This circuit generates the sound of the electronic ringer found in modern telephones, supplanting the 2-bell electromechanical ringers used previously. The ringing pattern follows the United States convention of 2 seconds on, and 4 seconds off. During the `on` interval, the tone alternates between two selectable frequencies at a rate of 20Hz. Refe
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ring to the schematic, NAND Schmitt trigger U1A is configured as a relaxation oscillator, adjusted with RV1 for a 40Hz waveform at test point TP1. This waveform is divided by flip-flop U2A to provide a 20 Hz, 50-percent duty cycle square wave at U2A`s Q output, and a complimentary square wave at U2A`s Q-not output. When U2A`s Q output is high, the relaxation oscillator formed by U1B is enabled. When U2A`s Q-not output is high, the relaxation oscillator formed by U1C is enabled. NAND gate U1D provides an OR function for the two oscillator outputs, and drives flip-flop U2B, which divides the waveform by two to ensure a 50 per-cent duty cycle. The resulting waveform at U2B`s Q output is a square-wave that alternates between two audible frequencies at a 20Hz rate. The pitch of these frequencies are individually adjustable from approximately 500Hz to 2500Hz with RV2 and RV3, and may be selected for a suitable sound output. A frequency divider chain consisting of U4, U5 and U6 is driven from the 20Hz waveform at U2A`s Q-not output. U4 and U5 provide a frequency division of 40, resulting in a 0. 5Hz square wave at U5B pin 13. This square wave drives U6, which is configured as a divide-by-3. U6`s "0" output is a 0. 167Hz waveform which is at a high state for 2 seconds, and a low state for 4 seconds. Paralleled gates U3A and D, driven by U2B`s Q output, drive one side of the piezo audible transducer, as well as the inputs of two...
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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