This is a continuation of my previous article regarding class d amp using 555 timer chip. Looking back to several schematics on that article, some of you may wonder why I include another 555 as U2 in the drawing. The main purpose of this U2 is to establish constant frequency trigger on pin 2 of U1 in such a way of maintaining stable PWM carrier fr
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equency during audio input modulation. By scrutinizing the behavior of the circuit in LT spice simulator, and listening to their sound thru the breadboard circuit layout, the sound is good and clean. Of course there are some interesting ways in doing this but the most interesting thing for me to satisfy my curiosity is to try to use U1 alone without the trigger U2 to conserve space and cost to the lowest value as possible. In this case, by feeding back the output pin 3 to the RC time network on pin 6 & 2 the resulting switching mode is astable with 50% duty cycle. I tried to apply music to pin 5 as usual but noticed a distorting sound even at lower volume settings. Fig. 1 Schematic of 555 circuit with negative FB added. Please take note that 2N3904 varies on their hfe depending on it`s production binning. So you may get different sound quality due to this variations. Better opt for opamp if you want. By implementing negative feedback thru the help of 2N3904 transistor to self bias it in a conventional way, (see fig. 1) the resulting sound was so good that it seems better than the sound produced by using 2 chips. Why Well, I don`t have specific answer for this question at the moment and by observing the behavior of the waveforms while the circuit is being modulated reveals a mixture of PWM and FM at the same time. It is quite surprising for me to hear a music in class d amp having a mixture of PWM with FM owing to the fact...
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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