Sandwich by David Cook

Sandwich is a line-following robot made from a Ziploc 
sandwich storage container. These containers can be found in
local supermarkets for less than a dollar each; yet they 
make rugged, easy-to-alter robot bodies.

Besides a power switch, Sandwich features a multi-position 
switch for line following. With the switch in the
center position, Sandwich remains powered up, but doesn't 
move, which is great for debugging. Toggled left, the
robot follows light lines on dark surfaces. Toggled right, 
the robot follows dark lines on light surfaces.

My favorite feature of this robot is the LEDs. Two white 
LEDs sit in the middle of pairs of ordinary
photoresistors for following the line. Three red LEDs sit 
inside a plastic m&mís candy-container axle, lighting it
up red. Three yellow and three green LEDs indicate what 
the robot is thinking about the brightness of the line
beneath it.

I designed this robot for a book I wrote, Robot Building 
for Beginners. Therefore, as you might expect, the robot
is easy to reproduce even by people without any robotic 

The robot runs for about 15 minutes on a rechargeable 
9 V battery.

Approximate cost of materials:
$5 Pair of LEGO wheels
$2 Container and candy tube
$5 Switches
$5 Pair of white LEDs
$30 Pair of motors
$20 Printed circuit board ($6 homemade)
$7 Molex KK connectors
$5 Spacers, washers, and screws
$10 Remaining electronics

So, probably around $100 total when you count the battery 
and miscellaneous stuff like glue.

I have posted a movie of Sandwich following a line course 
under a bridge, through hanging bells, over a ramp, and
crashing into a block wall. You can see the movie, along 
with pictures and additional information at:


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