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THE SYSTEMS DIAGRAM

V. Ryan © 2001-06

When planning a project a ‘systems’ diagram is essential. This will allow you to show your thinking regarding your idea(s) and whether or not they will answer the design problem. It also allows you to think systematically and logically about the design problem and how it can be solved. Above all, it keeps you ‘on track’ and does not allow you to wander too far away from the original design problem. A systems diagram is similar to a flow chart although on first sight it is much simpler and more precise. The diagram is usually part of either the ideas or development sections. However, do not restrict yourself to these two areas, if you feel it is necessary, use this type of diagram wherever you like in the design process.

Below is an example of a systems diagram for an alarm project. The alarm system is for a briefcase, when the case is opened by anyone other than

1. ALARM PLACED IN CASE.
2. ALARM ARMED.
3. TIMER REQUIRED - ALLOWS USER TO CLOSE CASE WITHOUT ACTIVATING ALARM ACCIDENTALLY.
4. CASE CAN BE CARRIED BUT ALARM WILL BE SET OFF (OPTIONAL).
5. KEY SWITCH FROM OUTSIDE THE CASE.

1. TIMER - THIS WILL ALLOW A TIME DELAY OF TWO MINUTES. A 555 OR ZN1034E TIMER WILL BE USED.
2. IF ACTIVATED THE TIMER WILL START AND THE BUZZER WILL EVENTUALLY SOUND.
3. A TILT SWITCH MAY BE NEEDED TO ACTIVATE THE ALARM IF THE CASE IS MOVED.

A CLOSED LOOP SYSTEM

A ‘closed loop system’ feeds back on itself. Some systems require what is called feed back. For example, a computer may monitor a house alarm continually. The program will check whether all the contacts and sensors are operating correctly and this is a continual process. The alarm system above is an open system in that there is an input, a process and finally an output and then the system ends.

You must produce at least one systems diagram as part of your project. You can set the drawing out in the same way as the example.

SAMPLE SYSTEMS DIAGRAMS