Hey guys, I am building this circuit for my mini project.

http://circuit-diagram.net/wp-content/uploads/2012/04/simple-fire-alarm-circuit.jpg

I tried this for like 10++ times already and it doesnt work for me! I do not know what is the problem. Do not know how to troubleshoot yet

Please, anyone can confirm to me whether this circuit is a working circuit or not ?

Thank you

 

okk, why not draw what you have set up? ignore that picture, and draw what you have actually built? also post pictures.. that diagram when your finished.. and do you have an oscilloscope?

 

What sort of thermistor have you use?

 

The schematic posted looks valid.
If reset (pin 4) = high, then run.


Likely error is the thermistor vs 470 ohms as noted by paulktreg

 

The schematic posted looks valid.
If reset (pin 4) = high, then run.


Likely error is the thermistor vs 470 ohms as noted by paulktreg

I am now using LDR...How can I able to increase the sensitivity of the LDR? Now I have to make it really dark to activate the alarm instead a light dark room

Thank you

 

I am now using LDR...How can I able to increase the sensitivity of the LDR? Now I have to make it really dark to activate the alarm instead a light dark room

Thank you

you need to adjust the lower resistor, so that the transistor comes on when its suitably dark.. just trial and error. you can use maths but trial and errors more fun