All posts by raudette

Realizing a 3D design

I haven’t worked in 3D at all before, and I was looking for a simple project.

As with the Brio/Duplo wagon, I was thinking about what was within my ability, and not commercially available.  I decided I would try to build a custom tire valve stem cap with my daughters’ school logo (a polar bear).

Polar BearLooking at freely available 3D modelling tools, I checked out Blender and OpenSCAD.  OpenSCAD seemed to be simple for someone starting out with designs built out of basic shapes.

I converted the bitmap logo I had to a vector drawing using Inkscape‘s “Trace Bitmap” feature.  Following an Instructables tutorial, I exported the bear’s outline and features to a DXF file, which can be imported into OpenSCAD.  I encountered number of difficulties (it has been a while since I completed the design – I can’t remember which issues, specifically, I encountered).  I tried again, with great results, using the Inkscape OpenSCAD export plug-in.

I merged the bear with a cap designed by Dan Ujvari, and printed it at the Toronto Public Library’s innovation lab.  I used a black permanent marker to highlight the bear’s details after printing.

Polar Bear Tire Valve Stem Cap
Polar Bear Tire Valve Stem Cap

It was interesting to learn that even with a simple project as this one, there are limitations to 3D printing.  It was almost impossible to remove the support material on the reverse side, as the bear is narrower than the cap. If I were to refine the design, I would make the bear the same width as the cap.  I definitely have more to learn about successfully designing an object around the limitations of current 3D printers.

This Polar Bear Tire Valve stem cap can be downloaded from or Thingiverse.

My First 3D Printed Object

I have been excited about the potential for 3D printing for quite some time.

Shortly after our local library acquired a couple 3D printers, I took the mandatory course, where we were taught the two primary rules of printing at the library:

Rule #1) Don’t touch the heating element
Rule #2) Don’t print guns

Course completed, I started to think about applications.  What can’t you just buy, what makes sense to print?

The idea of combining Duplo and Brio seemed like a great idea – I was thinking of an elaborate track with bridges over bridges, and Duplo seemed almost perfect for the job.  What I really wanted was a piece with a wooden train (Brio) top, and Duplo bottom.

A quick search revealed that I wasn’t the first person to think about this, someone had already designed a Duplo/Brio bridge support system.  Looking into this further, and loading these parts into 3D printing software revealed that each segment would take about 2 hours to print – the maximum time allowed on the library’s printer.  Given that a simple bridge would require at least four segments, I looked for alternate ideas and stumbled across the Duplo/Brio wagon.

I downloaded the file, went to the library, and printed it out.  83 minutes later, my train was completed.  I attached the wheels to the body with paper clips, and glued fridge magnets to the ends for the couplings.  I was quite pleased with the end product (see photo).  The library charged just under $5 for the printing time, which is about what a train car costs from a local toy store.


Lego and Brio - Endless Possibilities
Lego and Brio – Endless Possibilities

Taking this idea further, I thought I may try to design my own toy 3D printed TTC subway or street car for wooden train tracks.  I have  occasionally seen them available commercially, but they are generally hard to come by.



Two Rocket Canada Day – Part 2

After lunch, the girls and I hopped on the subway and headed to the Canada Day events hosted at Queen’s Park.  We ended up having a  great time – there were free bouncy castles, live music, hula hoops, and more.

But I thought the coolest activity was the build and test your own air rocket, hosted by Makerkids.

The children were given pipe insulation for the rocket’s body, and duck tape, scissors, cardboard, streamers, and everything else you would need to complete an air rocket.

With occasional help from Rachel, Tegan built her rocket.

Fueling the Air Rocket
Fueling the Air Rocket

The Makerkids team had several launching stations setup on University Avenue, which appeared to be similar to the Make design.

As scotch tape was used for some of the cosmetic touches, I warned Tegan that the rocket may not survive its first test flight intact.  She decided to launch it anyway.

See the video for the test flight results.

Two Rocket Canada Day – Part 1

Shortly after breakfast on July 1st, Tegan picked up a recently discarded brown cardboard box sitting beside our recycle bin.  She had a vision in mind: she wanted to build a rocket ship.  She needed some assistance – the cardboard box was too thick to cut with her scissors.  So she created a design.

Technical Design Documented Prior to Implementation
Technical Design Documented Prior to Implementation

First, I was assigned the window.  With a utility knife, I cut a circle out of the box. A clear plastic lid, also sourced from the recycle bin, was installed.  Tegan then made the fins from the box’s former flaps, and installed them using packing tape.

Next came the nose cone.  Rachel was a proponent of using the two remaining box flaps, and building an A-frame, triangular nose cone.  Tegan had her heart set on a true conical design, but couldn’t quite figure out how to achieve it with the materials at hand.  In the end, we taped 9 sheets of construction paper together, and rolled the now super-sized sheet into a cone, and installed it on the top of the rocket.

Together, the girls painted the rocket red.  To this day, it sits in a corner of their room.

Testing, Quality Assurance
Testing, Quality Assurance

Who connects to random WiFi hotspots?

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.

Community Wall Bulletin Board
Community Wall Bulletin Board

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


Homemade Dance Dance Revolution Mat

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).

Can you tell that it's home made?
Can you tell that it’s home made?
There’s an Arduino library (CapSense) that makes measuring capacitance really easy, and I found firmware called “Big Joystick”  that makes the Arduino UNO appear as a regular, USB, HID joystick.  Detecting steps works really well, and the whole thing works flawlessly with Stepmania.

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.

Lisa and Rachel playing StepMania
Lisa and Rachel playing StepMania

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.

Dance Mat Interface
Dance Mat Interface

Download Dance Mat Project Files

Robotics Projects for Kids

When I go to the library with the kids, I end up coming across books I wouldn’t ordinarily see.  I recently stumbled on Robotics: DISCOVER THE SCIENCE AND TECHNOLOGY OF THE FUTURE in the kids section.

Robotics book for kids
Robotics book for kids

Although this book is targeted at older children, and my children aren’t particularly interested in robotics, we still had fun completing a couple of the simpler projects at home.

First, we built a mechanical hand with cardboard, drinking straws, string, and a glue gun.  This was a great craft, because my six year old could complete all the assembly steps (given guidance) and the completed project was unanticipated, functional and fun.

Next, we built a drawing robot, which consisted of a plastic cup, tape, an electric motor with an added weight (like a mobile phone or pager vibrator), batteries, and markers.  This craft required more assistance – I connected the batteries, and the weight to the motor.  My six year old assembled the cup and the markers, and shot video footage.

Here’s what the output looked like:

Can your robot draw this?
Can your robot draw this?


WiFi Sailboat Passes Bathtub Test

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.
Field test on a rainy, windless day.  The bane of any sailor.
Field test on a rainy, windless day. The bane of any sailor.
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.
Web Interface - jQuery sliders control the sail and rudder
Web Interface – jQuery sliders control the sail and rudder

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.

It seems like overkill – an Arduino AND a Raspberry Pi for such a simple task?  I’d considered alternatives – using only an Arduino with Bluetooth or another wireless interface, or using the Raspberry Pi to directly control the servos – but in then end, I just used the parts I had on hand.

My initial design used a 7805 IC to supply the 5V for power – that didn’t work…  Everything would boot, the 7805 would get super-hot, and the Raspberry Pi would crash after moving a servo a few times.  A little reading lead me to pick up a switching regulator (I happened to pick up one from Castle Creations at my local hobby store).

I tested the design out with my assistant in our bathtub, and everything worked!

But, by the time everything was built, the city drained the reflecting pool I had intended to use for trials for the fall – I had to try it out in a nearby pond.  And, of course, there was no wind.  I’ll post more photos following a windy day test.

Check out these far grander projects – these individuals are trying to build autonomous boats that can cross the Atlantic:

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

Growing Popping Corn on a Balcony

The apartment we live in faces east, and in the morning, we get a lot of sun.  This year, I thought, wouldn’t it be cool to have a little natural shade?  As corn grows tall, it seemed like a good candidate.

We successfully grew 8 popping corn plants in two large pots.  It was pretty easy – plant the seeds, water daily, fertilize.  This was not organic corn.  The plants did grow tall, but 8 was not enough to provide us with any significant natural shade.

Popcorn, ready to harvest
Popcorn, ready to harvest

This year, we also grew pole beans, carrots, tomatoes, sun flowers and some other potted flowers.  It was a pretty good reminder of how dependant we are on big agriculture, farms, transportation systems, food terminals, and grocery stores to economically feed ourselves.  Given the start up costs of the containers and soil, these were not economically viable crops – it was vastly more expensive to grow than to buy.

Would your condo board allow this garden?
Would your condo board allow this garden?

The corn did pop.  We’ll likely do this again next year.




Electricity from a Toy Windmill

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.

Toy Windmill with Generator
Toy Windmill with Generator

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.

Toy Windmill Generator Circuit
Toy Windmill Generator Circuit

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!