Monday, 27 December 2010

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...

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