The idea is like a kid on a swing, though. This keeps it oscillating. And like the kid on the swing, it oscillates best at a fixed frequency. Wikipedia is nearly unreadable on this topic. It makes perfect sense and helps a lot. Perhaps we have different levels of understanding the English language. Sorry for the double post if only there were an edit button , but maybe Jake is right.
Perhaps I should stop visiting this site. Fewer readers. We try to put it at a level all can read, but evidently not always. Thanks, Jenny. It really is a good article. I just have the typical blindspots associated with being self taught. Keep up the great work. John, stuff about oscillators in general is where electronics starts to get pretty hairy. Thanks, Nop. Hey, this is HACK a day.
Look up, see the video that Dan posted? See the big boxed crystal with the case that is held shut by Philips screws? Those things are ancient but.. The neat thing is that since they are so large and easy to take apart you can hack their frequencies.
Many hams used to and a few still do take the case apart, remove the crystal wafer and draw on it with a pencil. A less common but also possible hack is to actually scrub the crystal with some sort of abrasive cleaner in order to shave just a little thereby raising the frequency.
It does work with smaller, more modern crystals too. You just have to very carefully cut the can open and solder it back shut or something when you are done. What kind of quarz or clock should I use considering price and practicallity? It looks like a TCXO would do the job to keep the frequency to my micro controller Atmega running Arduino for example stable enough to minimize the drift over that 30min timespan?
Does it need to remain synchronized with something else? How accurate is the other thing? How are you going to sync them to each other? Are you certain you need that degree of accuracy? For example if CL is Incorrect capacitor values will pull the crystal frequency slightly off the intended value. For frequency-critical applications such as frequency counters or instrumentation, a small variable trimmer capacitor may be used on one side, and the frequency adjusted with an accurate frequency counter.
I went through this exercise for the Crazy Clock. Even with the calculations, I wound up trying a bunch of crystals and a bunch of cap values until I found a pairing that was close. Even then, I wound up with a batch calibration factor so that the entire batch winds up box-carring inside of 10 ppm, which is the crystal tolerance that I apply to the timing in software.
That also allows me to calibrate individual units and apply the actual calibration for a specific crystal value-add service :D , which gets the initial drift down nearer 1 ppm or maybe ppb the calibration granularity is ppb. Great article. A number of years ago I worked at a plant that grew synthetic quartz for these applications, and before leaving the owner gave me a scrap bar. It weighs something like 10 kg and would have been wafered and used to make thousands of discrete parts.
Their business took a big hit when digitally synthesized tuning became a thing and CBs stopped needing 40 crystals. Thanks for this article.
I appreciated your clear wording and the use of humorous section titles and many illustrations. Please be kind and respectful to help make the comments section excellent. Comment Policy. This site uses Akismet to reduce spam.
Learn how your comment data is processed. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies. The devices with two pins are not oscillators, they are resonators crystals , which can be used in an oscillator circuit such as a Pierce oscillato r , and if used with the correct circuit will oscillate at or near the marked frequency.
The devices with four pins are complete circuits including a resonator and an active circuit that oscillates. They require power and output a square wave or sine wave output at or near the marked frequency. There are also ceramic resonators with three pins that act like crystals with capacitors. The way crystals and ceramic resonators work is that they are made of a piezoelectric material that produces a voltage when they are distorted in shape. A voltage applied will cause a distortion in shape.
The crystal is made into a shape that will physically resonate like a tuning fork or a cymbal at the desired frequency. That means that the crystal will act like a filter- when you apply the desired frequency it will appear like a high impedance once it gets vibrating, and to frequencies a bit different, it will be more lossy.
When put in the feedback circuit of an amplifier, the oscillation will be self-sustaining. Much more, and some math, here. If you think of a crystal as being a tiny bell, it's easy to see how, if you hit it with a tiny little hammer, it would ring with a pure tone just like a big bell would if you hit the big bell with a small hammer.
That's exactly what a crystal does, but the trick is that it's made of piezoelectric material which makes electricity when you hit it and changes shape when you shock it with electricity.
To make it produce that pure bell-like tone continuously, it's connected across an amplifier which works just like someone pushing you on a swing so that when you got to just a little past the peak of one swing they'd give you a push to make sure you came back for the next one. The piezoelectric nature of the crystal causes it to change shape when the amplifier output "pushes" it with an electric signal, and then when the amplifier lets go, the crystal springs back and generates its own signal which says "push me", and sends it to the input of the amplifier at just the right time for the amplifier to generate another push and regenerate the cycle, forever.
There's noise everywhere, and it's like zillions of tiny hammers hitting everything all the time. Some of that noise hits the crystal, and when it's hooked up to the amplifier and starts to ring a little from the noise hits, the amplifier gets the electrical signal from the crystal's physical ringing tone frequency , builds it up, and sends it back to the crystal.
That makes the crystal change shape even more, sending a bigger signal back to the amplifier when the crystal's shape springs back, until the system is oscillating continuously and is stable. A crystal does not oscillate on its own. You don't simply apply power and get oscillations out.
Think of a crystal as a very accurate and sharp frequency filter. You put it in the feedback path of a amplifier in the right way, and it causes the circuit to oscillate at the crystal's resonant frequency.
It's the circuit that causes the oscillations. They crystal kills all the frequencies except the one it's tuned for, which only allows enough overall loop gain for the circuit to oscillate at the crystal's frequency. Crystals below their resonant frequency appear mostly capacitive. Above their resonant frequency, they appear mostly inductive. At their resonant frequency, they appear mostly resistive.
Re-draw the Pierce oscillator three times, replacing the crystal with one of those components. It may help you understand how it works. Parallel resonant crystals are actually specified a little bit under the fundamental frequency. This makes the crystal appear a bit capacitive at the spec'd frequency. The additional capacitance adds a bit of additional phase shift to help the oscillator start and run.
The amplifier's input sees a bigger signal near the crystal's fundamental resistive, typically under Ohms ESR. The smaller off-frequency signals are diminished or blocked, so a signal at the fundamental frequency grows stronger after being amplified and dominates.
Push someone on a swing. No matter how hard you try, the swing really will only move back-and-forth at some fundamental frequency. Imagine a crystal as the surface of the water.
The crystal oscillators are used in research and measurement for the celestial navigation and the space tracking purpose, in medical devices and in the measuring instruments. There are many industrial applications of the crystal oscillator. They are widely used in computers, instrumentation, digital systems, in phase-locked loop systems, modems, marine, telecommunications, in sensors and also in disk drives.
Crystal Oscillator is also used in engine controlling, clock and to trip computer, stereo, and in GPS systems. This is an Automotive application. Crystal oscillators are used in many consumer goods. For example, cable television systems, video cameras, personal computers, toys and video games, cellular phones, radio systems.
This is the Consumer Application of Crystal Oscillator. We believe that the information given in this article is helpful for you for a better understanding of this concept. Furthermore, any queries regarding this article or any help in implementing electrical and electronics projects , you can approach us by commenting in the comment section below.
Here is a question for you, What is the main function of crystal oscillator? Wonderful web site. Lots of useful info here. And naturally, thanks for your effort! Greate post. Keep posting such kind of information on your blog. Im really impressed by your blog. I will certainly digg it and for my part suggest to my friends. I hope to present something back and help others such as you helped me.
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