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Animatronic Functional Sorting Hat

by ccreed

Published on March 12, 2018



a hat that genuinely sorted students in my class using random choices. I noticed that the microphone bit could fire a servo bit due to sound. This is perfect for robotic puppets with authentic audio from the MP3 bit.

The hat is just felt that has been treated to look like old leather. All the life in it is little bits.

Duration: 2 hours

How To Make It


I took an old hat and some craft matrix and shaped it into the shape of a sorting hat. I covered this hat in felt with hot glue and then covered that in liquid latex. Once dry, I sprayed the hat with Krylon Brown leather spray. I cut a hole where the mouth would go.


I recorded 16 Hat decisions based on house and personality. I numbered these files 1-16 and saved them to the micro-SD card on the MP3 player. Numbering the files helps the bit decide which file to play.


2 circuits are built. One is the MP3 circuit: power but, button, MP3, dimmer volume, and synth speaker bit. The second circuit is the servo circuit. It is power bit, microphone bit, threshold bit, wire and servo bit. The servo bit is hot glued in place on the hat and the hobby servo arm attaches to the cut in the hat. When the arm moves, it opens or closes the mouth. Move the speaker from the first circuit over top of the Microphone on the second circuit. Set the microphone bit to other. (Sound is too sensitive to control a servo). Use the threshold bit to further increase the sensitivity of the microphone bit. See how it reacts to sound. This part is pretty fussy.
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Place the hat on the head of your students. Watch the joy (or horror) as the hat chooses a house for them.


Servo control is a bit difficult. My servo bit gets in a feedback loop and the hat stops working. Randomness of the MP3 files can be achieved with an arduino bit. I'm waiting for another bitster to do this first so I can copy their code. If there was randomness, students could create charts to try to sort patterns in the hat choices. Students could develop hypotheses about what drives the hat choices.
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Turns out servos need to have neutral load at rest. My servo was under tension. I just removed and replaced the servo arm and all the shuddering stopped! A new video clearly shows the servo firing due to the microphone bit "hearing" the audio. I also submitted a lesson plan using the hat to evoke emotion in students as a pre-reading journal assignment for a Harry Potter and the Cursed Child unit: http://littlebits.cc/lessons/robotics-to-evoke-literary-emotion Please share and like this invention and comment if you have questions or ideas!
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