ffd

This doorbell system works such that when someone presses your calling bell switch during the night, not only the bell rings but the bulb connected to it also glows. In order to turn the bulb off, just press the reset pushbutton switch provided in the circuit. Place the bulb near the calling bell switch so that you can see the person pressing the calling bell before opening the door. So you can choose not to open the door to doubtful persons. During day time, the bulb doesn’t glow and only the calling bell sounds.  Doorbell with Security Feature Circuit Diagram When calling bell switch S1 is closed, the bell rings and simultaneously transformer X gets AC supply. The output of this 6V-0V-6V/500mA step-down transformer is rectified by diodes D1 and D2. The rectified output is filtered by 1000µF, 25V capacitor C1 and fed to the collector of transistor BC547 (T1) via 2.2k resistor R1. A light-dependent resistor (LDR) is connected to the base of this transistor. During the day, the LDR ...

The author had a problem: the neighbours  had exactly the same type of doorbell as he did (actually a 50 Hz buzzer), so it wasn’t always clear who needed to answer the door. To avoid confusion, the author augmented the existing doorbell with a wireless model a reasonably inexpensive option at current  prices. All that was necessary for this was to arrange for the existing button and wiring to also actuate the wireless doorbell. Circuit diagram : Tandem Doorbell Circuit Diagram The author opened up the button enclosure of the wireless doorbell and used a multi-meter to find out which set of contacts were closed when the button was pressed. This is where the relay output should be connected (see the schematic diagram). The circuit is virtually self-explanatory: when the existing doorbell button is pressed to actuate the  buzzer, the voltage is rectified by the bridge rectifier and regulated at 5 V by the 7805. This voltage drives the relay directly, causing the switch in the wireless ...

This doorbell control porch light using timer ic (ne555),can be used in doorbell in order to get indication of porch light with door alarm if any one rings the door bell. Doorbell Control Porch Light Circuit Diagram: The circuit of doorbell control porch light is build around timer IC NE555 (IC2) and is here used as astable multivibrator. The output at pin 3 goes high of IC1 when trigger is given to pin 2 from power supply. Here transistor T1 is used as relay driver transistor which energized relay when output from pin 3 of IC1 is high. After relay energized AC current flow via N/O terminal and switch on the porch light. Triac1 with Diac1 hear is used for switch in order to glow porch light during night and switch it off at day with the help of preset VR1 and LDR1. Note:- Here the power source of 230V AC is replaced by 110V with replacing transformer having primary 110V and secondary 12V. Rest of the circuit  of door bell controll porch light is same. PARTS LIST : Resistors (all ¼...