Actuators Workshop

Some rough notes from a workshop delivered by

Intro notes

  • Mechatronics
  • Non-magnetic actuators used in MRI machine (piezo).
  • Human reaction - we are tuned to recognise natural movement.

Gordon Pask

  • Cybernetic Serendipity 1968 (ICA electronic art) Gordon pask. Later toured US & Canada at the Exploratorium.
  • SAM (Sound Activated Mobile) - early senstor. Had to 'talk' to it in a steady murmur in order to atract its attention.
  • Examined animals for types of movements - Lobster leg.
  • Senstor looked scary when going through its test routine i.e. moving in its rigid way.
  • Hydraulics very quiet as pumps can be placed remotely.
  • Behaviour rather than appearance is important.
  • Evoluon - spaceship event.
  • Machines need maintenance.
  • Senstor in Holland on blocks.
  • Possibly one of the biggest computer art commissions.
  • Employed by UCL.
  • Recorded movements & from those movements could statistically identify if you were male or female.


  • Simon penny - artists - autonomous robot.
  • Ken Rinaldo - artist - dried grapevine. Cables create movement. Infrared sensors to detect movement. Sound sensors. MAchines whistle at each other. Fish in bowls move around.
  • Yves Amu Klien - Octofungi.
  • Driessens & Verstappen - Tickle Salon. Tassel strocks & builds a model of the person laying down.
  • Paul Granjon - Low tech robots. Sexed robots. Robustly built. Big battery.
    • The only maths you need to know

      Voltage = Current * Resistance. (V=IR)
      Power = Voltage * Current (P=VI)
      Power = Current2 * Resistance (P=I2R)
      Torque measured in Newton meters: (needed to spec installation).

      Very useful function - Constrain number range

      int rangeAdjust(float oldMinVal, float oldMaxVal, float newMinVal, float newMaxVal, float currentReading)
      float ratio = (currentReading-oldMinVal)/(oldMaxVal-oldMinVal);
      float newValue = ratio * (newMaxVal - newMinVal);
      newValue = newValue + newMinVal; // bump up the figure into the new range
      return newValue;


      • Solenoid - Linear motion. Digital action.
      • To drive 8 actuators use ULN2803 (has 8 transistors & diodes built in 500ma per channel)
      • Centrifugal fan for inflating fan
      • Speaker: 2 mirrors with laser.
      • Floppy drive (linear motion)
      • Hard drive head (make jumping robot.)
      • H-Bridge - L293D
      • Can make true analog output with resistor & capacitor - make an oscillator display an image.
      • Servo: can get metal ones. Lots of different types.

      Shops/Materials (for pump)
      Power supply from Rapid. £60.
      BOOK: Robotics, Mechatronics & artificial intelligence.
      BOOK: Muscle wire.


      Detecting position of motors:

      - Could use a cam to count spins i.e. cam makes switch go on one rotation.
      - Slots on a disk to count spins (optical encoder).
      - Slotted opto switch (found in printers etc.).

      Stepper motor

      1. List wires & measure resistance between pairs to work out which are connected.
      Standard degree shift: 1.8, 7.5, 15, 30

      Accelerometer and Servo example

      Accelerometer / Servo example


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