Alarm Systems Overiew. Alarm systems are essential for alerting the consumer that something is not in order. We have different types of alarm systems used in industrial, commercial and home applications. The most common alarm systems that we can find is the burglar alarm and fire alarm. Burglar alarms alert the user whenever a burglar or something triggers its sensor. An oversensitive alarm system may just trigger or sound an alert even if there are no burglars in sight. Thus a good alarm system should not only be very sensitive but it should also avoid false alarms. False alarms can cause mass panics and delays which could cause a loss in time and money. This is specially true in Fire Alarm systems where a false alarm can cause mass evacuation of an entire office. Hoever, there is no such thing as a perfect alarm system and every model of alarm system has its own tolerance when it comes to false alarms. Different models coming from different manufacturers have diferent sensitivities and specifications. More advanced units incorporate microcontrollers and even microprocessors to increase its sensitivity without an increase in the rate of false alarms.
A. Home alarm system - Alarm systems designed for home use are similarly designed to alarm sytems that are used in industrial applications. The only difference is that home alarm systems does not meet tighter industrial standards and that they can be manufactured at a lower price. Common home burglar alarm systems use cheaper contact switch sensors instead of the more expensive capacitive or inductive proximity sensors. Home fire alarm systems typically used ionization smoke chambers which is very cheap to manufacture.
B. Wireless alarm system - The main advantage of a wireless alarm system is that you can send an alarm signal without being too dependent on physical wiring. Wires can be intentionally cut by the burglar in the case of burglar alarms systems, and wires can be accidentally disabled by fire as in the case of fire alarm systems.
C. Car alarm system - A good car alarm system should have a back up battery on its own and should not be heavily dependent on the car battery. It is very easy to disconnect the car bettery and any car alarm system that is purely dependent on the car battery would be instantly disabled as soon as the car jacker disengages the battery connecting wires.
D. Burglar alarm systems - common burglar alarm systems use contact switches to detect if a door or window was opened. Contact switches are very cheap and effective that is we always see them in home burglar alarm systems. A good burglar alarm system should used multiple sensors instead of being dependent on contact switches alone. Contact switches easily corrode in a very humid environment, thus it may not even trigger at all even if it was tipped.
E. Fire alarm system - Fire alarm systems mainly use Ionization smoke chambers which uses a radioactive material in detecting smoke. The radiation in ionization smoke chamber is very low and you should not much of a concern. The other type of fire alarm sytem uses silicon sensors to measure the temperature of a room and some more expensive setups use sensors that sniff the Carbon Monoxide levels in a room.
F. Diy alarm system - A DIY alarm system or homebrew alarm system uses contact switches, silicon temperature sensors, photodetectors and perhaps Capacitive or Inductive sensors. Some hobbyists also incorporate a programmable microcontroller like the PIC16F877A to further increase the accuracy of a diy alarm system.
What are the sensors used in an Alarm system?
A. Passive Infrared sensor - These are semiconductor devices that are sensitive to infrared. They can detect the heat coming from medium sized living things suchs as dogs, cats and humans. Most infrared sensors are used to detect the presence of fire in a building.
B. Proximity Sensors - Proximity sensors are divided into two types. First we have the inductive proximity sensor which is good in detecting metallic and magnetic objects. The other one is the capacitive proxmimty sensor whis can detect non-metallic objects such as plastics, oil, and of course flesh.
C. Contact Switches - They are similar to light switches but they are usually softer to press. A slight push would instantly turn on the device.
D. Photodetectors - Are semiconductor devices which are sensitive to light. Manufacturers of alarm system would typically used phototransistors or LDR when making a cost effective alarm system.
