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Groups > sci.electronics.design > #450876 > unrolled thread
| Started by | rickman <gnuarm@gmail.com> |
|---|---|
| First post | 2017-03-08 17:51 -0500 |
| Last post | 2017-03-13 11:26 -0400 |
| Articles | 20 on this page of 81 — 21 participants |
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Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-08 17:51 -0500
Re: Low Frequency 3rd Overtone Crystal Osc Jon Elson <jmelson@wustl.edu> - 2017-03-08 17:04 -0600
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-08 19:57 -0500
Re: Low Frequency 3rd Overtone Crystal Osc Robert Baer <robertbaer@localnet.com> - 2017-03-10 00:01 -0800
Re: Low Frequency 3rd Overtone Crystal Osc dagmargoodboat@yahoo.com - 2017-03-08 18:02 -0800
Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-08 18:13 -0800
Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-09 09:11 -0500
Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-09 08:14 -0800
Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-09 11:24 -0500
Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 11:20 -0500
Re: Low Frequency 3rd Overtone Crystal Osc Neon John <no@never.com> - 2017-03-09 16:24 -0500
Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-09 14:23 -0800
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 18:16 -0500
Re: Low Frequency 3rd Overtone Crystal Osc Neon John <no@never.com> - 2017-03-13 19:59 -0400
Re: Low Frequency 3rd Overtone Crystal Osc John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-13 17:29 -0700
Re: Low Frequency 3rd Overtone Crystal Osc bill.sloman@ieee.org - 2017-03-13 18:43 -0700
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-13 21:54 -0400
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-10 10:15 +0000
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-08 22:33 -0500
Re: Low Frequency 3rd Overtone Crystal Osc o pere o <me@somewhere.net> - 2017-03-09 15:39 +0100
Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-09 09:41 -0500
Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-09 09:43 -0500
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 11:17 -0500
Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-09 20:42 -0500
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 20:55 -0500
Re: Low Frequency 3rd Overtone Crystal Osc piglet <erichpwagner@hotmail.com> - 2017-03-11 07:37 +0000
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 03:15 -0500
Re: Low Frequency 3rd Overtone Crystal Osc piglet <erichpwagner@hotmail.com> - 2017-03-11 09:52 +0000
Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 08:54 -0500
Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 09:00 -0500
Re: Low Frequency 3rd Overtone Crystal Osc Jasen Betts <jasen@xnet.co.nz> - 2017-03-11 23:58 +0000
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 22:13 -0500
Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-13 11:20 -0400
Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-13 11:47 -0500
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-13 23:44 +0200
Re: Low Frequency 3rd Overtone Crystal Osc Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-03-13 15:55 -0700
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-13 19:58 -0400
Re: Low Frequency 3rd Overtone Crystal Osc Jasen Betts <jasen@xnet.co.nz> - 2017-03-14 04:48 +0000
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-14 13:37 -0400
Re: Low Frequency 3rd Overtone Crystal Osc Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-14 22:29 +0200
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-14 20:59 -0400
Re: Low Frequency 3rd Overtone Crystal Osc Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-15 10:40 +0200
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-15 12:44 -0400
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-16 08:20 +0200
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 02:51 -0400
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-16 09:28 +0200
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 04:40 -0400
Re: Low Frequency 3rd Overtone Crystal Osc bill.sloman@ieee.org - 2017-03-16 05:09 -0700
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 12:47 -0400
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-17 00:22 +0200
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-16 19:14 -0400
Re: Low Frequency 3rd Overtone Crystal Osc John S <Sophi.2@invalid.org> - 2017-03-13 05:51 -0500
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-13 08:39 -0400
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 21:09 -0500
Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-09 20:15 -0600
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-09 23:36 -0500
Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-10 19:02 -0600
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 01:15 -0500
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-11 11:04 +0200
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 09:31 +0000
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 09:15 +0000
Re: Low Frequency 3rd Overtone Crystal Osc bitrex <bitrex@de.lete.earthlink.net> - 2017-03-11 10:50 -0500
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 16:46 +0000
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-11 15:36 -0500
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-11 23:50 +0000
Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-11 17:59 -0600
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-12 08:44 +0000
Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-12 20:23 -0500
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-13 12:21 +0000
Re: Low Frequency 3rd Overtone Crystal Osc "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-14 03:30 -0500
Re: Low Frequency 3rd Overtone Crystal Osc "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-14 20:50 +0000
Re: Low Frequency 3rd Overtone Crystal Osc Robert Baer <robertbaer@localnet.com> - 2017-03-09 23:57 -0800
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-10 05:51 -0500
Re: Low Frequency 3rd Overtone Crystal Osc Mike Jones <mikejones@gmail.com> - 2017-03-10 06:03 -0600
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-10 15:34 +0200
Re: Low Frequency 3rd Overtone Crystal Osc Tim Wescott <tim@seemywebsite.really> - 2017-03-11 12:51 -0600
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-12 00:33 +0200
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-12 01:00 -0500
Re: Low Frequency 3rd Overtone Crystal Osc upsidedown@downunder.com - 2017-03-12 10:45 +0200
Re: Low Frequency 3rd Overtone Crystal Osc rickman <gnuarm@gmail.com> - 2017-03-12 18:32 -0400
Re: Low Frequency 3rd Overtone Crystal Osc Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-13 11:26 -0400
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-14 20:59 -0400 |
| Message-ID | <oaa3ge$f2k$1@dont-email.me> |
| In reply to | #451814 |
On 3/14/2017 4:29 PM, Tauno Voipio wrote: > On 14.3.17 19:37, rickman wrote: >> On 3/14/2017 12:48 AM, Jasen Betts wrote: >>> On 2017-03-13, rickman <gnuarm@gmail.com> wrote: >>>> On 3/13/2017 6:55 PM, Lasse Langwadt Christensen wrote: >>>>> Den mandag den 13. marts 2017 kl. 22.44.42 UTC+1 skrev >>>>> upsid...@downunder.com: >>>>>> On 11 Mar 2017 23:58:12 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>>> >>>>>>> On 2017-03-11, rickman <gnuarm@gmail.com> wrote: >>>>>>>> On 3/11/2017 2:37 AM, piglet wrote: >>>>>>>>> On 10/03/2017 01:55, rickman wrote: >>>>>>>>>> >>>>>>>>>> Even so, that doesn't get around having 60 kHz on the board. >>>>>>>>>> 60 kHz is >>>>>>>>>> what I am measuring. >>>>>>>>>> >>>>>>>>> >>>>>>>>> Just wonder if having a strong 120kHz presence is wise if >>>>>>>>> trying to >>>>>>>>> measure a low level 60kHz signal? Would it be better to have a >>>>>>>>> more >>>>>>>>> complex harmonic relationship between high level oscillator and >>>>>>>>> low-level input? >>>>>>>> >>>>>>>> The 120 kHz is the sampling clock so I'm not worried about it >>>>>>>> getting >>>>>>>> into the signal. It gets sampled right back out perfectly. >>>>>>> >>>>>>> unless you have some way to synchronise your clock to the 60kHz, >>>>>>> sampling at 120kHz you could hit the zero-crossings, and see no >>>>>>> signal >>>>>> >>>>>> Quadrature (I/Q) demodulation should solve this problem. >>>>>> >>>>>> If you can lock into th signal, quadrature locking of Q will ensure >>>>>> that the I channel doesn't cancel the data. >>>>> >>>>> not surprising since IQ sampling is basically equivalent to >>>>> sampling at >>>>> twice the rate >>>> >>>> This part was resolved a long time ago. That's why the sampling >>>> will be >>>> 240 kHz with filters to resolve real and imaginary parts at 120 kHz. >>>> The multiplies are all 1, -1 and 0 so no actual multiplies. Sum the >>>> complex results over a time period and you get a *very* narrow band >>>> filter with complex results giving both amplitude and relative phase. >>>> >>>> That's why I prefer a 120 or 240 kHz crystal. We'll see what I end up >>>> with. >>> >>> http://www.golledge.com/docs/products/xtl_sm/cc4vt.htm >>> >>> dunno if they can provide "samples", I guessing you don't want to buy a >>> reel. >> >> I can get a reel from Digikey. >> >> >>> Have you considered doing the SDR thing instead? >> >> Software defined radio? So if this is a hard problem to solve, I should >> solve a different problem? > > > Maybe meaning DDS? > > I just wonder why the OP asks for a third overtone oscillator > for extremely low frequency (60 kHz) for a crystal. I wish to synchronously sample a 60 kHz signal at 240 kHz. I can't find either 120 or 240 kHz crystals. I *can* find 40 kHz crystals which would give me 120 kHz at the third overtone (or close to it). I've read enough about this to be thoroughly scared off the prospect and am now looking at using a 32.768 kHz reference (which I need anyway) to drive a frequency locked loop by tuning an LC oscillator. It would have an update rate on the order of 1 Hz, so the stability could be pretty close to that of the 32.768 kHz reference. In simulation the power consumption can be pretty low. I think I'm about ready to build one and give it a try. -- Rick C
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| From | Tauno Voipio <tauno.voipio@notused.fi.invalid> |
|---|---|
| Date | 2017-03-15 10:40 +0200 |
| Message-ID | <oaaugg$2rv$1@dont-email.me> |
| In reply to | #451876 |
On 15.3.17 02:59, rickman wrote: > On 3/14/2017 4:29 PM, Tauno Voipio wrote: >> On 14.3.17 19:37, rickman wrote: >>> On 3/14/2017 12:48 AM, Jasen Betts wrote: >>>> On 2017-03-13, rickman <gnuarm@gmail.com> wrote: >>>>> On 3/13/2017 6:55 PM, Lasse Langwadt Christensen wrote: >>>>>> Den mandag den 13. marts 2017 kl. 22.44.42 UTC+1 skrev >>>>>> upsid...@downunder.com: >>>>>>> On 11 Mar 2017 23:58:12 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>>>> >>>>>>>> On 2017-03-11, rickman <gnuarm@gmail.com> wrote: >>>>>>>>> On 3/11/2017 2:37 AM, piglet wrote: >>>>>>>>>> On 10/03/2017 01:55, rickman wrote: >>>>>>>>>>> >>>>>>>>>>> Even so, that doesn't get around having 60 kHz on the board. >>>>>>>>>>> 60 kHz is >>>>>>>>>>> what I am measuring. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Just wonder if having a strong 120kHz presence is wise if >>>>>>>>>> trying to >>>>>>>>>> measure a low level 60kHz signal? Would it be better to have a >>>>>>>>>> more >>>>>>>>>> complex harmonic relationship between high level oscillator and >>>>>>>>>> low-level input? >>>>>>>>> >>>>>>>>> The 120 kHz is the sampling clock so I'm not worried about it >>>>>>>>> getting >>>>>>>>> into the signal. It gets sampled right back out perfectly. >>>>>>>> >>>>>>>> unless you have some way to synchronise your clock to the 60kHz, >>>>>>>> sampling at 120kHz you could hit the zero-crossings, and see no >>>>>>>> signal >>>>>>> >>>>>>> Quadrature (I/Q) demodulation should solve this problem. >>>>>>> >>>>>>> If you can lock into th signal, quadrature locking of Q will ensure >>>>>>> that the I channel doesn't cancel the data. >>>>>> >>>>>> not surprising since IQ sampling is basically equivalent to >>>>>> sampling at >>>>>> twice the rate >>>>> >>>>> This part was resolved a long time ago. That's why the sampling >>>>> will be >>>>> 240 kHz with filters to resolve real and imaginary parts at 120 kHz. >>>>> The multiplies are all 1, -1 and 0 so no actual multiplies. Sum the >>>>> complex results over a time period and you get a *very* narrow band >>>>> filter with complex results giving both amplitude and relative phase. >>>>> >>>>> That's why I prefer a 120 or 240 kHz crystal. We'll see what I end up >>>>> with. >>>> >>>> http://www.golledge.com/docs/products/xtl_sm/cc4vt.htm >>>> >>>> dunno if they can provide "samples", I guessing you don't want to buy a >>>> reel. >>> >>> I can get a reel from Digikey. >>> >>> >>>> Have you considered doing the SDR thing instead? >>> >>> Software defined radio? So if this is a hard problem to solve, I should >>> solve a different problem? >> >> >> Maybe meaning DDS? >> >> I just wonder why the OP asks for a third overtone oscillator >> for extremely low frequency (60 kHz) for a crystal. > > I wish to synchronously sample a 60 kHz signal at 240 kHz. I can't find > either 120 or 240 kHz crystals. I *can* find 40 kHz crystals which > would give me 120 kHz at the third overtone (or close to it). > > I've read enough about this to be thoroughly scared off the prospect and > am now looking at using a 32.768 kHz reference (which I need anyway) to > drive a frequency locked loop by tuning an LC oscillator. It would have > an update rate on the order of 1 Hz, so the stability could be pretty > close to that of the 32.768 kHz reference. In simulation the power > consumption can be pretty low. I think I'm about ready to build one and > give it a try. This may be a heresy: There are plenty of small ARM Cortex-M chips with built-in counter-timers. Get one of them with a decent crystal (say in the range of 5 to 20 MHz) and divide from it with the built-in timer. The cost will be just some dollars for the components. A small Cortex evaluation unit can be had for some tens of dollars, and there are the crystal and board built-in, together with some means of getting the code in. -- -TV
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-15 12:44 -0400 |
| Message-ID | <oabqrl$32p$1@dont-email.me> |
| In reply to | #451923 |
On 3/15/2017 4:40 AM, Tauno Voipio wrote: > On 15.3.17 02:59, rickman wrote: >> On 3/14/2017 4:29 PM, Tauno Voipio wrote: >>> On 14.3.17 19:37, rickman wrote: >>>> On 3/14/2017 12:48 AM, Jasen Betts wrote: >>>>> On 2017-03-13, rickman <gnuarm@gmail.com> wrote: >>>>>> On 3/13/2017 6:55 PM, Lasse Langwadt Christensen wrote: >>>>>>> Den mandag den 13. marts 2017 kl. 22.44.42 UTC+1 skrev >>>>>>> upsid...@downunder.com: >>>>>>>> On 11 Mar 2017 23:58:12 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>>>>> >>>>>>>>> On 2017-03-11, rickman <gnuarm@gmail.com> wrote: >>>>>>>>>> On 3/11/2017 2:37 AM, piglet wrote: >>>>>>>>>>> On 10/03/2017 01:55, rickman wrote: >>>>>>>>>>>> >>>>>>>>>>>> Even so, that doesn't get around having 60 kHz on the board. >>>>>>>>>>>> 60 kHz is >>>>>>>>>>>> what I am measuring. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Just wonder if having a strong 120kHz presence is wise if >>>>>>>>>>> trying to >>>>>>>>>>> measure a low level 60kHz signal? Would it be better to have a >>>>>>>>>>> more >>>>>>>>>>> complex harmonic relationship between high level oscillator and >>>>>>>>>>> low-level input? >>>>>>>>>> >>>>>>>>>> The 120 kHz is the sampling clock so I'm not worried about it >>>>>>>>>> getting >>>>>>>>>> into the signal. It gets sampled right back out perfectly. >>>>>>>>> >>>>>>>>> unless you have some way to synchronise your clock to the 60kHz, >>>>>>>>> sampling at 120kHz you could hit the zero-crossings, and see no >>>>>>>>> signal >>>>>>>> >>>>>>>> Quadrature (I/Q) demodulation should solve this problem. >>>>>>>> >>>>>>>> If you can lock into th signal, quadrature locking of Q will ensure >>>>>>>> that the I channel doesn't cancel the data. >>>>>>> >>>>>>> not surprising since IQ sampling is basically equivalent to >>>>>>> sampling at >>>>>>> twice the rate >>>>>> >>>>>> This part was resolved a long time ago. That's why the sampling >>>>>> will be >>>>>> 240 kHz with filters to resolve real and imaginary parts at 120 kHz. >>>>>> The multiplies are all 1, -1 and 0 so no actual multiplies. Sum the >>>>>> complex results over a time period and you get a *very* narrow band >>>>>> filter with complex results giving both amplitude and relative phase. >>>>>> >>>>>> That's why I prefer a 120 or 240 kHz crystal. We'll see what I >>>>>> end up >>>>>> with. >>>>> >>>>> http://www.golledge.com/docs/products/xtl_sm/cc4vt.htm >>>>> >>>>> dunno if they can provide "samples", I guessing you don't want to >>>>> buy a >>>>> reel. >>>> >>>> I can get a reel from Digikey. >>>> >>>> >>>>> Have you considered doing the SDR thing instead? >>>> > Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail > From: Tauno Voipio <tauno.voipio@notused.fi.invalid> > Newsgroups: sci.electronics.design > Subject: Re: Low Frequency 3rd Overtone Crystal Osc > Date: Wed, 15 Mar 2017 10:40:27 +0200 > Organization: A noiseless patient Spider > Lines: 100 > Message-ID: <oaaugg$2rv$1@dont-email.me> > References: <o9q1nn$vi7$1@dont-email.me> > <6c60298f-a3ac-4046-8d50-21ec3d770838@googlegroups.com> > <o9qi9e$6sv$1@dont-email.me> <fQdwA.9654$zC6.395@fx29.iad> > <KSdwA.9655$zC6.5592@fx29.iad> <o9rv1o$gjq$1@dont-email.me> > <xwnwA.20641$Bp6.19953@fx36.iad> <o9t0sh$hvv$1@dont-email.me> > <oa09a5$rmn$1@dont-email.me> <oa0biq$1cm$1@dont-email.me> > <oa22uk$q4d$1@gonzo.alcatraz> <ig4ecc90du3f62hfe73d1fnv7fuklteesr@4ax.com> > <b8026a8a-7ad7-456b-8e3d-f628f8d119d2@googlegroups.com> > <oa7bir$1fg$1@dont-email.me> <oa7smf$9h9$1@gonzo.alcatraz> > <oa99iu$jse$1@dont-email.me> <oa9jmf$pou$1@dont-email.me> > <oaa3ge$f2k$1@dont-email.me> > Mime-Version: 1.0 > Content-Type: text/plain; charset=windows-1252; format=flowed > Content-Transfer-Encoding: 7bit > Injection-Date: Wed, 15 Mar 2017 08:37:36 -0000 (UTC) > Injection-Info: mx02.eternal-september.org; > posting-host="40c9f2bdaf628ad77edb8c7cd2696817"; > logging-data="2943"; > mail-complaints-to="abuse@eternal-september.org"; > posting-account="U2FsdGVkX1+4jNWAa6Rx6i9m9AtHd/58tCa5DdieuZk=" > User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:45.0) > Gecko/20100101 Thunderbird/45.8.0 > In-Reply-To: <oaa3ge$f2k$1@dont-email.me> > Cancel-Lock: sha1:uWhkJ84w4QwjGupj3PGAzg6VIrM= > Xref: news.eternal-september.org sci.electronics.design:458246 > > On 15.3.17 02:59, rickman wrote: >> On 3/14/2017 4:29 PM, Tauno Voipio wrote: >>> On 14.3.17 19:37, rickman wrote: >>>> On 3/14/2017 12:48 AM, Jasen Betts wrote: >>>>> On 2017-03-13, rickman <gnuarm@gmail.com> wrote: >>>>>> On 3/13/2017 6:55 PM, Lasse Langwadt Christensen wrote: >>>>>>> Den mandag den 13. marts 2017 kl. 22.44.42 UTC+1 skrev >>>>>>> upsid...@downunder.com: >>>>>>>> On 11 Mar 2017 23:58:12 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>>>>> >>>>>>>>> On 2017-03-11, rickman <gnuarm@gmail.com> wrote: >>>>>>>>>> On 3/11/2017 2:37 AM, piglet wrote: >>>>>>>>>>> On 10/03/2017 01:55, rickman wrote: >>>>>>>>>>>> >>>>>>>>>>>> Even so, that doesn't get around having 60 kHz on the board. >>>>>>>>>>>> 60 kHz is >>>>>>>>>>>> what I am measuring. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Just wonder if having a strong 120kHz presence is wise if >>>>>>>>>>> trying to >>>>>>>>>>> measure a low level 60kHz signal? Would it be better to have a >>>>>>>>>>> more >>>>>>>>>>> complex harmonic relationship between high level oscillator and >>>>>>>>>>> low-level input? >>>>>>>>>> >>>>>>>>>> The 120 kHz is the sampling clock so I'm not worried about it >>>>>>>>>> getting >>>>>>>>>> into the signal. It gets sampled right back out perfectly. >>>>>>>>> >>>>>>>>> unless you have some way to synchronise your clock to the 60kHz, >>>>>>>>> sampling at 120kHz you could hit the zero-crossings, and see no >>>>>>>>> signal >>>>>>>> >>>>>>>> Quadrature (I/Q) demodulation should solve this problem. >>>>>>>> >>>>>>>> If you can lock into th signal, quadrature locking of Q will ensure >>>>>>>> that the I channel doesn't cancel the data. >>>>>>> >>>>>>> not surprising since IQ sampling is basically equivalent to >>>>>>> sampling at >>>>>>> twice the rate >>>>>> >>>>>> This part was resolved a long time ago. That's why the sampling >>>>>> will be >>>>>> 240 kHz with filters to resolve real and imaginary parts at 120 kHz. >>>>>> The multiplies are all 1, -1 and 0 so no actual multiplies. Sum the >>>>>> complex results over a time period and you get a *very* narrow band >>>>>> filter with complex results giving both amplitude and relative phase. >>>>>> >>>>>> That's why I prefer a 120 or 240 kHz crystal. We'll see what I >>>>>> end up >>>>>> with. >>>>> >>>>> http://www.golledge.com/docs/products/xtl_sm/cc4vt.htm >>>>> >>>>> dunno if they can provide "samples", I guessing you don't want to >>>>> buy a >>>>> reel. >>>> >>>> I can get a reel from Digikey. >>>> >>>> >>>>> Have you considered doing the SDR thing instead? >>>> >>>> Software defined radio? So if this is a hard problem to solve, I >>>> should >>>> solve a different problem? >>> >>> >>> Maybe meaning DDS? >>> >>> I just wonder why the OP asks for a third overtone oscillator >>> for extremely low frequency (60 kHz) for a crystal. >> >> I wish to synchronously sample a 60 kHz signal at 240 kHz. I can't find >> either 120 or 240 kHz crystals. I *can* find 40 kHz crystals which >> would give me 120 kHz at the third overtone (or close to it). >> >> I've read enough about this to be thoroughly scared off the prospect and >> am now looking at using a 32.768 kHz reference (which I need anyway) to >> drive a frequency locked loop by tuning an LC oscillator. It would have >> an update rate on the order of 1 Hz, so the stability could be pretty >> close to that of the 32.768 kHz reference. In simulation the power >> consumption can be pretty low. I think I'm about ready to build one and >> give it a try. > > > This may be a heresy: > > There are plenty of small ARM Cortex-M chips with built-in > counter-timers. Get one of them with a decent crystal (say in the range of > 5 to 20 MHz) and divide from it with the built-in timer. The cost > will be just some dollars for the components. > > A small Cortex evaluation unit can be had for some tens of dollars, > and there are the crystal and board built-in, together with some > means of getting the code in. Thanks for the suggestion, but that does not fit the problem space. The FPGA board I am prototyping with has an oscillator on board, just not a multiple of 240 kHz. This is a very low power design and every ARM type CPU I have seen will consume mAs of current with the high speed crystal controlled clock. One good note. I discovered the oscillator frequency on this proto board is controlled by a resistor. You can also inject a current or voltage to modify the frequency creating a VCO. So I can make a first pass at frequency locking this oscillator. It won't be so low current, but it's still better than a multi-MHz crystal. -- Rick C
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| From | upsidedown@downunder.com |
|---|---|
| Date | 2017-03-16 08:20 +0200 |
| Message-ID | <65bkccttgadbrtf4j9ojv7s5lbjp19oecv@4ax.com> |
| In reply to | #451963 |
On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: >> >> >> This may be a heresy: >> >> There are plenty of small ARM Cortex-M chips with built-in >> counter-timers. Get one of them with a decent crystal (say in the range of >> 5 to 20 MHz) and divide from it with the built-in timer. The cost >> will be just some dollars for the components. >> >> A small Cortex evaluation unit can be had for some tens of dollars, >> and there are the crystal and board built-in, together with some >> means of getting the code in. > >Thanks for the suggestion, but that does not fit the problem space. The >FPGA board I am prototyping with has an oscillator on board, just not a >multiple of 240 kHz. This is a very low power design and every ARM type >CPU I have seen will consume mAs of current with the high speed crystal >controlled clock. How about a free running CPU clock running at a few MHz and a crystal in 0.5 to 1.5 MHz range generating an interrupt about every microsecond. The interrupt updates the NCO (numerical controlled oscillator) 16 to 32 bit phase accumulator and some bits are written to the output pins. The rest of the time, the processor is kept in a low power sleep mode. If sin/cos output is needed, insert a sine lookup table between the phase accumulator and output pins. These should not require many instructions, so the power consumption should be low.
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-16 02:51 -0400 |
| Message-ID | <oadcgn$sqo$2@dont-email.me> |
| In reply to | #452091 |
On 3/16/2017 2:20 AM, upsidedown@downunder.com wrote: > On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: > >>> >>> >>> This may be a heresy: >>> >>> There are plenty of small ARM Cortex-M chips with built-in >>> counter-timers. Get one of them with a decent crystal (say in the range of >>> 5 to 20 MHz) and divide from it with the built-in timer. The cost >>> will be just some dollars for the components. >>> >>> A small Cortex evaluation unit can be had for some tens of dollars, >>> and there are the crystal and board built-in, together with some >>> means of getting the code in. >> >> Thanks for the suggestion, but that does not fit the problem space. The >> FPGA board I am prototyping with has an oscillator on board, just not a >> multiple of 240 kHz. This is a very low power design and every ARM type >> CPU I have seen will consume mAs of current with the high speed crystal >> controlled clock. > > How about a free running CPU clock running at a few MHz and a crystal > in 0.5 to 1.5 MHz range generating an interrupt about every > microsecond. The interrupt updates the NCO (numerical controlled > oscillator) 16 to 32 bit phase accumulator and some bits are written > to the output pins. The rest of the time, the processor is kept in a > low power sleep mode. If sin/cos output is needed, insert a sine > lookup table between the phase accumulator and output pins. > These should not require many instructions, so the power consumption > should be low. I appreciate the suggestion, but why all the complexity? If I have a crystal creating a clock, I don't need the CPU. What you described is way more power and complexity than needed. -- Rick C
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| From | upsidedown@downunder.com |
|---|---|
| Date | 2017-03-16 09:28 +0200 |
| Message-ID | <fuekcct0911kumd3v1hmlek5kuvttvp6qa@4ax.com> |
| In reply to | #452094 |
On Thu, 16 Mar 2017 02:51:41 -0400, rickman <gnuarm@gmail.com> wrote: >On 3/16/2017 2:20 AM, upsidedown@downunder.com wrote: >> On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: >> >>>> >>>> >>>> This may be a heresy: >>>> >>>> There are plenty of small ARM Cortex-M chips with built-in >>>> counter-timers. Get one of them with a decent crystal (say in the range of >>>> 5 to 20 MHz) and divide from it with the built-in timer. The cost >>>> will be just some dollars for the components. >>>> >>>> A small Cortex evaluation unit can be had for some tens of dollars, >>>> and there are the crystal and board built-in, together with some >>>> means of getting the code in. >>> >>> Thanks for the suggestion, but that does not fit the problem space. The >>> FPGA board I am prototyping with has an oscillator on board, just not a >>> multiple of 240 kHz. This is a very low power design and every ARM type >>> CPU I have seen will consume mAs of current with the high speed crystal >>> controlled clock. >> >> How about a free running CPU clock running at a few MHz and a crystal >> in 0.5 to 1.5 MHz range generating an interrupt about every >> microsecond. The interrupt updates the NCO (numerical controlled >> oscillator) 16 to 32 bit phase accumulator and some bits are written >> to the output pins. The rest of the time, the processor is kept in a >> low power sleep mode. If sin/cos output is needed, insert a sine >> lookup table between the phase accumulator and output pins. >> These should not require many instructions, so the power consumption >> should be low. > >I appreciate the suggestion, but why all the complexity? If I have a >crystal creating a clock, I don't need the CPU. What you described is >way more power and complexity than needed. I understood that you originally had problems ordering a crystal for the exact integer multiple of 120 kHz. The NCO principle allows you to generate any frequency from an other frequency, which doesn't have to be harmonically related, as long as the Nyquist criterion is followed. Regarding timepiece crystals, NT cut crystals have been made for 32 and 131 kHz, while DT cut has been used for 272 and 327 kHz. So if you want 240 or 480 kHz, look for DT cut crystals. How many do you need ? Some small crystal house might even make single crystals, but the cost can be high. I do not know about DT cut, but I have ordered AT cut crystals in units of one for each frequency.
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-16 04:40 -0400 |
| Message-ID | <oaditf$esk$1@dont-email.me> |
| In reply to | #452097 |
On 3/16/2017 3:28 AM, upsidedown@downunder.com wrote: > On Thu, 16 Mar 2017 02:51:41 -0400, rickman <gnuarm@gmail.com> wrote: > >> On 3/16/2017 2:20 AM, upsidedown@downunder.com wrote: >>> On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: >>> >>>>> >>>>> >>>>> This may be a heresy: >>>>> >>>>> There are plenty of small ARM Cortex-M chips with built-in >>>>> counter-timers. Get one of them with a decent crystal (say in the range of >>>>> 5 to 20 MHz) and divide from it with the built-in timer. The cost >>>>> will be just some dollars for the components. >>>>> >>>>> A small Cortex evaluation unit can be had for some tens of dollars, >>>>> and there are the crystal and board built-in, together with some >>>>> means of getting the code in. >>>> >>>> Thanks for the suggestion, but that does not fit the problem space. The >>>> FPGA board I am prototyping with has an oscillator on board, just not a >>>> multiple of 240 kHz. This is a very low power design and every ARM type >>>> CPU I have seen will consume mAs of current with the high speed crystal >>>> controlled clock. >>> >>> How about a free running CPU clock running at a few MHz and a crystal >>> in 0.5 to 1.5 MHz range generating an interrupt about every >>> microsecond. The interrupt updates the NCO (numerical controlled >>> oscillator) 16 to 32 bit phase accumulator and some bits are written >>> to the output pins. The rest of the time, the processor is kept in a >>> low power sleep mode. If sin/cos output is needed, insert a sine >>> lookup table between the phase accumulator and output pins. >>> These should not require many instructions, so the power consumption >>> should be low. >> >> I appreciate the suggestion, but why all the complexity? If I have a >> crystal creating a clock, I don't need the CPU. What you described is >> way more power and complexity than needed. > > I understood that you originally had problems ordering a crystal for > the exact integer multiple of 120 kHz. The NCO principle allows you to > generate any frequency from an other frequency, which doesn't have to > be harmonically related, as long as the Nyquist criterion is followed. That's not entirely correct. To get an exact value the reference frequency and the target frequency must be related by the ratio of two integers. Fclk = Fref * NCOstep / NCOmodulus where NCOstep is the phase increment and NCOmodulus is the modulus of the phase accumulator. > Regarding timepiece crystals, NT cut crystals have been made for 32 > and 131 kHz, while DT cut has been used for 272 and 327 kHz. So if you > want 240 or 480 kHz, look for DT cut crystals. How many do you need ? > Some small crystal house might even make single crystals, but the cost > can be high. I'd be happy with a handful, 5 to 10. I've contacted crystal manufacturers and they don't want to make anything for me that isn't a standard item. > I do not know about DT cut, but I have ordered AT cut crystals in > units of one for each frequency. I can do without the crystal I think. I can use 32.768 kHz as my reference. I can buy real time clock chips with temperature compensation and a programmable output intended for a processor interrupt. That output can be set for 1 second or other rates and used to time an LC oscillator. The LC oscillator can be trimmed with a varactor from the frequency measurement. I may start testing this tomorrow. -- Rick C
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| From | bill.sloman@ieee.org |
|---|---|
| Date | 2017-03-16 05:09 -0700 |
| Message-ID | <2624740b-7d5e-400a-9bef-47bc481b88cb@googlegroups.com> |
| In reply to | #452098 |
On Thursday, March 16, 2017 at 7:41:08 PM UTC+11, rickman wrote: > On 3/16/2017 3:28 AM, upsidedown@downunder.com wrote: > > On Thu, 16 Mar 2017 02:51:41 -0400, rickman <gnuarm@gmail.com> wrote: > > > >> On 3/16/2017 2:20 AM, upsidedown@downunder.com wrote: > >>> On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: > >>> > >>>>> > >>>>> > >>>>> This may be a heresy: > >>>>> > >>>>> There are plenty of small ARM Cortex-M chips with built-in > >>>>> counter-timers. Get one of them with a decent crystal (say in the range > >>>>> of 5 to 20 MHz) and divide from it with the built-in timer. The cost > >>>>> will be just some dollars for the components. > >>>>> > >>>>> A small Cortex evaluation unit can be had for some tens of dollars, > >>>>> and there are the crystal and board built-in, together with some > >>>>> means of getting the code in. > >>>> > >>>> Thanks for the suggestion, but that does not fit the problem space. The > >>>> FPGA board I am prototyping with has an oscillator on board, just not a > >>>> multiple of 240 kHz. This is a very low power design and every ARM type > >>>> CPU I have seen will consume mAs of current with the high speed crystal > >>>> controlled clock. > >>> > >>> How about a free running CPU clock running at a few MHz and a crystal > >>> in 0.5 to 1.5 MHz range generating an interrupt about every > >>> microsecond. The interrupt updates the NCO (numerical controlled > >>> oscillator) 16 to 32 bit phase accumulator and some bits are written > >>> to the output pins. The rest of the time, the processor is kept in a > >>> low power sleep mode. If sin/cos output is needed, insert a sine > >>> lookup table between the phase accumulator and output pins. > >>> These should not require many instructions, so the power consumption > >>> should be low. > >> > >> I appreciate the suggestion, but why all the complexity? If I have a > >> crystal creating a clock, I don't need the CPU. What you described is > >> way more power and complexity than needed. > > > > I understood that you originally had problems ordering a crystal for > > the exact integer multiple of 120 kHz. The NCO principle allows you to > > generate any frequency from an other frequency, which doesn't have to > > be harmonically related, as long as the Nyquist criterion is followed. > > That's not entirely correct. To get an exact value the reference > frequency and the target frequency must be related by the ratio of two > integers. Fclk = Fref * NCOstep / NCOmodulus where NCOstep is the phase > increment and NCOmodulus is the modulus of the phase accumulator. A fractional-n divider can get you there with less hardware and a marginally tighter control loop. It took me a while to find the phrase "fractional-n divider" - haven't thought about them for many years. The highest common frequency of 32,768hZ and 120kHz is 64Hz - you have to divide the 32,768Hz by 512 to get that, and 120kHz by 1875. If you divide the 120kHz by 937 and 938 in successive intervals, you get something close to 128Hz. If you divide it by 468 over one interval, and by 469 over the next three intervals, you get something close to 256Hz. If you divide by 234 over five intervals and 235 over three, you get something close to 512Hz. For most practical purposes, counting three ticks of the 120kHz clock then four (and sometimes four again - specifically 205 three ticks and 315 four ticks) will let you lock exactly to the 32,768Hz clock. The phase error will gad about a bit in the short term, but a sufficiently slow four- or more-pole low pass filter in the feedback loop will clean that out. > I can do without the crystal I think. I can use 32.768 kHz as my > reference. I can buy real time clock chips with temperature > compensation and a programmable output intended for a processor > interrupt. That output can be set for 1 second or other rates and used > to time an LC oscillator. The LC oscillator can be trimmed with a > varactor from the frequency measurement. I may start testing this > tomorrow. Why bother with a varactor? The voltage controlled oscillator in a regular 4046 isn't all that noisy. -- Bill Sloman, Sydney
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-16 12:47 -0400 |
| Message-ID | <oaefdj$g9a$1@dont-email.me> |
| In reply to | #452103 |
On 3/16/2017 8:09 AM, bill.sloman@ieee.org wrote: > On Thursday, March 16, 2017 at 7:41:08 PM UTC+11, rickman wrote: >> On 3/16/2017 3:28 AM, upsidedown@downunder.com wrote: >>> On Thu, 16 Mar 2017 02:51:41 -0400, rickman <gnuarm@gmail.com> wrote: >>> >>>> On 3/16/2017 2:20 AM, upsidedown@downunder.com wrote: >>>>> On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: >>>>> >>>>>>> >>>>>>> >>>>>>> This may be a heresy: >>>>>>> >>>>>>> There are plenty of small ARM Cortex-M chips with built-in >>>>>>> counter-timers. Get one of them with a decent crystal (say in the range >>>>>>> of 5 to 20 MHz) and divide from it with the built-in timer. The cost >>>>>>> will be just some dollars for the components. >>>>>>> >>>>>>> A small Cortex evaluation unit can be had for some tens of dollars, >>>>>>> and there are the crystal and board built-in, together with some >>>>>>> means of getting the code in. >>>>>> >>>>>> Thanks for the suggestion, but that does not fit the problem space. The >>>>>> FPGA board I am prototyping with has an oscillator on board, just not a >>>>>> multiple of 240 kHz. This is a very low power design and every ARM type >>>>>> CPU I have seen will consume mAs of current with the high speed crystal >>>>>> controlled clock. >>>>> >>>>> How about a free running CPU clock running at a few MHz and a crystal >>>>> in 0.5 to 1.5 MHz range generating an interrupt about every >>>>> microsecond. The interrupt updates the NCO (numerical controlled >>>>> oscillator) 16 to 32 bit phase accumulator and some bits are written >>>>> to the output pins. The rest of the time, the processor is kept in a >>>>> low power sleep mode. If sin/cos output is needed, insert a sine >>>>> lookup table between the phase accumulator and output pins. >>>>> These should not require many instructions, so the power consumption >>>>> should be low. >>>> >>>> I appreciate the suggestion, but why all the complexity? If I have a >>>> crystal creating a clock, I don't need the CPU. What you described is >>>> way more power and complexity than needed. >>> >>> I understood that you originally had problems ordering a crystal for >>> the exact integer multiple of 120 kHz. The NCO principle allows you to >>> generate any frequency from an other frequency, which doesn't have to >>> be harmonically related, as long as the Nyquist criterion is followed. >> >> That's not entirely correct. To get an exact value the reference >> frequency and the target frequency must be related by the ratio of two >> integers. Fclk = Fref * NCOstep / NCOmodulus where NCOstep is the phase >> increment and NCOmodulus is the modulus of the phase accumulator. > > A fractional-n divider can get you there with less hardware and a marginally tighter control loop. It took me a while to find the phrase "fractional-n divider" - haven't thought about them for many years. > > The highest common frequency of 32,768hZ and 120kHz is 64Hz - you have to divide the 32,768Hz by 512 to get that, and 120kHz by 1875. If you divide the 120kHz by 937 and 938 in successive intervals, you get something close to 128Hz. If you divide it by 468 over one interval, and by 469 over the next three intervals, you get something close to 256Hz. If you divide by 234 over five intervals and 235 over three, you get something close to 512Hz. > > For most practical purposes, counting three ticks of the 120kHz clock then four (and sometimes four again - specifically 205 three ticks and 315 four ticks) will let you lock exactly to the 32,768Hz clock. > > The phase error will gad about a bit in the short term, but a sufficiently slow four- or more-pole low pass filter in the feedback loop will clean that out. > >> I can do without the crystal I think. I can use 32.768 kHz as my >> reference. I can buy real time clock chips with temperature >> compensation and a programmable output intended for a processor >> interrupt. That output can be set for 1 second or other rates and used >> to time an LC oscillator. The LC oscillator can be trimmed with a >> varactor from the frequency measurement. I may start testing this >> tomorrow. > > Why bother with a varactor? The voltage controlled oscillator in a regular 4046 isn't all that noisy. Who said anything about noise? -- Rick C
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| From | upsidedown@downunder.com |
|---|---|
| Date | 2017-03-17 00:22 +0200 |
| Message-ID | <303mcctas9ekomsgmd5q92ui9gib7d81l2@4ax.com> |
| In reply to | #452098 |
On Thu, 16 Mar 2017 04:40:52 -0400, rickman <gnuarm@gmail.com> wrote: >On 3/16/2017 3:28 AM, upsidedown@downunder.com wrote: >> On Thu, 16 Mar 2017 02:51:41 -0400, rickman <gnuarm@gmail.com> wrote: >> >>> On 3/16/2017 2:20 AM, upsidedown@downunder.com wrote: >>>> On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: >>>> >>>>>> >>>>>> >>>>>> This may be a heresy: >>>>>> >>>>>> There are plenty of small ARM Cortex-M chips with built-in >>>>>> counter-timers. Get one of them with a decent crystal (say in the range of >>>>>> 5 to 20 MHz) and divide from it with the built-in timer. The cost >>>>>> will be just some dollars for the components. >>>>>> >>>>>> A small Cortex evaluation unit can be had for some tens of dollars, >>>>>> and there are the crystal and board built-in, together with some >>>>>> means of getting the code in. >>>>> >>>>> Thanks for the suggestion, but that does not fit the problem space. The >>>>> FPGA board I am prototyping with has an oscillator on board, just not a >>>>> multiple of 240 kHz. This is a very low power design and every ARM type >>>>> CPU I have seen will consume mAs of current with the high speed crystal >>>>> controlled clock. >>>> >>>> How about a free running CPU clock running at a few MHz and a crystal >>>> in 0.5 to 1.5 MHz range generating an interrupt about every >>>> microsecond. The interrupt updates the NCO (numerical controlled >>>> oscillator) 16 to 32 bit phase accumulator and some bits are written >>>> to the output pins. The rest of the time, the processor is kept in a >>>> low power sleep mode. If sin/cos output is needed, insert a sine >>>> lookup table between the phase accumulator and output pins. >>>> These should not require many instructions, so the power consumption >>>> should be low. >>> >>> I appreciate the suggestion, but why all the complexity? If I have a >>> crystal creating a clock, I don't need the CPU. What you described is >>> way more power and complexity than needed. >> >> I understood that you originally had problems ordering a crystal for >> the exact integer multiple of 120 kHz. The NCO principle allows you to >> generate any frequency from an other frequency, which doesn't have to >> be harmonically related, as long as the Nyquist criterion is followed. > >That's not entirely correct. To get an exact value the reference >frequency and the target frequency must be related by the ratio of two >integers. Fclk = Fref * NCOstep / NCOmodulus where NCOstep is the phase >increment and NCOmodulus is the modulus of the phase accumulator. Increasing the phase accumulator width is usually cheap. Most people think about 16/24 bit phase accumulators. I have used 64 bit accumulators in some time keeping applications. Of course, this is ultimately limited by the accuracy of the frequency source. When doing the NCO in software using longer phase accumulators than the machine word, one has to be careful how the phase accumulator value is copied to the outside world from the ISR (interrupt service routine). Copying only the most significant machine word should be OK and let the ISR also increment locally the "invisible" low part of the phase accumulator should do the trick.
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-16 19:14 -0400 |
| Message-ID | <oaf63t$7vn$1@dont-email.me> |
| In reply to | #452177 |
On 3/16/2017 6:22 PM, upsidedown@downunder.com wrote: > On Thu, 16 Mar 2017 04:40:52 -0400, rickman <gnuarm@gmail.com> wrote: > >> On 3/16/2017 3:28 AM, upsidedown@downunder.com wrote: >>> On Thu, 16 Mar 2017 02:51:41 -0400, rickman <gnuarm@gmail.com> wrote: >>> >>>> On 3/16/2017 2:20 AM, upsidedown@downunder.com wrote: >>>>> On Wed, 15 Mar 2017 12:44:10 -0400, rickman <gnuarm@gmail.com> wrote: >>>>> >>>>>>> >>>>>>> >>>>>>> This may be a heresy: >>>>>>> >>>>>>> There are plenty of small ARM Cortex-M chips with built-in >>>>>>> counter-timers. Get one of them with a decent crystal (say in the range of >>>>>>> 5 to 20 MHz) and divide from it with the built-in timer. The cost >>>>>>> will be just some dollars for the components. >>>>>>> >>>>>>> A small Cortex evaluation unit can be had for some tens of dollars, >>>>>>> and there are the crystal and board built-in, together with some >>>>>>> means of getting the code in. >>>>>> >>>>>> Thanks for the suggestion, but that does not fit the problem space. The >>>>>> FPGA board I am prototyping with has an oscillator on board, just not a >>>>>> multiple of 240 kHz. This is a very low power design and every ARM type >>>>>> CPU I have seen will consume mAs of current with the high speed crystal >>>>>> controlled clock. >>>>> >>>>> How about a free running CPU clock running at a few MHz and a crystal >>>>> in 0.5 to 1.5 MHz range generating an interrupt about every >>>>> microsecond. The interrupt updates the NCO (numerical controlled >>>>> oscillator) 16 to 32 bit phase accumulator and some bits are written >>>>> to the output pins. The rest of the time, the processor is kept in a >>>>> low power sleep mode. If sin/cos output is needed, insert a sine >>>>> lookup table between the phase accumulator and output pins. >>>>> These should not require many instructions, so the power consumption >>>>> should be low. >>>> >>>> I appreciate the suggestion, but why all the complexity? If I have a >>>> crystal creating a clock, I don't need the CPU. What you described is >>>> way more power and complexity than needed. >>> >>> I understood that you originally had problems ordering a crystal for >>> the exact integer multiple of 120 kHz. The NCO principle allows you to >>> generate any frequency from an other frequency, which doesn't have to >>> be harmonically related, as long as the Nyquist criterion is followed. >> >> That's not entirely correct. To get an exact value the reference >> frequency and the target frequency must be related by the ratio of two >> integers. Fclk = Fref * NCOstep / NCOmodulus where NCOstep is the phase >> increment and NCOmodulus is the modulus of the phase accumulator. > > Increasing the phase accumulator width is usually cheap. Most people > think about 16/24 bit phase accumulators. I have used 64 bit > accumulators in some time keeping applications. Of course, this is > ultimately limited by the accuracy of the frequency source. > > When doing the NCO in software using longer phase accumulators than > the machine word, one has to be careful how the phase accumulator > value is copied to the outside world from the ISR (interrupt service > routine). Copying only the most significant machine word should be OK > and let the ISR also increment locally the "invisible" low part of the > phase accumulator should do the trick. Discarding (or rounding, same thing) part of the phase word before converting to a sine wave introduces a jitter which shows up as spurs close to the fundamental and so can not be easily filtered. Phase truncation creates real problems for many apps. -- Rick C
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| From | John S <Sophi.2@invalid.org> |
|---|---|
| Date | 2017-03-13 05:51 -0500 |
| Message-ID | <oa5tdh$4hp$2@dont-email.me> |
| In reply to | #450920 |
On 3/8/2017 8:02 PM, dagmargoodboat@yahoo.com wrote: > On Wednesday, March 8, 2017 at 5:51:15 PM UTC-5, rickman wrote: >> I know third overtone is used for higher frequency oscillators, mainly >> because fundamental are hard to make at higher frequencies. I need a >> 120 kHz crystal and can't find one without ordering a full reel. 40 kHz >> is easy to find however. How practical is it to run an X cut crystal at >> the third overtone? >> >> I plan to bend it anyway to make it into a VCXO, so if the overtone is >> slightly off from three times the fundamental, that should be ok. >> >> -- >> >> Rick C > > 60kHz is easy to find--60kHz x 2 = 120kHz. Or divide down from > high up. > > Cheers, > James Arthur > Would an XOR with an rc work as a frequency doubler?
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-13 08:39 -0400 |
| Message-ID | <oa63p6$9is$1@dont-email.me> |
| In reply to | #451600 |
On 3/13/2017 6:51 AM, John S wrote: > On 3/8/2017 8:02 PM, dagmargoodboat@yahoo.com wrote: >> On Wednesday, March 8, 2017 at 5:51:15 PM UTC-5, rickman wrote: >>> I know third overtone is used for higher frequency oscillators, mainly >>> because fundamental are hard to make at higher frequencies. I need a >>> 120 kHz crystal and can't find one without ordering a full reel. 40 kHz >>> is easy to find however. How practical is it to run an X cut crystal at >>> the third overtone? >>> >>> I plan to bend it anyway to make it into a VCXO, so if the overtone is >>> slightly off from three times the fundamental, that should be ok. >>> >>> -- >>> >>> Rick C >> >> 60kHz is easy to find--60kHz x 2 = 120kHz. Or divide down from >> high up. >> >> Cheers, >> James Arthur >> > > Would an XOR with an rc work as a frequency doubler? Not very well in this case. -- Rick C
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-09 21:09 -0500 |
| Message-ID | <o9t1mh$k1c$1@dont-email.me> |
| In reply to | #450876 |
On 3/8/2017 5:51 PM, rickman wrote: > I know third overtone is used for higher frequency oscillators, mainly > because fundamental are hard to make at higher frequencies. I need a > 120 kHz crystal and can't find one without ordering a full reel. 40 kHz > is easy to find however. How practical is it to run an X cut crystal at > the third overtone? > > I plan to bend it anyway to make it into a VCXO, so if the overtone is > slightly off from three times the fundamental, that should be ok. Looking at the tuning diode, I found some by Skyworks that look pretty good and are available at Digikey. But I can't tell what the reverse current is. It's not in the data sheet. They have parameters for the spice model, but I'm not confident in being able to create a model to then get the current. Can anyone divine the model data to glean that directly without having to do the simulation? SMV1251 LS = 0.7 nH CJO = 52.48 VJ = 100 M = 76 CP = 2.00 RS = 1.4 DIODEM Diode_Model IS = 1.00e-14 RS = 0 N = 1 TT = 0 CJO = C JOM = M VJ = V JEG = 1.11 XTI = 3 KF =0 AF =1 FC = 0.5 BV = VB IBV = 1e-3 ISR = 0 NR = 2 IKF = 0 NBV = 1 IBVL = 0 NBVL = 1 TBV1 = 0 TNOM = 27 FFE = 1 There appears to be no shortage of devices available. I guess I should look for one that has a model available. -- Rick C
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| From | "Tim Williams" <tiwill@seventransistorlabs.com> |
|---|---|
| Date | 2017-03-09 20:15 -0600 |
| Message-ID | <o9t21p$kpc$1@dont-email.me> |
| In reply to | #450876 |
FYI, crystal overtones are just that -- overtones, not harmonics. They're usually a little bit above harmonic. There may be more, and stronger, spurious modes around the overtone as well (depends on cut and holder design), and the tempco will be a lot stronger (also depends on cut). Normally, overtone crystals are cut for the purpose, to account for all of this. If you're going to do it, please do report back how well it worked out -- if you can, try to plot the impedance and bandwidth of the overtone, and the spurs around it, and see what happens at different temperatures. I would expect a tuning-fork style crystal to have a strong overtone, but I don't know that it will be useable. Good luck! On a related note, I have a 100kc crystal handy -- but it's not 120, and, as you might guess from the "kc", it's somewhat antique (dated 1959ish I think it was). Quite stately in its metal can. :-) Looks like a contemporary electrolytic capacitor, or octal audio transformer, but just two round pins. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com "rickman" <gnuarm@gmail.com> wrote in message news:o9q1nn$vi7$1@dont-email.me... >I know third overtone is used for higher frequency oscillators, mainly >because fundamental are hard to make at higher frequencies. I need a 120 >kHz crystal and can't find one without ordering a full reel. 40 kHz is >easy to find however. How practical is it to run an X cut crystal at the >third overtone? > > I plan to bend it anyway to make it into a VCXO, so if the overtone is > slightly off from three times the fundamental, that should be ok. > > -- > > Rick C
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-09 23:36 -0500 |
| Message-ID | <o9tabc$t7$1@dont-email.me> |
| In reply to | #451108 |
On 3/9/2017 9:15 PM, Tim Williams wrote: > FYI, crystal overtones are just that -- overtones, not harmonics. > They're usually a little bit above harmonic. There may be more, and > stronger, spurious modes around the overtone as well (depends on cut and > holder design), and the tempco will be a lot stronger (also depends on > cut). > > Normally, overtone crystals are cut for the purpose, to account for all > of this. > > If you're going to do it, please do report back how well it worked out > -- if you can, try to plot the impedance and bandwidth of the overtone, > and the spurs around it, and see what happens at different > temperatures. I would expect a tuning-fork style crystal to have a > strong overtone, but I don't know that it will be useable. Good luck! > > On a related note, I have a 100kc crystal handy -- but it's not 120, > and, as you might guess from the "kc", it's somewhat antique (dated > 1959ish I think it was). Quite stately in its metal can. :-) Looks > like a contemporary electrolytic capacitor, or octal audio transformer, > but just two round pins. Thanks for the offer, but I don't want crystals made in Kansas City. ;) I'm avoiding the overtone thing. All I need is an unstable oscillator. I'm going to find a 120 kHz crystal (not made in Kansas City) or I can use a 240 kHz crystal. 120 kHz would be lower power, but if I can trust my simulations, the oscillator power is going to be true flea power, perhaps not even reaching 1 uW. So doubling that at 240 kHz won't be a problem. This won't run all the time anyway, so power isn't as crucial as the circuit that runs all the time, but power consumption can add up if you aren't careful about every little piece. While I wait for crystal makers to get back to me I am looking at tuning the crystal. I've found a couple of varactors that might do the job although you wouldn't know by the simulation. Maybe my circuit isn't so good, but I can't get a change in load capacitors to change the frequency of the circuit in a measurable way. -- Rick C
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| From | "Tim Williams" <tiwill@seventransistorlabs.com> |
|---|---|
| Date | 2017-03-10 19:02 -0600 |
| Message-ID | <o9vi54$dkj$1@dont-email.me> |
| In reply to | #451120 |
"rickman" <gnuarm@gmail.com> wrote in message news:o9tabc$t7$1@dont-email.me... > Thanks for the offer, but I don't want crystals made in Kansas City. ;) > But so many wonderful things come out of KC -- barbeque, methamphetamines.... oh, well that might explain your reluctance for their crystal. )-; > While I wait for crystal makers to get back to me I am looking at tuning > the crystal. I've found a couple of varactors that might do the job > although you wouldn't know by the simulation. Maybe my circuit isn't so > good, but I can't get a change in load capacitors to change the frequency > of the circuit in a measurable way. Ah, but in a simulation you shouldn't expect to measure it anyway; you can't do it on AC Analysis because it's nonlinear, and you can't do it on Transient because it takes forever, at super-high accuracy besides (like RELTOL < 10^-4, and > 10^4 cycles of run time). Better to wave the hands; if you know the CRLC parameters of your crystal, you can calculate how far it will pull. Reality won't match exactly, for all the usual reasons, but it should be similar at least. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2017-03-11 01:15 -0500 |
| Message-ID | <oa04ga$gbo$1@dont-email.me> |
| In reply to | #451243 |
On 3/10/2017 8:02 PM, Tim Williams wrote: > "rickman" <gnuarm@gmail.com> wrote in message > news:o9tabc$t7$1@dont-email.me... >> Thanks for the offer, but I don't want crystals made in Kansas City. ;) >> > > But so many wonderful things come out of KC -- barbeque, > methamphetamines.... oh, well that might explain your reluctance for > their crystal. )-; > >> While I wait for crystal makers to get back to me I am looking at tuning >> the crystal. I've found a couple of varactors that might do the job >> although you wouldn't know by the simulation. Maybe my circuit isn't so >> good, but I can't get a change in load capacitors to change the >> frequency of the circuit in a measurable way. > > Ah, but in a simulation you shouldn't expect to measure it anyway; you > can't do it on AC Analysis because it's nonlinear, and you can't do it > on Transient because it takes forever, at super-high accuracy besides > (like RELTOL < 10^-4, and > 10^4 cycles of run time). > > Better to wave the hands; if you know the CRLC parameters of your > crystal, you can calculate how far it will pull. Reality won't match > exactly, for all the usual reasons, but it should be similar at least. Certainly any crystal would be pullable to compensate for initial accuracy, temperature (small ranges you would find in an occupied dwelling) and aging. For a reasonably good crystal that would amount to less than 100 ppm. The question is what does it take to pull that far? I found some varactors that will give a 10:1 capacitance range without requiring more than 3.3 volts. But I have no idea how much that will change the frequency of the crystal I can't get anyway. Lol. How would you calculate that from the crystal parameters? How much can you trust the data the crystal makers provide? I mean, will it be accurate enough to calculate this? I guess the calculations are just the typical filter calculations with the given topology of the crystal and load caps? -- Rick C
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| From | upsidedown@downunder.com |
|---|---|
| Date | 2017-03-11 11:04 +0200 |
| Message-ID | <bre7cc193d4liam7nvf1l9ikjfrdd9hahg@4ax.com> |
| In reply to | #451278 |
On Sat, 11 Mar 2017 01:15:22 -0500, rickman <gnuarm@gmail.com> wrote: >On 3/10/2017 8:02 PM, Tim Williams wrote: >> "rickman" <gnuarm@gmail.com> wrote in message >> news:o9tabc$t7$1@dont-email.me... >>> Thanks for the offer, but I don't want crystals made in Kansas City. ;) >>> >> >> But so many wonderful things come out of KC -- barbeque, >> methamphetamines.... oh, well that might explain your reluctance for >> their crystal. )-; >> >>> While I wait for crystal makers to get back to me I am looking at tuning >>> the crystal. I've found a couple of varactors that might do the job >>> although you wouldn't know by the simulation. Maybe my circuit isn't so >>> good, but I can't get a change in load capacitors to change the >>> frequency of the circuit in a measurable way. >> >> Ah, but in a simulation you shouldn't expect to measure it anyway; you >> can't do it on AC Analysis because it's nonlinear, and you can't do it >> on Transient because it takes forever, at super-high accuracy besides >> (like RELTOL < 10^-4, and > 10^4 cycles of run time). >> >> Better to wave the hands; if you know the CRLC parameters of your >> crystal, you can calculate how far it will pull. Reality won't match >> exactly, for all the usual reasons, but it should be similar at least. > >Certainly any crystal would be pullable to compensate for initial >accuracy, temperature (small ranges you would find in an occupied >dwelling) and aging. For a reasonably good crystal that would amount to >less than 100 ppm. The question is what does it take to pull that far? An HF fundamental crystal might easily pull 100 ppm, but an third order overtone crystal maybe only 11 ppm or (1/n²) Are you going to use the crystal in parallel or series resonance mode? IIRC, overtone crystals are often specified in series resonance. Pulling a parallel resonance can be done with a parallel capacitance, while a series resonance may need a tunable series inductance. >I found some varactors that will give a 10:1 capacitance range without >requiring more than 3.3 volts. But I have no idea how much that will >change the frequency of the crystal I can't get anyway. Lol. Such low frequency crystal may need a lot of extra capacitance, how much would the maximum capacitance be for that varactor ? >How would you calculate that from the crystal parameters? How much can >you trust the data the crystal makers provide? I mean, will it be >accurate enough to calculate this? I guess the calculations are just >the typical filter calculations with the given topology of the crystal >and load caps?
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| From | "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> |
|---|---|
| Date | 2017-03-11 09:31 +0000 |
| Message-ID | <L_adnWwaSdlgXl7FnZ2dnUU7-W_NnZ2d@giganews.com> |
| In reply to | #451278 |
"rickman" wrote in message news:oa04ga$gbo$1@dont-email.me... On 3/10/2017 8:02 PM, Tim Williams wrote: > "rickman" <gnuarm@gmail.com> wrote in message > news:o9tabc$t7$1@dont-email.me... >> Thanks for the offer, but I don't want crystals made in Kansas City. ;) the frequency of the crystal I can't get anyway. Lol. >How would you calculate that from the crystal parameters? Formula for shift from fs, and spice techniques given in my other post. -- Kevin Aylward http://www.anasoft.co.uk - SuperSpice http://www.kevinaylward.co.uk/ee/index.html
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