Function
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ASD 531, Technical description, T 140 416 en
2.2.2
Fan control
The physical and electrical properties of a fan cause a brief power surge when it is switched on and starts up, which in turn af-
fects the conductor dimensioning and the total power consumption of the fire alarm system.
A specially designed circuit therefore ensures that the fan cannot exceed a specific maximum power consumption in its start-
up phase. When the ASD 531 is switched on, the computer-controlled fan speed starts up slowly. After the fan has been pow-
ered up, the speed is kept constant.
Any blocking of the fan is detected by evaluating the motor speed. If the specified threshold is undershot, the fan supply is
switched off and a fault is signalled.
The ASD 531 aspirating smoke detector has a constant, specified fan speed. The speed is
5250 rpm
.
2.2.3
Microcontroller
The entire program and switching sequence is controlled by a microcontroller. The firmware is stored on a
Flash PROM
. Sys-
tem-specific configurations are stored in an EEPROM.
The program is monitored by the internal watchdog of the microcontroller. In the event of a failure of the microcontroller circuit,
an emergency fault is triggered. This is signalled on the device by the steady lit
Fault
LED. The “Fault” relay switches.