Solar Bug

by Trenton Henry

01/09/00

Overview

This robot was an experiment in power systems. The goal is to create a little bug who's sole purpose it to stay alive. It seeks the brightest light source and heads for it so it can charge up. It uses the same chassis as the Carpet Crawler, but instead of a battery it uses a 5.5V 1 farad capacitor to power the motors. The capacitor is charged via a solar cell. (There is a tiny header that allows me to rapid charge the capacitor using a 9v battery and voltage regulator.)

Mechanical

Same as Carpet Crawler.

Motors

The Lego "Micro Motor" is about the size of a 4 bump Lego cube. It draws 10 ma at 30 rpm with no load, and about 30 ma at about 20 rpm with a load. It runs on around 2v (though with little power or speed) up to 9v.

Electronics

The capacitor powers the motors. A 3v watch battery powers the electronics. The analog comparator in the processor is used to detect when the capacitor voltage drops to 3v. This allows the robot to detect when it is "hungry".

Processor

This time I used the Atmel 89C2051, which is a 20 pin 8051 derivative. It has 2K of flash ROM, 128 bytes of ram, and an analog comparator. Unfortunately, it has no EEPROM, but life goes on. I chose it because I had a bunch, and because I could program it in C using the Keil compiler. (Keil has an evaluation compiler that is limited to 2K hex files. Perfect, yes?)

Photocells

Same as Robigotchi & Carpet Rover.

Whiskers

Same as Robigotchi & Carpet Rover.

Software

All new...

Observations

It runs for about 5 minutes on a charge. It charges in about an hour in full sunlight. There is a lot of work left to do...