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A salad spinner can be a DJ controller

\n This project turns an ordinary IKEA salad spinner into a physical\n music controller. Crank the bowl and the song plays. Stop the bowl and\n the song stops. No soldering, breadboard, or custom Arduino program is\n required. You do not need prior electronics or robotics experience to\n follow this explanation.\n

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What is hardware hacking?

\n Hardware hacking means taking an everyday object and giving it a new\n behavior with electronics and code. Here, the salad spinner still\n spins salad—but a magnet, a sensor, and an Arduino let a web page\n notice that motion.\n

\n Nothing is being broken into. “Hacking” means experimenting, adapting,\n and understanding how parts can work together.\n

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The whole idea in five steps

\n A small magnet travels around with the spinner’s rotating bowl.\n
\n A Hall-effect sensor notices whenever the magnet passes nearby.\n
\n An Arduino turns that sensor change into data the computer can read.\n
\n Johnny-Five gives JavaScript a friendly way to work with the\n Arduino.\n
\n The browser estimates the spinner’s speed and chooses a music\n playback rate.\n

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The parts

\n You need an Arduino Uno, a 49E/LM393 Hall sensor module, one magnet,\n three jumper wires, a standard USB cable, and the salad spinner. The\n parts connect directly—there is no breadboard.\n

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\n Red supplies 5 volts, black is ground, and yellow carries the\n sensor’s digital signal to Arduino pin 9.\n

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Beginner safety

Unplug the Arduino before moving wires.
Double-check 5V and GND before reconnecting USB.
Secure the magnet so it cannot fly loose while spinning.
Keep loose wires away from the rotating bowl.
\n This project uses the Arduino’s low-voltage 5V power—not household\n electricity.\n

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What does Johnny-Five do?

\n Johnny-Five is a JavaScript library for robotics and electronics. It\n gives hardware familiar JavaScript concepts such as objects, events,\n and callbacks. Instead of writing a full embedded program for every\n interaction, JavaScript can listen for changes on an Arduino pin.\n

\nboard.io.pinMode(9, board.io.MODES.INPUT);\n\nboard.io.digitalRead(9, value => {\n  if (value === 0) {\n    // The magnet passed the sensor.\n  }\n});

\n This project runs a browser-compatible version of Johnny-Five and\n communicates over Web Serial. The Arduino runs StandardFirmataPlus, a\n general-purpose firmware that lets the browser configure and read its\n pins.\n

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How does the app know the speed?

\n Each magnet pass is one pulse. The app counts accepted pulses from the\n previous second and multiplies by 60 to estimate revolutions per\n minute. Very fast duplicate pulses are ignored because the physical\n sensor can occasionally blink twice during one pass.\n

\n The result selects one of three adjustable music speeds: half speed,\n normal speed, or double speed. If another pulse does not arrive\n quickly, the app pauses the music and freezes the illustrated record\n exactly where it stopped.\n

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Quick glossary

Arduino: \n A small programmable board that connects electronic parts to a\n computer.\n
Hall-effect sensor: \n An electronic part that detects a nearby magnetic field without\n touching the magnet.\n
Digital pin: \n An Arduino connection that reads a simple on-or-off electrical\n signal.\n
Firmata: \n The general-purpose Arduino firmware that lets software on the\n computer read and control pins.\n
Web Serial: \n A browser feature that lets a web page communicate with an\n authorized USB serial device.\n
Johnny-Five: \n A JavaScript library that provides approachable APIs for robotics\n and electronics.\n

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Try changing one thing

\n Hardware hacking becomes approachable when you change one variable at\n a time. Move the sensor slightly, adjust its potentiometer, or change\n an RPM threshold in the Speed bands panel. Observe what changes, then\n keep notes.\n

\n When you want the implementation details, wiring notes,\n troubleshooting, and complete algorithm, continue to the\n technical README.\n

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