SMA+Kit+experiment+results

Saturday Nov. 14th First Experiment with SMA....What did we learn? don't play with fire!!!

In case you are wondering how I got to this point in my research, please refer back to my older blogs which I will copy over from the google group soon after I finish with this blog. So I finally got the kit, opened it up and got to work, not knowing anything about Shape Memory Alloys. But guess what! I learned alot and that's what it's all about! The first experiment, was to assemble the test project that came with the kit. As you can see in this picture:



all this thing does, is that it measures the displacement of different types of Flexinol (SMA) wires and you can draw comparisons between them. I tried the 0.006" and 0.008" wires using different voltages and currents and came up with the following observations: Then I decided to somehow relate this project to our EDP somehow, so I pretty much invented the following item:
 * As a general rule of thumb (and to be on the safe side of things), in order to actuate 3" of Flexinol wire, a AA battery is used.
 * Flexinol is Current driven and __NOT__ Voltage driven. This means Higher Voltages than that of the AA battery will not damage the wire as long as the current supply is less or about the same (AC-DC adapters)
 * Overheating "ruins" the wire and it becomes useless (as I did a few time today :-D). This can happend by, for example cutting the wire shorter than 3" and using the AA battery to actuate it.



As you can see it is not so complicated. The two screw terminals are used to actuate the wire, the wire shrinks and presses against the skin and when the terminals are released, the wire relaxes again. At first and due to the shortness of the wire, I used a low current supply AC-DC adapter (about 0.6 A which is 1/4th of the AA battery). I was kind of amazed about the result at first! For the first time during the course of the project I was experiencing tactile feedback! However the "sense of touch" was not very effective, So I thought about increasing the impact by increasing the current. I tried the same thing with not just one but (stupid me) two AA batteries and then I smelled something burning...no it wasnt the wire, it was my skin! lol! yes, I sort of burned myself! The upside was that the impact (before the wire got too hot) was actually very noticable, and that was a step forward. I also killed the wire since it got overheated.

Conclusions? We can certainly take advantage of this SMA technology. Now that I know how it is operated, I am going to think about how to utilize it to directly or indirectly incorporate it into our project. I think it will be a neat and clean solution to our tactile/force feedback needs.

To do list:
 * Explore other uses of Flexinol related to the project
 * Order wires with larger diameter that did not come with the kit
 * Follow up with tactors and controllers --> (407) 645-5444