You cannot beat the Chinese. The project described in this article is a ready-made item from a $2. 00 shop! And it is made in China! It is a wireless doorbell with a cost of about $10. 00. It is so cheap, you could not build it from components for $10. 00! So, we have to change our attitude to building projects and use items such as this to learn how
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things work and modify them to suit our own requirements. This doorbell uses quality components. It`s not rubbish. The circuit is quite unbelievable. You can not obtain some of the components individually and the effectiveness is magic. We have so much to learn! The first thing you will notice is the clever circuitry. Some of the design goes against everything we have learnt in electronics. That`s why we have to study other people`s designs and realise "the more you know, the more you realise you don`t know. " The oscillator circuit is very interesting, but first we will look at the RF oscillator. The doorbell operates on the 303MHz band and the 30 metre range (100ft) is obtained without the use of an antenna! The circuit is actually radiating from the printed track of the tank circuit. The Tank Circuit is a single-turn coil and a small capacitor (5p & 4p in parallel). In this project we show how to add a small antenna to the circuit to get double the range - plus two other improvements to increase the range. Some of the improvements will load the circuit and alter the frequency at which it operates. Others can be done without any effect on the circuit. Fortunately, the transmitting stage is what we call "tight" and is not affected by surrounding "stray capacitance. " The circuit has been kept near the power rails by the use of a choke in the positive rail. The positive rail is then reflected to the negative rail via the...
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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