Look ! This marker is dancing to the Duke Nukem theme !

How was it done ??

Well it started with me buying some flexinol (muscle wire) to experiment :

So first I explored the use of this Flexinol as an actuator :

The 'muscle wire' contracts when running current through it (due to heating up). The wire expands again when cooling down. This motion is completely quiet, so I think it will be an excellent actuator for audio/midi related animation experiments.

This is the type of wire I am using :
Flexinol Wire Diameter : 0.05mm
Activation temperature : 70 dec C
Resistance : 510 ohm/m

And this is my first test setup, I experimentally tested several currents for good response time :

Tested wire length : 8cm
Resistance : 510 ohm/m = 40 ohm for 8cm
Applied Voltage : 5Volt
Resulting maximum current : 125mA

It works quite nicely, see this video where I use the current limiting of my power supply to control the wire, and test several settings :

So now that I tested the principle, I take a 30cm long Flexinol wire, and make a setup with the marker hanging completely on Flexinol. This will give the pen more swing.

The resistance for a 30cm wire at 510 ohm/m is 153 Ohm. To get 120mA through 153 ohm, I need 153*.12 = at 19.1Volt. I tested this worked fine as well.

To control the voltage I use a optical relay pcb from highly liquid : It is MSA-P, which is obsolete by now. The whole project has been published as open source.

This board has relay outputs with the following specs :

In reality the relay board looks like this :

I configure the board to react on general midi drum notes, using the freeware software sqwerl :

I connect output 2 between the flexinol wire and the power supply. The power supply is now set to 19.5V to get approx 125mA when switched on.

For the music, I use a dreamblaster X1 board, plugged on a CHiLL interface board. This interface board has optional midi thru, which I will use to link to the relay board.

So now everything is connected, lets play the famous 'grabbag' theme from Duke Nukem.

If all goes well, the pen should be jumping up every time the snare drum is hit. And yes it works.

Here's another video, where you can clearly see the wires :

Different music ? A more spectacular contraption ? A black background to hide the wires ?
Yeah what should be next ?