Wooden box repeats rhythm used when knocking on the lid

knock-box-build

[Paul Mandel] just finished building this knock box project. It’s a familiar concept that uses a solenoid to tap on the side of the box. The Arduino driven setup monitors vibrations on the lid. When you knock on the box, it records the pattern and plays it back using the solenoid.

He was inspired by a knock-detecting door lock. Using that code as the starting point he implemented a system that takes input from a simple push button and echos back the rhythm using the Pin 13 LED on the Arduino board. This is a great way to start as it removes the complexity of driving a solenoid and monitoring a piezo element. After a bit of success he implemented each of those hardware modules one at a time. You can get a look at the final product in the clip after the break.

One of our favorite version of this project is still the knock block from several years back.

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Echo box shakes itself to make sound

The echo box performs exactly as its name implies. If you tap out a rhythm on the lid, it will tap the same thing back to you. Except it isn’t tapping to make the sound, but vibrating.

The concept is similar to the Knock Block. In that hack, a piezo element detected a rapping on the wooden enclosure and repeated the rhythm by striking the lid with a solenoid. This iteration also uses a piezo element as the sensor. In the image above you can see a segment of PVC pipe in the upper corner. That houses the element, sandwiched between two pieces of wine bottle cork. That cork just touches the lid of the box, transferring the vibrations to the element.

The sound is created by a motor with an offset weight on its spindle. When the motor spins, it causes vibrations. The enclosure is one wood box inside of another, so the vibrating motor cause the inner box to shake against the outer one to make noise. Hear it for yourself in the clip after the break.

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Piecax the Poltergeist reinvents the Knock Block

piecax-the-poltergeist

[AndyGadget] built a haunted box as part of his Halloween preparations. This follows in the footsteps of the Knock Block we saw earlier this month but makes several hardware changes. He’s replaced the solenoid with a DC motor that rotates an arm to do the knocking. He’s avoided any CNC work by using a softwood box from a craft store as the enclosure. For control circuitry he’s used an 8-pin PICAXE Microcontroller that ‘listens’ for knocking on the box via a piezo buzzer. It will mimic knocks back to you, and if it hears the right combination The Addams Family theme song is played. This useless machine will make a great office conversation piece and with this simplified design it’s much easier to build than the Knock Block. See it perform after the break.

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Clock knock block full of puns

clock_knock_block

This Clock Knock Block has a bit of everything; milling, Arduino, sensing, solenoids, and plenty of dirty puns. Just knock on the box or on the table right next to it and the time of day will be played back to you in a series of crisp, clean knocks. A big part of the fun here is that the box is a musical instrument.

If you take a look inside you’ll find an Arduino, a piezo sensor, a solenoid, and a nine-volt battery. The piezo sensor detects your knocking as an input. It can even listen to and repeat back a series of your knocks. The Arduino actuates the solenoid, which strikes the wooden enclosure, producing the knocking sound.

We’ve embedded a video of this useless machine after the break (that’s where all the puns are). One note for your own build; this box is made out of mahogany and because it is used as a resonance chamber, this may not work as well if it isn’t milled from a piece of quality lumber. [Read more...]

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