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August 21, 2009

Introduction

This is a project to take balsa wood airplanes with propellers powered by rubberbands and replace the rubberbands with electric motors. My original idea was to build a circuit with a proximity detector and 2 LED's so that when someone steps close to the plane, the two lights turn on like a terroritoral animal warning of an attack. If someone gets even closer the motor will turn on (moving the plane forward towards the person) until it doesn't detect them anymore. So I epoxied a 1.5-3v Metal Gear DC motor from Radio Shack to the front of the plane and to the shaft of the propeller. The glue kind of got in the part of the plane that holds the shaft to the body, so I cut it off. This causes a bit of wobble :(. So I had an infrared proximity detector from Spark Fun which had a REALLY clean signal on the scope, but it only detected things maybe 30cm infront of it, so I ordered an ultrasonic one. I couldn't get it to keep a stable signal (I also plugged it in backwards when I first put it on the scope, so maybe I blew it :( ), so I went to Radio Shack and got a PIR motion sensor. Kinda sucks cause this is only an on/off deal. The proximity detectors would say if there is an object directly infront and how far away. So I changed the firmware so it turns the LED's on when it detects motion and if it still detection motion a time later it will start the motor until motion stops. Boring :(.

Anyway, this is a pretty simple motor control circuit. For a more complex one (multispeed) take a look at my Atmel Motor Control project and the Linksys Copter project that uses it.

Picture

	Here is the small test circuit from the schematic below.
Schematic	Update (September 3, 2010): I replaced the 2N2222 transistor with ZTA1049A. When I first made this I didn't bother to measure the current through the motor. It appears that it wants to pull 1.29A and the 2N2222 isn't made to do it. The ZTX1049A is :).

Source code
airplane.asm

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