I did a lot of research for this one – components weren’t that cheap.  They’re not earth-shatteringly expensive, but they’re the kind of price where you don’t want to be re-buying a lot of stuff if you keep making it set on fire.

Finding a motion sensor which would work with the 3.3v or 5v lines provided by the GPIO on the Raspberry Pi was the first step, followed closely by how best to provide power and receive a signal from it.

PIR Sensors

Passive Infra-Red (PIR) sensors basically detect temperature changes between sections of a viewing range.  This means if a person (a source of heat) moves between two sectors within the sensors field of ‘vision’ – this is detected as movement.  PIR sensors are well used in alarm sensors.  The great thing about being based on temperature is that they work in the dark and ideally suited for sensing people rather than…curtains in the wind (let’s say) which could cause problems for other, more literal interpretations of ‘motion’ sensors.

The overlap with security systems can be annoying.  Search for ‘PIR sensors’ on Maplin’s website and you”ll be fronted with the security system kind and motion activation security lights…none of which are useful for our purpose.  I found Rapid had a fairly good selection of PIR sensors which would work within the 3.3v-5v range the Pi can support.  I opted for the Panasonic one that they sell.  They come in a few varieties, but each has a fairly decent range (2.5-10m).

To get started, I went for the standard (5m) range component (in white – part no. 61-1502).  The plan being that if it worked, I might try the 10m one later.

Wiring it up

Someone else had already asked on the Raspberry Pi forum which resistors were best to use for this kind of sensor (which was helpful) – so in the end the circuit looked the same for mine. (NB: they also did a very helpful write-up of their project here)

Diagram for wiring motion sensor to the Raspberry Pi
Credit: http://www.sennir.co.uk/Journal/Raspberry_pi_Movement_sensor

One slight difference to this diagram – I attached the ‘out’ line to GPIO2 on p1-13. (NB: For a look at the GPIO pins and reading their names, check this resource)

I also left the LED hooked up from my first exercise with GPIO as a separate circuit as follows:

3.3v ->  620 ohm resistor (probably far too high, but it’s all I had in a reasonable range) -> Green LED (~2.1V) -> GPIO 7 (p1-07)

I will update with a breadboard layout diagram (which might be a bit easier to replicate) shortly.

The Software

Just to recap, we want the software to take the input signal from the sensor and, if there is movement detected, light the LED.

So here’s the Python script I wrote, using the RPi.GPIO library again:

from time import sleep
import RPi.GPIO as GPIO
GPIO.setup(13,GPIO.IN) # Pin 13 - input from motion sensor
GPIO.setup(7, GPIO.OUT) # Pin 7 - output to LED
while 1:
        move = GPIO.input(13)     # Check input from sensor False=no movement, True=movement
        GPIO.output(7,not(move))  # Turn LED on/off
        print move
        sleep(0.5)                # Wait 0.5 seconds

Interestingly, I haven’t changed any settings with the GPIO pins – so the way my LED is set up sending ‘False’ turns the LED on and vice versa – hence the not(move) statement.

And that’s it really.  The (pretty rubbish) video of the finished thing is here:

I have some close-up photos of the breadboard with the circuit a little clearer – I will update with them soon.

Thanks for reading – hope this is helpful!

The focus of the Raspberry Pi project as a whole has been machines for education – enthusing children to get low-level and learn how computers work.  At £30 they are a great educational tool – if you do something wrong, it isn’t the end of the world.  Likewise, the project has had a great response from hobbyists for pretty much the same reason.  Although similar devices have been around for a fair while (think Arduino, Pandaboard, etc.) it’s been tough to escape the buzz the Pi has generated.

So, on to my motives for getting my grubby paws on one.  I enjoy getting my hands dirty and making things.  With computing, that’s been largely limited to software.  The Pi offers many ways to interface with hardware, allowing me the opportunity to dust off my soldering iron, re-live my Electronic Products GCSE and try my best to keep the magic smoke inside the device where it belongs.

I’ll try to post my progress here, starting with this.  A whistle-stop rush through Maplin and a bored Saturday morning and I give you….a flashing LED:

Fairly simple, I know, but you gotta start somewhere I guess.  So the circuit goes:

5V -> 620 ohm resistor (probably far too high, but it’s all I had in a reasonable range) -> Green LED (~2.1V) -> GPIO 4 (pin 13)

Not really complicated enough to warrant a diagram, so that’s your lot.

All this is driven by a Python program based on the RPi.GPIO library, which looks like this:

from time import sleep
import RPi.GPIO as GPIO
GPIO.setup(13, GPIO.OUT) # Set GPIO 4 (pin 13) to output mode
while 1:
     GPIO.output(13, False) # Set GPIO 4 low
     sleep(1)
     GPIO.output(13, True) # Set GPIO high
     sleep(1)

So, by setting the GPIO pin low/high you turn the LED on/off (with a 1 second delay, in this case).

Although this is a fairly simple accomplishment, I had a lot of fun doing it and I’m looking forward to trying something else with GPIO fairly shortly.

I’ve done a lot of reading about the Pi, GPIO, RPi.GPIO, LEDs, electronics and the like, but I’d really like to thank RaspberryPiBeginners over on YouTube, I found this video and accompanying materials really useful.

Thanks for reading, hope to have something else to show you soon!

It was much easier than I expected to be honest and I’m sure it will be worth it, with less constrictions and more tools to play with

For those who haven’t come across a hackathon before it’s an event where people involved in app development (programmers, designers, graphical designers etc.) gather together, split in to teams, lock themselves in a room with caffeine and pizza for a day or two and make (or ‘hack’) something.  It’s meant to be intense, creative and challenging – a day or two isn’t a long time to make something and this is coupled with long hours and often working with strangers.  For people interested in software development and with a high enough caffeine dependency, it’s a pretty cool way to spend a weekend.

My motivation for taking part was simple – I really like programming.  Having spent my career to date in academia, I don’t often get to actually make products that people might use.  Making something exciting with other people is what I think development should be about, not merely making tools for a job.  This offered an opportunity to be really creative with what we do.  Studying for a PhD can also be suffocatingly isolating and so working with other people appealed greatly.  I haven’t really worked on software with other people – I have always been a solitary coder, so this was set to be an interesting experience.  I did have high hopes for the event and it didn’t disappoint.

The brief for this event (referred to as ‘goodhack’) was to create an application which would be for ‘the social good’ – or would benefit society in some way.  It could be a website, mobile app, bio-mechanical implant, whatever – so long as it would benefit people, somehow.  We had just 12 short hours to make this product (although it ended up more like 9) so we needed ideas that fit the time frame.

In a typically British manner, we settled on tackling weather-based issues – namely the chaos that semi-frozen rain often invokes throughout the nation.  We looked towards mapping accident blackspots during snowy/icy weather (based on data from the government) and augmenting this with real-time information from Twitter feeds.  The ultimate aim of this was to suggest areas which required gritting, or roads to avoid during the worst of the wintry weather.

And so, Gritly was born.  Well…it took a bit more work than that, but you get what I mean.  I won’t share a link yet, as it I’m not hosting it, but if I can in the future, I will.  For now, here’s a screenshot:

While we chose the students union in Cardiff as the demo location, it turns out there weren’t many accidents in it’s vicinity, but you can see the yellow circle which indicates the location on the map.

Martin and Matt handled getting/organizing the historical data, plotting it on a map and eventually launching the app.  Accidents are displayed according to their severity and can be clicked on to get more information, such as the weather/road conditions at the time.  My responsibility within the project was the real-time data from Twitter including getting tweets with a certain hashtag, extracting the (mandatory) postcode from the tweet and translating it in to a lat/long co-ordinate so they could also be placed on the map.  In all, the division of labour worked, and we had an hour to kill in the pub before the group demos.

This event produced some great apps, especially given the short time frame.  They ranged from mobile apps to help people navigate Cardiff, to automatically translating tweets and Twitter streams, to web-based games.  Each team (some even worked solo) introduced their app, and gave their motivation for making it, the technologies they used and what they planned to do to finish it off.

After the demos, judges appointed by BoxUK chose their favourite app, a runner up and the best individual participant.  The prize giving was a School of Computer Science whitewash, with a group of first year undergraduates taking the runner up prize for their online noticeboard, a third year undergraduate winning the best individual and gritly being awarded the judges favourite app.

So that was my adventure in hackathons – it was a great way to spend my Sunday and I’m very glad I went.   I’m also very grateful to my team-mates and to BoxUK for putting on the event in the first place.  I will definitely be attending more events like this and I highly recommend you do the same.

Here are some other (much better – they even have pictures) write-ups of the event, by various people involved:

http://www.boxuk.com/news/box-uks-public-hacking-event-a-resounding-success

http://martinjc.com/2011/11/22/boxuk-for-the-social-good-hackday/

http://johngreenaway.co.uk/hack-day-for-the-social-good

http://www.cardiff.ac.uk/news/articles/diwrnod-hacio-7933.html

http://www.cs.cf.ac.uk/newsandevents/hackday.html

Since the Monday after Creamfields 2010, I’ve been looking forward to donning my neon gear, painting my face and partaking in Creamfields 2011, so the fact that we’ve left the triple figures fills me with child-like glee.  The fact that the Chemical Brothers are there this year has only heightened this excitement to near embolism levels!

GET ME THERE NOW!!!!

They quickly apologised for people misinterpreting this Tweet as nothing but a shallow attempt to get lots of publicity as a condition of their support for victims of a horrible disaster.  They also said that they’d donated the full $100k…but not before they’d had a few retweets I would imagine.

Meanwhile, on the other end of the search spectrum, Google released this tool which tries to help unite people affected by the quake with the people around the world that are worried about them and looking for news.  People affected by the quake can post messages, which can then be searched through.  It was hurriedly put together by a team of people in Google’s Tokyo office, and thanks to efforts from people across the company (and the world) it was up and running just an hour after the quake.  While I’m writing this, it’s showing over 145,000 messages posted, meaning that it is currently helping a lot of people.  On top of this, according to this blog post by one of the Tokyo office employees responsible for the tool Google also donated $250,000  to the relief effort – two and a half times that which Bing gave, no tweets required.

They’ve also produced a quick access guide to up-to-date information and news feeds at the Google disaster response site.  Here there are phone numbers, locations of shelters and aid on a map and an aggregated news feed for minute-by-minute information.  An important measure, where access to information is critical.

Response to disasters like this is important and any tools that can be provided in the hope of alleviating the burden on those affected should be made available.  While it may not help everyone and may not save lives, getting people in touch with their loved ones is both important and difficult in these situations.  Phone lines are down, infrastructure in ruins, but leaving a lasting message somewhere people can find it might just help some people out.   Granted, not everyone will have access to a computer and the internet there yet, but apparently there’s been 145,000 uses for it so far.

The quick-thinking of Google in response to new information challenges means, in this case, it comes out on top for me – no competition.  Providing both tools and aid to the relief effort or a cheap, half-thought-through marketing/aid campaign – not really a tough one.  I know, Google are gonna get lots of praise for this, and lots of publicity so I guess we could debate their motives behind it, but given this was produced rapidly in the Tokyo offices (affected themselves) I have to assume this was more a humanitarian gesture…one that they deserve the publicity for.

Festival regulars such as Tiesto, David Guetta and Calvin Harris are to be joined by the likes of Laidback Luke, Magnetic Man, Erol Alkan and last but definitely not least – The Chemical Brothers!  Very exciting

After putting on an awesome show last year, the Swedish House Mafia tent is back on the Sunday this year – with SHM headlining themselves.  Annie Mac will also have her own tent again this year and will be the headline act – I’m aiming to get there early this year as the crowd was bulging out of the tent for her awesome set and laser show last year.  Some other personal highlights lined up for the weekend: Example , Chicane and Skrillex – looking forward to em all.

Tiesto is (currently) down to headline the Clublife tent on the Saturday after closing the festival on the Main Stage in front of a massive crowd last year.  I hope his set and The Chemical Brothers (who are headlining the North Stage) don’t overlap.

According to the Creamfields website there are some more acts to be announced, including on the North Stage for the Sunday.  I am hoping that another big act is announced play out the weekend there (fingers crossed for Daft Punk at the moment – would make the best weekend ever!).

Needless to say after the lineup announcement the F5 spamming started over at ticketline.com waiting for tickets to go on sale.  We did okay and it didn’t take long before we had parted with a fair chunk of cash to secure our place.  So now all that’s left to do is get excited

A countdown to the festival has been added to the front page of the website so that I (and you) will keep getting reminded that it isn’t far away.  My Spotify playlist with my favourite tracks from the artists at the festival is now under construction – I’ll post more about it when there’s some progress.

Ciao for now!

The Twilight Sad have been a rather recent (but extremely welcome) addition – ever since I heard they were supporting to be honest.  They’re rapturous music with stunning, gritty vocals (with accent in tact) make them definitely worth a listen.  They’re set was burdened by the fact that the sound system was blatantly not set up for them; a great shame as they gave an energetic, emotional performance.  The drummer, Mark Devine, was manning the merch stall afterwards and was getting a lot of praise.  I’m glad, because the crowd didn’t seem to get all that in to it – and they were getting heckles from some (rather drunk) people behind me.

Mogwai didn’t have sound system problems – they sounded awesome.  All but for the vocals on Mexican Grand Prix, their third encore song.  While I can recognise songs, I can never tell you what they’re called, so I can’t give specifics, but they were very tight.  Impressively so, given the complexity of their particular brand of music.  Two disappointments, no Mogwai Fear Satan or Glasgow Mega-Snake (though I thought they played this, I was mistaken…again with the rubbish with the names thing).

All in all, good times had by all I think – ‘cept £3.50 for a crappy bottle of Fosters…that was a joke!  We got pretty close to the front for Mogwai’s set – was easily done as it wasn’t a ‘mosh-pit’ style gig.  We were surrounded by pricks for the second half of their set, who tried to get the crowd to ‘dance more’ despite having no rhythm.  There’s always one or two…and they tend to always find me.

For those interested the setlist is here.

I also took the chance to buy (and get signed) the long awaited (first half of) Volume 4(a) of The Art of Computer Programming covering combinatorial algorithms (see pics below).

While I don’t think I’m infringing anything using this image (I found it somewhere and took the crap white background off it – copyright symbols still there though) I found it here – credit where it’s due.

Well, I only really did this to procrastinate – lots of work to do, better get back to it.

See yas later!