About Crystals in microcontroller......

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Discussion Overview

The discussion revolves around the functioning of external quartz crystals in microcontrollers, specifically focusing on how these crystals generate electrical frequencies and the role of mechanical vibrations in this process. The scope includes technical explanations and conceptual clarifications regarding oscillator circuits and piezoelectric properties.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the source of mechanical vibrations needed for the quartz crystal to produce electrical pulses when connected to a battery.
  • Another participant states that the quartz crystal does not generate an electrical frequency by itself but is part of an internal oscillator circuit when connected to a microcontroller.
  • A different viewpoint describes the quartz crystal as behaving like a high Q LC circuit that can oscillate at a specified frequency when placed in the correct oscillator circuit and loaded appropriately.
  • Historical context is provided regarding the ability to slightly change crystal frequencies by physical alterations, such as sanding or using pencil lead.

Areas of Agreement / Disagreement

Participants express differing views on the role of the quartz crystal in generating electrical frequencies, with some emphasizing its passive role within an oscillator circuit while others explore its mechanical properties. The discussion remains unresolved regarding the exact nature of mechanical vibrations and their necessity.

Contextual Notes

There are limitations in the discussion regarding the assumptions about mechanical vibrations and the specifics of oscillator circuit designs, which are not fully explored or defined.

ujjval rathod
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I have a question that if we use external quartz crystal in Microcontroller and connect it to battery... Crystal gives regular and very accurate electrical frequency... But it should get mechanical vibration from somewhere to give electrical pulses... From where it receives mechanical vibrations?
 
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The crystal does not do anything by itself.

The quartz-crystal is a piezoelectric material, and you can apply a voltage across it. The crystal, when it is connected the microcontroller, becomes part of an internal oscillator circuit.

There are different ways to make an oscillator circuit. Try reading through the following link:

http://www.electronics-tutorials.ws/oscillator/crystal.html

So just to summarize: The crystal does not output an electrical frequency.
 
The quartz crystal essentially behaves like a high Q LC circuit tuned to the specified frequency. Put it in the proper oscillator circuit and load it correctly and it will cause the circuit to oscillate at the correct frequency.

Back in the olden days we could change crystal frequencies slightly by sanding the quartz or scribbling on it with pencil lead.

FT-243+Crystal.jpg
 
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