About this project
***** AVAILABILITY AFTER THE KICKSTARTER HAS FINISHED: I'm currently in negotiations with some Raspberry Pi stores to offer the kit. Please keep checking here and at www.pocketmoneytronics.co.uk to find out where you can lay your hands on one. And thanks for all the fantastic support! I'm pleased to say that these three great Raspberry Pi shops have agreed to stock the tree when it's available in a few weeks' time:
Dawn Robotics: http://www.dawnrobotics.co.uk/
The Pi Hut: http://thepihut.com/
Ryanteck: http://www.ryanteck.uk/Hello! The Raspberry Pi is a great device for learning about controlling hardware and, like many of you out there, I've enjoyed connecting LEDs to the GPIO pins and controlling them with Python.
I had the idea to make a fun, festive GPIO project for the Pi and also to try out an interesting LED-interfacing technique called 'Charlieplexing'. The result is the GPIO Xmas Tree for the Raspberry Pi!
If you look-up Charlieplexing on Wikipedia then you may think it's an intimidating technique but, really, it's quite simple. It has one big advantage: you can connect lots of LEDs to a small number of GPIO pins. My Xmas tree uses just four GPIO pins to control 7 LEDs (although four pins could drive as many as 12 LEDs!). I'll explain all about Charlieplexing in the updates as the campaign progresses and also in the final instructions, but don't worry if it sounds complicated: I'll provide plenty of examples of Python code that will make it easy.
Why do I need your help? I think this is a fun project that many Pi-owners will enjoy, whether they just want a fun Christmas gizmo to solder, or whether they want to learn about Charlieplexing. However, PCBs are expensive to produce in small quantities and I need your help to place a big enough order to get the cost of the kit into the 'pocket money' price range (low-cost 'pocket money' electronics kits are a big project of mine at the moment: see my project at www.pocketmoneytronics.co.uk ) The PCB you see in the photo and video is very nearly the finished version: there's just a few small tweaks to be made that will help with soldering and programming.
*** STRETCH GOAL 2 ***
Just on the off-chance that there are still some willing backers out there, I've set one last stretch goal: if the total reaches £1400 then I'll upgrade the bi-colour LED to a "Super-Bright" version. I've been playing with one tonight and, with it, there's no concerns about it being dimmer than the other LEDs... in fact, you might want to tweak the code to *reduce* its brightness!
>>> STRETCH GOAL 1 <<<
We're getting very close to 200% funding! If we hit that value (i.e. £1080) then, as well as the yellow LED at the top of the tree, I'll include a 'bi-colour' LED which can be used in this position (read on for a few limitations, though). I've been experimenting with a nice Red/Green LED which can be red or green or, if you flick quickly between the two, a funny mixture of the two colours. There's a small limitation, though: the bicolour LED is slightly dimmer than the other red LEDs. This can be compensated for to some extent by modifying the software so that the bi-colour LED is illuminated for slightly longer in the sequence than the red LEDs and, consequently, I'd suggest its of most interest to more advanced experimenters (I'll post a suggestion to something that the less brave users can do with this LED instead, though!). It's just a little something to say 'thank you' for supporting this Kickstarter and making this project happen!
News regarding Charlieplexing: here's a video I've made about how the Charlieplexing works http://youtu.be/57wRBMdOm9U or you can read about Charlieplexing in this Kickstarter update: https://www.kickstarter.com/projects/1937541932/gpio-xmas-tree-kit-for-the-raspberry-pi/posts/1037203
News regarding kit multipack: I've now added the option of 2 kits for £10 for UK backers... please feel free to update/adjust your pledge to take advantage of this option! ;-) If you're one of the kind people who has already bid a multiple of £6 for multiple kits, please contact me and I'll arrange something so that you're not out of pocket.
NEW! I've just posted some Python code! https://www.kickstarter.com/projects/1937541932/gpio-xmas-tree-kit-for-the-raspberry-pi/posts
NEW! Now shipping Worldwide! (Hoping to ship very early in December, but please understand that I can't guarantee arrival before Xmas for international orders, sorry)
Risks and challenges
There's not too much risk here, really... I've made several prototypes using PCBs from a prototyping firm and they work quite nicely. The biggest risk relates to timescales - I want to make sure you all get them before Christmas! However, I plan to use a very reliable PCB manufacturer (the excellent ragworm.eu) and will place the order as soon as it's apparent that the campaign will be successful. The main risk, really, is that international buyers may not receive them before Christmas as it all depends on the postal system... so please bear this in mind when ordering internationally!Learn about accountability on Kickstarter
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