Disk Hack Creates Persistence Of Vision

October 20, 2015 by Rud Merriam 11 Comments

[Adam Antok] was compelled to create this repurposed hard drive persistence of vision hack after seeing a toy of the same nature.

He used the frame, disk and motor from a drive and added LEDs under the spinning disk as the light source. The disk has 8 small holes drilled equidistant around the disk, and spiraling slightly toward the center. As the holes pass by the LEDS they are flashed by the ATtiny2313 processor to create images. To determine the position of the platters a Hall effect sensor is monitored by the 2313 to detect a magnet on the underside of the disk. There is room to display ten characters at one time. Each cursor position can scroll through the character set by rotating an encoder. For all the precision needed to coordinate the LEDs with the spinning holes the electronics and software code are amazingly simple. That’s a really nice job, [Adam]!

Persistence of vision hacks are to hackers like flames are to moths. One really nice thing about [Adam’s] project is that you can interact with it while it’s running. Check it out after the break.

For a novel take on POV, check out this slow swinging pendulum clock.

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Firing Blanks With Laser Tag

June 2, 2014 by Brian Benchoff 37 Comments

glock Last year, [Tony] was asked to develop a lasertag system with ultimate realism. This meant a system that used a blank firing replica gun, and a system to detect blank rounds being fired. Very cool, and the way he went about it includes some interesting electronics.

Because the system requires a blank to be fired before shooting a laser at a target, the entire system must be able to detect a blank being fired. [Tony]’s first attempt used a piezo sensor to detect the shock from being fired. This system had a lot of noise and was ditched for a much better solution: a magnet mounted to the slide, and a hall effect sensor mounted to a 3D printed frame that turns this replica into a carbine.

A little bit of tweaking in software was required to inhibit the laser when the operator cocks the gun, but it looks – and sounds – really good. It’s also very, very realistic: the only way to shoot an opponent is to physically reload. Video below.

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Levitating Wireless LED Ring

December 1, 2013 by James Hobson 10 Comments

magnetic levitation

Here’s an impressive example of a completely home built magnetic levitation setup… with wireless power transmission to boot!

[Samer] built this from scratch and it features two main sub-systems, a electromagnet with feedback electronics and a wireless power transfer setup.

The ring of LEDs has a stack of neodymium magnets which are levitated in place by a varying magnetic field. This levitation is achieved by using a Hall effect sensor and a PID controller using a KA7500 SMPS controller.

The wireless power transmission uses a Class E DC/AC inverter that operates at 800KHz. Two coils of wire pass the current between the stand and the LEDs.

It’s very similar to a build we featured last year, but it’s a great hack, so we had to share it! Check out the video after the break.

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Hall Effect Limit Switches For A 3D Printer

April 3, 2013 by Mike Szczys 39 Comments

hall-effect-limit-switches

We’re used to thinking of limit switches as a mechanical device that cuts the motor connection before physical damage can occur. [Anthony] decided to try a different route with this project. He built this set of no-contact limit switches using a hall effect sensor. The small black package sticking out past the end of the protoboard is the sensor. It is used to detect a magnetic field.

[Anthony] chose to use an Allegro A3144 sensor. Apparently it is no longer in production but was easy to find for a song and dance on eBay. When thinking about the design he decided to add two LED indicators, one lights when the switch is open and the other when it has been tripped. This would have been easy to do with just one LED, but he needed to add more parts to get both working. In the lower left corner of the protoboard you can see the configurable gate device (74LVC1G58) he added to monitor the hall effect sensor and switch the output and LEDs accordingly.

Theremin Takes The Touch Out Of Multitouch

June 9, 2012 by Brian Benchoff 11 Comments

Multitouch builds are all the rage now, so it’s not surprising someone would come up with a multi-touchless interface sooner or later. [Hanspeter] did just that; his Multi-touchless ribbon controller, a.k.a. Polymagnetophonic Theremin is multi-touch without the touch.

[Hanspeter]’s touchless ribbon controller uses an array of 24 Hall effect sensors that activate whenever a magnet mounted on a thimble is placed near a build. These sensors go to an ARM-equipped Maple Mini to record multitouch events and send them out over Ethernet.

Even though [Hanspeter] is only using his “multi-touchless ribbon sensor” as a theremin, there’s no reason why it couldn’t be put to other uses. It’s entirely possible to place several of these magnetic sensors in an array and build a real Minority Report interface where the user interacts with a computer without touching anything.

After the break is a video demo showing off how much control [Hanspeter] can get with the thimble/magnet setup. There’s also a few demo songs made with SuperCollider showing off a trio of sitar/Moog/harpsichord synths.

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Your Theme Song Greets You At The Front Door

March 6, 2012 by Mike Szczys 16 Comments

One thing you can look forward to when arriving at home after a long, arduous day at the office is some peppy theme music when you walk in the door. [Sebastian Sommer] built the system, and shows it off in the video after the break by dancing to James Brown’s I feel good.

The setup uses an Arduino as a microcontroller. It monitors a hall effect sensor on the jamb which detects a passing magnet on the door. We guess this means the system doesn’t know if you’re coming or going but perhaps a future upgrade would add an infrared beam to detect your legs as head out the door. The music itself is played by an SparkFun MP3 shield which has a decoder chip, microSD slot, and audio jack for the powered speakers. [Sebastian] grabbed a copy of [Bill Porter’s] mp3 shield library to get the project up and running quickly.

This is a pretty cool addition if you’re already using an Arduino for a door lock or vice versa. Or maybe you’re not home enough to make this hack worth it, in which case you simply must take this music playing Tesla coil hat along on your commute.

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DIY Earthquake Detector

June 8, 2011 by Jeremy Cook 20 Comments

Some animals seem to be able to detect earthquakes. Some animals also navigate using the earth’s magnetic field. From the idea that there may be some relationship with these two things, this experimental earthquake detector was born. [Bob Davis] built this device, which uses an Arduino and several Hall effect sensors to detect and record magnetic fields. Possibly after enough data is recorded, a correlation can be found between the two phenomena.

The sensors in this device are arranged to measure magnetism in four directions as well as in the vertical axis. Part of the idea behind this is that before an earthquake the quartz in the ground moves producing a magnetic field.

In the video after the break, Bob gives some background on the theory behind this device and talks about the first version (built way back in the year 2000) which uses a PC for control and recording. Really interesting stuff so be sure to listen to Bob’s explanation after the break. Continue reading “DIY Earthquake Detector” →