Specifications

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4.5.2 Choice of Sensor
Almost all of the current household applications that require distance or proximity
sensing utilise Ultrasonic or Infrared Light (IR) sensors. The market available choices
are large and vary in specifications and range in price from around $40 - $120 each.
Many hobbyist robot builders choose to construct IR sensors to save a lot of cost and
custom design them to suit the necessary requirements.
For the purpose of the Mobile Manoeuvring Robot, it was decided to construct three
separate Infrared Sensors from parts commonly available at electronic stores.
4.5.3 Design and Construction of IR Sensor
The design and construction of the Infrared sensors took a very large portion of the time
and effort spent on this project. Lack of information on the chosen parts made it
difficult to realise their true operations and many other factors postponed the successful
creation of the sensors.
After thoroughly researching other robot builders’ attempts to build IR sensors, a
commonly available 38 KHz receiver was chosen from Jaycar Electronics along with
the same IR LED’s used in the odometry sensors. To tune the IR light suitable for the
receiver it was decided to use a 555 timer in astable operation to pulse the light at a
square wave at 38 KHz with a duty cycle of 50% in accordance with the data sheet of
the receiver. This circuit was simple to construct and the schematic shows the detail
below in figure 4.11.