Flatbot

Flatbot was inspired by Simon Fraser's Fred Flatbot. I always liked the form factor of this bot, and I didn't want all my photovores to look the same. Flatbot is a miller photopopper with some modifications.

He is powered by a massive 37 x 66mm Solarbotics solar cell that puts out 6.7V at 30mA! When designing Flatbot, I knew that the motors had pretty lousy torque, and putting any kind of wheel on them parallel to the ground would result in wasted energy. Luckily i had two 1381-U's sitting around to put that voltage to work.

The next challenge was keeping the flat aesthetic. I managed to find 4 small 1000uF capacitors that I wired in parallel to give it 4000uF. I also boosted his .22uF timing caps to 1uF. This would hopefully increase the engines 'on' time enough to provide more power to the wheels, which was my main concern with this bot. At the back you can see a bead on a bent paperclip to provide minimal drag on the back of the bot, although this was later removed as it actually hampered the robot's movement.

You can also see here that I built the solar engine with the heads of the transistors/1381s together to provide more ground clearance. If I were to re-build this bot I would have rotated one side facing upward so the sides would mirror each other, which would have made the build much easier!

Overall this robot moves as well as could have hoped. A lot of power is wasted in the pager motors while attempting to turn over. Despite all the power to the motors, this bot only manages 1cm steps. This is due not only to the flat nature, but also to its length. Like Simon's Flatbot, mine is not very phototropic either.

After building this bot, I came across a post about motor start capacitors; a cap connected across the motor terminals that could help build torque by ramping up power to the motor slower rather than in one big burst, avoiding burning through current in a stalled motor.