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This project is my son Alex's entry for the Mindstorms NXTLog 2007 Halloween Building Challenge.
It's built only from LEGO elements, with 1 controller, 3 motors and an Ultrasound Sensor. Bellow you can find some pictures and a video of the Claw as well as the program that runs on the controller.
History:
October 21, 2007: initial upload
October 22, 2007: added download files
The idea came as Halloween was creaping up on us, so it just seemed perfect to build and submit it as an entry for the NXTLog Halloween Challenge.
This robot does pretty much what you expect from it: makes sure to give a heart attack for those unsuspecting victims who want to remove the treats from its palm.
The construction is fairly simple. First build a flat frame that looks like a triangle and attach motors to the sides.
The finger moving mechanism was the hardest to come up with, so 1 motor can move both joints of a finger. The motors on the front move 2 fingers each, on the side 1 moves the thumb.
Once the fingers were built, just needed to build a flat surface on the top and add an upside-down radar dish as candy-holder.
The last steps were adding the ultrasound sensor, the NXT controller and wiring up the whole robot.
Be careful if you build this robot or a similar one! The claws can hit someones hand or fingers and cause injury or damages in the model. We do not take responsibility for these or similar accidents!
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Images
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Ready for the Trick-Or-Treat'ers
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Gotcha
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The Claw opened
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The Claw closed
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Video of the Claw
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Programming
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The program for this robot was implemented in NXT-G. It has 2 threads.
The first thread implements an infinite loop. The thread waits until something gets close enough to the palm (measured by the Ultrasound Sensor) and closes the fingers with all 3 motors simultaneously. After waiting a little while, the motors reverse and the fingers open. Simultaneously with closing the claw, it also plays an evil witch laugh sound effect.
The other thread also in an infinite loop randomly selects one of the onboard Halloween sound effects and plays them to scare the bywalkers.
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There are 2 downloads below:
Firstly you need the 4 sound effect files that the program will use. You need to copy these files in the sound directory of your NXT-G installation. This directory typically can be found at Program Files\Lego Software\Mindstorms NXT\Engine\Sounds.
Then you can download the program that runs on the controller. You can open the program in the Mindstorms NXT-G application then compile and download to the controller.
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