then there’s a quick overview of Edo-era (1600’s to early 1800’s) clocks, followed by an essay of what Edo life used to be like. There’s also an article on Little Edo, a small town north of Tokyo that recreates life from that time (Edo is the original name of what is now Tokyo). Some of the other articles show different styles of antique clocks, celestial clock mechanisms, and even wind-up timers for flint-lock pistols. The original clock that kit #28 is based on did have the bell mounted on it. Other articles show celestial clocks (for predicting the locations of the sun, moon and the inner planets) from around the world, plus some ancient star maps. There’s an overview of the effect of the speed of light and gravity on the perception of time, again, and a piece on the human body’s own “time keeping” mechanisms (for controlling heart rate, sleep cycles and so on). The rest of the mook is on reader-built science kits (what looks like a home-made satellite and a marble machine), and there’s a manga showing what happens when a body dies and decays (might be a bit too much for younger readers, and “sensitive” adults. However, if you watch CSI, this is nothing.)

Overall, this is a better kit than the Slow Clock, because it’s quieter and runs longer between rewindings. It’s cool to see a clock that you’ve built running correctly, and you can glue on LEDs and have them light based on a Japanino sketch if you like. At 2900 yen ($35 USD) Japanese price, the import price may be a bit high for what you’re getting. Otherwise, recommended.


The background:
According to multiple sources, the primary one being the Japanese Clock entry on wikipedia, early time keeping in Japan consisted of burning columns of incense, and marking off the time in units of 6. Numbering for time started at “9” at the top of the new incense column and burned down to “4” at the bottom (numbers 3, 2 and 1 were reserved for Buddhist calls to prayer). What was important at that time was the amount of daylight available for farming. So, a “day” started with sunrise (when the stars were no longer visible in the sky) and ended with sunset (when the first stars became visible again). This led to two different counting systems – the 6 time periods during “day” and the 6 during “night”.

Because the length of the day changes with the seasons (the longest “days” being in the Summer and the shortest in the winter), time keeping had to constantly be adjusted every few days to keep up with the actual occurrences of sunrise and sunset. As an example, on August 21st, 2010, sunrise in Tokyo occurred at 5:04 AM. Sunset at 6:24 PM. This gives a “day” of 800 minutes, and a “daytime hour” (800/6) of 133.3 minutes. Plus, a “night” of 640 minutes, with a “nighttime hour” that is 106.6 minutes long. Just 1 week later, on the 27th, sunrise was at 5:09 AM and sunset at 6:16 PM, with the “hours” changing to 131.2 and 108.8 minutes respectively.

“6” was at sunrise and then again at sunset, so a farmer would get up at “6” in the morning, work from “5” to “4” to “9” (when a new column of incense was started) and then back down to “6”. It would now be sunset and the end of the “day”. “Night” would run from “6” down to “4”, then jump back up to “9” again with new incense and work back down. In addition, the hours were given the names of the animals from the Chinese lunar calendar, with “6” being the “hour of the rabbit”, “5” being the “hour of the Dragon”, etc. (the others being snake, horse, ram and monkey).

Then, in the 1500’s, Dutch and Portuguese traders arrived in Japan, bringing with them the technology for western-style clocks. In 1641, Japan entered its isolationist phase, and Japanese clock makers were left on their own to come up with their own timepiece mechanisms. This led to the mechanization of the earlier incense-based time keeping system.

The What:
The Edo-era kit from Gakken has a clock face divided up into 12 equally-spaced units, running from 6 at our “9:00” position on the left, with 9 at “12:00”, and 6 again at “3:00”. The bottom half of the clock is the same, with 9 at the “6:00” position. The top half represents daytime, and the bottom half is night. The clock only has the “hour” hand, making timekeeping kind of approximate at best. In order to convert Edo time to modern western time, we need to know when sunrise and sunset are. If the clock is at roughly “day” 4.2 on August 21, then that would be 5:04 AM + (6 – 4 + 0.2) * 133.3 = 10:40 AM.

Again, the clock would need to be readjusted every 2 weeks or so to match up with sunrise and sunset as they changed with the seasons (this would usually be done after the clock ran down and needed rewinding).

The How:
Effectively, we need two clocks. One that is calibrated to advance at one rate from sunrise to sunset, and the second calibrated to advance from sunset to sunrise. For the design we’re interested in right now, we want to use a horizontally-rotating pendulum, meaning that our clock is going to have two horizontal pendulums. (Stand-mounted clocks were weight-driven; smaller designs for sitting on a shelf or table were wind-up spring-driven).

The trick then is to switch between the two pendulums. This is accomplished by adding a gear that advances whenever the hour hand hits “6”. This gear causes a cam rod to rotate 90 degrees. There are two cams on this rod. One cam raises its pendulum bar up out of the way of the escapement, while the second cam lowers its pendulum down into place.

(Side view of the clock showing the two horizontal pendulums. Underneath them you can see the cylindrical sawtooth gear. The cam ensures that only one pendulum engages the sawtooth gear at a time.)

(Closeup of the sawtooth gear with the “daytime” pendulum engaged.)

Only one pendulum interfaces with the escapement at any given time. You then adjust the time by turning the threaded weights on the two pendulums to make them rotate faster (weights closer to the center of rotation) or slower (farther from the center). The original Edo-era clocks used standardized weights at fixed locations on the pendulum arms.

The final enhancement is to add a gear mechanism to ring a bell “on the hour”, which on the Gakken kit is implemented by connecting the leaf switch to the Japanino (the Japanino then drives a servo which swings a brass rod at the bell).

I hope this is clear enough. For a better understanding of what the actual components look like, check out the Gakken site’s assembly instructions.


I’ve kind of been busy with work, the Garo magazine write-ups, and so on, so I haven’t spent all that much time on working with Gakken’s Edo-era clock (kit #28). However, there’s also been another complication that delayed me – the color LCD shield from Sparkfun.

I got this shield for my birthday, and it arrived without documentation. Although the Sparkfun site had some example code for running it, that code was written for the Arduino Mega, which has a lot more memory than the Japanino does. So, I had to rip out the Mandlebrot and raw RGB display routines, and slowly piece together what I needed and what I didn’t. Another complication is that there are two driver sets for the Nokia LCD panel – Epson and Phillips – and I had to figure out which driver I needed (Epson). Additionally, when I posted a request for help on both the Sparkfun and Arduino forums I got ignored, initially. Fortunately, I decided to check out the Analog Clock demo on the Fun with Microcontrollers (FwM) site and the sketch I found there gave me code for drawing lines, rectangles and text on the LCD shield. Naturally, the Analog clock circuit included a 1-wire real time clock, which I don’t have, so I had to pull that code out also.

Anyway, I got the barebones code to work for drawing the Edo analog clock on the LCD Shield, which I think looks pretty cool. This also gave me the code for writing debug text to the shield, which made life a lot easier from that point on, too. The next step was figuring out which pins were still available for connecting to the real Edo clock (I decided to double up on pins 3 and 5, which are assigned to 2 of the 3 pushbuttons on the LCD shield) and to find out just how bouncy the Edo clock leaf switch is. Actually, it’s really badly bouncy. It takes about 8 minutes for the connection to become steady. Meaning that I had to throw in some debounce delays in the Japanino sketch. Fortunately, the final code is just about 12K, and the Japanino has 14K of code space, which is fine for my needs.

Link to the video.

Gakken suggested mounting a bell on top of the Edo clock, and then using the Japanino to drive a servo with a brass bar tied to it to ring the bell when the leaf switch closes. I decided to be a little more silly. A year ago I got a birthday card with a built-in sound chip and speaker – the kind where when you open the card it plays “Tequila”. Turns out that you can run the sound chip off one of the Japanino output pins. Just pull the button batteries out of the card, and connect the card’s power pads to the Japanino output pin and ground. Write a “HIGH” to the appropriate pin and the card plays just fine. That meant that all I had to do was add a small delay to the sketch and then have it write a “LOW” to the pin when I wanted the music to stop. Alternatively, if you don’t want to drive yourself insane listening to Tequila all the time, you can replace the sound chip with an LED.

Side notes:

Initially, the cams didn’t seem to be rotating for me. Turns out that when I took the faceplate off the clock in order to install the leaf switch, the cam spring fell out and disappeared. After I discovered where the problem was, I replaced the lost spring with 1/2 of a spring from a ballpoint pen. Works fine.

There’s no particular reason to use the leaf switch supplied by Gakken. It’s really nothing more than 2 pieces of bent metal screwed down to a separator block. If you plan on connecting the Edo clock to an alarm circuit, you’re better off using a commercial roller-type microswitch and hot gluing it in place in the clock. That way you’ll avoid the problem of having to debounce the switch.

Since the Edo clock doesn’t have a fixed rate for sweeping out 1 “hour” of time, it’s not that important that the kit doesn’t have a minute hand. You’re looking at rough approximates for the current time of the day no matter what you do. Still, it’s a fun look at Japanese technology history.