UM3561 high temperature detector circuit diagram
This heat detector alarm electronic project is designed using the UM3561 sound generator circuit and some other common electronic parts . This heat detector circuit project uses a complementary pair comprising npn and pnp transistor to detect heat .
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 .
The relay used in this project must be a 6 volt / 100 ohms relay and the speaker must have a 8 ohms load and 1 watt power .
This electronic project must be powered from a 6 volts DC, but the UM3561 IC is powered using a 3 volt zener diode , because the alarm sound require a 3 volts dc power supply .