Fire alarm can be made with a light sensor (LDR) as in the article with the title of Fire Alarm with this LDR sensor. Principles of fire detection Fire Alarm with LDR sensor is to detect the presence of smoke through the LDR. LDR in the series Fire Alarm does not stand alone in detecting a fire, but the LDR in the pair with the light shining on the LDR.
Hence, in the detected smoke from the fire then the intensity of light received by the LDR LDR decreases and eventually trigger an alarm system on a series of Fire Alarm with this LDR sensor. Part 2 that in the series of Fire Alarm with Sensor LDR are some of the sensors, tone generator, audio power.
Circuit diagram of Fire Alarm with Light Sensor LDR
Function Section of the Fire Alarm with Sensor LDR
Part of LDR and light sensor facing to fire smoke detection
Part trigger using transistors and regulators as a trigger tone generator 7805
Tone generator section with IC UM66
Power audio section uses an audio power IC TDA 2002 which is equipped with voleme control (R3)