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A very simple heat detector alarm electronic project can be designed using the UM3561 sound generator circuit and some other common electronic parts . This heat detector electronic circuit project uses a complementary pair comprising npn and pnp transistor to detect heat Collector of T1 transistor is connected to the base of the T2 transistor , while the collector of T2 transistor is connected to RL1 relay T3 and T4 transistors connected in darlington configuration are used to amplify the audio signal from the UM3561 ic. When the temperature close to the T1 transistor is hot , the resistance to the emitter –collector goes low and it starts conducting . In same time T2 transistor conducts , because its base is connected to the collector of T1 transistor and the RL1 relay energized and switches on the siren which produce a fire engine alarm sound. This electronic circuit project must be powered from a 6 volts DC power supply , but the UM3561 IC is powered using a 3 volt zener diode , bec...

D. Mohan Kumar is most popular in India for his electronic project, to day i share his project with you. This simple circuit monitors the mains distribution box constantly and sounds an alarm when it senses a high temperature due to overheating, helping to prevent disasters caused by any sparking in the mains box due to short circuits. It also automatically switches on a bright white LED when the power fails. The LED gives ample light to check the mains box wiring or fuses in darkness. The circuit beeps once when power fails and again when power resumes. The AC mains is stepped down by transformer X1 to deliver a secondary output of 9V AC at 500 mA. The transformer output is rectified by diodes D1 through D4. Capacitor C1 bypasses the ripple. LED1 indicates the power-on condition. Resistor R1 acts as the current limiter for LED1. Simple Mains Box Heat Monitor Circuit Diagram Germanium diode D5 (1N34) is the temperature-sensing element, which is connected in the reverse bias mode. At no...