Look around for heart rate sensors that interface easily to microcontrollers, and you’ll come up with a few projects that use LEDs and other microcontrollers to do the dirty work of filtering out pulses in a wash of light.
[Thomas] was working on a project that detects if water is flowing through a pipe with a few piezoelectric sensors. Out of curiosity, he taped the sensor to his finger, and to everyone’s surprise, the values his microcontroller were spitting out were an extremely noise-free version of his heart rate.
The piezo in question is a standard, off the shelf module, and adding this to a microcontroller is as easy as putting the piezo on an analog pin. From there, it’s just averaging measurements and extracting a heartbeat from the data.
It’s a much simpler solution to measuring a heart rate, and since two people haven’t heard of this technique, it’s likely a lot more people haven’t heard of this technique either. If you’re looking for an entry to The Hackaday Prize, this would be a great jumping off point for anything in either the fitness or medical domains.
Pressing the power button on your computer usually isn’t too much trouble, unless your computer is stored away somewhere hard to reach. [Joonas] has been hard at work on a solution that would also impress his friends, building a knock sensor to turn on his PC.
For around $10 in parts he put together an ATTiny45 that emulates a PS/2 device, which takes advantage of his computer’s ability to boot upon receiving PS/2 input. The build uses a Piezo buzzer and a 1M Ohm resistor as a knock sensor exactly as the official Arduino tutorial demonstrates, and one of those PS/2-to-USB adapters that are most likely lurking in the back corner of every drawer in your office.
[Joonas] used AVRweb to disable the 8X clock divider so there’d be enough clock cycles for PS/2 communication, then loaded some test code to make sure the vibrations were being detected correctly. You can check out his Github for the final code here, and stick around after the break for a quick video demo. Then check out a similar hack with [Mathieu’s] home automation knock sensor.
Continue reading “Turn a PC on with a Knock and an ATTiny”
After finding an old piezoelectric delay line in an old TV, [Mike] decided to figure out how it works and in the process stored his name in sound waves reflecting inside a piece of glass
[Mike] was intrigued by these old-fashioned delay lines after watching [Dave] from EEVblog’s teardown of an circa 1985 camcorder. [Dave] found a piezoelectric delay line in his camcorder – a device that is able to store digital data by sending a sound wave into a glass plate, letting the sound wave bounce through the plate. and picking up the sound on the other end. It’s actually not too dissimilar to a mercury delay line used in the earliest computers.
After sending a pulse through his piezoelectric delay line, [Mike] picked up an echo almost exactly 64 microseconds later. After hooking up a simple circuit constructed out of a 74-series chip, [Mike] found he could ‘loop’ the delay line and keep a pulse going for up to 3 milliseconds.
Three milliseconds isn’t much, but by injecting serial data into the delay line, [Mike] was able to spell out his name in binary, as seen above. It’s just 32 bits stored for a fraction of a second, making it a very volatile, low-capacity memory, but functionally equivalent to the old mercury delay lines of yore.
It’s certainly not what [Mike] or [Dave]’s delay line was designed to do; these video delay lines were used to hold the previous line of video for a form of error correction. Outside [Mike]’s workbench and a few museums, though, you won’t see a delay line used as a form of computer memory. A very cool build and an awesome history lesson, and we thank [Mike] for that.
Researchers at Georgia Tech have developed a biologically inspired system to control cameras on board robots that simulate the Saccadic optokinetic system of the human eye. Its similarity to the muscular system of the human eye is uncanny.
Joshua Schultz, a Ph.D candidate, says that this system has been made possible in part to piezoelectric cellular actuator technology. Thanks to the actuators developed in their laboratory it is now possible to capture many of the characteristics associated with muscles of the human eye and its cellular structure.
The expectation is that the piezoelectric system could be used for future MRI-based surgery, furthering our ability to research and rehabilitate the human eye.
As we wrote the title to this feature we can see why [Jeff Ledger] calls it an electronic flute and not a recorder; this is a musical instrument and not something for archiving audio. Confusion aside, we’re all familiar with these plastic ‘musical’ instruments. Many elementary schools in our area require students to buy one as part of music class. So it shouldn’t be hard to find one if you want to try this for yourself (heck, [Jeff] grabbed his a the dollar store).
Basically, he’s replaced the finger holes with momentary press switches, then uses a Propeller dev board to turn the button presses into music. It’s simple and quick, but what does it for us is the breath actuator. Sure, you can set this up to play whenever a button is depressed, but [Jeff] went that extra mile and added a piezoelectric element to the bottom. When you blow through the instrument it flexes slightly, generating a tiny current that can be measured by the microcontroller. Check out the short clip after the break.
Do a little more work and you could turn this into some type of musical game controller. We’re thinking Zelda!
Continue reading “Electronic recorder conversion”
[Destin] has been doing some high-speed and high-resolution video photography using a standard DSLR. He accomplishes this using a bit of ingenuity to capture images of repetitive events at slightly different points in time.
The banner image above shows a bullet travelling through a set of matchsticks. [Destin] uses the sound of the gun firing to trigger the flash that captures the image. A piezeo transducer picks up the sound, triggering a precision pulse generator. That pulse generator then triggers the flash, adding a delay based on the settings. In this way, [Destin] can capture video by firing a bullet for each frame, but adjusting the delay period of the pulse generator to capture the image when the bullet is in a slightly different place from the previous frame. It’s an old technique, but after some post-processing it produces a high-quality output without sinking thousands of dollars into an actual high-speed camera. Check out the video we’ve embedded after the break.
We like this guy’s style. We saw him strapping a camera onto a chicken back in December and we hope to see a lot more from him in the future.
Continue reading “Faking high-speed video photography of repetitive events”
Back in October we reported on the I-Swarm robotics project. [Travis] sent us some more information. These tiny robots are programmed optically and are able to respond to programming commands via an infrared signal. Locomotion is facilitated with piezoelectric actuators and the power to the units provided through a solar cell. It is not clear that this project is still ongoing as the I-Swarm web page lists a project termination date of 6/31/2008. That being said, the video embedded after the break was posted two days ago showing swarm movement and detailing the programming, testing, and hardware specifics. Continue reading “I-Swarm robot update”