LEAP#447 Measuring Capacitance with Digital Logic

Capaci-meter is a Boldport remix of a classic capacitance measurement circuit designed in high school by Jez Siddons of Peak Electronic Design.

The device takes a very interesting approach - rather than trying to measure the actual capacitance or charge time, it uses a derivitive function (the capacitor’s effect on the frequency of a 555 timer) to infer capacitance.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo (more...)

LEAP#446 RGB Joule Thief Night Light

I recently got hold of some 5mm RGB Flashing LEDs from a seller on aliexpress - some slow and fast flashing varieties just out of curiosity. Here I’ve put one the slow-flash kind in a “night light” circuit.

I decided to power from a little 1.5V CR1216 coin cell. To boost the voltage sufficient to power the LED, I’ve attached a toroidal joule thief circuit. The oscillating voltage produced by the joule thief is (more...)

LEAP#442 Boldport ResPot

As any good electronics hobbyist must have done, I’ve already built a decade programmable resistor box - see LEAP#414 - but this is one with the Boldport twist. Yes, real pots.

A decade box is an old-fashioned bit of test equipment, allowing an arbitrary resistance to be dialed up to order.

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


LEAP#441 Pollen8

“Pollen8” is an exploration of contrasts and patterns in a freeform wire circuit.

I was interest in playing with a design that avoided the harsh angularity of most electronic circuits, instead using graceful lines that attempt to mimic a more organic structure.

The second goal was to achieve a chameleon-like LED display, where the visual effect depends on the perspective of the viewer: random from some angles, but clearly sequenced from others.

I created this (more...)

LEAP#440 Logging Data with Adafruit IO

I wanted a simple way to log the voltage of the LEAP#439 QX5252 Solar Night Light, rechargeable battery to get a sense of the overnight discharge and daily recharge pattern.

It didn’t need to be particularly accurate, but I did want to get a fairly continuous log at least every 5 minutes or so. Sounds like a perfect case for some Arduino-powered data logging!

I could just capture some data locally to an SD (more...)

LEAP#439 QX5252 Solar Night Light

Inside most solar-powered garden lights is an ingenious little circuit comprising a rechargeable battery, solar cell, inductor, LED and a little IC that does all the magic:

  • when voltage is detected from the solar cell, the LED is off and the battery will charge
  • as the solar cell voltage drops off (gets dark), the chip runs a switching converter (using the inductor) to boost the voltage from the 1.x V battery sufficient to drive (more...)

LEAP#437 QX5252 Joule Thief

I recently “discovered” solar LED driver ICs, such as the QX5252 and YX805. They are mainly designed to drive LED lights from a low-voltage rechargeable battery, with colar powered charging.

A core function is a boost converter circuit (similar to a joule thief) that allows LEDs with a forward voltage of over 2V to be driven from a 0.9V-1.5V battery.

As a test and demonstration, I’m ignoring the solar charging aspect here, and (more...)

LEAP#436 Vivian the Vibrating BEAM Bot

Whatever happened to BEAM robotics? Perhaps it was just a 90’s fad, now rendered irrelevant by cheap microprocessors. But just as we still enjoy tinkering with 7400-series logic, old and irrelevant technology has a special attraction for some;-)

And it turns out that these days there are some new tricks - such as using the QX5252/YX805 solar LED driver to boost the output of the photovoltaic cell (it’s like a joule thief in a TO-94 (more...)

LEAP#434 Boldport Krell

The Krell is a handheld DSP synthesiser, with Buttons and potentiometers dial up a range of sounds. The Boldport project is a typically beautiful remix of a soldering project by James Hutchby of MadLab.

At the core of the circuit is a Microchip dsPIC33EP128MC202-I/SP. It’s an interesting choice - a digital signal controller that is really designed for precision motor control, now put in service of creating music (or at least weird sounds).

This project (more...)

LEAP#433 0-30V/3A Adjustable Power Supply Kit

The 0-30V/3A Adjustable Power Supply Kit at the heart of this build will no doubt be instantly recognisable to anyone familiar with the usual online electronics market places. It features continuously variable output voltage, and a variable current limit with overcurrent indicator/shutdown.

It appears the curciot design may have originated from SmartKit in Greece, been improved by various people, and at some point the “canonical design” was picked up for mass production (instantly identifiable (more...)

rclone Systemd startup mount script

rclone Rclone is a command line utility used for reading and writing to almost any type of cloud or remote storage. From Google Drive to Ceph, rclone supports almost any cloud-based remote storage platform you can think of. You can perform upload, download or synchronisation operations between local storage and remote cloud storage, or between remote storage

gitignore file for Go Projects

This is a gitignore file for a Go project to ensure temporary files and build files are not added to git repository commits. [crayon-5bbdc2270ee85958079321/]

List of Bank Holidays For England in SQL Format

First off, create a table to store the bank holiday values. You may need to adjust this slightly depending on your SQL server technology being used (this was tested on MySQL Server).  [crayon-5bb4e0b3b1755979540269/] Insert the bank holiday values below. This table is currently for 2012 up to 2019 for England and Wales.  [crayon-5bb4e0b3b175d512369946/] For a

MySQL/ MariaDB Error Code: 1329. No data – zero rows fetched, selected, or processed

The above error can occur when calling a cursor results in no rows, or no more rows if called in a loop. Whilst the error message is descriptive about what has happened physically, you may wish to catch the error so that you can do something else, or simply replace the generic database error with

How to exit from a MySQL/ MariaDB Stored Procedure/ Function Prematurely

MySQL and MariaDB enable you to define your own error conditions and to report back to the SQL client both a return code and an error message. As soon as you raise the condition then MySQL/ MariaDB will halt any further execution of the code and report the error back to the client. This can

CockroachDB systemd script

This is a simple systemd script for CockroachDB. It works for single node installations or multiple nodes, however you’ll need to manually join each node to the cluster before using the systemd script. Create the systemd file and add the following content: [crayon-5bb2054895a8d904003843/] [crayon-5bb2054895a94089396086/] If your host belongs to a cluster create a hosts file

gitignore file for Eclipse Projects

This is an example of a .gitignore file for an Eclipse project to ensure temporary files, build files and project settings are not added to repository commits. [crayon-5bae3d499e098261603457/]

How to change the listening port for PostgreSQL Database

The default TCP port for PostgreSQL is usually 5432, however this can easily be changed in the postgresql.conf configuration file, which is the main configuration file for the database server. In addition to a TCP listening port, PostgreSQL will also a local socket if the server is running in a Linux/ Unix environment. A local socket is

gitignore file for Nodejs Projects

An example gitignore file for Nodejs projects to ensure that local environment variables, build related output and modules are not committed to the git repository. [crayon-5bad139c32c17821581453/]

gitignore file for Netbeans Projects

A gitignore file for most Netbeans projects to keep the build and local configuration files out of your git repository. [crayon-5bad139c338b6810432445/]