I usually can`t hear the doorbell when I`m in the basement. This project describes how to add an inexpensive remote doorbell to your existing household doorbell. My doorbell runs off of a 24VAC transformer that is live all the time. Someone presses the button and the bell sounds. To implement this project, it is necessary to tap 3 conductors from the system: 24VAC,
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common, and doorbell. The doorbell signal is the one that is live only when the button is pressed. You also need a remote doorbell kit. I found a very inexpensive one on eBay, consisting of a small transmitter unit with a pushbutton, and a receiving unit with a speaker. The transmitter is very simple. It takes a tiny 12V battery (supplied), and you`re supposed to stick it next to your door with double-sided tape. The receiver takes 2 AAA batteries. As a bonus it sounds numerous tunes, including christmas carol jingles, so you`re bound to find one that you like. I don`t like products like this that use batteries that require replacement, and you`ll find in my project none are needed. I designed this circuit for the sending unit: A 555 timer, powered on all the time, is used as a timed one-shot. The timer is triggered by the signal from the doorbell button, conditioned by a 78L12 regulator and a 2N3904 transistor. The remote transmitter is triggered by the output of the 555, using a small reed relay. The relay I used was a 5V unit, so I placed a 560 ohm resistor in series to the 555 timer. 12 volts from the relay switch is applied to the transmitter module battery terminals. Oh yes, you must short the pushbutton in the transmitter module for this to work! Remove the transmitter from its case, short out the pushbutton and connect two wires to the battery terminals. When the doorbell button is pressed, the 555 is triggered and...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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