Light Canvas - LEDs 1: Known Unknowns

This is the more complicated part; or at least I have little idea what I'm doing when it comes to electronics. I know basic theory (e.g. Ohms law), and what various components do, but - so far - no practical experience beyond giving glowing red eyes to a toy raven.




The electronics for this shouldn't be too tricky though, as it's all simple analog circuits, with no digital components. The plan is to have:

1. A mains power source (I don't want the hassle and inefficiency of batteries), connected to an input socket in the frame, which itself connects to...
2. An on/off switch, which connects to...
3. A linear fader, to control brightness of...
4. A bunch of LEDs, set up to give an even glow through the canvas (some subtle pattern would be acceptable though).

So, onto the known unknowns:

• What voltage and amperage should the power source provide? It'll depend on the number and specification of LEDs  it'll be supplying - which I don't know yet. I'm thinking 12V is a fair place to start, and conveniently I've got a 3.5 - 12V adapter to prototype with.
• I've got a little toggle switch of the type I want to use, but don't know what power it's rated for.
• The fader could be a potentiometer - or might need to be something else, if the electrical load is too high for a pot. I bought a mixed bag of pots to play around with a while back, and it contained just one linear fader - hopefully it'll be suitable.
• LEDs - this is the biggest area of uncertainty. There are lots of LEDs with differering specifications available, and I don't know which type and how many I'm going to need for the canvas to glow like I want it to. Aspects to consider:
  
  • Brightness (enough to shine through the canvas)
  • Viewing angle (wider is better, as I want an even glow, not visible bright points)
  • Number of LEDs to use (more at lower brightness would give more even illumination)
  • Clear vs diffuse finish (at last, an easy one - diffuse)
    
  • Configuration - rows and columns, random distribution, or some other pattern?
  • How to choose and wire up the right combination of LEDs?
  • Cost - no need to start taking out loans for a hobby...

I think this a fair example of too many choices, not enough knowledge, so I decided that the only way to get started was to just buy some LEDs and fit everything else around that.

Time passing whilst I researched LEDs will be represented by this post ending, and a new one starting...

Light Canvas - Frame

I tend to think about all the different aspect of a project (in this case, frame, LEDs, canvas) at roughly the same time, gradually figuring out how each part will work, independently and together with the others. That would be an utter nightmare to write up though, so these posts will mainly focus on one aspect at a time. Let's start with the easy one: the frame

This is relatively simple - I know the dimensions of the canvas print (135x45cm), so I know I want my canvas to be 135x15cm.

I little research suggests that getting a pre-built frame this size will be difficult or expensive. To be honest, most of the research was watching YouTube videos on stretching canvases. Woodworking is kinda fun, so I elected to make this myself.

After a while trying to think of a way to add a bevel to regular planks (to make sure the canvas doesn't have lumps due to the frame, I realised I could simply use a simple beveled architrave.

The frame is simply two horizontal and two vertical pieces, glued and nailed together with mitre joints, plus vertical braces inside for strength.


Cutting a mitre joint with a plastic mitre box wasn't very accurate - I ended up sanding down the cuts, and hoping that glue would make up for where the surfaces didn't quite meet up.


Positioning the braces was one of those things where it was totally unclear how many were needed and how to space them, until the four frame pieces were laid out on the floor, at which point it was obvious that two braces at thirds of the width would be ideal. The braces are at the back of the frame, so the shouldn't stop light bouncing around the inside of the frame too much - I want the whole canvas to glow, rather than having several compartments. Here's all the pieces laid out (but not glued or nailed):


Also in that pic is a large piece of fibreboard from the Ikea clearance corner - thanks to H and Bic for letting me bring it back with us :-) This will be cut down to size, have the LEDs mounted on, and will be screwed onto the back of the frame.

In keeping with family tradition, my place is full of tools and materials in progress during all this:


Ideally I would've used some corner clamps to ensure that the frame was square when I glued the pieces together - but I don't have any, and the local DIY shop didn't have any. Instead, I lined up the pieces to a roofing square that I bought for the cupboard project, PVA glued them all, then nailed them all (with pre-drilled holes). The braces needed a bit of encouragement to keep them in the right place whilst waiting for the glue to cure.


Cut the fibreboard to size, and that's pretty much all the woodworking finished!



This is all about white light, so the frame gets painted with a matt white, to reflect as much light as possible, without specular highlights.


I'll need to make some modifications to fit electronics, but the frame is done for now.

Light Canvas

Another new project! This one started around October, and is a result of three different threads coming together:

1. I bought a canvas print for my bedroom, a rather nice false-coloured X-ray photo of flowers (probably based on Nick Veasly's work).

2. I need a decent bedside light to replace the rather inelegant broken anglepoise I use at the moment - and preferably something dimmable so I have the option to introduce myself to the day gently.
3. My guitar lights project (more on that later) has been stalled for around two years, and I could do with a simple LED project to learn and gain some experience with electronics.

The predominantly black canvas immediately suggested a short, wide white canvas emitting white light. I think it could look very cool, and give a nice diffuse light to the room through a rough canvas texture. Including a fader will allow me to control how bright it is.


The basic design is:

• A wooden frame the same width as the print, but a third of the height. I was vaguely thinking about the rule of thirds when I chose that height, but mainly it was a good fit for the space between the bedhead and print.
• White LEDs in the frame, with on/off and fader controls, and power supplied via an external switched adaptor (e.g. a typical wall-wart). The LEDs might need some sort of diffuser so the canvas emits light reasonably uniformly.
• A white canvas stretched over the frame. Obviously, this needs to be thin enough to let the LED light through, but be thick enough to be durable. It should have some texture, for the aesthetic.

From that design, there are a lot of details to work out, starting with:

• What LEDs do I need? How many? How should I arrange them? What rating power supply will they need? How do I wire it all up?
• Do I really want canvas - what other options are there?
• How do I get the frame? Buy pre-made or construct it myself?

Stay tuned for answers to all these questions and more...

You gets what you pays for

I bought three webcams matching one I already had, for a total of £16 off eBay.

The good new is they all work.

The bad news is that they can't all work at the same time, as they saturate the entire USB bandwidth.

I now know that cheap webcams send a raw stream of video frames over the wire, whereas more expensive ones compress it (with mjpeg or similar) before sending it over the wire. I now also need to buy more webcams - but more expensive ones.

Bugger.

Webcam videowall

So - a new project. Actually an old one (circa 2008) that I'm making a new start on - a webcam videowall:

When I saw Radiohead at Victoria Park as part of their In Rainbows tour, I was quite taken by their visual show - a big rig of LED columns, and video screens. "It'd be cool to do something like that for a Witches gig", I thought.

I'd messed around a bit with freej, and made some progress, but the interface was a bit of a hassle (or rather;I was too lazy to learn it), and I only had one webcam, so that stalled.


Fast-forward to a couple of weeks back, and using the magic of the GStreamer framework on Linux, a couple of cameras borrowed from work, and some essential help from the GStreamer mailing list, I can feed four webcams into one video stream, using this command:

gst-launch-0.10 v4l2src device=/dev/video0 ! video/x-raw-yuv,width=320,height=240,framerate=30/1 ! alpha ! queue ! videomixer name=mix ! ffmpegcolorspace ! \
  xvimagesink sync=false \
  v4l2src device=/dev/video1 ! video/x-raw-yuv,width=320,height=240,framerate=30/1 ! alpha ! videobox left=-320 border-alpha=0 ! queue ! mix. \
  v4l2src device=/dev/video2 ! video/x-raw-yuv,width=320,height=240,framerate=30/1 ! alpha ! videobox top=-240 border-alpha=0 ! queue ! mix. \
  v4l2src device=/dev/video3 ! video/x-raw-yuv,width=320,height=240,framerate=30/1 ! alpha ! videobox left=-320 top=-240 border-alpha=0 ! queue ! mix.

All the programs needed to make this work are available through Ubuntu's package management, so it was dead easy to install.

The Scene:

The Stream:

The cameras producing the top two corners are much older than the bottom two, hence the poorer quality picture.

I found GStreamer to be a bit of a pain to get started with - it's easy to get something simple running by following examples in the documentation (like showing one webcam), but more complicated pipelines are tricky for the newbie as it can be hard to work out why a pipeline won't run.

Still, that's what learning is all about, and there is plenty of documentation, and a very helpful mailing list (thanks!) - it's just quite complex, so don't expect to pick it up straight away.

Next steps will involve looking at:

• Performance (some cameras are very laggy, which might be due to the cameras, or might be GStreamer - I don't know yet)
• Different layouts
• Filtering the videos to make them look more interesting.

Anyone Can make a music documentary - but it won't be cheap

How To Wake Up

Oxford is mostly known for the University, it's buildings, and Morse - but it has produced some important bands over the years, with probably Radiohead and Supergrass being the most widely known.

Anyone Can Play Guitar is Jon Spira's independent documentary film about 30 years of the Oxford music scene - bands who made it to international stardom, bands who didn't (and why), and the unique music community in Oxford that fostered them. The international impact of (at least) Radiohead warrants a look at Oxford's people, bands, scene - and how they faired with the music industry, so I hope you might see your way to help fund it!

I met Jon through my own small part in the scene, and know him as a scriptwriting teacher, short film and music video director, and owner of the late great Videosyncratic video rental shops - but more importantly here, as a passionate fan of music and film, and I can't imagine anyone better suited to a film about Oxford music than Jon.

Joy Through Work

Around May 2007 local venue The Zodiac closed, prior to AMG converting it into The Carling Academy. The demise of this key fixture of the scene was Jon's prompt to interview band members, film gigs, and collect as much other footage of the diverse bands as possible - so he could tell the story behind it all.

Three and a half years on, the film is yet to be released - even though the main content of the film (sound & video edit, narration) has been finished for a while - it still needs some capital to finish it:

• a cash injection of £10k for the sound mix and picture grade before it's actually a finished film, and
• about 30k to legally clear all of the music and footage.

(Initial quotes were £20k for the sound and picture, and up to £60k for music clearance - ouch! Happily, other work Jon completed since finishing putting the film together has attracted interest from people who then saw the film and wanted to help get it finished.)

Jon is pursuing crowdfunding at indiegogo (please visit and contribute some funds!) for the £10k to finish the film ($15k on indiegogo), and once that's done he'll have something he can actually sell to cover the £30k for clearances.

As usual for this sort of crowdfunding there's a range of funding options you can choose from; starting at a credit on the DVD for $15, up to $800 for Executive Producer credit, vip tickets to the premiere, a copy of the dvd, and a poster signed by Jon and some of the bands/artists featured.

Got It Made

Crowdfunding permitting, the film is approaching completion. I would like to have a closer look at the finances but if I spend much longer on it, this post will never be finished. I'll just quickly mention the some key aspects...

Funding

A rough breakdown:

• Jon and others' personal investment
  
• Camera, lights bursary from OFVM
• Sound mix - crowdfunding
  
• Picture grading - crowdfunding
• Rights clearance - to be funded via distribution rights

Of course, at an estimated £30,000 to £60,000, the big cost is music clearance, which has a whole mess of copyright issues to itself.

Not funding:

• UK Film council
  
• Screen South
  
• European arts funding
  

Jon's blog describes some of his less than satisfying experiences with funding of film and TV projects, and the UK Film Council, in particular.

Tango Borracho

To wrap up - I'm really looking forward to seeing the film (and gutted that I didn't see the OX4 preview as I was already busy), and you should support it. Shame I don't have a spare $800 lying around - it'd be nice to have an Executive Producer credit!

This post was all put together from chats with Jon, reading his blog, and general Oxford music stuff on the web. Anything wrong in it is probably due to me mis-remembering - or plain imagining - conversations. If you spot something wrong here, please let me know in the comments.

Finally - it's cheesy I know - but the headings are all names of tracks from some of my favorite Oxford bands; go and listen to some great music!

• How To Wake Up -From Light To Sound
  
• Joy Through Work - Borderville
• Got It Made - Family Machine
• Tango Borracho - Les Clochards

How to tell if your representative represents?

When I previously emailed my MP, I hoped that he would try to learn about the subject.

Today I received his response:

Dear Mr Balch

Thanks for the email.

I have written to the Secretary of State for Business, Innovation and Skills taking up your concerns.

I will also liaise with other MPs concerned about this,

Best wishes,

Yours sincerely

Rt Hon Andrew Smith MP

Now it may be that the Rt Hon Andrew Smith MP actually has tried to learn about the issues I raised, and has formed an opinion about them. You certainly can't tell from that letter though.

Hopefully I'm just being cynical and he actually is pursuing the issue...