Category Archives: Electronics

A teapot stand that reminds me to pour the tea

I like drinking tea, however it’s not unusual for me to make the tea then get distracted and forget until 20 minutes later; this results in warm, stewed cup of disappointment instead of the tea I’d intended. To help prevent such tragedies, I’ve made myself a teapot stand that reminds me to pour the tea once it’s sufficiently brewed:
A teapot stand constructed from a HDD platter with a lead snaking out of the back and the edge of a circuit board just about peeking out from underneath Continue reading

Adding wi-fi to a Raspberry Pi without a powered hub

It is a commonly known problem that the Raspberry Pi cannot provide enough power for most USB wi-fi adapters. This can be solved with the use of a powered hub, however I have plans to integrate the Raspberry Pi into other devices; due to space constraints I decided that it would be better to convert a dongle to draw power separately to its data connection, also taking the opportunity to reduce the distance that it projects past the end of the board.
The modified dongle plugged into the top USB port of a Raspberry pi Continue reading

Adding OTG functionality to a multi USB lead

I recently got my hands on a Nexus 7 tablet; while it is capable of supporting USB peripherals, like most tablets it lacks a USB A socket. Instead, the micro USB socket must be used with a USB OTG (On-The-Go) cable; this utilises the otherwise unused fifth pin in the micro USB plug to switch the tablet into host mode. To avoid having to carry around an extra, I’ve added a switch to allow a lead to function both in standard and OTG mode.
A multi USB cable with a switch added to enable OTG functionality Continue reading

Making a mains adapter for a Canon Powershot A800

I recently bought a new camera; it’s a Canon Powershot A800. Although it’s only a basic compact camera, I specifically chose one that can run CHDK; this is a replacement firmware that allows access to just about every feature imaginable. One thing I wanted to try was to take regular shots over the course of a night so that I could combine them to create a photo of star trails. I quickly realised that powering the camera with batteries limited shooting to a couple of hours and the cost of batteries was going to start mounting up. With canon wanting about £50 for an official mains adaptor it was time to make my own. This is what I came up with:
The AC adapter and the completed camera lead Continue reading

Improving the aerial on a mini bluetooth dongle

I, like many people, have a soft spot for the online purveyor of tat that is ebay. When I wanted to add bluetooth connectivity to my desktop I went bought myself a miniature bluetooth dongle for about £1.50.
The miniature bluetooth dongle
It certainly manages being miniature and providing bluetooth connectivity, although the advertised 10m range is a little optimistic. After having troubles with proximity mains control due to a couple of dead spots, I got thinking about ways to improve the signal. Quite quickly I realised that the aerial was a good place to look. Continue reading

Revisiting parallell port mains control

Since my last post on this topic, there has been quite a lot of interest; this post is to cover some slight tweaks to the box itself and to include some extra details. I’ve added a second parallel socket to the side of the box and connected each pin to the corresponding pin on the other socket. This allows one socket to be connected to the computer and the other connected to further parallel devices. I plan to build several more similar boxes, which will be able to be controlled simultaneously from a single parallel port.

The socket box with the faceplate off to one side in order to show the connections. Continue reading

Controlling the mains via the parallel port

Today I’m looking at controlling a 240V socket with the parallel port on my Linux desktop; this design can take the full 13A available and can control any device or extension lead with a 13A plug. I’m currently using it to turn lights and monitors off at night, but I have also used it in the past to check live weather reports and automatically turn a fan on. The only limitations to its use are the number of appliances with plugs and your imagination. Continue reading