Magic Pendulum of Wisdom




I always loved the mesmerizing chaotic movements of double pendulms. A while ago i saw a video where this guy attached an UV-LED to track down the path that the pendulum is taking. ( )I loved this effect so much that I decided to built my own version of it. But I wanted to add a little twist and thought of a way i could use the chaotic physics to make decisions. It is impossible to forecast the behavior of a double pendulum - that is why it is called chaotic theory. So I basically bulit an mechanical random generator, but see yourself..

Step 1: What You Need

Beside the things on the picture you will need:

- a piezo buzzer

- some sheets of wood (i used plywood for the base)

- a 3D-Printer (if you choose to print the parts for the pendulum -- it is also possible to build these from wood)

- soldering Iron

- hacksaw

- jigsaw

- white paint , clear varnish

Step 2: Baseplate

I cut the baseplate out of a sheet of plywood. I punched a nail in what I eyeballed the middle and attached a pencil with a string to draw the circle before cutting it with the jigsaw. You can also use your wall directly as base and just paint a circle on it. I used white paint first as a base color and mixed fluorescent powder with clear varnish for the second layer. I used black insulationtape to seal the cutting edge. Pull out the nail and drill a 8mm hole in the middle where you can mount the threaded rod with some nuts for later holding the pendulum.

Step 3: CAD Design

I designed the parts in Onshape and 3D printed them with my modified Creality CR-10. I used clear filament so that you might see the light through it but the color turned out rather cloudy what I liked in the end.

Step 4: Wiring

I soldered everything according to the wiring diagram and fit it in the electronics compartment. I glued the LED in its hole and used a small spring to contact the battery cell. I used a 18650 cell so that the setup is rechargeable. (You might also try to use a mini powerbank, then you won`t need a BUC and have charging electronics included)

Step 5: Programming

I created the Code in Arduino IDE.

The Pendulum counts how often the second stage runs by the first stage. If you give it a push the amount of times that this will happen is completely random. Is the number even the answer is no (sad tone) if it is odd the answer ist yes (happy tone).

You can also copy my code if you like its not very complicated. Then just upload it to the arduino.

Step 6: Mounting

Carefully press in the bearings and glue the magnet so that it is alligned with the hall sensor. Insert the battery cell and close the compartment with screws.

Step 7: Hang It on the Wall an Have Fun! :)

You can ask you pendulum any question it will always have an answer :)

Step 8: Have Fun With Your Friends :)



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    3 Discussions


    Question 25 days ago

    Great 'ibble. Do nothing machines are fascinating. Thanks for posting.
    Are there some 'magical' lengths or ratio for the pendulum sections?

    1 answer

    Answer 25 days ago

    Hi, thank you for your comment! In my case the ratio is 210/170 but i did not calculate the lengths. You are right the behavior of the pendulum is based on the lengths, but also on the weight distribution. Since there is a fairly heavy lithium battery in the second stage I thought i just estimate the lengths and try them out. :) I liked the behavior in the end! It would be a fun project to design a double or even triple pendulum with movable/addable weights to experiment with different setups.


    4 weeks ago

    Neat project! The movement is fun to watch; adding fluorescent powder makes the effect even better. Good instructable!