Immutability and Phoenix LiveView

30 September 2019 ⋅ 2 min read ⋅ elixir

In my daily work I’m going back and forth between Rails and Phoenix with the healthy dose of LiveView. This change in paradigm sometimes shoots me in the leg. This post is written in the form of a self-reminder.

Quadropod - First moves

29 September 2019 ⋅ 1 min read ⋅ diy quadropod

Parts printing and assembly has finished. After initial calibration, I’m now writing simple scripts to see the limits of the platform. We started with push ups:

With that done I’ve looked into how to lift the leg without tipping over. It took a bit of time to figure out the angles of the rest of the legs so that the center of mass shifted backwards slightly.

![alt](/assets/images/quadropod/2019-09-29 09-23-32.jpg)

At this point I start to believe I’ll need to write a library with some geometry calculations in it. Doesn’t come as easy as I imagined starting this project. LOL.

Quadropod - New version

27 September 2019 ⋅ 1 min read ⋅ diy quadropod

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This is the second generation of Quadropod. Features:

Replaced logic board. Moved from ESP32 to Arduino UNO + Servo Shield (16 servo, 2 DC motors). Although nice, ESP32 was giving me headaches with generated PWM for servo. Sometimes the signal was interrupted, giving wrong position to a servo. Plastic gears didn’t like that at all. 3 servos went out of order.
Upgraded motors from SG90 with plastic gears to MG90S with metal ones for more reliability and power.
Upgraded design of some plastic parts. Replaced parts that required extra assembly with solid ones.
Tips of the legs can now be augmented with rubber pads for more control on slippery surfaces.

Printing and assembling…

Writing mnesia data migrations in Elixir

7 June 2019 ⋅ 3 min read ⋅ elixir mnesia

Migrating data in Mnesia is traditionally a dark matter. Even if you understand the concept of translating tables, it’s still not clear how to organize your migrations so that they are picked up and run during the application start.

Схема проверки КТ117А

25 April 2019 ⋅ 1 min read ⋅ electronics

Cхема проверки однопереходного транзистора КТ117А с небольшим описанием.

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R1 управляет скоростью заряда C1
R2 - R3 устанавливают пороговое напряжение открытия перехода
C1 в паре с R1 управляют частотой открытия Q1
Q1 открывается на 2/3 - 3/4 от порога (см R2 - R3) и закрывается на 1/2 порога

Aquarium lighting timer on Arduino ESP8266

19 March 2019 ⋅ 2 min read ⋅ arduino esp8266 diy

In this article I’d like to tell the story of building the lighting timer for my small 120 liter aquarium. Just when they said lights should go up and down on schedule I knew it it’s not going to happen in my house. Just won’t work that way. So I decided to automate it.

Linking ESP8266 with Arduino

29 November 2017 ⋅ 2 min read ⋅ arduino

I found it super-hard to find meaningful info on how to link a tiny little ESP8266 (ESP-01 in my case) to an Arduino and talk to it.

FFMPEG fade in/out expressions

19 October 2016 ⋅ 1 min read ⋅ ffmpeg

I’ve been playing with FFMPEG lately mulling over a plugin for Appcelerator Titanium and figured we’ll need a text rendering with nice fading in/out effect. There’s text drawing filter in FFMPEG, but not a function to easily fade it, so I came up with a couple of expressions of my own. I’m working with alpha channel here, but it can easily be applied to other properties.

Easy options parsing in shell scripts

16 July 2016 ⋅ 4 min read ⋅ shell

This is an attempt to systemize my own knowledge of options parsing in shell scripts. I mainly work in Zsh, but this is compatible with Bash and possibly others.

Elixir meets Docker.io

16 July 2016 ⋅ 4 min read ⋅ elixir docker

In usual conditions it’s preferable to deploy your Elixir / Erlang apps with exrm and a-la Capistrano derivatives like edeliver. There are cases when you either need to make it easily installable or handable to a client. In this rare cases packaging the app in the Docker image is worth the effort.