The last section presented a number of basic free-air laser light communications projects. You learned how to modulate a He-Ne laser beam using a transformer, transistor, and even a piece of Mylar foil stretched in a needlepoint hoop. You also learned various ways to electronically modulate laser diodes and recover the transmitted audio signal. Th
Click here to download the full size of the above Circuit.
is section presents advanced projects in free-air laser-beam communication. Covered are methods of remotely controlling devices and equipment via light and how to link two computers by a laser beam. Everyone is familiar with Touch-Tone dialing: pick up the phone and push the buttons. You hear a series of almost meaningless tones, but to the equipment in the telephone central office, those tones are decoded and used to dial the exact phone you want out of the millions in the world. You can use the same technique as a remote control for actuating any of a number of devices, such as motors, alarms, lights, doors, you name it. The tone signals are sent from transmitter to receiver via a laser light beam. With the right setup, you can remotely control devices up to several miles away, and without worry of interference or FCC regulations. The Touch-Tone (or more simply tone control ) system supports up to 16 channels. Each channel is actuated by a pair of tones. Tone selection depends on the buttons pressed on the keypad. Dividing a common 16-key keypad into a matrix of 4 by 4, as illustrated in ill. 14-1, shows how the tones are distributed. E. g. , pressing the number 5 key actuates the 770 Hz and 1336 Hz tones. Pressing the number 9 key actuates both the 852 Hz and 1477 Hz tones. The dual tones help prevent accidental triggering, but they also present a somewhat difficult decoding dilemma. The first tone dialing circuits used...
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: