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Archive | July, 2013

Using the Lots of Pots Board for Raspberry Pi

lop3

Here’s how to use the Lots of Pots Board for the Raspberry Pi. The daughterboard (or shield; what are we calling Raspberry Pi add ons these days?) sits on top of the Raspberry Pi and breaks out the various GPIO pins in a useful and labeled manner. It also has an 8 channel MCP3008 analog to digital converter on board, which is hooked up to the hardware SPI pins on the GPIO header. This tutorial will describe the features of the board and cover how to read analog inputs from the ADC.

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Algorithmic Ballyhoo: Using Processing to Make Hundreds of Unique Posters

MFBlogPost

This post describes a process I like to call algorithmic ballyhoo; using a Processing program to generate many different unique poster designs. We needed a poster for the Rhode Island Mini Maker Faire this year, so I decided to use a Processing sketch to do the work for me. Modern Device will be at the Mini Maker Faire, and will have a new Bytebeat-based kit for the soldering workshop.

poster-final-600p

Algorithmic ballyhoo is nothing but sheer randomness without some sort of seed or design constraint. The Mini Maker Faire is embedded in AS220’s Foo Fest, and Xander Marro is this year’s Foo Fest artist-in-residence. Xander designed the Foo Fest posters (pictured to the right) and I decided to use the same elements in the Mini Maker Faire poster.

Read on for the Processing code. It’s pretty straightforward; the key is to use the processing.pdf library to record a printable version of everything you’re drawing on the screen. Then, just bring it to your local copy shop (or fine art large format printer). Remember that your drawing grid is at 72dpi. In the final PDF all graphics will be drawn as scalable vector art, but any included bitmap images will be drawn at screen resolution, so make sure any included PNGs are at least 4 or 5 times the final size, then shrunk down.


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Making a Wind Tunnel, Part 1

Screen shot 2013-07-16 at 4.46.24 PM

Constructing a wind tunnel in theory is not a hard thing to do. I first did some internet research as to how I might build a simple wind tunnel, starting on the Internet.

NASA has some links up for educators and I looked through them but didn’t really find much at the level I needed.

Next I used one of my preferred Internet search techniques – doing a Google search, viewing the “images” option, then clicking through to the pages which display promising images: https://www.google.com/search?q=wind+tunnel+construction (The preceding link may be browser specific and may not work for you.)

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Wind Sensor Calibration and the Wind Tunnel

Chart

We’ve been selling a little wind sensor, which has found its way into lots of hobbyist projects and even some “harder” science projects including one by the US EPA, but we’ve never had the kind of solid data that would make the sensor really useful for a range of people. We decided that some hard data was long overdue.

At the top of this post you see the plot of wind speed vs sensor output voltage for two different temperatures. Without too much consideration you can see that the output of the sensor is temperature sensitive and that the curve is fairly flat as the wind speed increases. Both of those facts mean that it is fairly easy to confuse a shift in temperature with a shift in wind speed. Or that recalibration will be required when the temperature changes greatly.

Obviously this greatly limits the utility of the sensor, so to remedy this we have a number of ideas in mind, including an Arduino Sketch that uses the temperature output on the wind sensor for calibration and several new schematics and designs for wind sensors.

Before we could do any of that however we had to have a tool to verify wind speed, but not just any wind speed, we needed to be able to precisely control temperature along with wind speed. Building the wind tunnel has been a lot of fun and I’ll cover its construction in several blog posts. I’ll also be posting more data about the wind sensor, as I type up my first handwritten data journals (that look something the image below).

EPSON scanner image

You may wonder about the manual data entry effort. I am worrying about it too, and wondering why I’m not automating all the logging procedures to save the data entry. This is really just the first flush of  excitement at having a research instrument that can provide good data – so there is lots of room for improvement in my technique. The anemometers that I’m calibrating against don’t have any connection to the computer, so if I automate the procedure I will still need to read the anemometers manually and get that column of  numbers in by hand, and also synch it with the other data. I think some kind of semi-automated system still makes sense though. Many experiments can also be done without actually entering any of the data, or even saving much data. More work to do.

So you probably want to see what a DIY research table-top wind tunnel looks like, and I’ll oblige you with a teaser photo just now. Many more details will be provided in the next week, as to the design choices that went into its construction. Yes it does still look like a table full of wires, that aspect kind of comes with designing things as you figure out how to do them. As I decide which parts of the apparatus seem good enough for  my purposes, I’ll harden them up.

WindTunnel