Wednesday, September 25, 2019

Aitendo kits

One of the things I usually do when I go to Akihabara is to visit the Aitendo electronics store. Aitendo store kits are very reasonably priced and there is a great variety. Note that I have already talked about other kits in the past, check the FM microphone and Achandeino. In this post, I wanted to introduce two new kits that I bought and I liked them.

The first kit is a hearing aid circuit (補聴器キット Hochōki kit).

As you probably guessed, the circuit captures sounds through a microphone and amplifies them with a transistor. The user with hearing problems listens to them through headphones.

The second kit is a Tesla coil plasma speaker (テスラ電光音発生器 Tesura denkō-on hassei-ki). By the way, there are now other Tesla kits with larger coils.

This circuit is somewhat more complicated to explain. Basically, it is a high-frequency oscillator that accumulates energy in the coil. The oscillator wave is amplitude modulated by another input wave, for example, music. Bringing a screwdriver to one end of the coil produces an electric arc discharge and makes noise. That noise when modulated by the song turns the coil into a speaker.

It is best to see it with your own eyes. Watch the video I recorded.

You can also use the kit to light a fluorescent lamp.

Saturday, February 23, 2019

Kung Fu movies

If you were born in the early 80s, then there is a reasonable chance that you were a Kung Fu films lover like me. I remember myself going every week to the video rental shop to check if a new Kung Fu film had arrived.
The first Kung Fu film I watched was "Incredible Kung Fu Mission" (Shi xiong shi di zhai chu ma) created in 1979. I watched it by chance when I was about 6 years old and it was in Betamax format. Probably the only film I've watched in such format. This is the quintessential Kung Fu movie, I really like it.

One of the things I like the most about Kung Fu movies are those crazy jumps. They actually have a name in chinese 轻功 (qīnggōng) which is a useful keyword to look for images on Google.

Electric street light switch

When I walk on the street, I often try to spot devices that make our lives easier without us knowing. If I stop for a second and look around, I usually found myself surrounded by a lot of stuff that I don't always understand or pay attention to.

For example, I found this weird looking device inside a cabinet on the street. I took a picture of it to look it up on the internet later. It turns out that this is an electric street lamp switch (called EE switch by Panasonic). In other words, a device that automatically regulates the current that goes through a street light based on the ambient light.

Wednesday, February 13, 2019

Fixing my Sunto wrist watch

I rarely wear a watch nowadays. Most of the time I prefer to use the phone instead to tell the time. However, sometimes I like to dress up and wristwatches are nice accessories that make you look better.

Unfortunately, my otherwise excellent Suunto watch wasn't looking that good with all those scratches. I needed to get rid of them. Fortunately, during the last few years, I assembled quite a few plastic scale model kits and learned a few tricks along.

To remove the scratches from the Suunto surface, I first applied a fine-grained (number 1000) piece of Tamiya sandpaper. Remember that the higher the grit number, the finer and more polished appearance you get.

Once I removed the main scratches from the surface, I applied Tamiya polishing compound with a cloth multiple times. I didn't know about compound until I built this Greyhound scale model.

The end result was quite satisfying. The crystal was now transparent and smooth, just as I wanted. I also replaced the battery and the O-ring with Suunto battery replacement kit.

Thursday, February 7, 2019

Mt. Kōbō

A couple of weeks ago, I went hiking Mount Kōbō (弘法山 Kōbō-yama). Mount Kōbō is an easy day trip from Tokyo or Kanagawa with good access through the Odakyu Odawara line. This time I got off at Hadano station, climbed Mount Kōbō and then went walking towards Tsurumakionsen station where I had a relaxing thermal bath (onsen).

I suggest doing this hike in Winter when the air is clean and you have greater chances to see Mt. Fuji and the surrounding areas.

Near the mountain, there is a nice farm with sheeps grazing and waiting for you to give them some food. Their hairy body is really warm.

DNA fingerprinting at Bioclub

Last month, I co-organized a DNA fingerprinting workshop at Bioclub, Shibuya. The workshop consisted of a pre-orientation session on Tuesday and 2 days of wet lab experiments during the weekend.

We had a total of 5 attendants, and it was quite challenging to coordinate all of them to complete the workshop in time. Fortunately, the students were all extremely nice and never had a problem with them.

I spent quite a lot of time creating the slides of the pre-orientation session. You can see them above if you want to know the details of the workshop. On Saturday, we extracted DNA from pig and cow liver and amplified a region of the mitochondrial DNA called Cytochrome B by using PCR. Then we mixed the PCR product with a solution of taq1 restriction enzyme and let it digest overnight. On Sunday, we conducted a gel electrophoresis to identify the length of DNA fragments that remained after the digestion. The pattern observed allowed us to distinguish pig tissues from cow tissues.

Tennis in Japan

Recently I got a tennis racquet from Yahoo auctions and I have already played a few times. I am a complete beginner but also a fast learner. At the moment, I am able to serve quite fast but with low accuracy. I also need to control the strength I use to hit the ball.

If you are alone but you want to play tennis, or if you have a group but you don't know how to reserve a tennis court, I suggest you use the Tennisoff website. For example, you can apply to entries containing the sentence 参加者募集中, which means "recruiting participants". Also, if you live close to Tokyo there are tennis meetups where you can participate.

Thursday, January 17, 2019

Open Source Conference Tokyo Fall 2018

I forgot to report on Open Source Conference (OSC) Tokyo/Fall 2018. This is probably about the 8th time I attend OSC, but I have only reported it a couple of times. The next one will be in February!

As usual, the event was held at Meisei University, about 15 minutes walk from the Tama Zoo and its station. Actually, I'm embarrassed to say that I have never visited the zoo. Maybe I'll do next time.

The talks. You can find them listed on the event website both for the 27th and 28th sessions. The first talk I went to was given by ftake, and it was useful to catch up with  Btrfs and its transactional updates. I also attended a talk about project Sebastien (android sample).

Apart from the talks, the booths were impressive as usual. In particular, I got interested in Musashino's which was full of second-hand routers modified to run OpenWRT. Some keywords I annotated while I was checking out the booths:

Conclusions: going to OSC is always a good learning experience. I got interested in hacking some second-hand router. I also found super cool the telescope made by @nanbuwks, and I was impressed by Murachue's Linux porting to the Nintendo64.

Tuesday, January 1, 2019


In October 2018, I had the chance to attend the Automated Testing Summit and the Embedded Linux Conference in Edinburgh thanks to a sponsorship by the Linux Foundation. I spent most of my time working, attending meetings and discussing projects.

I used the little free time I had to explore the streets of Edinburgh. I was impressed by the city's architecture, and I loved the cobblestone paths and old-style buildings.

In particular, the Edinburgh castle, which is on top of a hill in the middle of the city, was astonishing. The Linux foundation organised a sweet party inside the castle, and even a better one in the National Museum of Scotland, another must-see.

After my hiking trips in Snowdonia and the Black Mountains in Wales, as well as my trip to the Lake District in North West England, I had always wanted to hike in Scotland. I didn't have time for a long route, but luckily Edinburgh has a hill called Arthur's Seat within walking distance.