Thursday, December 8, 2016

How to run the LTspice circuit simulator on Linux

I often use LTspice for simulating my circuits or even organizing workshops. Unfortunately, LTspice is distributed as a Windows application. In this post, I'll explain you how to run LTspice on your Linux distribution using WineHQ.
 $ sudo dpkg --add-architecture i386   
 $ sudo add-apt-repository ppa:wine/wine-builds  
 $ ls /etc/apt/sources.list.d/  
 $ sudo apt-get update  
 $ sudo apt-get install --install-recommends winehq-devel  
 $ mkdir WINE  
 $ echo "export WINEPREFIX=$HOME/WINE" >> $HOME/.bashrc  
 $ source $HOME/.bashrc  
First, you need to install Winehq using the instructions for your Linux distribution. The instructions above are for Ubuntu LTS 14.04 Trusty (64 bit). The folder WINE represents the Windows filesystem hierarchy (e.g. WINE/drive_c/ represents the C:/ folder in Windows).
 $ wine64 LTspiceXVII.exe  
Then, download LTspice from Linear Technology's homepage and execute the binary with wine64. Here I'm using the latest version XVII, but you can also install the version IV without problems.
 Menu > Wine > LTspiceXVII  
After the installation is complete you can use LTspice as in Windows. You can launch LTspice from the menu or from the generated Desktop icon. During the installation and execution of LTspice, WineHQ may need to download extra dependencies. Just click on yes and everything should go smoothly. If you are new to LTspice check out these slides and videos.

Thursday, December 1, 2016

Making your own PCB with the toner transfer technique

This is something that I had wanted to do for a very long time. There are several methods for making your own PCB. Out of them photolithography will probably give you the best results. However, toner transfer is one of the easiest and cheapest.

For my first toner transfer PCB, I used a Kicad project (a transistor checker) from the great Japanese electronics magazine Transistor Gijutsu (lit. transistor technology). I opened the project on Kicad with pcbnew and printed the B.Cu (Backside copper) layer on a photo paper (the one in the picture is popular among Japanese hobbyists) using a laser printer. Reflecting back, I should have also printed the drill holes (just mark the "real drill" checkbox when you print the B.Cu layer) and add a copper-pour ground plane to save Ferric Chloride. Then, using an iron at the lowest possible temperature I transferred the footprint from the paper to a copper board. You have to be patient here (it took me 12 minutes) and apply enough pressure.

Next, put the board in hot water and remove the paper slowly with your fingers. Don't worry about the ink, it won't come off from the copper plate.

Clean deeply using a multipurpose or window cleaner.

Check the tracks carefully. If you notice that some tracks are not completely black cover them with a water-resistant pen. In this case I used a very strong pen especially made for PCBs. However, I would recommend using a normal one because this one was too strong and it was hard to remove it later.

You can easily cut your copper plate with a P-cutter tool.

Next put some Ferric Chloride into a zip bag together with your board, and swing it slowly inside a bucket with hot water (makes the reaction faster). Make sure you always wear rubber gloves and goggles when you handle Ferric Chloride because it's a very dangerous material. You will see how the exposed copper is slowly consumed by the Ferric Chloride. Once the copper is gone take the board out of the bag. Don't leave it for too long or the Ferric Chloride will attack your tracks from both sides.

This is the result. Notice how the tracks are still covered with the ink from the laser printer which prevented the Ferric Chloride from reacting with the copper.

Now take that ink off with acetone or a nail polish remover.

Drill the holes with a hand drill. I am using Tamiya's fine pin vice with a 0.8mm bit from Proxon.

Next solder your components into the board. Here I'm using lead-free solder which requires higher temperatures than lead solder. If your components are fragile or you are not quick enough with your soldering iron use lead solder instead.

Once the board is soldered it's time for testing. A typical multimeter will emit a sound when it finds a short.

If you make a mistake such as connecting a component in the wrong way, you can use desoldering braid or wick. Make sure your soldering iron is at a high enough temperature. Check other desoldering techniques here.

If you are unlucky like me, you may need to debug further your circuit. In my case, I simulated the circuit on LTSpice and found out that there was a mistake in the footprint. I solved it by cutting a track with a normal cutter.

And there you go, the transistor checker board is now working!.

Finally, make sure that you neutralize the PH of the resulting liquid (copper chloride) with sodium carbonate to a value between 7.0 and 8.0 (use a PH testing paper). Then, solidify the solution with cement and dispose of it. Never put it down the drain because the residual copper ions left in the solution can damage your pipes and the environment.

My first diorama

This November I made my first diorama and presented it to the 8th 1/48 scale modellers contest organized by Tamiya's plastic model factory shop in Shinbashi.

After watching several documentaries I chose to make a winter scene with the famous T-34/67 Russian tank. I'll explain the process I followed below.

After assembling the T-34/76 (1), add a layer of oxide with acrylic colours, coat it with laquer varnish and then apply hair spray (2). Once the hair spray dries, apply the base acrylic colour (3). Soon after that, moisten the surface with water (4) to get a nice chipping effect (5).

Here is a more detailed view of the chipping effects on the upper hull and the turret.

For the base of the diorama I used a cheap plant saucer made of plastic. I created a basic shape using a polystyrene sheet, and on top of that I added a layer of air clay.

It's important to think about what you want to show in your diorama. It should be easy to understand what the characters are doing.

These small wooden tweezers glued to a stick made it easier for me to paint the figures.

To place the figures on the diorama you can attach a short piece of metal wire to the shoes and insert them into the air clay layer. The dirt on the lower hull, caterpillar and wheels was made by mixing plaster with pigments and enamel thinner.

I used real grass from the backyard. Just open a small hole and glue them with bond glue.

For the melted water I used Tamiya's transparent epoxy resin.

The snow is made with Tamiya's snow effect texture paint.

A total of 48 models were submitted. Out of them 15 models received a prize. Unfortunately mine didn't. Check previous contest winners here: 1, 2, 3, 4, 5, 6, 7.

Tuesday, November 29, 2016

Plastic models: Tamiya 1/35 US Tank Destroyer M10

This October I participated in the 8th minikiyakon plastic model contest organized by Kiyahobby, one of the most well-known plastic model shops in Japan. This time the topic was Tamiya's recently released 1/35 US Tank Destroyer M10.

For comparison you can see what other people presented here, here, here and here. Our plastic models also appeared on the Armour Modelling magazine, one of the most famous plastic modelling magazines in Japan. You can see the final winners here. Unfortunately I didn't win anything but being a beginner I wasn't expecting it either. Participating in the contest was good as motivation.

Saturday, November 19, 2016

The girl with pigtails

Here is another try with the trace and watercolour painting technique that I explained a few days ago.

This time I did the stretching beforehand. Stretching is useful to prevent your paper from buckling when you paint with watercolours. The process isn't too complicated: wet your paper with a sponge or a paint roller and wait for about 10 minutes. Your paper will expand. Then, use gummed craft paper tape to fix the wet paper to a board. The gum in the paper tape is activated by water. Make sure you use a thick board that doesn't bend easily. Finally, wait 24 hours for the paper to dry and stretch. Check out this video if you have any doubts.

You want to use an application for extracting the major lines from the photo you are about to trace. For example, you can use the pencil sketch effect from the tool Print the result and trace it into your watercolour paper with a pen. I always use a red pen because it makes it easier to see what lines I've already traced.

This time I skipped the grayscale layer and applied colour directly. I started with the lighter tones and then progressively I applied darker ones.

This is the final result. I'm not satisfied yet, but I learned a few things. For example, I think that next time I should try to simplify the tracing part. Note that I cheated and removed a few tracing marks from her face with the computer.

Sunday, November 13, 2016

My first 10 life drawing sessions

Last night, it was my 10th time going to a life drawing session since I started this Summer. Here is a selection of my art from each session (in chronological order). Each time I tried a different approach just for the sake of challenging myself and having fun. So far I've tried with ink, poster colours, oil painting, watercolours, and pastels. There are long pose sessions (1 or 2 hours) and short pose sessions (20', 10', 5', 3').

Saturday, November 12, 2016

Nishizawa valley hike

I joined a meetup in August and hiked the Nishizawa valley (西沢渓谷 - Nishizawa Keikoku) which is famous for its 7 waterfalls. You can find some Japanese leaflets scanned here and here.

We met at 8:15 AM at Enzan station (JR中央本線 塩山駅) and took a bus (山梨交通) towards the bus stop 西沢渓谷入口バス停 from where we started the hike. You can see my GPS log on Google Earth for a detailed description of the route. If you want to take your own I suggest using the "Easy GPS logger" application on your smartphone. It produces a .gpx file that you can read from Google Earth.

The hike was really pleasant. Most of the route goes through a forest along a river with wonderful waterfalls. Definitely a nice mountain to try in Summer.

You'll also have the chance to cross a hanging bridge. Nothing to be scared of!. After the hike, we went to a Japanese hot spring (onsen) for a relaxing bath. Finally, I had some grapes from this region (Yamanashi prefecture) and went back home by train.