Robots I have built:

Then one for the Melexis safety trophy in Belgium in 2004

The challenge was to find and pick up a tennis ball then carry it to a flashing beacon 20 meters away while avoiding concrete blocks and hot cans, whilst knocking over cold cans.


 What it had: 

  • 2 main drive motors and gearboxes – Ex electric screwdrivers
  • 1 door open & close motor – Ex CD reader track positioning motor
  • 7 relays - to control the 3 motors plus one for fast / slow mode
  • 4 Floor tape sensors – LEDs and photodiodes monitoring returned beam
  • 4 bumper switches – standard micro-switches
  • 6 Beacon direction detect photodiodes arranged in a circle
  • 1 Beacon roof sensor – standard micro-switch
  • Object detection - 2 laser pointers modulated at 1Khz and under PC control
  • Road sign illumination - 2 LEDS one red & one blue modulated at 1Khz under PC control
  • Object sensors - 4 photodiodes ( 3 behind focussing lenses)
  • Hot & cold can detection - 1 Melexis IR sensor
  • Object sensor sweeping – 2 servos, one for right to left and one for up and down controlled by PIC micros
  • 2 16F877 PIC micro controllers on boards with regulated power supplies running at 20Mhz and doing 5 million instructions per second each
  • 4 object sensor op amp based filters and amplifiers
  • 4 laser and LED modulator circuits and 2 regulated laser power supplies
  • 4 floor tape sensor signal amplifiers & comparators
  • 1 PIC controlled relay board controlling the 7 relays through Darlngton drivers
  • 1 Motor supply board with 3 regulators
  • 1 regulator board cooling fan
  • 4 battery systems – one for each of the PICs, Lasers, servos & motors
  • 6 Display LEDs – One on each PIC board & 4 others in a group
  • Assorted switches & loads of wire, nuts, bolts and tape

One PIC controls all the motors (via Darlington drivers & relays), the beacon sensing (it measures highest analogue value over a half second period), floor tape & bumper sensing and provides the strategy and move sequences for each phase of the course.

The other PIC monitors all the modulated light and IR sensors and works out whether an object seen is a nice one to home in on or a nasty one to avoid. It also establishes its direction and how close it is. It talks via a handshaking protocol to the motors board to tell it what it is seeing.

All the code is written in FED WizPIC assembler code. There were 1768 instructions on the motors board and 1249 instructions on the vision board.

When switched on any of 15 tests can be run on either board to check out the various subsystems.