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lego city 7734 cargo plane

When my son was three, his grandparents gave him a Lego cargo plane. It took us about two hours to put it together. I'd hand him the piece, show him the instructions, and point to the place where the brick should go. I didn't want to put any pressure on him to finish the plane, so I would have been happy to quit whenever he wanted. But, he didn't quit. That was the first time I saw in him the same obsessive-compulsive drive that pushes me to keep working on all my random projects.

Fun, Messy, and Challenging Activities for Smart Kids

paper_mache_shell

The first time I explored basic electronics was building EON, my submarine Since then I've discovered making simple circuits on a breadboard is a lot like building a Lego kit; There are lots of little parts that turn into something cool when you follow the instructions. And, my son enjoys blinking lights as much as I do. I wanted to make a quick project that would give us lots of time to play together, but rather than focusing on one area of interest, I decided to combine everything we love doing together and put it all in one project. The result -- a remote controlled red turtle shell. Here we go!

The Build

We started with some paper mache which gave us a chance to get messy and play with finger paint. Then we chopped out the bottom of the shell and reinforced the base so we could attach the motors. At night, when he was asleep, I took care of the software. The VEX controller was donated by someone who was going to throw it away. Unfortunately, the receiver didn't have a decoder, so I had to dig around online for a library that could decode the PPM stream from the receiver. That library knocked out three of my PWM pins, so I had to create software PWM signals to control the motors. The rest of the hardware is pretty simple. A dual H-Bridge IC lets us run both motors in forward and reverse, PWM from the Arduino gives us variable speed, and we made a simple 5-volt power regulator. I soldered everything onto perfboard and mounted it in the shell.

The Results

It works, but it could be better. I'd like to make the top of the shell spin independent from the bottom to make it look more like the shells on Mario Cart. Maybe I'll add some translucent plastic and multi-colored LEDs so the shell color could change from green to red to blue.

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