Shematic.net

Smoke content signaling (Fire-alarm system)

Smoke content signaling circuit (Fire-alarm system).

The device is intended for the timely warning about beginning of catching fire. A light weakens when smoke gets between a light-emitting diode D1 and photodiode D2. On this account resistance of photodiode begins to grow, and tension on the contact 2 microcircuits 555 goes down below than a 1/3 tension of power supply. The tension on the output 3 becomes high. This high tension (near +9 V) is used for the start of sound generator COB. A signal from a generator is given on the integrated circuit of note magnifier TDA2002. The sensitiveness of circuit relies on distance between a light-emitting diode and photodiode, and also from resistor R5. The Reset button provides cancel an alarm.

added 16.12.07 14:31:37 | looked over 10806 times