Hardware Overview

Hardware Overview

The robots were designed carefully to save money without sacrificing too much functionality. The greatest cost savings were made in the mechanical design. The robots are just one printed circuit board (PCB). The wheels are the only custom mechanical parts; everything else is an off-the-shelf component, compatible with standard electronics manufacturing techniques, soldered to the PCB. As a result the platform is economical and its manufacture simple, for researchers and electronics assembly firms alike. Further savings were made in the choice of components mass produced for consumer electronics. Motors used to vibrate mobile phones were chosen for drive because they are compact and cheap. Small wheels, and the robot's very low weight make gearboxes unnecessary. Power is from lithium polymer cells which are ubiquitous in consumer electronics.

Summary of Hardware Features

  • Drive: Two coreless DC motors, 4mm diameter, as used in
    mobile phone vibrators. Direct drive via 3.5mm neoprene wheels friction-fit on shafts. Differential steering.
  • Battery: 320mAh lithium polymer. This is sufficient for 1.5 to 2 hours of continuous, autonomous movement.
  • Onboard charge regulator and copper terminals/ground skis enable robots to self-charge from a simple "bay".
  • Microcontroller: MSP430F2254; 16kB of flash program memory, 512 bytes of RAM.
  • Communications: Three IR LED/Photodiode phototransistors with multi-frequency FSK modem scheme. Range >50mm, variable with lighting conditions.
  • Sensors: down-looking IR photoreflective sensor measures floor reflectivity. May be used for "food" detection of reflective objects. IR comms receiver phototransistors double as light sensors, enabling light-seeking behaviour, etc.
  • Display: Bi-colour LED enables red/green/yellow behavioural "mood" status output

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Mechanical drawing of Formica robot

 
Mechanical diagram

 

 

Rear view of Formica robot

Rear view; illustrating drive scheme 

 

Side view of Formica robot

 
Side view; illustrating charging contacts (copper) IR LEDs (white) and IR phototransistors (black).

 

Formica assembly festival

 

Twenty-five robots were assembled and tested by a team of nine in a single (but long) day. 

 

The circuit design will be covered in the next page ->

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