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.
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.
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.
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.