TREE

Here is an AC triggered Multitone, polyphonic doorbell. It gives eight melodious tunes for 2 minutes. On each press it will give a new tone which will continue till the melody is over. The circuit is too simple and battery operated It uses the popular melody generator IC UM3481. The circuit uses the popular melody generator IC UM3481. It generates music tones like Jingle bell, Santa clause is coming, Silent night, Holy night, Joy to the world, Rudolph, Red nosed reindeer, Merry Christmas, O come, All Ye faithful, Hark and the herald angel sing.UM 3482 generates 12 music tones. Capacitor C1 and resistor R2 are the oscillation components. Pin1 can be triggered either by DC or AC. Here low voltage AC is applied to the trigger pin 1 through R1 and D1. The circuit works off two pen cells which last for more than one year Polyphonic Door Bell Circuit Diagram Caution: The circuit is connected to high volt AC. Do not touch any parts when it is powered to avoid lethal shock AC187 Pinout

This is a simple project of Tandem Doorbell Circuit Diagram .The author had a problem: the neighbors  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. Tandem 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 t...