Lego Mindstorms Drawing Machine. Harmonograph.

[alexsplanet]

http://www.youtube.com/watch?v=q1e_xWL66UI

[JGW3000]

Simple and elegant, well done!

[deraven]

Great mechanism, and very nice results. Thanks for sharing!

[DrJB]

Very nice. Reminds me of the spirograph.

Now, I'm curious as to the programming/math behind this. Do you simply generate various patterns by changing speed/phase between the two motors or s it way more complicated? I'm already thinking 'Inverse Kinematics' and very complex math ... but hope none of that is needed.

[Blakbird]

It works mechanically the same as PG52s spirograph. The difference is that it uses NXT motors to vary the speed instead of a transmission.

[DrJB]

Correct, though I'd add that the spirograph uses a polar set of coordinates that might be 'difficult' to replicate with the smart brck ... the math could get very ugly.

[Nalyd997]

It works mechanically the same as PG52s spirograph. The difference is that it uses NXT motors to vary the speed instead of a transmission.

But also the fact that it has no turntable. I guess to produce a complicated pattern extremely different ratios must be needed as with the spirograph the pattern of the arms in relation to the board of PGs finishes quite quickly

[JGW3000]

Perhaps the trickiest part is the correct type of writing instrument. Adding turntables or non-concentric gearing is rather easy.

[SevenStuds]

Sleek and simple! The studded enclosure gives it a very elegant look. I'm wondering if a similar result is possible using PF and two speed remotes.

[roppie11]

using pf and train remote control would give you 7 speeds for one motor(if you count 'not moving' as a speed) and 7 for the other.

7*7= 49 different patterns. right?

[schraubedrin]

the starting points and turn direction influence the graph also dramaticaly.

so there would be a whole lot more than 49 patterns.

[roppie11]

the starting points and turn direction influence the graph also dramaticaly.

so there would be a whole lot more than 49 patterns.

oh yeah i forgot that. I know it is mentioned in the video but i watched it a few hours before.

[SevenStuds]

With 7 speeds in each direction for each motor and and multiple start points, there should be enough variability IMO. Building the Spirograph was fun, so now this has just been added to my build list as well. I reckon a version with two rechargeable battery boxes would do the trick.