[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.
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.
Drilling square holes
We’re still a bit baffled by the physics of this, but apparently it’s possible to drill a square hole with a round bit. This video shows square holes being milled using a cutter which is offset from the center of the bit. [Thanks Jordan]
LED Motorcycle headlight driven by mains
[William] found a way to use a big capacitor and bridge rectifier to run this H4 LED headlight bulb in a mains sconce lamp.
Electronic slide whistle
Here’s an electronic instrument that [Dorian] made. It uses a linear potentiometer and a button and works much like a slide whistle would.
Robot rocks out to Daft Punk
[Adrian] didn’t just make a robot arm out of CD cases and a mints tin. He built the arm, then made a music video featuring it.
More light-pipe sensor experiments
[Uwe] has been working on an input sensor using a flexible light tube. It is a similar idea to these optical flex sensors, but [Uwe] tried several variations like filling the tube with alcohol.