Question on Ceramic Resonators - Electronic Circuits Projects Diagrams Free

bigal_scorpio · 23rd June 2008, 07:46 PM

Hi to all,

I just realised that though I have a few different Ceramic Resonators, I don't know how to use them!

I was pondering building a new PIC circuit and though I didn't have the correct value crystal I had a C.R of the correct value.

Then came the puzzle, I have always connected PICs the same way with crystals across Osc1 and Osc2 then grounding both through small caps.

Then I remembered reading that C.Rs don't need the caps that crystals need, so do I just connect the C.R across Osc1 and Osc2 and job done? Or do I need some other connection to the C.R?

Then it struck me that there are 2 pin and 3 pin versions of the C.R! Now I'm even more puzzled.

I tried Googling for an explanation but all I found was why one was better than the other and how they could soon both be replaced by something new (silicon oscillators)! Just something else to confuse me.

So can anyone tell me how to use C.Rs on a PIC explaining both 2 and 3 leg varieties? Or point me to a site that can?

Thanks for looking..............Al

picbits · 23rd June 2008, 08:10 PM

Get a 3 lead CR as these have the caps built in.

Center pin to ground and the other two to OSC1 OSC2

If you use a 2 pin CR then you still need caps as you would do with a Crystal.

picbits · 23rd June 2008, 08:11 PM

2 Pin CR treat as a Crystal (without caps) - you will need caps with these.
3 Pin CR treat as a Crystal with inbuilt caps.

bigal_scorpio · 23rd June 2008, 08:20 PM

Thanks for the quick reply Picbits!

Just one more quick question?

Same value caps for C.Rs as Crystals or is there some way of working it out?

Thanks...............Al

picbits · 23rd June 2008, 08:22 PM

Not a clue - I always use the 3 pin variety.

Maybe have a chopsy at the datasheet and see what they suggest. If not then I'd start with the suggested caps for the Crystal.

picbits · 23rd June 2008, 08:27 PM

Had a quick look at the 3 pin datasheet. The 4Mhz ones I have use 20pF caps.

picbits · 23rd June 2008, 08:29 PM

The 10Mhz ones I have use 30pF caps ........

bigal_scorpio · 23rd June 2008, 09:00 PM

Cheers mate,

Thanks for all the help mate, I'm off to make some magic smoke now with my new found information

Al

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23rd June 2008, 07:46 PM	(permalink)
bigal_scorpio	Question on Ceramic Resonators Hi to all, I just realised that though I have a few different Ceramic Resonators, I don't know how to use them! I was pondering building a new PIC circuit and though I didn't have the correct value crystal I had a C.R of the correct value. Then came the puzzle, I have always connected PICs the same way with crystals across Osc1 and Osc2 then grounding both through small caps. Then I remembered reading that C.Rs don't need the caps that crystals need, so do I just connect the C.R across Osc1 and Osc2 and job done? Or do I need some other connection to the C.R? Then it struck me that there are 2 pin and 3 pin versions of the C.R! Now I'm even more puzzled. I tried Googling for an explanation but all I found was why one was better than the other and how they could soon both be replaced by something new (silicon oscillators)! Just something else to confuse me. So can anyone tell me how to use C.Rs on a PIC explaining both 2 and 3 leg varieties? Or point me to a site that can? Thanks for looking..............Al __________________ Founder member of the Campaign to do Something about the none existant word "Somethink"

23rd June 2008, 08:10 PM	(permalink)
picbits	Get a 3 lead CR as these have the caps built in. Center pin to ground and the other two to OSC1 OSC2 If you use a 2 pin CR then you still need caps as you would do with a Crystal.

23rd June 2008, 08:11 PM	(permalink)
picbits	2 Pin CR treat as a Crystal (without caps) - you will need caps with these. 3 Pin CR treat as a Crystal with inbuilt caps.

23rd June 2008, 08:20 PM	(permalink)
bigal_scorpio	Thanks for the quick reply Picbits! Just one more quick question? Same value caps for C.Rs as Crystals or is there some way of working it out? Thanks...............Al __________________ Founder member of the Campaign to do Something about the none existant word "Somethink"

23rd June 2008, 08:22 PM	(permalink)
picbits	Not a clue - I always use the 3 pin variety. Maybe have a chopsy at the datasheet and see what they suggest. If not then I'd start with the suggested caps for the Crystal.

23rd June 2008, 08:27 PM	(permalink)
picbits	Had a quick look at the 3 pin datasheet. The 4Mhz ones I have use 20pF caps.

23rd June 2008, 08:29 PM	(permalink)
picbits	The 10Mhz ones I have use 30pF caps ........

23rd June 2008, 09:00 PM	(permalink)
bigal_scorpio	Cheers mate, Thanks for all the help mate, I'm off to make some magic smoke now with my new found information Al __________________ Founder member of the Campaign to do Something about the none existant word "Somethink"