McLVDT: A Straw-based Sensor

December 1, 2009 by Mike Szczys 13 Comments

We saw [Kevin’s] home-built Linear Variable Differential Transformer in a YouTube video last week and wanted to know more. We’re in luck, he agreed to share all the details as well as a bunch of information on these sensors. An LVDT is used to measure distance along a straight path. Unlike a linear optical encoder, this method uses measurements of inductance between two electrical coils to judge the distance.

[Kevin] used some magnet wire wrapped around two straws of different diameter to fabricate his sensor. A signal generator is connected to the primary coil and the resulting signal induced in the secondary coil is measured to reveal the change in physical position. Check out the video after the break to see the results.

It’s not hard to get your hands on a McDonald’s straw (hence the name ‘Mc’LVDT), a smaller inner straw, and a few feet of magnet wire. This will be a fun one to try when those dark winter days start to get to you.

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Building Capacitive Sensitive Floor Tiles

November 22, 2009 by Mike Szczys 38 Comments

That title’s a mouthful but you’re already familiar with the technology and application of foot pads as sensors in games like Dance Dance Revolution. The usbddr project sought to make a USB connected DDR controller from scratch. The microcontroller used is an Atmel ATmega8 running the V-USB firmware for connectivity and uses the analog to digital converts to read in data from the capacitive sensors.

The physical implementation is cleaver. The base plate has a capacitor plate attached to the top of it and the tile has the other capacitor plate attached to the bottom of it. The two are separated by some weather-stripping which is spongy enough to allow compression, bringing the two capacitor plates together.

We’re not convinced of the long-term durability of the system. We certainly don’t think it will hold up to very much hard-core DDR playing. But we would love to see a Super Mario RPG style puzzle to unlock the door to the ‘castle’ at a child’s birthday party.

[Thanks Hans]

Rotating Radar Visualization

November 16, 2009 by Jakob Griffith 32 Comments

[flickr video=http://www.flickr.com/photos/peplop/4106571163/]

We ask, who wouldn’t want a rotating motion and distance tracking radar? Sure in today’s day and age anyone could purchase a wide-angle sonar or IR solution that achieves the same goal, but [LuckyLarry] took it old school and made his own rotating radar. He used an Arduino, servo, and ultrasonic sensor as a base to gather data, and the open source programming language Processing to draw the data on the screen. He says it’s a little inaccurate currently, but will try out some other sensors in the future.

SparkFun Kegerator Goes To Eleven

September 10, 2009 by Phil Burgess 19 Comments

It started with a simple need: keep tabs on SparkFun Electronics’ in-house kegerator so the beer won’t run out at inopportune times. But of course SparkFun and “simple need” make strange bedfellows…throw beer in the mix, and you know this can’t end well. The result, as you might imagine, reads like a who’s-who of electronics hackery buzzwords.

Arduino? Check. Custom PCB? Check. Web interface? Check. Twitter feed? Check.

They’ve assembled a nice build tutorial on how this all went together, including code, example circuits, an explanation of some of the sensors used, and links to other tutorials for such things as Twittering and persistent storage in EEPROM using Arduino. Not to mention the eye candy: a custom Arduino shield (solder mask and all), custom acrylic tap handle, custom SparkFun pint glasses. They never do anything halfway, do they?

Passive Infrared (PIR) Sensor Tutorial

August 21, 2009 by Phil Burgess 18 Comments

pirsensor

[ladyada] has a freshly-published and amazingly thorough tutorial on passive infrared (PIR) motion sensors. Most often seen in security floodlights and automatic doors, in creative hands these sensors can be put to other uses—cat flaps, camera triggers and purely artistic applications—as you’ll see in several demo projects and videos. For the curious, the tutorial provides a good amount of background theory on how PIR sensors work, along with the associated fresnel lens optics. And for those who just want to get hacking, most PIR sensors (like the one above) come in a simple-to-interface module containing all the support hardware and providing a simple digital output; the article wraps up with one such example.

Custom Flex Sensors

July 25, 2009 by Zach Banks 14 Comments

flex

Flex sensors, like the ones used in the Nintendo Power Glove, are generally expensive and hard to find. However, [jiovine] demonstrates that they are easy enough to make from spare parts. He sandwiched a strip of plastic from ESD bags between pieces of copper foil, and wrapped the whole thing in heat shrink tubing. The sensor is able to detect bends in either direction, unlike the original power glove sensors. His version had a nominal resistance of about 20k ohms, but by choosing a different resistive layer you could create sensors that are more or less resistive.

Related: 5-cent tilt sensor

Controllable Bristlebot

June 16, 2009 by Zach Banks 19 Comments

[sprite_tm], whose projects we have covered in the past, took the popular bristlebot to an extreme and created a controllable version. A bristlebot consists of a small vibrating motor mounted with a battery on the head of a toothbrush. These micro-robots buzz around randomly, and he attempted to tame them. He used a platform of twin bristlebots and added an optical sensor from a laser mouse and an ATtiny13. The optical sensor is used to determine the relative motion of the robot, so that the motors can be adjusted accordingly. He also has a video of the bot using the sensor to find a mark on the floor and stay within bounds. Although it isn’t as accurate, it acts like a traditional line-following robot.

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