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Why crystal oscillator used for microcontrollers?


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Answered 2013-12-19 20:25:26

Oscillators are connected externally with the microcontroller to provide high frequency signal to the oscillator circuit in the microcontroller. The oscillator circuit provides the clock signal to the micro controller. Usually "PIEZO CRYSTAL OSCILLATORS" are used in micro controllers.

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crystal oscilators mostrly of 11.05.... or 12MHz are used with microcontrollers,


Crystal Oscillators are more stable oscillator. and used as Local Oscillator in Radio Receivers


a crystal 32.768kHz oscillator.


A local oscillator can be a crystal oscillator.


The oscillator provides the basic clock of a microcontroller to be able to execute the instructions in a stable, periodic way. It is often used for other peripherals too, like timer, UART, etc. as frequency base, usually divided by a clock divider for integer factors, or by PLL for rational factors. If the timing accuracy of these functions is not important, a simple RC oscillator can be used. Many microcontrollers have it internally. Accuracy is in 1...10% range. For better accuracy and temperature stability, a resonator can be used. For applications where timing is critical, a crystal can be used. Most micros have built-in oscillator, so only a crystal and two caps are needed. For those which have no built-in oscillator, external crystal oscillator module may be used. There are OCXO and TCXO modules available for very high stability needs.


To increase the efficiency. Comparison between crystal oscillator and ceramic resonator.


A quartz crystal oscillator with the crystal kept in a constant temperature oven.



oscillator frequency is different.crystal working piezo electric effect


c1 and c2 capacitors with crystal eliminates the Harmonics(Unwanted frequencies) .


A crystal oscillator is often used in very delicate clock mechanisms such as those in high performance computers, medical equipment and sometimes even space technology for N.A.S.A.


SOME kind of oscillator is required, to create the AC signal that will be modulated, amplified, and eventually sent up to the antenna to be transmitted. It doesn't have to be a crystal oscillator, though.


A: Crystals are mechanical oscillator and depending on the mass they will oscillate at a specific frequency.



we can use rc or lc oscillators also but crystal oscillator makes it to have longer life time


Piezo-electric quartz crystals are used to define the frequency in a crystal-controlled oscillator. Quartz is a hard material that tends to oscillate mechanically at a high frequency (up to about 20 MHz) when maintained by the maintaining amplifier. The signal produced is far more stable and predictable than an L-C oscillator, especially when the crystal is placed in a dedicated oven with a controlled temperature.


the crystal is used to produce oscillations according to the signal received and send through mobile.vibration in mobile is only due to crystal circuit


difference between local oscillator and controlled oscillator


Crystal oscillators are piezeoelectric materials since they works on the principle of piezeoelectric effect. piezeo means squeeze or press .This effect states that electric charge accumulates when a pressure or mechanical stress is given. Crystal oscillator is the most used oscillator in digital circuits, Because of the following advantages when compared with Hartley and colpitts oscillator. 1.Stable at high temperatures 2.High frequency response 3.Good resonance 4.High frequency stability 5.More oscillations are produced 6.good resonating or operating frequency crystal oscillator gives desired frequency of oscillations for given bias voltage, since, Digital circuits works on clock pulse signals so crystal oscillator suits for this applications.crystal oscillator has wide range of applications.Depending up on type of applications type of crystal changes in the oscillator circuit.There are three types of crystal used in oscillators.They are: 1. Rochelle salt crystal 2. Tourmaline crystal 3. Quartz crystal This type of crystal differs in there characteristics i.e., 1.Mechanical strength 2.Frequency of oscillations Here different crystal have different resonating frequency. Among this crystals quartz crystal have moderate or optimum characteristics while Rochelle salt crystal has less mechanical strength and output is good and it is vice versa for tourmaline crystal.output is AC in crystal oscillators. In this way each crystal has there own Applications. Eg:-signal generators,oscilloscopes, electronic gadgets like computers,digital watches, calculators,radios,cellphones etc.


frequency of an oscillator crystal


for accurate time rc oscillator is common in non time critical stuff


microprocessor's speed is determined by its clock rate. is normally determined by the frequency of an oscillator crystal . Typically a crystal oscillator produces a fixed sinusoidal waveform.


A: When exited a crystal will oscillate at precise frequency due to its mechanical make up. An electronic oscillator external influences can make it to shift frequency very easily


IF = Intermediate Frequency A crystal oscillator is an oscillator circuit whose frequency of operation is primarily decided by the frequency for which the crystal was cut. An intermediate frequency oscillator is the oscillator which operates at a specific frequency depending on it's purpose. For an FM receiver, the IF is 10.7MHz. For an AM receiver, the IF is 455kHz. For TVs, it's different for the luminance/chrominance/audio information. When two frequencies are sent to a nonlinear mixer circuit, the frequencies output include both the original inputs, F2-F1, and F2+F1 where F2 is the higher frequency. So, if Fs (signal from antenna) and Fi (intermediate frequency, say 10.7MHz) are both sent to a nonlinear mixer, then Fi+Fs (along with others) will be output, which means that your desired signal (music from the radio, etc.) is NOW on a 10.7MHz carrier, where it can be singled out (via filter) and the signal is worked with at 10.7MHz instead of potentially 107+MHz. It's a lot easier to design a circuit at 10.7MHz then it is at 107+MHz. If the crystal is cut to resonate at the IF, a crystal oscillator can be used for the IF oscillator. So, the IF oscillator COULD be a crystal oscillator. Hope that helps :-)


There are two kinds of crystal oscillators. One operates at what is called the "series resonance" of the crystal. This resonance is the frequency at which the (AC) impedance between the pins of the crystal is almost zero. The frequency is independent of how much capacitance happens to be in parallel with the crystal - its inside the oscillator and part of the circuit board, etc. But, even frequency that the oscillator runs at.The other kind of oscillator oscillates at "parallel resonance"of the crystal. At this frequency, the impedance from pin to pin of the crystal is almost infinite. This frequency depends on how much capacitance is connected in parallel with the crystal. This parallel capacitance is called "load capacitance". Generic signal-inverter oscillator is this kind of oscillator.The common oscillator connection is for the crystal to be connected from the inverter output to the input. And, there is a capacitor at each end of the crystal to ground. The NET load capacitance is SERIES equivalent value of those two capacitors.PLUS stray capacitance from the circuit board and the guts of the oscillator. Suppose that the crystal is rated for 22pF load capacitance. The stray capacitance is about 7pF. So, that leave 15pF to be made up from discrete external capacitors. If the external capacitors are equal, then their equivalent is half of their individual value. Thus, in this case, we would want a pair of 30pF capacitors.



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