The Flow Of Time Draws On A River

river

You would think Hackaday would see more projects from public art exhibitions. They really do have everything – the possibility to mount electronics to just about anything in a way that performs interesting but an ultimately useless function. So far, though, [Richard Schwartz’s] Flow of Time is on the top of a very short list of public art installations we like.

The idea behind the build is a German phrase that means something similar to ‘time trickles away’. [Richard]’s project implements this by printing the current time onto the surface of a flowing river in [Richard]’s native Innsbruck.

The build uses five micro piezo pumps to dispense food coloring from a bridge. Every minute, an Arduino pumps this food coloring in a 5×7 pixel digit to ‘write’ the time onto the surface of a river.

Surprisingly, [Richard]’s installation doesn’t require much upkeep. The pumps only use about 70ml of food coloring a day, and the entire device – including the Raspi WiFi webcam – is solar powered with a battery backup.

You can see a video of the time printing on a river below.

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Reactive target range for Nerf, Airsoft, etc.

reactive-target-range

Taking the time to build a reactive target range really adds to the fun of toy weapons. It lets you move beyond just point and shoot to actual games of skill.

The project is anchored by an Arduino board. It connects to a piezo element on the back of each of these sheet metal targets. Detecting when a projectile hits the target works pretty much the exact same way the ever popular Knock-block works. To provide interactive enjoyment each target has an LED which, when lit, indicates that the target is active. From here it’s just a matter of coding to add different challenges. So far [Viktor Criterion] has implemented quick draw, timed, and rapid fire modes. The demo after the break shows off everything, including the slick modular design he came up with to make the system portable.

We’d love to see these targets mounted on motorized tracks. Each round would have the targets moving closer to you at a faster pace to keep you on your toes.

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Space invaders played on a 16×2 character display

character-lcd-space-invaders

This Space Invaders game does more with less. [Rjk79] managed to make a video game using a two-line character display. The game consists of a wave of invaders on the top line, with the defender cannon on the bottom. The invader isn’t just stationary, but randomly moves to the left and the right. The image above captured a little bit of motion blur from the defender moving into position before firing on the enemy.

An Arduino board controls the 16×2 HD44780 character display. The game also includes sounds generated by the piezo buzzer seen on the breadboard. All the way to the right you can see the Wii Nunchuk breakout board which provides directional control and the firing trigger. If you want to recreate this one for yourself [Rjk79] is sharing the source code on Pastebin. There’s also a demo video found after the jump.

If you don’t have a character LCD on hand you might try this other Space Invaders clone that uses an 8×8 led matrix.

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Music challenge has you flapping your wrist to make sounds

glove-based-music-challenge

This glove controller let you play a musical game. The challenge is to perform the correct wrist motions at the right tempo to play the intro to the song Where is my Mind by the Pixies. This is demonstrated in the video clip after the break.

We often see flex sensors used on the fingers of glove projects, but this one does it all with an accelerometer. That module, along with the Piezo buzzer used for playback are affixed to the small breadboard on the back side of his hand. Rubber bands connect the Arduino to his third and forth fingers. The tempo and rhythm are pre-programmed but the tone generated is based on the gravity reading at the start of each note. If you don’t have your hand positioned correctly the wrong tone will be played.

The code was published in link at the top. It would be fun to see this altered as a hacked Simon Says game.

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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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How to make your own piezoelectric speaker

Piezoelectric speakers are found all around you, from musical greeting cards to the tweeters in your car stereo setup. Making your own piezo speakers is actually very easy, as [Steven] shows us after replacing the speaker in a clock radio.

Piezo speakers require a small crystal with piezoelectric properties, so this build is the perfect followup to [Steven]’s tutorial for making Rochelle salt crystals. After attaching two strips of aluminum foil to his Rochelle salt crystal, [Steven] took the wires that previously went to the clock radio speaker, connected them to the crystal, and turned on the radio. When attached to a tin can, the newly created piezo speaker created a little bit of sound, but the results weren’t very impressive.

To boost the sound output of his homemade speaker, [Steven] needed to increase the voltage across his piezo speaker. At first he tried a doorbell transformer with somewhat better results, but much more sound was produced when he used a transformer taken from a microwave oven.

After experimenting with his microwave transformer and Rochelle salt, [Steven] moved on to piezo elements found in BBQ and cigarette lighters. These homemade speakers were much clearer than the chunk of Rochelle salt he was using previously, and surprisingly produced about the same audio quality as a commercially made piezo speaker [Steven] picked up at Radio Shack.

You can check out the build video for [Steven]’s crystal speaker after the break.

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