Post by thread:[PIC]: Oscillator options, or Oops, I bought a ser

So I was digging through the parts box in search of a 20 Mhz crystal , and I turned up a few. Remembering when I bought them and not trusting myself, I looked up the part number at Digikey and sure enough, they're listed as series cut crystals. Digikey Part Number CTX-062. My question is this: can I rescue this crystal from oblivion and use it on my current demo board project? I'd really like to get fairly good accuracy out of the crystal for this project, since I'll be using it as a develop platform so I can finally flush my breadboard. I might be okay with as high as a 200 ppm error...HELP!!! Mike H. _________________________________________________________________ MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. http://join.msn.com/?page=features/virus -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu>

I found about 160 ppm error with a 20 mhz serial xtal using 18 pf capacitors. As long as you know this, you can take it into account when doing timing via TMR0, 1 etc. Larry At 06:06 PM 5/11/2003 -0500, you wrote: {Quote hidden}>So I was digging through the parts box in search of a 20 Mhz crystal , and I >turned up a few. Remembering when I bought them and not trusting myself, I >looked up the part number at Digikey and sure enough, they're listed as >series cut crystals. > >Digikey Part Number CTX-062. > >My question is this: can I rescue this crystal from oblivion and use it on >my current demo board project? I'd really like to get fairly good accuracy >out of the crystal for this project, since I'll be using it as a develop >platform so I can finally flush my breadboard. > >I might be okay with as high as a 200 ppm error...HELP!!! > >Mike H. > >_________________________________________________________________ >MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. >http://join.msn.com/?page=features/virus > >-- >http://www.piclist.com hint: To leave the PICList >.....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu Larry Bradley Orleans (Ottawa), Ontario, CANADA -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu>

>> >>My question is this: can I rescue this crystal from oblivion and use it on >>my current demo board project? I'd really like to get fairly good accuracy >>out of the crystal for this project, since I'll be using it as a develop >>platform so I can finally flush my breadboard. >> >>I might be okay with as high as a 200 ppm error...HELP!!! Therein lies the rub. It will almost certainly run, but it won't run at the nameplate frequency in a parallel circuit. Don't even try to put it there. All crystals have a series and a parallel resonant point, fairly close together, but they cannot be at the same point. It's behavior is only certified at one point though. I'm not clear on what compromises they might make to the behavior on one side, to optimize the other. I would suggest putting it in circuit, and checking the frequency with a counter or SW receiver. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Dave VanHorn <.....dvanhornKILLspam.....CEDAR.NET> wrote: > It's behavior is only certified at one point though. I'm not clear on what > compromises they might make to the behavior on one side, to optimize the > other. None whatsoever. It's simply a question of which mode the crystal was calibrated for during the manufacturing process. If it was calibrated to a certain frequency in series-resonant mode, there's simply no way you can pull it to the same frequency in parallel mode. -- Dave Tweed -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> >None whatsoever. I talked to a fellow at california crystals years ago, he told me that they did things to optimize the operating point, that compromised the other point, but he didn't want to clarify it. I've taken that as an operating principle to use xtals in their proper mode, and not to try taking them places they might not want to go. :) I don't need even a 1 in 10000 incidence of "osc won't start reliably".. >It's simply a question of which mode the crystal was >calibrated for during the manufacturing process. If it was calibrated to a >certain frequency in series-resonant mode, there's simply no way you can >pull it to the same frequency in parallel mode. Absolutely. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> My question is this: can I rescue this crystal from oblivion and use > it on my current demo board project? I'd really like to get fairly > good accuracy out of the crystal for this project, since I'll be > using it as a develop platform so I can finally flush my breadboard. > > I might be okay with as high as a 200 ppm error...HELP!!! How much trouble is it worth to save a <$1.00 part? I would buy the right crystal and keep the othwer ones around. Some day they may be just what you want, or you need a stand alone crystal oscillator you can make with a few CMOS inverters. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads