Dissecting a Sandwich

Mark Gordon

Engineering 315

December 9, 2002

What is Sandwich?

• Line Following Robot

• From Robot Building for Beginners– David Cook

• Follows Either a Light Line on a Dark Surface or Dark One on a Light Surface

Sensors

• Cadmium Sulfide Photo-Resistors– Variable Resistances Cause Variations in the

Voltage Drop

• White LED– Reduce Shadow Effects– Allow for ‘Night Runs’

Feedback

• Voltage Comparator Chip– Senses which Set is Closer to the Line– Produces a Ground or Disconnect

• A Pullup Resistor Converts it to Ground or High

– High Causes the (Opposite) Motor to Run

Building

• Circuit– Breadboard

• LED Circuit• Headlight Circuit• Other

– Sensors, Motors, Side LEDs, and Comparator Chip

– PCB

Building

• Body– Ziplock Sandwich Container– Lego Wheels– Gearhead Motors– Coupler

Debugging

• Side LEDs– Show Which Motor Sandwich Thinks Should

be Running

• Check Overall Resistance– Check Individual Resistances– Find Bad PhotoResistor

Parameters

• LED Brightness– Brighter LEDs

• Sharper Reactions– Will Turn Sooner

• Picks Up Lower Variations in Color

– Dimmer LEDs• Uses Less Power• Reactions are not as Abrupt

– More Likely Both Motors will be Running

Demonstration

Credits• Electronics Aid

– Chuck Holwerda

• Machine Shop Aid– Dave Ryskamp

• Time Provider– Professor Ribeiro

• Book Writer– David Cook

• Putter-Upper-Wither– Rachel McNamara

Questions?