Tampilkan postingan dengan label Rangkaian Alarm Kebakaran. Tampilkan semua postingan
Tampilkan postingan dengan label Rangkaian Alarm Kebakaran. Tampilkan semua postingan

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Alarm Kebakaran

Kamis, 15 Maret 2012 by skemarangkaian

Di dalam bagian ini di bahas tentang suatu rangkaian-sirkuit alarm,dan dalam bab kali ini adalah alarm untuk mengidentifikasi kebakaran. alarm seperti sangat penting bagi komplek-komplek perumahan yang padat sehingga adanya api bisa diketahui lebih awal,dan akan disajikan link-link ke situs-situs yang menyediakan tutorial elektronika dan free circuit. Untuk mendapatkan gambar yang jelas dari circuit ini klik pada gambar rangkaian tsb
Untuk alarm ini,sistem kerjanya adl bila ada asap yang ditimbulkan oleh api melewati antara bola lampu dan LDR sehingga penerimaan cahaya di LDR menjadi berkurang,sehingga nilai tahanan dariLDR menjadi lebih besar mengakibatkan tegangan diCOB/chip cukup untuk on/hidup,sehingga menghasilkan bunyi peringatan/alarm, dan suara tersebut diperkuat dengan amplifier TDA 2002 sehingga bunyi yang dihasilkan menjadi lebih keras.silahkan mencoba!!!! 

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Rangkaian Alarm Kebakaran NE555

Rabu, 14 Maret 2012 by skemarangkaian

Fire alarm circuit using LDR (Light Depending Resistor) as light sensor. It warns the user against fire accidents. It relies on the smoke that is produced in the event of a fire. When this smoke passes between a LED and an LDR, the amount of light falling on the LDR decreases. 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 NE555 then activated the alarm.

The thermistor offers a low resistance at high temperature and high resistance at low temperature. This phenomenon is employed here for sensing the fire.



The IC1 (NE555) is configured as a free running oscillator at audio frequency. The transistors T1 and T2 drive IC1. The output (pin 3) of IC1 is couples to base of transistor T3 (SL100), which drives the speaker to generate alarm sound. The frequency of NE555 depends on the values of resistances R5 and R6 and capacitance C2.When thermistor becomes hot, it gives a low-resistance path for the positive voltage to the base of transistor T1 through diode D1 and resistance R2.


Capacitor C1 charges up to the positive supply voltage and increases the the time for which the alarm is ON. The larger the value of C1, the larger the positive bias applied to the base of transistor T1 (BC548). As the collector of T1 is coupled to the base of transistor T2, the transistor T2 provides a positive voltage to pin 4 (reset) of IC1 (NE555). Resistor R4 is selected s0 that NE555 keeps inactive in the absence of the positive voltage. Diode D1 stops discharging of capacitor C1 when the thermistor is in connection with the positive supply voltage cools out and provides a high resistance path. It also inhibits the forward biasing of transistor T1.

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