I do.  Even in an era of smartphones and data plans, every once in a while, I find myself searching for open WiFi hotspots.

Who else does?  I set out to find out.  I built a WiFi hotspot that served up an open-to-everyone community wall.

To build it, I set up my Raspberry Pi with a WiFi USB dongle, and configured it as a WiFi hotspot (with WPA security disabled).  I needed a name that would encourage people to choose my hotspot over the others in the area – “CommunityWiFi” seemed like a suitable name.

I chose to use my Raspberry Pi because:

• its cheap enough I could leave it anywhere without worrying about it getting stolen
• its small
• it can run off a USB battery pack, so it can be taken anywhere

But there’s nothing special about this hardware setup – you could set this up with any laptop, a hacked Android phone, or home router.

The system is setup with a DHCP server, a DNS server (dnsmasq) configured to redirect all dns requests to the Pi, and a webserver  configured to send all requests to the Community Wall page.  The Community Wall consists of a couple PHP pages backed by SQLite.

Once the user attempts to visit any web page while connected to the hotspot,  the system will direct them to the Community Wall, where they can read and post messages.

I took the system to our local library one morning.  I tested it out with my smartphone, and everything worked great, but I received no posts over the hour or so I had it running.  This is likely because most library users will have already saved the connection to the library’s own WiFi.  I will be trying this out in other busy areas, without free wifi, and report back.

Some people have taken this idea much further than myself – check out PirateBox by David Darts.  A PirateBox is a mobile WiFi hotspot that allows any user to connect, chat with other connected users, and share files.

Download Community Wall Project Files

It’s been a long winter.  I love taking the kids outdoors, even when it’s cold, but sometimes, it can be fun to play indoors too.  I haven’t acquired a game machine, the kids haven’t expressed much interest in playing video games, but we DID have fun playing a Dance Dance Revolution (DDR) type game at an arcade in hotel we stayed at once.  What would it take to play at home?

Searching around, I came across StepMania, an open-source, DDR type game.  I thought I’d look for a used mat on Craigslist, but when I started researching dance mats, I was surprised to see that many people actually preferred homemade mats over the cheap roll-up mats.

The simplest designs I came across measured the capacitance of the body on aluminium foil to detect steps.  I took a cardboard box from our closet, some sheets of aluminium foil, connected the foil to some resistors, connected to an Arduino.  I covered the aluminium foil with packing tape.  What’s cool with this design is I had everything in the house already, except suitably sized resistors, so the whole thing cost me $1 (plus tax).

What I didn’t get right was the positioning of the pads – it seems harder to get the steps/combinations right than I remember it being at the arcade.  Lisa thinks they are too far apart. But other than that, the sensors work really well.

I’m trying to think of other applications where a large “switch” like this one would be useful.  With the right configuration, these sensors will also sense proximity – not just touch.

Download Dance Mat Project Files

Last summer, I built a pop-bottle sailboat with my (then) four year old.  After trying a couple of designs with keels in our bathtub, we settled on a catamaran style design with two pop bottles.  We tied a string to it, threw it into the pond, let the wind carry it away, and then pulled it back to shore.

And I thought, wouldn’t it be cool to add remote control functionality?

So I did.  I finished my smartphone controlled, WiFi sailboat on Saturday.

The sailboat consists of:

• 2 x 2L pop bottles
• Rubbermaid body
• Plastic shopping bag sail
• Dowel mast, plywood rudder
• 2 servos
• Raspberry Pi with USB WiFi adapter
• Arduino Uno
• AA Battery pack with a 5V regulator

I configured the Raspberry Pi to act as a WiFi hot spot.  Using any smart phone, you can connect to the boat, and visit its web page.

The page has two jQuery slider controls.

When re-positioned, the slider controls drive a PHP page which sends commands over the USB interface to the Arduino, which then controls the servos.

Check out these far grander projects – these individuals are trying to build autonomous boats that can cross the Atlantic:
http://gotransat.com/
http://www.gpss.force9.co.uk/autop.htm

With a little more money, and a little more time, I think it would be fun to build a boat I could launch in lake Ontario, at the foot of Yonge St., to sail autonomously down the St. Lawrence to Brockville, where friends in Ottawa could retrieve it.

Download Sailboat Project Files

Electricity and energy are such abstract concepts.  We just plug things in and they work.  One day, my daughter brought home a toy windmill from school, and I guess I thought I could take that understanding a little bit further.  So I told her: “We can make electricity with that”.

I did a little reading beforehand, and found a few people who had made wind generators online, so I had a rough idea of what I was going to build, and what parts I needed.  We took the subway to Active Surplus, picked up a couple of electric motors, some flashlight-sized light bulbs, some LED lights, and some diodes.

First, I connected the windmill to the motor, and the motor to a flashlight bulb.  I didn’t do any math.  It may come as no surprise to some of you that we couldn’t get enough power from the windmill to drive the bulb.

Plan B.  I built a bridge rectifier with the diodes I picked up, to get DC power from the motor, and connected it to an LED light.  It worked!  I was able to illustrate that we could convert wind energy to light: harness energy from the wind, make a little electricity, and generate light.  Every toy windmill needs this built in!