阿部真央 Don’t let me down

One of the best finds in the racks at Tower Records Fukuoka福岡市. It's been years since I last got to browse a record store in Japan; I'm glad they still exist, with stacks of CD players queued up to sample. And a huge relief to see the indie rock scene is just as vibrant as I remember!

LittleArduinoProjects#203 Homopolar Motor

What happens when electric fields cut across magnetic fields? A force is generated, and the homopolor motor is the classic demonstration.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.

LittleArduinoProjects#202 LM3915 Audio Level Kit

The LM3915 is a useful IC for simple audio level displays. This is a cheap kit build which largely follows the reference circuits in the datasheet.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.

A New Version Of Ceph Has Been Released, Ceph Jewel

The latest version of Ceph has been released codenamed Jewel with version number 10.2.0. Ceph Jewel has been released as a long term support (LTS) version and will be retired in November 2017. The Ceph Jewel release marks the first stable release of CephFS. Whilst some have been using CephFS for some time, this is the

LittleCodingKata: Hardware Excuse Generator with gRPC

gRPC is a very interesting lightweight middleware framework for language-neutral, cross-platform RPC.

When I heard about Natalie Silvanovich's Hardware Excuse Generator on Embedded.fm, I immediately recognised a better "Hello World" for testing out gRPC.

Introducing "The Explainer": my programming exercise to learn basic cross-language request/reply with gRPC.

I haven't completed the whole matrix of client-server possibilities yet, but here's a sampling...

Start up a server (e.g ruby version)
$ ./explainer.rb 

Proxmox 4.2 is now available

A new version of Proxmox has been released building on the solid foundations laid down with the version 4 branch of Proxmox VE. The latest version 4.2 brings a new GUI, integration with Let’s Encrypt, updated packages and countless bug fixes. You can download the ISO from https://www.proxmox.com/en/downloads/category/iso-images-pve Highlights of the 4.2 release: Based on Debian 8.4 New

Embedded: Specialization is for insects

embedded.fm has fast become my favourite podcast of the moment (always excepting QOTD). Great ideas shared in an inclusive and warm-fuzzy way.

Elecia's end-of-show quote always makes it worth listening right to the end. Until I heard #146's,
I'd struggled to find words to express exactly this. It's a quote from Robert A. Heinlein:

A human being should be able to change a diaper, plan an invasion, butcher a hog, conn (more...)

LittleArduinoProjects#201 Yet Another Doorbell

aka door-fart according to my better half ... 555 Timer-based oscillators are not exactly the most musical creatures.

#201 is a kit build. Ridiculously cheap on aliexpress, it even came with extra components, so a bit of a bargain impulse-buy.

The kit turned out to be a simplified version of a circuit I've built before. It lacks the power control circuit, and draws about 4mA when idle - so if you actually use it, expect (more...)

GlusterFS Error cannot open /dev/fuse

After installing glusterfs-client on my Debian server I received the below error when trying to mount a remote GlusterFS volume. The error indicates that the device at /dev/fuse cannot be found, however ls showed that it was available. This was the error displayed in the Gluster log after running the mount command: [crayon-572d5352c18c9145311546/] A quick check of the kernel fuse

GlusterFS Error volume add-brick: failed: Pre Validation failed on BRICK is already part of a volume

I received the below error today after I tried to add a ‘new’ brick to a GlusterFS volume. I’ve put the word ‘new’ into quotes because although the brick was new to the GlusterFS volume, the disk being added had been used as a brick before. The disk had all data removed from it, however somehow

GlusterFS Mount failed. Please check the log file for more details.

You may get the following error when trying to mount a GlusterFS volume locally. The error displayed gives no indication why the volume failed to mount, but it does hint at where you can get more information about the error. This is the error presented when running the mount command: [crayon-572d5352c4d8b286000463/] The log file could be in numerous

Change Listening Port of MySQL or MariaDB Server

The MySQL and MariaDB server both use a file called my.cnf for parameters that are used to configure the server. This is where the port number and, if you use it, the local socket can be configured. A local socket is the prefered method of connecting to a database as it removes much of the overhead of creating

Reset The root MYSQL/ MariaDB Password

If you’ve lost or forgotten the root user password on a MySQL or MariaDB server you’ll want to reset it and leave all the other accounts and data intact. Fortunately it’s possible, but you’ll need access to an SSH account hosting the instance and the ability to stop and start the database service. Before going any

LittleArduinoProjects#200 Mini Solenoid Engine

Solenoid engines? They definitely fall into the the category of because you can.
Some people take it to a whole other level (like this V8 model).

What I have here is much more modest - a single-cylinder engine powering an impromptu-wire-art drive train. The mini-solenoid used here has a very small effective stroke - about 8mm - which necessarily constrains the gearing. I was inspired by 30GB's similar model for the layout.

As (more...)

LittleArduinoProjects#199 CD4026 Bucket-brigade LED driver

This is an extension if the ideas in #196, demonstrating how it's possible to build a "bucket-brigade" of CD4026 chips to drive an arbitrary number of 7-segment LEDs with a single data line.

It just requires the carry-out from the first CD4026 to be chained as the clock input for the second and so on.

As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.

LittleArduinoProjects#198 Hall Effect Switch

Hall-effect sensors generally support one of three modes:
  • switch - turn on in the presence of a magnetic field of a specified polarity
  • latch - turn on in the presence of a magnetic field, and stay on until exposed to the reverse polarity
  • linear sensor - output is proportional to the magnetic field strength
The components I have for testing are marked "44E/938" and are nominally compatible with the A3144 or OH3144. These are switches (more...)

Persistent Ceph Mount Point

Once you’ve got a Ceph cluster up and running you’re going to want to mount it somewhere. This guide assumes that the mount point will be on a machine that isn’t running Ceph, however if you’re mounting the storage on one of the Ceph server nodes then you can skip the package installation steps. Install

Small Scale Ceph Replicated Storage

I’ve written a few posts about Ceph, how it works and how it’s set up and it mostly revolves around large scale storage for storing things like virtual machines. This post will focus on using Ceph  provide fault tolerant storage for a small amount of data in a low resource environment. Because of this, the

LittleArduinoProjects#197 Wien Bridge Audio Tone Generator

A Wien bridge oscillator is essentially an RC Band Pass Filter with a high Q factor at the resonant frequency, and generates a nice sine wave. I wanted a simple audio-frequency test signal generator, and a Wien Bridge turned out to be perfect for the job.

As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.

A good old LM324 does triple duty in the circuit:

LittleArduinoProjects#196 Driving a 7-segment display with CD4026 Counter

Here's yet another way to drive a 7-segment single-digit display unit - using a CD4026.

The CD4026 is a 5-stage Johnson decade counter with decoded 7-segment display outputs and display enable. With RESET and CLOCK INHIBIT low, and DISPLAY ENABLE IN high, the 7-segment display outputs progress through the 0-9 sequence on the rising edge of the CLOCK pulse.

It's an interesting alternative to a shift register for driving a 7-segment LED (as in (more...)