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william chan
01-11-2009, 03:27 PM
Hi,

Can I replace my 5Mhz crystal directly with a 4Mhz resonator and just ground the middle pin?

Thanks.

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Leon
01-11-2009, 06:47 PM
Those three terminal ceramic resonators have built-in feedback capacitors. It would be better to use one without the capacitors (two terminals). Why don't you want to use a crystal?

Leon

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Suzuki SV1000S motorcycle

william chan
01-11-2009, 07:31 PM
Resonators are cheaper....
I don't know why they are cheaper.

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Cluso99
01-11-2009, 07:49 PM
They are cheaper but are not as accurate

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Phil Pilgrim (PhiPi)
01-12-2009, 12:49 AM
William,

Cluso99 is correct. One place you may notice the consequences is with video output — especially composite color, which requires a very accurate timebase.

-Phil

william chan
01-12-2009, 10:50 AM
In my application, accuracy is not crucial.
I just need to run faster than 20Mhz.

In order to reduce the effects of the built-in capacitors in a 3 pin resonator, should i leave the middle pin unconnected?
The Propeller datasheet seems to lack info on which types on resonators will work.

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Leon
01-12-2009, 01:02 PM
As the internal circuit of the resonator looks like this:





--------X---------
| |
C C
| |
---------
|





You should be able to simply leave the ground connection disconnected. A two-terminal resonator would be cheaper, and more convenient, though.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle