Wednesday, April 13, 2011

Smoke detector circuit

This causes the resistance of LDR to increase and the voltage at the base of the transistor is pulled high due to which the supply to the COB (chip-on-board) is completed. The sensitivity of the smoke detector depends on the distance between bulb and LDR as well as setting of preset VR1.
Thus by placing the bulb and the LDR at appropriate distances, one may vary preset VR1 to get optimum sensitivity.
We have not build this smoke alarm detector.

For smoke detector installation and maintenance use a near electrician.


  1. what exactly is the chip on board for the above circuit?

  2. Thanks for sharing the information. I found the information very helpful. I really like this post.

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  3. Thanks so very much for taking your time to create this very useful and informative site. I have learned a lot from your site.

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  4. what is this chip on board in this circuit.....plz explain this

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