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Fire Alarm Control Panel

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bing2005

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I want to design a conventional fire alarm control panel with PIC16F877A.
I want this device compatible with most of the conventional detector.
How i going to do it? How i design a system that can support different type of detectors?
Thanks a lot.
 

Most of fire detectors will have just a relay "Normally Closed" which can be easily connected to 0-5V system with PIC. Some industrial fire detectors will have 4-20mA output but the also support a relay option (example: **broken link removed** ). If you design an input that if required will support termination resistor to convert current to voltage you will cover this option too.
There is also a way of sensing faults in cables (by adding resistors in series and sensing resistance value when the loop is closed) and this method is used in good alarm systems. In this case instead of having simple digital input you add a window comparator build of 2 simple opamps (LM324, 358 ...).
Regards,
IanP
 

Thank you so much for your responsed.
So far, i had try to use a heat detector and a smoke detector within my design. It works fine because their output were around 4.4Vdc when triggered.
These detectors using 24Vdc as their supply voltage.
Do you have any idea that detect the signal from these detectors through 24Vdc?
Thanks again!!!
 

The easiest and safest way will be to use an optocoupler and connect 24V output through a resistor to input diode, and the output from OC transistor can be directly connected to PIC's pin.
Regards,
IanP
 

Yes, i used optocoupler now.
I found that some fire alarm control panel used DF005 in their input.
How do this IC function?
It is a single phase bridge rectifier.
It can support DC input as well??? Or only AC input?
Thanks a lot!!!
 

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