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Electronics => Beginners => Topic started by: int2str on February 17, 2015, 01:34:01 am

Title: Crystal / resonator circuit
Post by: int2str on February 17, 2015, 01:34:01 am

Alright, I give up....

I'm trying to learn how to make a crystal driven circuit as well as a resonator driven one.
I've looked into "Pierce oscillators", but can't figure out what makes it "tick".

Here's what I have on hand:
1x ZTT 16MHz resonator (looks like it's a crystal with built-in capacitors)
1x 16MHz quartz crystal
1x 74HCU04 hex inverter (since it looks like I need it)
+ various resistors (nothing in the mega ohm range though) /LEDs etc

Is there a simple circuit i can put together that lets me measure the frequency and analyze it?

I've seen a lot of circuits like this:
http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Pierce_oscillator.svg/220px-Pierce_oscillator.svg.png (http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Pierce_oscillator.svg/220px-Pierce_oscillator.svg.png)

But I don't see where one would add power to make it, well, a circuit?

Thanks!

Title: Re: Crystal / resonator circuit
Post by: T3sl4co1l on February 17, 2015, 02:00:15 am

Power is from the gate's supply/gnd pins (not shown).  The resistor is probably ok as low as 100k, but it's usually in the megs, because it's only needed to supply bias voltage to the gate's high impedance input.

Detecting frequency without a frequency detector... well, I suppose you can try it like the old timers did -- set up a resonant circuit, detector and galvanometer... but you need to know the resonant circuit is even correct.  Lecher lines might be a bit impractical at 16MHz or harmonics, I'm thinking.

Frequency counter, oscilloscope or spectrum analyzer would of course be the best choices here.

Tim

Title: Re: Crystal / resonator circuit
Post by: mentaldemise on February 17, 2015, 05:42:49 am

I just tried this out with an Arduino crystal I had laying around and seems to work. I don't know much though. I was looking for the same thing myself the other day:
http://jaunty-electronics.com/blog/2012/08/simple-oscillator-as-crystal-tester/ (http://jaunty-electronics.com/blog/2012/08/simple-oscillator-as-crystal-tester/)

I found it in another post on here about the same thing.

Title: Re: Crystal / resonator circuit
Post by: atferrari on February 17, 2015, 10:47:18 am

I recall testing an oscillator built around a transistor. I think it was 10 MHz.

In my ignorance, I said, "it is not working" because I expected something like 5V pk-pk. Actually it was much less than that and worked OK. Maybe influence of being used to see square waves of clocks for digital techinques.

Title: Re: Crystal / resonator circuit
Post by: dannyf on February 17, 2015, 12:12:36 pm

Since the gate is unbuffered, sticking the crystal across its input/output will get it to oscillate. If that doesn't work, put a 1M - 10M resistor in parallel with the crystal.

Cannot be simpler than that.

Title: Re: Crystal / resonator circuit
Post by: w2aew on February 17, 2015, 02:18:39 pm

Have seen my video on building a crystal oscillator?

#123: Build a crystal oscillator from schematic thru prototype construction and testing - DIY (https://www.youtube.com/watch?v=blalAktxFoI#ws)

Title: Re: Crystal / resonator circuit
Post by: int2str on February 17, 2015, 06:22:11 pm

Thanks guys!
Tried a few more things last night, but came up crickets so far on the logic analyzer.

Ordered a scope, so hopefully can learn more about these circuits soon.