Skip to main content

Posts

BBC Micro:bit Toothbrush Timer

A few months back I bought a BBC Micro:bit at the Science Centre in Glasgow and it's been fun building apps with the single board device. I thought I'd write a blog entry about the latest project which will be a more permanent installation in our bathroom.

A toothbrush timer!

Kitronik sell an add on board which provides power from a coin cell battery and a piezo buzzer called a Mi:power, they also sell a Mi:power case which is designed to fit around a Micro:bit fitted with the Mi:power. This assembly combined with some code offers a neat toothbrushing timer. By using the display on the front we provide a short countdown - with a little tune through the buzzer. The program show 6 areas of the mouth to brush each for 20 seconds before showing a toothy grin and a finishing tune. Each time the area of the mouth changes it plays a 'level up' style jingle.



Links to the parts:
Mi:power https://www.kitronik.co.uk/5610-mipower-board-for-the-bbc-microbit.html
Mi:power case htt…
Recent posts

12 Factor Config for .Net on Mono in a Docker

Recently I've been thinking about how to run a .Net application using Mono inside a Docker, along with this we'd like to use Twelve Factor config.

Whilst it is possible to use some library to access environment variables instead of using appSettings it becomes difficult for database and message broker URLs which other libraries may expect to find within the App.config or Web.config file.

The solution I came up with follows:
Build the application without an App.config moving the existing configuration file renaming it App.config.template. 
Substitute any environment variables you want with ${}.  E.g:
<amqp> <connections> <connection name="rabbit" server="${RABBITMQ_URL}" password="${RABBITMQ_PASSWORD}" /> </connections> </amqp>
Include within the Docker image a script named sub.sh similar to this and add it to /conf:
#!/bin/shwhile read line doeval echo "$line"done Add your config template to /conf
Then …

Howto: Node-RED Change Hue Lights Temporarily On Door Open

We fitted a LightwaveRF magnetic sensor to a door to detect whether it is open or closed. The main driver behind this was to increase the level of the hallway lights for a predetermined period of time whenever the door was opened. Since we’re using coloured lights it makes sense to put the light back to how it was once the time period as elapsed. 
Node-RED does not offer a node as a means of storing state between, but it does offer functions which have access to a context object which can be used to store state between flows. 
I’ve created a flow which listens to the `domoticz/out` MQTT topic filters messages based on their Domoticz IDX value and furthers filters on the door switches `nvalue` where 1 indicates door open and 0 indicates door closed. 
https://dl.dropboxusercontent.com/u/174818/FrontDoorLight.json
On Door Open: Retrieve state of current light and if nothing already stored, store the current bulb state in the context. Change the state of the bulb to a bright white. Res…

Howto: Node Red Subflow for Hue Bulbs

When writing some flows for Node-RED controlling my Philips Hue bulbs; I wanted to read from a bulb do some work then write that same colour back to the bulb. When you perform a GET on a bulb, you get all of the information, whilst good this means it is a bit more inconvenient to PUT that back into a bulb as that API has a slightly different resource shape where the colour mode is determined by which values are submitted.

After using a group of nodes in one flow which did exactly this, I needed the same block in another flow. So I created a sub flow by selected those nodes, clicking the hamburger menu in the top right and choosing 'Subflows > Selection to Subflow'. This replaces the selected nodes with a single node which you can edit in a 'subflows' menu group in the left pane.

Download this selection and make your own subflow:
https://dl.dropboxusercontent.com/u/174818/HueInputToOutput.json?dl=1

Automatic Kitchen Lights

We recently purchased Hue bulbs for our Kitchen they’re great, but since we already have an RFXCom 433 unit (as per my blog on automating hifi), we wanted to automate the lights and invested in a Lightwave PIR motion sensor. 

I downloaded Domoticz [http://domoticz.com/] on an SD Card for my Raspberry PI and also installed node-red [http://nodered.org/] a tool for filtering and processing MQTT messages. 
Domoticz is used to store the state of the motion sensor and is configured to emit an MQTT message whenever the state changes. 
We also wanted the lights to have a different colour depending on the time of day we enter the kitchen, for example during the evening we might want a relaxing light, meal times a white light above the dining table and during the day some multi coloured lights, but not change them if they've already on. 
For each of the time slots of the day, a template has been created containing the settings of each of the main and dining lights and will send these o…

Linn DS Homebrew RCU with Playlist Support

After installing a hidden Linn DS for my bathroom, I found controlling it tricky, whilst using the phone is okay, I'd still like the convenience of a remote to switch off the music on the way out.

I worked around this problem by extending the alarm clock functionality already in use for my kitchen to include a 'set standby' option. This would place the bathroom DS into standby mode at known times. Not ideal, but more useful.

The Linn solution to this is a control panel on the wall which offers volume, power and a remote IR sensor. Whilst this gives me the ability to switch off on the way out. It would mean having a remote control in the bathroom to change source and not something I'd like. Since I'd added functionality to schedule stored playlists to start as well as the radio I convinced myself I also wanted the ability to preload a known selection of music at the press of a button. I'm a coder and after watching the RI Christmas lectures on 'hacking your …

Test Driven Development

Recently I watched David Heinemeier Hanson's controversial railsconf keynote and I thought I'd express my views.

His main argument suggests TDD is dead. Oddly I agree with many of his headline views which I try to document below. I just not convinced of his supporting arguments.

DHH appears to have a dim view on TDD practicing developers; whom he generalises write simple unit tests having 100% code coverage, use many mocks, but test nothing real. His example was a bug in Basecamp which lost customer data, their code had 100% code coverage, but still didn't work. I really doubt there are many developers who just stop when they hit 100% unit test coverage?

I'm not going to speak for everyone else; I only started using TDD (not exclusively) about 18 months ago despite 12 years developer experience writing some really cool stuff, some well designed and some not so well...

The well designed stuff has tended to be driven by TDD. I've never used code metrics, I use TDD to…

Linn DS Alarm Function

Update 2014 - An alternative to this is available on GitHub which uses Node.js and should be cross platform. Linn DS Playlist and Alarm Server

Switching the radio on in the kitchen in the morning is a low priority amongst setting table, pouring cereals, carrying children, etc. The Sonos has an alarm clock facility which allows you to switch on the radio at a set time avoiding hassle of starting a controller.

When I upgraded to my Linn Sneaky DS, I no longer had this function, though the remote control made it easy if I forgot to take my phone downstairs with me.

Last week I decided to figure it out. I have a Linux machine which runs Ubuntu and runs all the media servers, backups and network shares. I decided to investigate how to control my DS from the command line.

Conveniently, the DS can be controlled via a web api, so after reading the docs and a few examples I was able to switch off and on and change source via Postman (Chrome REST client).

I then set about writing a curl…