Pressing the pushbutton of the transmitter, a sound and/or light alert is activated in the receiver. The system uses no wiring or radio frequencies: the transmitted signal is conveyed into the mains supply line. It can be used at home, in any room from attic to cellar, simply plugging transmitter and receiver in the wall mains sockets. Transmission range can be very good,
Click here to download the full size of the above Circuit.
provided both units are connected to the mains supply within the control of the same light-meter. Q1 and Q2 are wired as a Darlington pair to obtain the highest possible output from a Hartley type oscillator running at about 135KHz frequency. The 220Vac mains is reduced to 30Vdc without the use of a transformer by means of C1 reactance, a two diode rectifier cell D1 & D2 and Zener diode D3. The 135KHz sinewave generated by the transmitter is picked-up from mains wiring by C1 and selected by the tuned circuit L1-C3. Q1 greatly amplifies the incoming sinewave and converts it in a 12V-peak squarewave. D4 & D5 limit the input voltage at Q1 base to less than 1V-peak to avoid damaging of the transistor due to the high voltage transients frequently occurring on the mains line. D6 eliminates any negative component of the signal and Q2 drives the load. C7 is necessary to smooth the signal residues appearing across the load. The tuning of the coils at 135KHz frequency should be obtained with the ferrite core almost totally inserted in its slot, if 455KHz IF transformers are used for both L1s. Using IF transformers different from those specified, a change in both C3s value can be needed. The value of these capacitors may be varied from 1 to 3. 3nF but must be the same in transmitter and receiver. The load can be a beeper, a LED or both. Omitting the beeper and choosing the LED as the only load, its limiting resistor R7 should be...
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.....
characters left: