Wireless controlled Door-bell

Posted on Feb 6, 2014

The controlling range of wireless doorbell is 100M. Transmitter:- This transmitter section is designed around oscillator transistor (BF194B) T2 followed by two transistor (BC148) T1 and T3. Transistor T2 generate special radio frequency determined by trimmer (variable capacitor) and coil. Transistor T1 is used as pulse generator. The output from transistor

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T3 is given to emitter of transistor T2 in order to get radio frequency from its collector. Trimmer VC1 is used to adjust the transmitter frequency. An aerial is used to receive the transmitted frequency from remote which is further amplified by amplifier and trigger circuit. The whole receiver circuit utilizes seven transistors. Transistor T4 get frequency from hand unit and further send to tuned circuit made from capacitor C6 and coil L2. Transistor T5 is used as comparator which further send amplify voltage to capacitor C11 for filter. The filter voltage is passed through detector stage i. e. rectify and given to base of transistor T6. Transistor T6 is adjusted in amplifier mode for amplifying the signal voltage. The amplified voltage from transistor T6 is given to base of transistor T7, used in complementary mode. The positive voltage at collector of transistor T7 let transistor T8 in conducting state and T9 in non- conducting state. The positive voltage available at collector of T9 is given to base of transistor T10. Transistor T10 is used here in blocking oscillator mode which further produces bird sound combining with output transformer.

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