I Built a Thing

I have not been active in the Lego community for some time; this is an issue that I definitely need to correct since it's such a fun community and legos (legoes?) are really so much fun. Awhile back I had bemoaned to @galenkp that I have a number of lego sets still sitting unopened. Sadly, they are still sitting unopened. Soon! I have plans.

But for now, I have built a thing! I have combined three of my favourite things - film photography, legos, and robotics - and built a thing.

This thing, to be exact.

I like to develop my own black and white film. I don't even use chemicals to do it - I use a combination of instant coffee, vitamin c powder, water, and powdered laundry detergent to create a concoction called caffenol. It works well, and I enjoy it. What I don't enjoy is slowly rotating the developing cannister for 7 1/2 minutes to evenly develop all the film.

That is where my contraption, this thing, comes into play. I decided to build a contraption that will slowly spin my film cannister for 7.5 minutes so I don't need to.

It's pretty simple as machines go which, as any engineer will attest, is the right method of building. Using a simple machine is more efficient than a complex machine.

The large two wheels hold the base of the cannister and are attached to lego NXT motors (more on the NXT shortly). The front smaller wheels are free rolling and intended simply to let the cannister roll freely.

The Lego Mindstorms NXT itself is a "CPU brick" which can be programmed to perform various functions. It really was designed to teach robotics to youngsters. In this picture you can see three ports, two of which are in use. These three ports can power one motor each. I chose to use two ports and two motors, one for each wheel. I had considered using only one motor and building a series of gears and pulleys to do what I wanted, but I felt ultimately that this was simpler. Obviously, you can see that I used a small number of technics parts to hold it all together.

Incidentally, the bottom of the brick has an additional 4 ports which can be used to connect various sensors (not motors), such as a touch sensor, a colour sensor, sound sensor, and even a balance sensor. I used to coach teams that would compete in leagues to build robots using Mindstorms to perform a variety of tasks. Fun stuff.

My purpose here was much more simple than what we used to do in those competitions.

This is a very simple program:

1. Start
2. Enter loop and repeat 15 times:
   1. spin wheels slowly (15% power) one direction for 15 seconds
   2. spin wheels slowly (15% power) in the other direction for 15 seconds
3. make a noise so I know it's complete
4. stop

To test I filled the cannister with water so it weighs as much as it would with film and developer, then set it to spinning.

This is a very simple contraption and it does exactly what I wanted it to. I'm planning on using it this weekend for the first time!

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(c) All images and photographs, unless otherwise specified, are created and owned by me.
(c) Victor Wiebe

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