Happy Birthday, and variations thereupon

Northackton is 3 years old this month.  The exact week can be derived from reading the first few posts in the archives, and/or by looking at flickr, but I won’t spoil it for you.  To celebrate, Andy had suggested an informal competition to produce devices that play the Happy Birthday tune.

A number of entries were made, and here they are for your enjoyment:
Andy’s recreation of our first attempt to play music bottles with servos.  He authentically captured our discovery that servos aren’t very good at this
 
Andy’s second entry was an Arduino piezoplayer:
  
Adrian made a xylophone using old pinball chime solenoids.  It only had three notes, but it played them really well!
 
Mine was another Arduino player, but with a mini speaker in a little box.  I don’t have any video of it yet, it’ll have to go up in a second post.
However the show was stolen by newcomers Mike and James who came for help making their ring modulator work.  Happily they’d got it almost entirely right, and some slight tweaking and a lot of soldering produced a very special song.
 

Hack evening workshop #1 a success

Well we’ve had our first workshop, and the three talks given by Martin, Alan, and Stephen went down very well, and covered a range of topics and abilities.  Martin explained how to design physical 3D objects and manufacture them in the home (or pay someone else to, for the less brave).  Alan taught us that bigger softer running shoes aren’t always the best answer, and Stephen explained the many different ways data can enter a computer.

The slides for these are on the wiki.  The Yeoman of England appears to be a great venue, and so it’s already booked for next month on Monday 6th September 2010.  We also have permission to bring some equipment along, but I don’t think we can devise anything too messy.

Next week we have the traditional pub meet and there we’ll finalise the logistics for the Ballistics Day, and plan the September workshop.  More pictures follow

Arduino Rocket Launcher

Feeling the need to create something needlessly complicated to short a battery across the ignitor of the chemical rocket motor I turned to my Arduino Mega.

I already have a dot matrix display for my Arduino and have been using it to scroll the word ‘NortHACKTon’ when we go to the NortHACKton pub meets so that those people looking for geeks in a pub know who we are ”(cos we would’t stand out enough without it :P)”. I figured the dot matrix could be used to provide a visual countdown and the Arduino could activate a relay which connects the 9V supply directly to the rocket and then whoosh off it goes.

Schematic
It’s a very simple little board, consisting of a driver chip and a relay and the connection to the dot matrix display. I chose to use the ULN2003 to switch the relay primarily because the package already contains a freewheeling diode and can be directly driven from the arduino and secondly because I have 3 tubes of them in the shed already due to a misorder on a previous project. The dot matrix was also used on the same project. It is the 0832 from sure electronics and can be brought pretty cheaply on ebay, for only £7 inc P&P.

Arduino Program
Being an arduino most of the code is already written in other projects, (that is after all why we use arduinos isn’t it?). The program needs to read in the input from the micro switch to determine when the countdown should be running, it should only count down while the switch is depressed. When the countdown reaches zero the arduino should trigger the relay should be activated. Both of these functions are standard IO type code using digitalRead and digitalWrite. The DotMatrix is driven by the “Matrix Display” Library. The display is initialised when the program starts and images displayed by turning single pixels on and off.

I modified the Font.h file slightly to incorporate more of the ascii characters so I have included my version of the Matrix display library in the source code attachment. If someone were to be really keen I would suggest moving the character mapping function into the header too and creating the rest of the ASCII characters for the display. It’s on my list of things to do along with a variable width font, but that list is already pretty large so this won’t be done for some time.

The scrolling display displaying the NortHACKton url is created using the drawString functions provided as part of the library. The rocket and abort animations are defined as byte arrays at the top of the code and drawImage function simply calculates the visible part of the array and writes that data to the display.

Arduino Source Code

Steve setting up the rocket

The arduino rocket launcher ready for action

Demo Video

More photos of the rocketry day can be found here

Meet #3 write-up

The third meeting of NortHACKton took place on the 15th of June 2010, after Martin and I dropped in to see the NSME again, as they were having a group meeting in the park. A smaller meeting this week, but still rather productive. It would be difficult to point fingers at the World Cup as we were meeting during the Brazil vs. NorthKorea match.

Point of note for Tuesdays, the Malt Shovel does not serve food. Igor and and his girlfriend arrived and we had a discussion of the comparison of the Spanish and English climates, and sources for Arduino hardware. We also compared different embedded microprocessors, and talked about the FEZ platform, which is an open source microprocessor that is programmed in .NET instead of C. It’s £55 at cool components, which is a little more expensive than the other new entry, the mbed, but is a faster processor.

Yet another discussion was had about a high altitude balloon launch, and I think a long term goal of the group will be to support such an endeavour, as it certainly captures the imagination effectively. It may also be a good recruiting tactic, particularly if we were to send up something that had room for a secondary payload. Importantly though, it would be a technically complex job that requires some financial investment. It was agreed that postponing this until at least next year would allow for practice and research in the area.

Upcoming event: Rocketry

In lieu of a balloon launch, NortHACKton will have a rocketry day in the Racecourse park. This gives a chance to do something easy and fun. We’ll launch a range of water bottle rockets and hopefully some chemical ones as well. People can bring their own bottles and turn them into rockets and have them launched. This is relatively family-friendly, but under 18s must be accompanied by their parent or guardian. We will

PLEASE ENTER YOUR FREE DATES HERE. This will be closed in a week. If you’re planning on bringing kids or plus ones, then tell me to weight your votes appropriately.

We’ll hopefully have some guides on producing your own rockets if you’d like guidance or you’ll be able to make them on the day. There will be a separate blog post once a date has been chosen.

Upcoming event: T-shirt hacking

Another idea that was considered at the meeting was the idea of sewing microprocessors and LEDs to some T-shirts. Rather than buying Lilypads that are nice but cost more than the T-shirts, it was suggested we use PIC10s or ATtinys that are small and cost £1-2. These would need dedicated programmers, but be easier to sew.

We could have an evening trying this with some pre-programmed processors, and interested people can bring their own T-shirts to modify. A second possibility is that we have shirts printed with the NortHACKton robot logo on it, and add LEDs to the robot face and background.

Positive and negative feedback on this idea is welcomed. This would be run in the Community Centre on a Monday in July-August.

Links from the discussions

  1. Seeed studio: open source hardware. Thanks to Igor
  2. FEZ open source microprocessor running .NET. Thanks to Igor
  3. CUSF balloon launch this week.

Date of next meeting: 20th July 2010.