Where good frequency stability is required, in applications such radio transmitters, basic LC oscillators cannot guarantee to hold their frequency without some drifting, which can be caused by quite small changes in supply voltage (although stabilised power supplies help avoid this) and changes in temperature. The effects of resistance and stray
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capacitance within the circuit can also cause the oscillator to operate at a slightly different frequency from that calculated using just the values of L and C. In most cases this can be overcome by making the tuned tank` circuit have as high a Q factor as possible. With ordinary inductors and capacitors, Q factors more than a few hundred are not possible, but by using quartz crystals Q factors well in excess of 10, 000 can be achieved. Crystals may be used increase frequency stability in RF oscillators such as Hartley and Colpitts. The crystal may be used either in parallel mode` e. g. as an inductor operating at a frequency between ’1 and ’2 as part of the resonating tuned circuit, as shown in the crystal controlled Colpitts oscillator in Fig 2. 5. 1, or in series mode` where the crystal is acting as a highly selective low impedance at ’1 in the feedback path as shown in a Hartley oscillator in Fig. 2. 5. 2. The quartz crystal is a piezo-electric device, and will both produce a voltage across it when it is subjected to some mechanical distortion such as slight bending, or will distort slightly when a voltage is applied across it. Therefore applying regular voltage pulses will cause the crystal to bend, and the bending will in turn create voltage pulses in phase with the applied pulses, that will reinforce them and cause oscillation. The frequency at which this reinforcing effect occurs is the resonant frequency of the...
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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