Comments on: Low cost fire alarm circuit.

By: Denz

Denz — Thu, 23 Jun 2011 13:46:10 +0000

Hi guys.. the circuit may work but take note you can’t use it as a standard fire alarm in rooms especially ventilated one,you need to heat the room first or the room is already on flames to activate the alarm and you can’t control the fire anymore. For kitchen you can used heat sensing alarm like this and other fire alarm circuits using heat sensing component such as thermistor where smoke alarm will be not suitable but for rooms use smoke alarm which is cheaply available for safety reason.

By: zia

zia — Sat, 28 May 2011 06:09:38 +0000

hi!
it’s realy works.

By: swapnali

swapnali — Wed, 12 Jan 2011 14:47:30 +0000

hi!this is swapnali(TE E&TC)student..i want miniproject with report or with more ideas.so please sir help me…

By: rohit

rohit — Wed, 17 Nov 2010 13:26:11 +0000

it will be helpfull 4 us if u provide a vedio

By: Seetharaman

Seetharaman — Sun, 03 Oct 2010 09:24:56 +0000

Hi Zack you can replace it with 2N2905. the symbol shown for Q3 is wrong it should be similar to Q1 as it is also a PNP transistor

By: zack

zack — Sat, 02 Oct 2010 15:11:23 +0000

sir i hv try to find Q3 AC128 but unvailable,can i change that AC128 to another trans?
help pls

By: juls

juls — Tue, 17 Aug 2010 05:32:24 +0000

can i supply this ckt by 24 volts? and regarding the n.c – n.o output of this ckt is it respect to ground or to the com. terminal of the relay.

By: juls

juls — Tue, 17 Aug 2010 05:22:58 +0000

hi, i want to know how to connect the detector to the ckt. from the base of bc177 respect to the ground?

By: seetharaman

seetharaman — Thu, 17 Jun 2010 07:02:22 +0000

Hi Elgardo you are right Q3 is wrongly shown as NPN transistor it should be PNP with collector to relay and emitter to positive. otherwise the circuit is correct and will work as per the design.

By: Edgardo Diolola

Edgardo Diolola — Thu, 17 Jun 2010 06:05:53 +0000

Sir,
I am studying the circuit diagram and I got confused.
Is it the collector of Q2 will be connected to the base of Q3? (It says on the text :The emitter of Q2 (BC 108)is connected to the base of Q3(AC 128).)
Or is this a typographical error?
Please help.