piezo

101 Articles

Cool Off With A Piezo And A Glass Of Water

August 21, 2020 by 21 Comments

Some cool-mist humidifiers work by flinging water at a vaporizer, but our favorite kind uses a piezoelectric transducer. These work by using high-frequency sound waves to pound the surface of the water with mechanical energy. That energy introduces standing waves that force the water to break apart into a fine mist on the surface of the piezo disk.

The driving circuit for this DIY mist maker uses a 555 to generate 113 KHz, a trimmer potentiometer to fine-tune it, and a MOSFET to amplify the signal. You don’t need much more than that and a handful of passives to recreate this cool junk box experiment, but the spec of the piezo disk is quite important. The circuit is designed for atomizing transducers, which have a resonant frequency of 113 KHz — much higher than your average junk box piezo. Check out the demo and build video after the break.

Atomizing transducers can do way more than than moisten the air for our comfort. They’re not picky about where the water comes from, so if you have enough of them, you can dry a load of laundry in a few minutes.

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Secret Knock Unlocks Door

May 25, 2020 by 12 Comments

Watch any movie about the years of prohibition, and you’ll probably see character gain admittance to a speakeasy by using a secret knock on the door. In the old movies, a little sliding door would open so the doorman could check you out and let you in. With [IsmailSan’s] electronic lock, the secret knock automatically unlocks the door. You can see a video of how it works, below.

(Ed Note: Grrr…GitHub repo got pulled between writing and publication. Go check out the in-links in the bottom paragraph if you’re interested in knock-detectors.)

The device uses a piezoelectric speaker to detect the knocking. A speaker is a transducer and like many transducers, it will work — to some extent — in either direction. A servo motor manages the deadbolt. An Arduino runs the whole thing.

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This Camera Captures Piezo Inkjet Micro-Drops For DIY Microfluidics

April 15, 2020 by 6 Comments

In microfluidics, there are “drop on demand” instruments to precisely deposit extremely small volumes (pico- or nano-liters) of fluid. These devices are prohibitively expensive, so [Kyle] set out to design a system using hobbyist-level parts for under $1000. As part of this, he has a fascinating use case for a specialized camera: capturing the formation and shape of a micro-drop as it is made.

There are so many different parts to this effort that it’s all worth a read, but the two big design elements come down to:

  1. Making the microdrop using a piezo element
  2. Ensuring the drop is made correctly, and visually troubleshooting
Working prototype. The piezo tube is inside the blue piece at the top. The camera is to the right, and the LED strobe is on the left.

It’s one thing to make an inkjet element in a printer work, but it’s quite another to make a piezoelectric element dispense arbitrary liquids in a controlled, repeatable, and predictable way. Because piezoelectric elements force liquid out with a mechanical motion, different liquids require different drive signals and that kind of experimentation requires a way to see what is going on, hence the need for a drop observation camera.

[Kyle] ended up taking the lens assembly from a cheap USB microscope and mating it to his Korukesu C1 USB Camera with a 3D printed assembly. Another 3D printed enclosure doubles as a lightbox, holding the piezo tube in the center with the LED strobe and camera on opposite sides. The whole assembly had a few false starts, but in the end [Kyle] seems pretty happy with his results. The device is briefly described at a high level here. There are some rough edges, but it’s a working system.

Inkjet technology has been around for a long time (you can see a thirty-plus year old inkjet printer in action here) but it’s worth mentioning that not all inkjet heads are alike. Most inkjet printer heads operate thermally, which means a flash of heat vaporizes some ink to expel a micro-drop. These heads aren’t very suitable for microfluidics because not only do they rely on vaporizing the liquid, but they also don’t work well with anything other than the ink they’re designed for. Piezoelectric print heads are less common, but are more suited to the kind of work [Kyle] is doing.

Wheelbarrow Bass Drives A Sound Garden

April 2, 2020 by 11 Comments

One of the best things about making music is that it’s so easy to do. There are countless ways to make interesting sounds out of nearly anything if you’re willing to experiment a little bit — just ask anyone who has ever made a guitar out of a cigar box and a broom handle.

[Vicious Squid] dug in to the fertile soil of the garden implement world and cultivated a three-string upright bass with a rich, soulful sound from a familiar workhorse — an aluminium wheelbarrow. Much of the build is made from reclaimed wood, like the solid mahogany neck from an old door frame, and a broom handle.

The bass is constructed arch-top style, meaning that the soundboard — the wood on the front with the f-holes — is a flat piece tacked to curved ribs that span the width of the ‘barrow. A broom handle sound post mounted front to back pushes vibrations from the soundboard to the aluminium body. To round out the agricultural aesthetic, [Vicious Squid] strung it with weed-whacker bass strings, which are no doubt inspired by the use of actual trimmer line.

It’s already plenty loud, but [Vicious Squid] added a piezo pickup for wheeling it into the recording studio. Slap your way past the break to hear a little ditty.

Are your instrument-building skills at the sapling stage? Start with something simpler, like a sliding rubber bandolin.

Continue reading “Wheelbarrow Bass Drives A Sound Garden” →

Rubber Bands Can Secure Your Sanity

March 19, 2020 by 4 Comments

One of the greatest joys of being a child was figuring out that rubber bands make awesome sounds when they are plucked, and that the sound is easily changed by stretching the band to different lengths. For those of us who need firsthand experience to truly understand how the world works, these types of self-discovery are a pretty great way to learn about physics.

If you’re looking to build a physical music lesson or musical physics lesson into your burgeoning home school curriculum, look no further than the junk drawer, the broom closet, and the 3D printer. [Ham-made] used to stretch his bands across an empty tissue box, but came up with a much more professional implementation based on a broom handle. Check out this fat sound!

You don’t even need to find a spare broom handle, because none of this is permanent — the headstock piece with the hooks is meant to slide up and down to create cool sounds, and the tailpiece threads on in place of the broom bristles. Inside the tailpiece is a piezo disk and a 1/4″ jack so you can plug it in to your amp stack and start an impromptu jazz group. Just keep it under 10 people, okay?

You’ll need to mic your chanteuse, so keep the physics fun going with this plastic cup microphone.

DIY Music Controllers For Raging With Machines

December 9, 2019 by 13 Comments

[Tristan Shone], aka Author & Punisher, found a way to make industrial music even heavier. This former mechanical engineer from Boston crafted his one-man band in the university fab labs of Southern California while pursing an art degree. He started machining robust custom MIDI controllers that allow him to get physical while performing, instead of hunching over tiny buttons and trying to finesse microscopic touch pad-style pitch sliders.

Starting about ninety seconds into the video after the break, [Tristan] explains his set up and walks through each of his handmade controllers, all of which are built on Arduinos and Raspberry Pis.

Our favorite is probably Grid Iron, because it looks like the most fun. Grid Iron is a rhythm controller that works by running back and forth and side-to-side over a grid of machined textures that act like speed bumps. A spring-loaded stylus picks up the textures, and an encoder translates them to sound. Eight buttons along the 3D-printed pistol grip let [Tristan] make changes on the fly.

Tired of twiddling tiny knobs, [Tristan] made Big Knobs, a set of three solid aluminum knobs that look to be 3-4″ in diameter. These are assigned jobs like delay and filter, and their weight combined with ball bearings allows them to spin almost indefinitely while [Tristan] injects other sounds into the mix.

[Tristan] has made a few custom microphones to make the most of his voice. One is a trachea mic made from four piezos strapped to his throat that picks up every possible vocal utterance and other guttural sounds quite nicely. The other is an 8-pack of mics built into a curved metal box. He can assign a different effect to each one and do things like turn a breathy scream into the sounds of swelling cymbals.

There are more machines not covered in the video, and you can read about those on [Tristan]’s site. In a bonus video after the break, [Tristan] discusses a trio of pneumatically-driven mask controllers he made.

Don’t have a machine shop at your disposal? Dig out that fidget spinner and get moving on your own MIDI controller.

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Build This Handy Leak Detector For $1.02

October 23, 2019 by 23 Comments

You’ve probably noticed that modern life has become rather complicated, and the projects we cover here on Hackaday have not been immune to the march of progress. We certainly aren’t complaining, but we’ll admit to the occasional wistful daydream of returning to the days when the front page of Hackaday looked more MacGyver than Microsoft.

Which is precisely why this hacked together water alarm from [dB] is so appealing. Dubbed the “SqueakyLeaks”, this gadget started its life as a simple wireless intruder alarm from the Dollar Tree. When the magnet got far enough from the battery-powered base, a 90 dB warble would kick in and let you know somebody had opened a window or a door they shouldn’t have.

But with a little rewiring and two Canadian pennies serving as contacts, the alarm has been converted to a water detector that can be placed around potential leaky appliances like the water heater or in areas where you want to be alerted to water accumulation such as sumps. They’re basically “set and forget”, as [dB] says the three LR44 batteries used in the alarms should last about two years. Though with a BOM of $1.02 CAD, it’s probably cheaper to just make multiples and throw them out when the batteries die. Continue reading “Build This Handy Leak Detector For $1.02” →