Ultrasonic Combo Lock

December 14, 2011 by Mike Szczys 3 Comments

[John Boxall] took a different route for a single-input combination lock. This unit uses a Ping ultrasonic range finder to input a four digit code. It’s a hardware upgrade, but uses the same basic concept as his button-based combo lock. That design used an Arduino to measure how long you hold down a single button, with a one second pause between inputs, to enter the code. This one also uses timing to establish when each digit is read, but that digit is grabbed as the distance between your hand and the sensor.

There are things we like and dislike about the redesign. This is obviously much more expensive than other button-based locks like this garage door opener we built. If we were to run with [John’s] design, we might spring for the Ping sensor (because it’s a pretty cool input) and replace he character LCD with an LED or two. The other drawback that we see here is that it may be easy for someone to steal your code by watching from afar. Still, we love the project and think you will too after seeing the demo clip below.

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Music-synced Christmas Light Suit

December 14, 2011 by Brian Benchoff 11 Comments

Ah, the end of the 4th financial quarter – the magical time of increased sales, being at work the entire time the sun is up, and holiday parties. For [Andy] at National Instruments, though, things don’t seem too bad. He built a neat Christmas light suit to entertain everyone with his brilliant persona.

[Andy] always loves great Christmas light displays (he even blogs about them), so he figured a wearable light display synchronized with music would be very doable. The build is controlled with LabVIEW to convert .WAV files to power levels and frequency bands. This info is then piped into the Arduino that controls the lights.

[Andy] actually made two light suits, one for him and one for his friend [Richard]. Both guys have two light-up Christmas staffs to wield light mage powers on their coworkers. The lighsuits are controlled by Arduino/Xbee setups – one each for each suit and staff. The result is phenomenal, and should really get everyone in the holiday spirit.

Chrono-tomic Shield Helps Your Arduino Keep Perfect Time

December 11, 2011 by Mike Nathan 28 Comments

chronotomic-arduino-shield

[Josh] and his lab partner [Eric] needed a final project for their Embedded Systems Design class, and thought that designing an Arduino shield would be a cool idea. They noticed that there are plenty of ways to get an Arduino to keep time, though none that they knew of utilized WWVB (Atomic Time) signals directly.

The Chrono-tomic Arduino shield uses a C-MAX radio to demodulate the WWVB signal, demodulating it and passing it along to a PIC16F1824 microcontroller. The PIC decodes the data frame and verifies it is valid, sending the time to an MCP79410N real-time clock module.

We can hear the “Yo dawg I herd you like microcontrollers so I put a microcontroller on your microcontroller shield” jokes already, but the pair says that they offloaded the time processing to the PIC in order to let the Arduino focus on whatever tasks it has been delegated. The Arduino code merely needs to request the time from the RTC whenever it is required, rather than deal with the decoding itself.

Is it overkill? Perhaps – though we think it heavily depends on your application and configuration. We can certainly conjure up situations where it would be useful.

Detecting Seismic Waves With A Piezo Element

December 11, 2011 by Mike Nathan 14 Comments

While we normally see piezo elements being used to output audio, [Veedo] thought that they could be used in a more useful manner. He bought way too many piezo film tabs and decided to use them to build a makeshift seismic sensor.

The piezo tabs came with weights attached at one end, though while testing them, he found that they more or less only detected vibrations with frequencies in the KHz range. Since earthquakes tend to produce vibrations in the 30-80 Hz range, he had to tweak his setup to detect the proper frequencies. To do this, he attached a weight made of a screw and washers, checking the output signals on his oscilloscope until the dominant sensed frequencies were in the range of 40 Hz.

The sensor was attached to a breadboard, then wired through a charge amp to create a small AC signal, which floats on 2.5Vdc. The bottom half of the wave is chopped off with a diode, after which it is fed into an Arduino Mega. The seismic data is then pushed up to his Pachube account for storage, though he can view the feeds locally via the a web server programmed into the Arduino.

We’re not sure how much advanced notice this sort of setup would give you in the event of an earthquake, but it seems like a fun project to build either way.

Buzzer Project For Classroom Team Games

December 9, 2011 by Mike Szczys 6 Comments

Want to host a Jeopardy tournament with your friends? Looking to add a bit more fairness to your school’s knowledge bowl? Perhaps you should build some buzz-in hardware of your own.

Here you can see [Matt Hanson’s] take on this idea. He used one Arduino to gather not just buzzer info, but also keypad data from four satellite controllers. Each has an RJ45 jack, allowing it to connect tot he base unit with an Ethernet patch cable. We like the color coding that [Matt] chose, which matches the color of the arcade button to the keystone jack on the base. And of course the fantastic look of the water-jet cut cases isn’t lost on us either.

You may wonder why he included a key pad on each controller? It looks like he and a few others worked together to develop a team-based math game for use in school.

Color Sensing With An RGB LED And Photoresistor

December 8, 2011 by Mike Szczys 11 Comments

[Fjord Carver] brings together an RGB LED and CdS Photoresistor to make a color sensor. Those Cadmium Sulfide lights sensors usually have a very wide swing of resistance when exposed to varying levels of light sensitivity. That makes for great resolution when reading them using the ADC of a microcontroller. The LED comes into play by shining known wavelengths of light on the surface being measured. Three separate readings are taken with each of the LED’s different colors, then used to extrapolate the RGB value of the test material. We saw the very same method used a couple of years back. This time around it’s an Arduino doing the measuring instead of a PIC.

So why isn’t that sensor shown in this picture? It’s because we appreciate the application which [Fjord] is using for this sensor. He built a lamp that shines the same color as the surface on which it is placed.

Christmas Tree Water Sensor Gets An Upgrade And A Fancy New Box

December 7, 2011 by Mike Nathan 9 Comments

xmas-tree-water-sensor

[Eric Ayars] has a nice cast iron Christmas tree stand at home, but the only drawback is that the stand makes it hard to see just how much water is available to the tree. Last year we covered a small gadget he created to help keep tabs on the water level, but as several of you predicted, the system eventually failed.

His previous solution used copper plated proto board to sense how much water was in the stand, but the leads corroded in about a week’s time. With Christmas just around the corner, he decided to give things another try.

His revamped water level sensor relies on measuring capacitance changes in a copper strip board when under water rather than detecting a complete circuit like the previous model. To protect his sensor this time around he coated the board with polyurethane, which should provide a decent corrosion barrier.

Using the Arduino CapSense library, the sensor can detect the presence of water, signaling an alarm if the base needs refilling. One of our readers suggested that he use the tree itself as a low water indicator, which is just what [Eric] did this year. If the water is somewhat low, the Arduino-controlled relay powering the tree is switched off and then on again, every 5 seconds. If the base is nearly dry, the tree asks for water by blinking the word “Water” repeatedly in Morse code.

We think that this year’s solution is pretty clever, and we’re glad to see that [Eric] didn’t give up after last year’s setback!