Yenya's World

Tue, 31 Dec 2013

PF 2014

I wish a pleasant year 2014 to everyone who reads this blog.

PF 2014

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Sun, 15 Dec 2013

Slot Car Tyres

The tyres of our slot cars are not as good as they used to be, so I wanted to buy new ones. However, the local seller has been less than helpful, so I searched the Net. Apart from U.S. slot car supply sellers (tyres for US$ 7.50, shipping into the Czech republic for US$ 25+), I have found this page, so I have decided to create my own tyres. The original tyres look like this:

Firstly, I have created the box for a new mold, using heavier paper with smooth finish:

The tyres are fixed at the opposite sides using dual-side adhesive tape. This allowed me to make a single-part mold only, and provide the pouring and air escaping holes:

The mold is made from OOMOO 30 silicone, bought at www.silikonycz.cz. I have used parafine release agent to avoid the original tyres sticking to the mold, but I think it was not necessary after all.

The mold removed from the paper box:

Removing the original tyres from the mold. OOMOO is really stiff and soft, my previous experience with Lukopren 1522 silicone is worse - Lukopren would snap off when removing the models so deeply enclosed in the mold.

For the tyres I have used urethane rubber. I have tested two types with a different hardness. The red one is softer - Vytaflex 30, and the blue one is harder - Vytaflex 40. I have used So Strong pigments for making the rubber red and blue. All those materials were also acquired from www.silikonycz.cz.

And here is the final product:

It is much softer than the original tyres, and a bit looser on the rims (I have not used any glue so far, though). With the original tyres, the best lap time with F1 cars was slightly under 7 seconds. After the short testing ride with the Vytaflex tyres I clocked the best lap of 5.15 seconds, and average laps around 5.50 seconds. Impressive.

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Thu, 28 Nov 2013

A Not-so-New Pet

I have forgot to write about our new pet, so with an appology for the delay, here it is:

Testudo Hermanni Testudo Hermanni

It is Hermann's tortoise (želva zelenavá in Czech). It is about year and half old now. FWIW, we didn't bought it from the pet shop, but from the breeder at www.euzelva.cz.

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Tue, 21 May 2013

Cell Phone Operators

Few weeks ago I have moved my cell phone number to a different phone operator (don't ask :-). Today, I've got an interesting call:

Caller: "Hello, I am a representative of $my_new_operator, do you have a minute or two?"

Me (thinking about possible problem with $my_new_operator, with payments, or whatever): "Well, only a minute."

Caller: "OK, then. We have a great offer for customers of $my_old_operator. If you move to $my_new_operator, you can save much money."

Apparently the $my_new_operator's representative does not know that I am already their customer.

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Fri, 26 Apr 2013

Tinyboard: ATtiny universal board

Having learned how to design PCBs, how to solder SMD components, and how to work with Atmel microcontrollers, I wanted to use this knowledge in more projects. I have thought about two or three things which I could do with ATtiny MCUs, but I didn't want to design a single-purpose board for each of them. Let me introduce Tinyboard, a multipurpose 24x50mm printed circuit board for 8-pin ATtiny MCUs (Tiny25/45/85, or Tiny13). The list of features includes:

Tinyboard

A Tinyboard with a single step-up converter, MCP1703AT voltage regulator, USBasp programming connector, and unstabilized power input. The MCU itself is on the bottom side.

More details are described in the Tinyboard project page. So far I have built a step-up converter with it, and I am considering using it together with 9V battery (the size is about the same) as a lighting solution for my kids' bikes. The PCB fab allows boards up to 5x5cm size, so I have put two Tinyboards in a single design, receinving a total of 20 tinyboards. So I definitely have spare Tinyboards. If you have a project using 8-pin ATtiny and you are near Brno, let me know.

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Tue, 23 Apr 2013

LinkedIn Endorsements Again

A while ago, I wrote about the new feature of LinkedIn - endorsing skills of each other. I have publicly stated that this is a nonsense, and that I didn't want anyone to endorse me, and I would not endorse the skills of my connections. Half a year later, I have to say I was right:

My public profile contains several endorsements for things I barely know they exist, for example for a programming language which I didn't write a single line of code in.

Moreover, I have discovered that I am supposedly "following" several things like "higher education", "computer software", or "Masaryk University". I am not aware that I have willingly decided to "follow" these things, maybe LinkedIn has added them by itself (I have clicked on "unfollow", so I don't follow them anymore). Apparently this is another misfeature designed to make it look that LinkedIn network is big and deeply interconnected.

What do you "follow" on LinkedIn?

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Tue, 22 Jan 2013

New GPG Key (please re-sign it!)

My PGP key is almost 16 years old now - it has been created on 1997-03-15. It is a 1024-bit RSA key, which is not so strong by today's standards. So I have generated a new GPG key 4096R/A45477D5. I plan to phase out my other two keys, 1024R/D3498839, and 1024R/F0BEFD45 in the near future, and publish revocation signatures for them. My new GPG public key signed by both old keys is available at the following locations:

The fingerprint of the new key is: B634 17E5 731B 4F42 69FA 57FF 9453 3581 A454 77D5

I hereby ask everybody who has signed some of my previous keys, or who has any means of verifying the above fingerprint by an independent channel (e.g. over the phone) to sign my new key and send me a signature. It is possible to do this in Linux using the following steps:

1. Obtain my public key

gpg --keyserver pgp.mit.edu --recv-key A45477D5

or use another keyserver instead of pgp.mit.edu, or get the key from our webserver

wget -O - https://www.fi.muni.cz/~kas/pgp-A45477D5.txt | gpg --import

2. Display the fingerprint

gpg --fingerprint A45477D5

Verify the fingerprint (should be the same as above; you can also call me over the phone).

3. Sign the key

gpg --sign-key A45477D5

4. Export the key

gpg --armor --output A45477D5-signed.txt --export A45477D5

Now send the resulting file A45477D5-signed.txt to me. Thanks!

NOTE: The plain-text version of this blog post, signed by my old key 1024R/D3498839, is available here.

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Wed, 02 Jan 2013

PF 2013

I wish happy year 2013 to everyone who reads this blog.

PF 2013

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Tue, 20 Nov 2012

SMD Soldering

For the first time in my life, i have tried to solder SMD components (as I have written before, I am working on DYI LED lights for my bike). The component side looks OK, and soldering through-hole components went without problems. The SMD parts were a bit tricky, though.

bike lights board bike lights
board


I have used an ordinary soldering station with temperature regulation, but the results are not pretty. I wonder what is required to achieve this level of quality (watch from 14:10). One possible problem might be that some components on my board (especially the smallest sensing resistors) are connected to the highest-current and thus thickest paths, which suck great amounts of thermal energy when soldering.

Anyway, from the preliminary testing, it seems that my board works. So far I have found the following problems:

Now it's time to finish the firmware and to start adjusting the mechanical parts. I have already made the front spotlight and rear spotlight, and I want to make a LED string. Any tips about making a waterproof LED string out of 3mm through-hole LEDs will be appreciated. Should I use silicon, shrink-wrap tube, or what?

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Thu, 15 Nov 2012

Printed Circuit Boards

For my bike lights I needed a PCB. Out of several services for manufacturing PCBs, I have chosen Itead Studio PCB prototyping service (the other candidate was Seeed studio). Here are the preliminary results:

bike lights PCB

I have placed my order on October 29th evening (Central European Time), according to Hong Kong post, the package was received by them on November 7th, it left Hong Kong on November 11th, and I have received it today, on November 15th.

They also have an interesting "Open source" program - the customer declares that his design is open source (mine is anyway), they make few more boards in addition to those the customer has ordered, and they send them to their other customers. The original customers gets his orderd boards, and in addition to that, two more boards from other open source projects. I have in fact got their demo board (on the right side), and one open source board (the white one). Apparently, it is Arduino 512KB SRAM expansion board. I currently don't use Arduino, so if any Arduino user is interested in this PCB, just let me know.

Okay, now it's time to take a soldering iron and play more with the hardware :-)

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Tue, 06 Nov 2012

DNS Lookup :-)

It seems my registrar will discontinue their "free" hosting (as in "bundled with the domain registration") soon, so I will have to move my domain yenya.net mail and WWW servers elsewhere. There is no problem with that - I have a 24/7 running computer at home with good connectivity. There is one challenge, though:

The new DirectNIC service allows only one A record in the registered domain, when the domain is hosted on their DNS servers (no AAAA and no DNSSEC). So I am considering running my own DNS server in addition to mail and WWW servers. This would allow me to have A and AAAA records, SSHFP, and possibly the new DANE records. So I need someone to host a secondary DNS server. The requirements are:

Of course, I am willing to provide the same service to the other party. Is anybody interested? Thanks in advance.

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Tue, 30 Oct 2012

Bike Lights

I have a new personal project: I am trying to build a set of lights for my bike. So far my setup is quite simple: I use a 700 mA Buck Puck current regulator to feed a front Cree XM-L white LED and three rear 350 mA red LEDs. It can only be switched on or off, and cannot blink at all. So I wanted to make something more sophisticated.

pcb front pcb back

I have been playing with electronics many years ago in my teen-age years, but I have been doing only software since then. So I have taken this as an opportunity to find out what progress the world of DYI electronics has made, and to learn programming of microcontrollers. I want the resulting electronics to have the following features:

I have managed to learn how to use the gEDA suite of tools, and created my first PCB with it. Yesterday I have sent the result to the fab. Anyway, I have made the Project Bike Lights page for my project, where it is possible to watch the progress or look at the firmware code, schematics, and PCB design.

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Sat, 13 Oct 2012

Those Annoying Endorsements

Recently LinkedIn has added a new feature, endorsements. The most annoying thing is that the requests for endorsements are now near the top of the page, and people are clicking on it. So I have several mails each day saying "$somebody has endorsed you!" (with an "and you are expected to return the favor" subliminal message). So, my dear LinkedIn contacts: feel free to not endorse me and don't bother to write recommendations, as I don't plan to do the same either.

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Tue, 09 Oct 2012

Zacyklení 2012

I like outdoor puzzle-solving games, and last weekend I managed to take part in a really special kind of puzzle-solving competition:

zacykleni

Zacyklení is a puzzle-solving outdoor game for cyclists. And what is even more interesting, we have managed to create a purely recumbent team for this game. Those who can read Czech, here is the report from the game. Those who can't, follow the link anyway for more photos :-). We have not made it in time, but among all the teams we have finished somewhere around 5th place. Congratulations to the winners, and thanks to the organising team!

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Thu, 20 Sep 2012

Hanwag Boots

Afters about 10 years, my Hanwag Alaska boots have disintegrated while I've been walking in the forest during this year's Svíčky. I will need a new boots. Which boots do you recommend, my dear lazyweb?

I have been satisfied with Alaska, and I have chosen them because the big part of the boot is made from one piece with only one seam i the back. However, the middle part of the sole has completely disintegrated. The consipration theory follows: I wonder whether it could be intentional from the manufacturer, in order to not allow their customers to use the product for more than 10 years. In my opinion it should be possible to find a material which lasts almost indefinitely. That said, from my previous experience the sole was the weakest part of all my previous boots in terms of endurance. So maybe it is perfectly OK to expect the boots to last only 10 years. What do you think?

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