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Simple HomeMade Fire Alarm Control Panel Circuit

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tomhop16

New Member
Hello all,

i am designing a simple fire alarm system consisting of some smoke detectors, and i control panel , so far i have one smoke detector which i have fitted with a relay.

the fire alarm circuit is going OK so far but i am using more relays then i would like to as i dont have enough and dont want to have to buy any, is there anyway i can use transistors instead? i have loads of diodes and loads of resistors and some transistors. the circuit is allot more complicated then it probably needs to be but any suggestions of how i can make it better would be much appreciated.

also, how am i going to get the relevant led light to come on when its detector is activated?

Please look and the schematic and i would be thankful of any suggestions of improvement, thanks,

Tom :)
 

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Gary B

New Member
You should be able to get away with 1 relay to drive the siren. Put power to one side and the relay on the other to ground. Connect power to one side of the relay through a momentary NC switch. Ground from any detector through a diode will pull in the relay sounding the alarm. Also connect that ground through another diode so the relay locks until the cancel switch is pushed. If you connect a LED from the input side of the diode to power through the appropriate resister (about 330 to 470 ohms), you can even see active zone sources.

Since I don’t see from your drawing how much current a detector can sink, you may need to include either a transistor driver or a very low current input relay for each zone.
 

tomhop16

New Member
Hi Gary,
sorry for the long gap, ive been busy lately and haven't had time for this project, i understand what you said and i have some idea now of what im gonna do :) thanks for the reply, il let you know how i get on when i get round to it :)

Thanks :)
 
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