Building a Better Colour Changer – Part 3 – Revising the design

Well, it’s been a while, but it’s well past time we had another look at the continuing saga of Circuit design and Colour Changers.

The good news is I haven’t been idle and now we’re up to like prototype 5.  The bad news is there’s still a bit to go before it’s reliable and repeatable enough that we can sell them.

Close though, I think we’re on the last but final!

So, as to delays……

One of the big problems with trying to capture a design process from start to finish is you end up with a hell of a lot of footage.

Turns out, editing hours of footage in to a watchable 5 to 10 minute video is something I suck at.  Inevitably when I promised myself I’d do it I sat down and promptly continued the design process again.

Which of course meant I now had even more footage.  Anyone who does the maths can see the problem with this.  So many hours of terrible, boring footage.

So here’s a peak at version……3….. I think.  Click on through for some of the videos I did actually did manage to finish!

I’m much better at Renders than Photos.

Tweaking the design.

In this video I managed to do a pretty good run through on what I changed between my first prototype and the latest.  Turns out it’s a lot easier to narrate things on the fly.

Circuit boards

And here’s where I currently have stupid amounts of unwatchable video footage.  I did all my design in KiCAD, fortunately the internet has plenty of watchable videos on how to use it.  I recommend Sparkfun’s Beginners Guide to KiCAD.

There has been three iterations of design.  Version 1 and 2 looked pretty much the same:

These boards are pretty sweet.  Complete custom build, Arduino compatible, makes chirpy noises, doesn’t really work.  Well, two of the five I built worked, I suspect I’ve got a dud batch of chips.  What a headache.

Enter version 1.2 (or 2.0, stupid version numbers.)

This model lets me use a fully functioning Arduino Nano instead, saving me a bunch of fiddly soldering.  And, if they are screwed, plug and replace!

All this stuff is available on Github, so have a look!


Introducing 450+ lines of my typically terrible Arduino Code.  It’s not much too look at and you can check that out in the Github repo too.

Much more fun to look at the results.

It’s not quite fully user re-programmable yet, but at least Sarah doesn’t need to reflash the prototype each time she wants to switch between 2 and 3 colour knitting.

Get on with it!  How much already?!

Uhhhh, I spend much gold?  I’ve totally lost track.  I’ve cut a lot of prototypes, I’ve built 5 circuit boards to varying levels and I’ve run tests on so many servos (metal gears, only way to fly.)

All for science of course.  SCIENCE!

I do have a fairly good idea as to what the final cost will be and hopefully soon we’ll be selling these units for between $80 and $100 AUD (once I’m happy with the finish) so watch this space!

8 Replies to “Building a Better Colour Changer – Part 3 – Revising the design”

  1. This is amazing! I’ve been enjoying your prototyping process, I have a KH910 but no AYAB or colour changer yet.
    Is there a mailing list we can sign up to for when you start producing these for sale? 🙂

    1. Hi Melanie

      We don’t have a mailing list as such, but there will be a blog post here and they will be listed on our etsy site.

      I must admit development has been slowed lately. A couple of other major, time sensitive projects have taken priority although I can assure you the changer is back up high on the list.

      Sarah has been using the 1.2 prototype very heavily and successfully. The servos that move the little arms actually record the number of times they are used and are up to close to 20,000 operations and I’m very happy with the reliability. There’s definitely another blog post about software long overdue.


    2. Oh, and thank you for your interest!

      Every time I get a post like this I feel equal parts guilty for not doing more and invigorated to get back in to it! 🙂

    1. Hi Gerd

      Thanks for the interest. I admit to putting off answering due to generally feeling guilty about not being further along.

      I ran in to a small hardware bug that I’ve got replacement parts for today. With any luck I’ll have a very limited number available for sale in the next few weeks (and a pre-order button for anyone that misses out).


  2. John, really impressive bit of engineering, I bought my partner a KH910i for her birthday last year. Then we got and assembled an AYAB 1.4 interface and built and Ubuntu laptop to drive it. Sarah’s fab work on Double Jacquard means a KR850 ribber will be on the shortlist – oh and your colour changer. We live in the crofting area of the Scottish Highlands surrounded by sheep – so I can see us spinning our own wool at this rate.
    Next job is a 3D printed cover for the 910 where the control board has been removed.
    Great job!.

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