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How to sense when the (plastic) blades replica light sabers are touching something
I have a pair of reproduction light sabers with polycarbonate blades. They´re modified from the original Hasbro ones, and have power LEDs in the hilt with blades that are lightguides, making them tougher if you go around whacking things with them.
My first such lightsaber was broken by my buddy at work, when he was testing the sound effects, he was hoping that the speaker in the hilt would give off that characteristic angry crackle that two light sabers do when the blades are pressing against one another. Think of that scene in ROTJ where Palpatine is baiting Luke and finally Luke takes a swing, but Vader blocks Luke´s blade with his own. While the two blades are touching, there´s a constant, angry buzzing and crackling.
What I´d like to do is sense, somehow, that the blade is touching something, and then reproduce that crackling sound, and maybe have the LED flash a bit, too. The original electronics use accelerometers to tell if you´re swinging the saber and if you hit something with it, but they can´t be expected to know what´s going on if the blade is pressed against something and not really moving.
Things I´ve thought of are capacitive changes, or a strain gauge. I´d love some suggestions.
You might try attaching a piezoelectric transducer to the blade. You can probably find an appropriate device at Radio Shack sold as a speaker or noise maker. Remove the ceramic element from the plastic housing and attach. I think you would get a substantial voltage output burst when it touches something.
Chris, I expect to see a video of these in action once you get them working. :D Best regards, Ian WilliamsLinear Applications EngineerPrecision Analog and Sensing Products
Thanks for the idea. Right now there´s a pair of accelerometers that sense when the blade hits something. It has to be a pretty decent jolt. I´m sure the piezo electric element would register a change in voltage, but would it do so continually, to sense constant contact between the blade and something else?
The piezo approach would not detect a continuous static force or strain on the blade. It would, however, produce some AC output during scraping or any action that produced vibration. Output would be pretty high--much higher than a strain gauge. I would not be surprised to see several hundred mV AC output burst during a strike.
May the force be with you.
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