MIRROR: G K BHAT
The aim of installing the detectors in fire safety system to alert the people on time. Therefore the detectors are connected to main control panel of the system. When the alarms are generated, the hooters are activated. However at high noise areas, the hooter sounds are not audible some time. To overcome this problem, strobe lights are fitted at various places. The strobe lights are the light emitting devices in the form of flash lights. The intensity of the flash should be minimum 30 meters from the device. The flash of the light should capable of alerting the people who are standing at a distance of thirty meters facing towards opposite side or in other words , the person whose back is towards the strobe light should able to visualise the flash of the light emitted by the strobe light .
The hooters and strobe lights get activated either through detectors or when manual call points are activated. When the detectors are activated due to various conditions as we discussed in our previous discussions, the signal from the device is transmitted to the fire control panel. The fire control panel activates the alerting systems.
The alerting systems are built in at the location of control panel and at all over the places where these alerting devices are located. These devices are connected through the cables running for the purpose. There is no requirement of running separate cables for detectors and alarms. The common cable for both can be used. However the load on the respective cards of control panel will be as per the manufacturers’ specifications.
The logic can be built in the system for alerting such a way that the entire premises by activation of a single device or alerting the particular zone where the activation has taken place. When any device is activated people will get alerted. If we activate the entire premises, where there is no any threat of fire, it will be wastage of time and creating panic, where it is not necessary. Therefore always it is better to alert the people of affected area only. To enable this logic, the zones have to be created and loops of the system have to be designed in such a way that, when the system alert is sent it should be to only the effective zone. We will discuss the same when we discuss the fire control panel and its design.
The logic of the fire alarm is made by transmitting the alert signal by the device to the control panel. The control panel immediately get activated and supplies the required power to the devices to get it activated.
a typical strobe light circuit diagram is shown below
The strobe light should have a good metal reflector placed at the backside of the light so that intensity of the light is increased.
The strobe light can be part of the hooter or it can be a separate device. In the fire control panel, there are separate cards provided for hooters and strobe since the required supply of power is different. However it is based on the system and its design.
We will discuss in detail about the hooters used in fire detection system in our next topic.
G K BHAT
MIRROR: G K BHAT