In this fire alarm circuit project, a thermistor works as the heat sensor. When temperature increases, its resistance decreases, and vice versa. At normal temperature, the resistance of the thermistor (TH1) is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature ncreases beyond 100°C. The circuit uses readily available components and can be easily constructed on any general purpose PCB. Check out the fire sensor circuit.
Fire alarm circuit diagram
Timer IC NE555 (IC1) is wired as an astable multivibrator oscillating in audio frequency band. Switching transistors T1 and T2 drive multivibrator NE555 (IC1). The output of IC1 is connected to npn transistor T3, which drives the loudspeaker (LS1) to generate sound. The frequency of IC1 depends on the values of resistors R5 and R6 and capacitor C2. To prevent the thermistor from melting, wrap it up in mica tape.
The home fire alarm system works off a 6V-12V regulated power supply. LED1 is used to indicate that power to the circuit is switched on.
We have not tested this fire alarm systems project.
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dear can u give me description on fire alarm on ma id
it is very good circuit of fire alarm
am doin dis uin ma mini project . . .i need a brief desrription in working part
u call me on ma no. i had made this project in ma lst year
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y u gove number u flirt
i am doing dis project. so i need a brief description of working of dis circuit.
Will you please give me more information about this ckt diagram……
this circuit is not giving a proper output and the thermistor gets melted give a solution
pls what is the function of D1 and C1. i implemented the circuit without the two and it still worked.
are all thermistors having the same resistance?
sir,
iam doing this fire alarm as the miniproject.so, i want brief explanation in this aspect.
bullshit
please i need more information about
this fire alarm circuit diagram and the function D1 an C1
Please, I will like to write a project on fire alarm, can you feed me with information.
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Senfiretech: CAN U HELP ME ABOUT THE FINAL YEAR PROJECT what will be like this pproject etc..
Please sir, before the buzzer i thought there is supposed to be a relay.
Please sir what hels can we reprecent instent of thermistor
I maked this circuit and thsi is works
I maked this circuit and this is works
i m also made this ckt bt it will not work can u plz help me. what problem arises on this ckt … its urgent plz help me ……
I just like this
I was able 2 carry out this project and it worked.
sir,
iam doing this fire alarm as the miniproject.so, i want brief explanation in this aspect.
what else can i say?…..a very big THANK YOU!…this pretty small thing did saved my Electronics research lab from fire hazard. cheers!!!!
sir,
iam doing this fire alarm as the miniproject.so, i
want brief explanation in this aspect.
pls send it to my id.
give me ur id ill help u…….
hii… sir plz help me about this ckt
f u hav any information about this project
plz… send me fast becoz my project summit date is 28 navamber……… plz help me
i required more informatn bout it pls sir send it to my id
please give me the pcb layout and its working information on my id.
this circuit is working perfectly,but changing the value of the thermistor into 15k will increase the sensitivity of this circuit,thanks…:-)
thermistor that model you used?
i need more information to complete my project.plz snd it to my id.
sir, i’m doing this one as my mini projects
could u please send me the details regarding the working of this circuit.
plz give me the pcb layout at my mail id…
i required more informatn bout it pls sir send it to my id sir please.
what type of thermistor should I use? model?
Sir,as I am going to do this for my project,could you please help me in details of writing process and how does it work. As soon as possible
can i get the full details of the project…
Plz sir i want its Manual urjent…. Can u send me that ??????????
<3
this ckt put alram when it is kept in sun light…………..is thier is any way ?
Hai…..
Can i get more information about this project.like discription,component rage,working process…..anybody plz send to my id….
hiii..
if u hav any information about this project
plz… send me fast becoz my project summit date is 28 navamber……… plz help me
Hey. I’m in need of a circuit in addition to a fire alarm to warn of smoke and carbon monoxide as well. PLEASE. Help? Thanks
hello sir i need a complete discription abt tis prjct…. can we use this same circuit in AC rooms… what type of heating element should i use to explain…
A have made this circuit but it not works
Welcome the club of disappointed hobbyists. Remember that unlike humans, electrons never make mistakes.
First recheck your wiring avoiding assumptions like: I checked that detail before so it is OK.
Verify that T1 is NPN and T2 PNP. Measure cold resistance of thermistor.
Divide circuit in half and test part of it. For instance, tie pin 4 of the 555 to +6V to see if the audio annunciator functions.
Measure input voltage to D1 with voltmeter and determine that it changes with temperature.
To set the temperature threshold more accurately, it may be necessary to replace R8 with a 5K pot.
Above all, do not give up easily because what you eventually learn will improve your future trouble-shooting skills.
it is possible to make a special fire alarm basically for more marks in my project.
its really help me doing finish my project ,thank you and sir i want to learn more
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sir can u send me the pcb layout of this circuit… because i dont know how to make it and it is my project …
if snd it i m so thankfull to you..
please ask me………………………………..i make this project bu notwork……………….use bc549 and bc556 an replace sl100 with 2n2222 this can be my priblem?
ican measure thermistor with ohmmetr can i test it?
i made this circuit bt after giving suply it will not works . plz help me ….
This is a repeat of a reply made in Sept.
Welcome the club of disappointed hobbyists. Remember that unlike humans, electrons never make mistakes.
First recheck your wiring avoiding assumptions like: I checked that detail before so it is OK.
Verify that T1 is NPN and T2 PNP. Measure cold resistance of thermistor.
Divide circuit in half and test part of it. For instance, tie pin 4 of the 555 to +6V to see if the audio annunciator functions.
Measure input voltage to D1 with voltmeter and determine that it changes with temperature.
To set the temperature threshold more accurately, it may be necessary to replace R8 with a 5K pot.
Above all, do not give up easily because what you eventually learn will improve your future trouble-shooting skills.
everything is correct still its not working…