This section describes an experimental low power, low bandwidth data signaling system that was initially made to operate at 55 MHz (television channel 2 in the U.S.). Before operating a radio transmitter, find out what kind of transmitter operation, if any, is permitted in your locality. Radio transmitter operation is a serious legal matter. This design can be readily adapted to different frequencies and lower power levels. If you choose to build and operate the transmitter described here, you do so at your own risk. I'm only publishing this as an example of what can be done, and to show how easy it is to build a simple but functional receiver.
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This is a simple, low cost RF data link that can send data reliably over a distance of one to two meters, enough for bench top or desktop use. The data protocol supported by the encoder and decoder provides 16 device addresses, three message types, and a toggle bit. Pulse frequency modulation is employed to make the receiver design less demanding and to reduce the susceptibility to noise. The encoder and decoder are based on Atmel microcontrollers, though the protocol can be easily implemented on most micro controllers. The transmitter is an oscillator that is biased on and off by the encoder chip. The receiver is a tuned radio frequency (TRF) detector without preamp followed by an 40 db AF amplifier that drives a comparator, which provides pulses suitable for driving the digital input pin on the decoder. Most of the gain is provided by the op amp, where gain is easy and cheap, and the RF section is minimized and simplified.
The only things that really need any tweaking to get the demonstration circuits to work is one hand wound inductor in the transmitter and one hand wound inductor in the receiver. The trick is to get the transmitter and the receiver on the same frequency. Having them "almost" on the same frequency will result in poor performance - very short range and unreliable decoding. Use a small wooden or plastic tool to deform the coils. Expect to spend some time at it, and don't be disappointed if you have to...
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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