crystal sync

[Mikko]

What makes the crystal synched camera run at constant speed? Yeah I know it's the crystal thing, but how? And what the hell is this crystal anyway?

Mikko

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[#Pedro]

A crystal is an element, that once connected to a supply voltage begins to swing with a very constant frequency, which is determined by it?s unique nature. That frequency is different with different types of crystals, but, what is the most important thing for us, it?s value is REPRODUCABLE. Each 24.000.000 Hz crystal swings exactly at THIS frequency. The output of a crystal is an AC voltage with this natural constant frequency.

The developer can take advantage of this nature to control time critical processes, f.e. built electonic watches. For this, the natural frequency of a crystal is simply divided down until we get 1 swing a second and feed a display or a pointer with it.

For crystal accurate speed controls, we can use this natural frequency to hook motors, turntables, any kind of drive etc. to that frequency.
To do so, the drive to be controled must be equipped with a kinda sensor that reports the actual speed/frequency of the drive. On the other hand, our crystal outputs that frequency that we would like to have, f.e. 24 Hz.
Now we only have to COMPARE the two frequencies at every moment, the actual and the target one and see what we could do to adjust the actual in a way that it comes as close as possible to the target.
Depending on the determined difference of this two frequencies, a special regulation circuit will now influence the running speed of our drive (camera). If during the comparement the drive was FASTER than the crystal, the regulation circuit should cut down it?s supply voltage or current, in order to make it slower, until the speed fits with the crystal frequency.

This is the way, crystal sync cameras, or synchronizing in general is working.

Pedro

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[MovieStuff]

<BLOCKQUOTE><font size="1" face="Courier, Arial">quote:</font><HR>Originally posted by #Pedro:
A crystal is an element, that once connected to a supply voltage begins to swing with a very constant frequency, which is determined by it?s unique nature.
<HR></BLOCKQUOTE>

Hi, Pedro!

Good explanation. I think you want to use the term "vibrate" instead of "swing", though.

"Swing" sounds like an 'Austin Powers' phase. Hmmmm, then again, so does "vibrate"...

Roger

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Roger Evans
MovieStuff
http://www.afterimagephoto.tv/moviestuff.html

[#Pedro]

Hi Roger, I think so, too! But the word "vibrate" wasn?t present in my English vocabulary, so I tryed to keep with sth popular. And "oszillate" I tryed to avoid in an explication that should be easy to understand.
Pedro

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[Konton]

Yeah Pedro,

You rock man. I can't wait to get your diagrams and everything up on my site. Right now all I have is a lame post on my message board complete with typos: http://www.super8mm.org/cgi-bin/ikon...orum=1&topic=4
I find your explainations to be much more eloquent than mine.

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Konton the Grey

[Mercutio]

Pedro;

As always, a very elegant and detailed technical answer. You are a great value to the board.

I think Austin Powers used ostilicize in the second movie, so I guess that term is out.

Merc

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[Mikko]

Thanks Pedro! I think I'll print that answer.

M

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