| Intermediate Technology Education | Control Technology | Design Stage 2 | Topic 6 | Optional Activity 4 |

Introduction to Computer Control

To introduce the hardware components and computer software that will be used in the computer control activities that follow
  • Identify the various electrical and electronic devices that will be used in the computer control activities
  • Identify the software used to control the devices you will attach to the computer
  • Learn how to install that software

Hardware

The basic hardware components required to complete the computer control activities consists of

  • Motor Controller
  • Geared DC motors and wheel kit
  • Incandescent lamp and socket

Motor Controller

The motor controller is used to control small direct current (DC) motors and lamps under computer control using appropriate software. The controller used in the control activities is called a Phidget motor control and is available from Phidgets Inc. at

The motor controller attaches to the computer via a universal serial port (USB) and power for the controller and attached devices is supplied by a 6 volt DC power supply.

Note. To avoid damage, use only the power supply furnished with the Phidget controller


Figure a) Phidget motor controller b) Power supply c) USB cable

Geared DC motor

The DC motor used in the activities is 6 volt servo motor that has been modified so that it can turn continuously. This motor comes with accessories such as plastic disks and arms that attach to the motor shaft and some rubber grommets and screws that can be used to mount the motor.

In addition, a wheel kit consisting of plastic wheels and traction bands which also can attach to the motor shaft, are supplied for a mobile robot platform. A ball castor, which is a ball bearing in a plastic mount, is used as a support for the mobile platform. This is supplied as a kit of two and requires assembly.

The geared DC motor, wheel kits, and ball castor are available from hobby stores including:


Figure a) Plastic wheels b) Traction bands c) Ballcastor d) geared DC motors

Figure a) Mounting hardware b) Disk and arm accessories

Note:  Some kits may come with the motor not properly modified for Continuous rotation.   Unmodified motors will have an additional gear.  Instructions for modifying them are in the Your Turn section.

Incandescent lamp

Any incandescent lamp with a rating of between 6 and 7.5 volts and a current draw below 1 ampere can be used for the activities involving light control. A lamp socket base with screw terminals is recommended as an easy-to-connect accessory. Lamps and sockets are available from electronics stores such as:

Wire

Wire will be needed to connect the lamps to the motor controller and to extend the wire on the geared DC motors when fabricating a mobile robot platform. Any insulated, solid or stranded wire from #20 to #26 gauge is suitable for the lamps. Stranded wire of the same size is recommended for extending the motor leads as it will resist breaking better than solid wire when moved.

Wire can be purchased from the same suppliers as the lamps.

Software

Software for the control activities is divided into 3 categories:

  • Phidget library
  • Phidget monitor
  • Control software

The Phidget library is required by the windows operating system (Windows XP, 2000, 98). It allows applications written in a programming language such as Visual Basic to communicate with the Phidget motor controller. It must be installed first.

The Phidget monitor is a small program that verifies that the Phidget controller is connected and communicating with the computer.

Control software has been written in Visual Basic 6.0 and exported as an executable file (.exe). This software will be downloaded to your computer each time you do an activity.  These programs run without the need to install Visual Basic.

When you are ready, go to Your Turn