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The scribble pack is a solution for those who want to "draw" with PIXIE. It is particularly useful to generate evidence of what the children have done and to give them something to take home. It must be emphasised that PIXIE cannot make accurate drawings, hence the name "scribble pack".
As you can see from the picture, "squares" are unlikely to join up. The bigger the scribble, the bigger the error would be. If you want some kind of drawing instrument, you should perhaps look at PIP.
Lots of people have attempted to make PIXIE "draw". As it is impossible to put a pen at the centre of PIXIE and PIXIE is not very accurate, I had always discouraged this and users were left to attach pens using tape for themselves. When I was presented with two examples of practitioners using PIXIE in just this way in the space of two days, I was forced to change my attitude and decided that we should make available a method of attaching pens to PIXIE that was at least practicable.
It seemed to me that Berol marker pens were the most suitable as many schools and settings already have these. The only problem is how to attach them. If the pens are rigidly attached to PIXIE they will, on a slightly uneven surface, either lift PIXIE's wheels off the surface and stop it moving or they will lift off the surface themselves and stop drawing.
Any solution had to be retrofittable to all the existing PIXIEs without the use of any tools.
It is also important that the children can find out what happens when pens are attached in different places.
Our solution solves these problems, but there is nothing I can do to make existing PIXIEs more accurate.
What you get
What you get is a piece of foam that has been cut to fit closely over PIXIE. There is an extra cut-out to avoid the on/off switch. The foam has 8 holes punched in it for 8 alternative positions of the pens. You also get 4 aluminium tubes and 4 Berol pens. The tubes fit into whichever holes in the foam you want to use and the pens slide up and down in the tubes. You might start off with just one pen at the front or back of PIXIE and work up to all four. I do not recommend using more than 4 pens at a time.
This set-up has two colours of pens; one on each side of PIXIE. The program is
forwards, right
forwards, right
forwards, right
to make PIXIE go round a "square" to the right. It is clear that the outer line in the scribble comes from the left-hand pen. At each corner, PIXIE turns away from the left-hand pen and scribbles an arc. The cumulative error in PIXIE stops the line from joining up. This kind of drawing, made with a single pen, is about the easiest one to explain.
The centre part of the scribble, the bit made by the right-hand pen, seems harder to explain. It is important to realise that the pen can only do two things. It will only draw a straight line when PIXIE is moving straight. It will only draw an arc when PIXIE is turning. The centre scribble has 4 clear straight lines that were drawn when PIXIE ran the "forwards" instructions. You can also see the four arcs that correspond to the "right" instructions.
The centre scribble makes better sense when you realise that the right-hand line was drawn at the same time as the left-hand line of the outer scribble.
So, the first part of the scribble is two parallel lines. This is followed by two 90 degree arcs centred on the middle of PIXIE when it did the turn. This arc joins the right-hand and bottom lines of the centre scribble. The rest of the scribble is the same pattern repeated four times.
It may be best to show the finished pattern and discuss why it looks as it does and then draw just a "forwards" instruction and see what you get. Follow this with "forwards" and "right" and see what you get. Finish up with "forwards", "right", "forwards" and then you should have a set of scribbles that allow you to explain the finished pattern.