Computer Control – CCEA

In this project there was a number pieces of equipment used.

The program used to write the control commands is PIC Logicator 1.6. Logicator is the natural visual design medium for creating, testing and modifying measurement and control systems. Systems are created as flowcharts by dragging commands onto the screen and drawing routes between them.

Watch Powerpoint

Download Powerpoint

• The control box – This box is an interface between the computer and what is being controlled. One of the main reasons for this box is to allow an increase of power so that external devices can be powerer. The output voltage from the computer is very small and is not high enough to drive these external devices, the control box used in school has an output voltage of 12 volts which gives enough power.
• The computer – This is the main source of inputting the information. The program allow the used to see what the program will do on the screen. To launch the program you go to START – ALL PROGRAMS – TECHNOLOGY AND DESIGN – PIC LOGICATOR 1.6. This will open the screen to allow you to write the program.
• The Hardware – The hardware used in this project is a model of the Mahon and Armagh road junction. There are three set of lights, two of which together and the third works in a different sequence. At each set of lights there is a push button which simulated the pelican crossing when pushed. The hardware is connected to the control box as shown in the picture.

The main focus in this project is to make the pupils aware of the function of traffic lights and the sequence of lights to allow the safe passage of cars at a junction.

Arrive alive is a site set up to explore the function of traffic lights and shows the sequence of lights. The sequence of lights is further explored using the interactive set of lights, when one light is switched on it triggers a sequence of lights representing a real life junction.

The main junction studied was the one at the Mahon Road and Armagh Road.  Here there are three set of lights and a pelican crossing at each set of lights. The traffic lights work to control the flow of traffic to and from Armagh and the Mahon road, they work to keep the traffic moving as smoothly as possible. The pelican crossing allows pedestarians to cross the road at any one of 3 locations, this is done by switching the lights from the stndard operating sequence to one which all 3 sets of lights are red and a buzzer sounds. With the 3 sets of lights at red all the traffic should be stopped and the pedestarians can cross the road safely.

In order to achieve the switching of the lights to the pelican crossing the program needs to be change to allow a MACRO program to be included. The macro is controlled by a DECISION box in the main program, in this decision box there needs to be a question asked about the use of the pelican crossing button. Whenever the main program is running to control the lights, it ignors this decision box unless a pedestarian pushes the buttom to indicate they wish to cross the road. When the button is pushed the macro program is called the the sequence of lights follows the commands in this program. The macro program is a separate program which is linked to the main program.