SReflec
From JimWIKI
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UPDATE!
I posted this as an instructable here which was picked up by Make Blog and Hac-A-Day!!! --Jim 12:11, 16 December 2009 (UTC)
The Seismic Reflector
This is a project about Earthquakes. On the 29th September 2009 a strong, magnitude 8 earthquake struck of the coast of Samoa. It happened early in the morning and caused a Tsunami which killed nearly 200 people. It was evening, after work when I heard the news here in the UK. The next day at work I was curious and wanted to learn more about this event, so I looked up the USGS website and started reading. As I looked around the site, I came across a page with a picture of the globe on it and a large yellow square over the Samoan Islands. As I looked at this chart, and briefly refreshed the page, another large square, this time Red, appeared over the coast of Indonesia. The mouse-over read that it was a magnitude 7.6 earthquake. It had occurred minutes, if not seconds before I saw that red square appear.
I had just witnessed an Earthquake occur on the other side of the world. While part of me was geeking out over how cool the technology was, a much larger part of me spent those next few minutes thinking about the human impact, and what it must be have been like. The UK is not known for it's seismic activity, it's not something I'd spent much time thinking about before. However, because of the immediacy of the information, I felt much closer to it.
I told everyone in the office about what I'd just seen, but there was nothing on any of the regular news outlets about this, Only the red box on the map. It was about 1/2 hour later when the news of this Earthquake broke on Reuters, AP and the BBC, with their first pictures of the devastation. Although slightly less strong than the Samoan Earthquake of the night before, the Sumatran Earthquake struck much closer to a densely populated area. More than 1000 people lost their lives, over 130,000 homes were destroyed. At least 20 countries have responded to the disaster with aid. My response is significantly less practical but I'm hoping it can help somehow, even if only on a psychological level. [Wikipedia sources here and here]
The Aim
This project has two strands, a software and a hardware component. The aim is to build a device, which I'm calling 'The Seismic Reflector' which responds to earthquakes being reported in near-real time via the USGS RSS feeds. The device responds by illustrating the magnitude of the reported earthquake via two fairly chunky vibration motors of the kind used in video game controllers. The device is connected to a PC via a virtual com port over USB (thanks to an on board Arduino). On the PC, an application sits there checking the RSS feed periodically and when a new event it posted to the RSS feed, the desktop app parses the data out of it and presents the magnitude of the quake to the Arduino which interpreters this as rate at which to activate the vibration motors.
Hardware
The Seismic Reflector is powered by an Arduino, which makes it a dream to program. The arduino firmware will be fairly simple, the only complexity will come in exactly how a Magnitude passed along the serial line should be interpreted as motor movement. I have at my disposal a unexpectedly large number of video game controllers, so I have an abundance of these vibration motors. I plan to use both high frequency and low frequency vibrations blended together to give a fairly complex shaking pattern.
I've not used an Arduino to power motors before so I'm going to have to learn this as I go along. As a base for experimentation, this ITP article will be very useful, as will this one.
Essentially, I'm going to need:
- High current transistors to switch the motors on and off with some kind of PWM-like control
- ITP recommend an NPN-type transistor called a TIP120.
- I suspect these 6 N Channel logic level power MOSFETs (FDP6030BLs) could do the Job.
- So I've just bought some 2N7000s and 2N5551s, as that's pretty much the limit of the stock at my local maplin's I'm hoping that either of these will be suitable.
- Some kind of diode to stop the current produced when the motor slows down being pushed back into the circuit.
- Again, I've picked up a 1N4001S from Maplin which I hope will be useful.
