ENVIRONMENTAL SENSOR DESIGN PROJECT
The aim of the project is to produce an environmental monitoring system for use in a clean room environment. It should be capable of monitoring various environmental factors including, but not limited to temperature, humidity and air speed (of the ventilation system). It should be possible to connect a reasonable number of sensors and not just ones of different types. These readings for the various sensors should be presented in a format that can be easily read by the user. This implies some sort of suitable display system. The system should also be capable of alerting the user if any environmental factor drifts outside an acceptable range. These ranges would be programmed into the system by the user and an alarm of some form would sound if these limits were breached. Some form of user interface will need to be provided so that the user can programme the system in this way. Ideally the system would also have the ability for remote monitoring or data logging, perhaps over a network. Finally all of this system should be created using readily available off the shelf components and development boards that are available in the department.
A clean room is a room or facility where the environmental conditions need to be kept under strict control to reduce or eliminate airborne dust, particles or contaminants that may affect the fragile nature of the work carried out within them. Clean rooms are typically found in specialist manufacturing or biochemical process environments or even in hospitals to prevent the spread of infectious diseases. By comparison, a human hair is about 75-100 microns in diameter and a particle 200 times smaller (0.5-micron) than the human hair can cause major disaster in a clean room . As an example, this happens through the contamination of the coating adhesion on a wafer or chip that forms part of miniature circuit. This could lead to expensive downtime for the facility.
Depending on the type of clean room the air pressure may need to be higher or lower than the atmospheric pressure. For an electronics clean room the air pressure is slightly higher than atmospheric so that no particles can enter the room via the air. For a microbiology clean room the pressure needs to be slightly lower than atmospheric so that no potentially harmful microbes can leave the room via the air. These conditions are achieved by means of filtered forced ventilation in and out of the room. For example to achieve higher pressure there is more air entering the room than there is leaving. This means that the air flow in and out of the room also needs to be kept under observation and control. In addition to the potential air pressure requirements, the two other most important factors that need to be controlled are the temperature and the humidity. Should one of these drift outside a desirable range the work being carried out could be ruined completely
To maintain the strictly controlled clean room environment, poses the need for some form of monitoring equipment which could take constant readings of these conditions and alert the user if any of these environmental factors drift outside acceptable ranges. This way the user could take action to remedy the problem or stop work before it is too late and the work is ruined. Such equipment should be small and unobtrusive for example an embedded system.