Shizuoka Hobby show 2017

In May, I attended the most important event in the world about plastic models: the Shizuoka hobby show. Shizuoka is the place where Tamiya was born, and is easy to reach by Shinkansen, although this time I used the cheaper Tokaido line.

The place was divided into two parts. One part was composed of commercial booths where companies were introducing their latest model kits. Doi-sensei held a nice workshop on figure painting using Turner Acrylic Gouache at the Model Art magazine booth. There was also a bookstore where I bought an awesome book titled 機械昆蟲制作のすべて (all about building machine insects).

The other part was composed of hundreds of tables where plastic model fans were exposing their dioramas and models. There were amazing pieces of art, and I learned a lot from them. There are many different genres in this hobby, and I kind of liked this kind of dioramas representing Japanese street scenes from the Shōwa era.

It was actually on the fans side where I met the author of 機械昆蟲制作のすべて who took the time to sign my book with this beautiful drawing. Thanks a lot!

Day trip to Karuizawa from Tokyo

Last May, I had some days off and I decided to visit Karuizawa. The only thing I knew about it was that John Lennon used to stay over with his family during the summer holidays. Karuizawa is very easy to reach from Tokyo. Using the Shinkansen, it only took me about 1h15 to get there.

Although the main roads were full of tourists and souvenir shops, there were also quiet neighborhoods composed of single houses with wide backyards that most probably only very rich people could afford. The presence of Christian churches, such as the Shaw Memorial Church above, was also notable.

I went past the Shaw Memorial Church and kept walking for a while until I ended up climbing a little mountain. The hike is really nice but make sure you bring some bells to avoid accidents with bears. I met very few people on my way up.

The views from the top are impressive and you can see the famous, and still, active volcano Mt. Asama which is near Karuizawa. By the way, Karuizawa is in Nagano prefecture but very close to the border with Gunma prefecture.

After the hike, I was a bit tired so I had some quality soba and a cup of tea nearby just before heading back to town on this colorful bus. Then, after some walking around the major road and buying some souvenirs I returned to Tokyo by Shinkansen. A really nice day trip.

DIY mini drill press and router table all-in-one

I bought a Dremel 4000 rotary tool about 4 years ago. However, during all that time I had only used it a few times. One of the problems with the tool is that it's kind of hard to be precise when you use it free handed.

Then, I saw this awesome video on Youtube a few weeks ago and I thought: "I have to built my own!". The design is very well thought and contains some clever ideas. It is also simple and can be made with common tools and materials. I built mine at Kitewa, guided by the experience of its friendly owner Tim.

On one side, it is a drill press. A lever is used to push the Dremel down towards the piece of wood where you want to make a hole. Then, a extension spring connected to the back of the Dremel's board brings it back to its original position. The Dremel tool is hold in place by using two stainless-steel hose clamps. The main body parts are connected through 4mm screws and I used countersinks to make sure the surface was smooth. Another key tool for achieving nearly perfect right angles was the combination square.

On the other side, it is a router table. The Dremel's board has an insert nut on the right edge that allows us to lock its position with a knob. The groove where the knob slides down was made with the help of a plunge router. The design also includes a convenient fence to ensure that we sand or cut to the specified width.

Conclusions: the build took only two days, specially thanks to Tim. During the process I made multiple mistakes: the wood I used was a bit weak, specially for the base; the first extension spring that I bought didn't have enough strength to bring the Dremel back; and I made some holes in the wrong places. However it was overall a very satisfying learning experience for me.

Writing an oscilloscope frontend with PyQT

In previous posts, I talked about two DIY oscilloscopes that I had built (not dessigned): one based on Arduino and another one based on a dsPIC controller.

Although building my own DIY oscilloscope was fun, I had always wanted to get a real one. A few months ago I decided to buy a used one on Yahoo auctions. In particular, it was an Iwatsu BRINGO DS8812 digital oscilloscope (DSO).

Although there were good oscilloscopes for lower prices, the DS8812 fitted all my requirements:

• Cheap (10,000yen, about 78 euro).
• Small size, because my workspace was getting full of devices.
• Enough bandwidth, channels, sampling rate and memory length.
• DC~100MHz, 2 Channels, 500MS/s, 100kword/channel
• A remote control protocol (through RS-232C) that was documented.

The only problem that this oscilloscope had, and the reason for its low price, was that the right menu was hard to see. I tried disassembling the oscilloscope and touching different connections but I wasn't able to improve it. For that reason, I decided to create a GUI interface to control and visualize the oscilloscope remotely through the RS-232C interface.

In order to control the oscilloscope, a cross serial cable was required. In my case, I already had a straight serial cable so I only had to buy a null-modem converter which worked great.

 $ picocom -c --omap crlf -b 115200 -f h /dev/ttyUSB0
    --omap crcrlf: outputs CR/LF instead CR (set osc to CR/LF delimiter)
    -h: enables RTS/CTS
    -c: local echo 

The most tricky part was passing the appropriate parameters to the serial terminal. Picocom is my favourite serial terminal, and these are the parameters I used.

With that in place, I finally managed to get a response from the oscilloscope using the command "DATE?" (commands that end with a question mark represent requests to the oscilloscope).

I programmed the frontend using PyQT (Python bindings for the QT GUI library). I found the QT designer to be particularly easy to use and robust. The source code is on my github account and it uses pyserial for communicating with the oscilloscope, and matplot for displaying waveforms.

Here is a snapshot of two square waveforms on each channel. The app is not very sophisticated but it does its job and can be easily extended in case I need more functionality.

For example, here I implemented an FFT view of the acquire waveforms. This was a paid functionality on the original oscilloscope.

Conclusions: I'm glad that I got a oscilloscope that I could controll remotely. Now I can easily store waveform data, analyze it or save it as an image file. I really enjoyed working with PyQT and the QT designer. They are very powerful and easy to use. Last but not least, I summarized my "endeavour" in a few slides and presented this project at OSunC in Kawagoe.