On Oct 18, 12:12=A0pm, "langw...@fonz.dk" <langw...@fonz.dk> wrote:> I had the crazy idea of using a serial flash, too bad the 45lf010 > isn't available anymore > it had a read command 0xff, so you could just tie din high and clock > it and it would spit > out bits forever. you could use a config flash for an fpga but they > are a bit expensive > > program the flash with Don Lancasters magic sine waves, or run a > sinewave through a delta-sigma > modulator > > -LasseThat's good idea, really. That's the ultimate self-clocking shift- register. -- Cheers, James Arthur
Stepped sine wave
Started by ●October 13, 2011
Reply by ●October 19, 20112011-10-19
Reply by ●October 19, 20112011-10-19
On Wed, 19 Oct 2011 06:39:57 -0700 (PDT), George Herold <gherold@teachspin.com> wrote:>On Oct 18, 11:10�pm, whit3rd <whit...@gmail.com> wrote: >> On Monday, October 17, 2011 6:50:40 AM UTC-7, George Herold wrote: >> > You can get 0.1% resistors from Sussumu for ~$0.20 each. >> >> Twenty cents each? �If they stock values from 100 to 100k ohms, >> that means they have to have about 7000 standard values? >> Cool! >> >> One zero-ohm resistor, and two (maybe four) of the smallest resistors, >> can be 1% values, without undue error. �So, there's room to squeeze >> the $2 figure down a little. > >Ahh, they only have the 'standard' 1% values. Here's 10k ones in 0805 >package. >http://search.digikey.com/us/en/products/RG2012P-103-B-T5/RG20P10.0KBCT-ND/1241041 > >To get the exact values to 0.1% I'll have to mix some 0.1% resistors >with smaller 1%ers. > >If you can use one thousand of 'em then they're only ~$0.1 each. >Pretty amamzing really, you can make amps with a gain of >10.00(something)If you can deal with 25ppm/C, DigiKey has them by the reel for under $.04 each.
Reply by ●October 19, 20112011-10-19
On Oct 18, 11:49=A0pm, dagmargoodb...@yahoo.com wrote:> On Oct 18, 11:15=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > > > On Oct 17, 10:02=A0am, George Herold <gher...@teachspin.com> wrote: > > > > On Oct 16, 11:43=A0pm, dagmargoodb...@yahoo.com wrote: > > > > > On Oct 16, 6:09=A0pm, "k...@att.bizzzzzzzzzzzz" wrote: > > > > > > On Sun, 16 Oct 2011 10:42:48 -0700 (PDT), dagmargoodb...@yahoo.co=m wrote:> > > > > >On Oct 16, 8:55=A0am, "k...@att.bizzzzzzzzzzzz" wrote: > > > > > >> On Sun, 16 Oct 2011 06:25:38 -0700 (PDT), dagmargoodb...@yahoo=.com wrote:> > > > > >> >So, we've got several versions: 10 steps with one chip, 16 st=eps with> > > > > >> >three chips, or 32 steps for five chips. Or, as always, you c=ould use> > > > > >> >a PIC :-) > > > > > > >> Or an 8-bit counter (e.g. '579), ROM, and DAC. =A0256 steps, t=hree chips. ;-)> > > > > > >> The synchronous counter is the limitation, here. > > > > > > >Hey, how about two 'HC4017's, driven out-of-phase. =A0Clock one =rising,> > > > > >one falling. =A0That's 20 steps, two chips, dirt-simple. > > > > > > An FPGA. =A0Hundreds of steps, one chip. =A0Pick your poison. =A0=;-)> > > > > Come to think of it, I suspect staggered 'HC4017's doesn't work. ==A0Each> > > > output of "B" would straddle (be active during) two output states o=f> > > > "A", and the simultaneous equations fail. =A0You'd need to buffer '=em so> > > > you could enable just one 'HC4017 at a time, which is messy & takes > > > > more chips. > > > > > So, it's either one 'HC4017, or a PIC. =A0(Or a 555, details left a=s an> > > > exercise for the student.) > > > > > -- > > > > Cheers, > > > > James Arthur > > > > Dat's OK James, =A0I'm still pondering your idea of multiple > > > switching... using each resistor four times during a cycle. =A0(I'm a > > > bit slow so it takes me a while to digest what you are suggesting.) ==A0I> > > must admit that the symmetry is appealing. > > > > George H.- Hide quoted text - > > > > - Show quoted text - > > > Well I stuck a switch cap filter on the output. (LTC1063, I know only > > 50kHz, which doesn=92t =91meet my spec', but I had one lying around.) > > > I clocked it at 16 times the stepped sine wave so the 3dB point was > > 1.6 times the fundamental. =A0Here=92s the spectrum before the SC. > > >http://imageshack.us/photo/my-images/404/sc1s.png/ > > > And after it.http://imageshack.us/photo/my-images/6/sc2h.png/ > > > The second harmonic goes up more than 10dB! =A0And there is all this > > other =91fluff=92 at low frequency. =A0Some new peak stands up at 2.5 k=Hz.> > I moved the 3dB point up to 3.2kHz and the 2nd harmonic was a few dB > > better... the weird signal at 2.5kHz moved out to 5 kHz? =A0Not sure I > > like switched cap filters. =A0We used the same SC on a different projec=t> > and it also added =91out of band=92 curd... at similar levels. > > > I=92ll try an analog multi pole Butterworth. =A0 Maybe a Sallen-Key. > > > George H. > > I've got two articles in the hard drive vault that use a squarewave > into a switched cap filter, overclocked >100:1, to generate a > sinewave. =A0The first architecture is fixed 1kHz: > =A0 =A0TLC555 =3D=3D> 19kHz RC-lowpass =3D=3D> MF6CN100 (Nat'l Semi), cla=ims> harmonics are 60dB down. > > The 2nd generates squarewaves with a uC. =A0That drives a 64x > overclocked MAX292 (8th-order Bessel directly). =A0"Clean" sinewave is > all they say. =A0They run the MAX292 bipolar off +5v, using a 10k-10k > divider for a virtual rail. =A0Funky. > > I could e-mail you the articles if interested, but they _really_ don't > say much more than what I already wrote. > > 1) Simple circuit generates clean sine waves, EDN, June 19, 1997, pg. > 99 > 2) Microcontroller-based Sine Wave Generator Has Crystal Accuracy, > Electronic Design, Dec. 14, 1998, pg. 74 > > -- > Cheers, > James Arthur- Hide quoted text - > > - Show quoted text -Gee thanks, but please don't bother. I'm now looking for a VCO to drive the whole chain. I was going to try the VCO in one of the 4046 PLL chips.. they are cheap enough. But I also found this 'synchronous' V-F converter. AD7741 it comes in an DIP which is nice. George H.
Reply by ●October 19, 20112011-10-19
On Oct 19, 10:20=A0am, George Herold <gher...@teachspin.com> wrote:> On Oct 18, 11:49=A0pm, dagmargoodb...@yahoo.com wrote: > > On Oct 18, 11:15=A0am, George Herold <gher...@teachspin.com> wrote:> > > Well I stuck a switch cap filter on the output. (LTC1063, I know only > > > 50kHz, which doesn=92t =91meet my spec', but I had one lying around.) > > > > I clocked it at 16 times the stepped sine wave so the 3dB point was > > > 1.6 times the fundamental. =A0Here=92s the spectrum before the SC. > > > >http://imageshack.us/photo/my-images/404/sc1s.png/ > > > > And after it.http://imageshack.us/photo/my-images/6/sc2h.png/ > > > > The second harmonic goes up more than 10dB! =A0And there is all this > > > other =91fluff=92 at low frequency. =A0Some new peak stands up at 2.5=kHz.> > > I moved the 3dB point up to 3.2kHz and the 2nd harmonic was a few dB > > > better... the weird signal at 2.5kHz moved out to 5 kHz? =A0Not sure =I> > > like switched cap filters. =A0We used the same SC on a different proj=ect> > > and it also added =91out of band=92 curd... at similar levels. > > > > I=92ll try an analog multi pole Butterworth. =A0 Maybe a Sallen-Key. > > > > George H. > > > I've got two articles in the hard drive vault that use a squarewave > > into a switched cap filter, overclocked >100:1, to generate a > > sinewave. =A0The first architecture is fixed 1kHz: > > =A0 =A0TLC555 =3D=3D> 19kHz RC-lowpass =3D=3D> MF6CN100 (Nat'l Semi), c=laims> > harmonics are 60dB down. > > > The 2nd generates squarewaves with a uC. =A0That drives a 64x > > overclocked MAX292 (8th-order Bessel directly). =A0"Clean" sinewave is > > all they say. =A0They run the MAX292 bipolar off +5v, using a 10k-10k > > divider for a virtual rail. =A0Funky. > > > I could e-mail you the articles if interested, but they _really_ don't > > say much more than what I already wrote. > > > 1) Simple circuit generates clean sine waves, EDN, June 19, 1997, pg. > > 99 > > 2) Microcontroller-based Sine Wave Generator Has Crystal Accuracy, > > Electronic Design, Dec. 14, 1998, pg. 74 > > > Gee thanks, but please don't bother. =A0I'm now looking for a VCO to > drive the whole chain. =A0I was going to try the VCO in one of the 4046 > PLL chips.. they are cheap enough. =A0But I also found this > 'synchronous' V-F converter. =A0AD7741 =A0it comes in an DIP which is > nice. > > George H.Don't worry about all the chit-chat--none of it obligates you, we're just playing. You're already on a pretty good path. -- Cheers, James Arthur
Reply by ●October 19, 20112011-10-19
On Oct 19, 10:05=A0am, dagmargoodb...@yahoo.com wrote:> On Oct 18, 11:15=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > > > On Oct 17, 10:02=A0am, George Herold <gher...@teachspin.com> wrote: > > > > On Oct 16, 11:43=A0pm, dagmargoodb...@yahoo.com wrote: > > > > > On Oct 16, 6:09=A0pm, "k...@att.bizzzzzzzzzzzz" wrote: > > > > > > On Sun, 16 Oct 2011 10:42:48 -0700 (PDT), dagmargoodb...@yahoo.co=m wrote:> > > > > >On Oct 16, 8:55=A0am, "k...@att.bizzzzzzzzzzzz" wrote: > > > > > >> On Sun, 16 Oct 2011 06:25:38 -0700 (PDT), dagmargoodb...@yahoo=.com wrote:> > > > > >> >So, we've got several versions: 10 steps with one chip, 16 st=eps with> > > > > >> >three chips, or 32 steps for five chips. Or, as always, you c=ould use> > > > > >> >a PIC :-) > > > > > > >> Or an 8-bit counter (e.g. '579), ROM, and DAC. =A0256 steps, t=hree chips. ;-)> > > > > > >> The synchronous counter is the limitation, here. > > > > > > >Hey, how about two 'HC4017's, driven out-of-phase. =A0Clock one =rising,> > > > > >one falling. =A0That's 20 steps, two chips, dirt-simple. > > > > > > An FPGA. =A0Hundreds of steps, one chip. =A0Pick your poison. =A0=;-)> > > > > Come to think of it, I suspect staggered 'HC4017's doesn't work. ==A0Each> > > > output of "B" would straddle (be active during) two output states o=f> > > > "A", and the simultaneous equations fail. =A0You'd need to buffer '=em so> > > > you could enable just one 'HC4017 at a time, which is messy & takes > > > > more chips. > > > > > So, it's either one 'HC4017, or a PIC. =A0(Or a 555, details left a=s an> > > > exercise for the student.) > > > > > -- > > > > Cheers, > > > > James Arthur > > > > Dat's OK James, =A0I'm still pondering your idea of multiple > > > switching... using each resistor four times during a cycle. =A0(I'm a > > > bit slow so it takes me a while to digest what you are suggesting.) ==A0I> > > must admit that the symmetry is appealing. > > > > George H.- Hide quoted text - > > > > - Show quoted text - > > > Well I stuck a switch cap filter on the output. (LTC1063, I know only > > 50kHz, which doesn=92t =91meet my spec', but I had one lying around.) > > > I clocked it at 16 times the stepped sine wave so the 3dB point was > > 1.6 times the fundamental. =A0Here=92s the spectrum before the SC. > > >http://imageshack.us/photo/my-images/404/sc1s.png/ > > > And after it.http://imageshack.us/photo/my-images/6/sc2h.png/ > > > The second harmonic goes up more than 10dB! =A0And there is all this > > other =91fluff=92 at low frequency. =A0Some new peak stands up at 2.5 k=Hz.> > I moved the 3dB point up to 3.2kHz and the 2nd harmonic was a few dB > > better... the weird signal at 2.5kHz moved out to 5 kHz? =A0Not sure I > > like switched cap filters. =A0We used the same SC on a different projec=t> > and it also added =91out of band=92 curd... at similar levels. > > > I=92ll try an analog multi pole Butterworth. =A0 Maybe a Sallen-Key. > > > George H. > > Ideas: I'd suggest you aren't clocking the LIC1063 fast enough, and > need a small anti-aliasing pre-filter. =A0(Doesn't it need 100x anyhow?)SC clocked at 160kHz (1.6kHz corner), stepped sine clocked at 10kHz, output at 1kHz. Clocking the SC faster helped a bit...> > Choosing the filter clock frequency as some integer multiple of the > DAC clock rate will kill most of the intermodulation products.I am clocking everthing from the same source. I mumble, "inter modulation distortion". But I really don't know what that means. (OK, sure freq. X mixes with freq. Y and you get a little sum and/or difference at the output. But how does it happen?) I was wondering if I choose some prime number divider if that would help? Run the SC at say 17 times the clock to the stepped sine. I'll see what a little pre-filtering does. George H.> > -- > Cheers, > James Arthur- Hide quoted text - > > - Show quoted text -
Reply by ●October 19, 20112011-10-19
On 10/19/2011 09:29 AM, dagmargoodboat@yahoo.com wrote:> On Oct 16, 11:10 pm, Phil Hobbs > <pcdhSpamMeSensel...@electrooptical.net> wrote: >> On 10/16/2011 11:43 PM, dagmargoodb...@yahoo.com wrote: > >>> Come to think of it, I suspect staggered 'HC4017's doesn't work. Each >>> output of "B" would straddle (be active during) two output states of >>> "A", and the simultaneous equations fail. You'd need to buffer 'em so >>> you could enable just one 'HC4017 at a time, which is messy& takes >>> more chips. >> >>> So, it's either one 'HC4017, or a PIC. (Or a 555, details left as an >>> exercise for the student.) >> >> >> We really need a 4017 with tri-state outputs. ;) >> >> You could take advantage of the particular phase choice that George >> used, i.e. one phase is disconnected, and use a bunch of SIPO shift >> registers. Do a synchronous reset of all of them when the last stage >> goes high, and use an R-S flipflop to inject a 1 into the first stage >> when that happens, reset from the output of the first stage. >> >> It would also need a missing pulse detector or something like that to >> make sure that it doesn't just sit there producing all zeros forever. >> You could get 8N+1 phases for about N+2 packages and 8N resistors. > > Not bad--that's pretty simple. > >> Alternatively, adapting your folding trick, it might be possible to use >> a bunch of universal shift registers and just shuttle the 1-state back >> and forth from end to end, by changing the shift direction when it hits >> the end. That way you'd get 16N or maybe 16N-1 codes for N + 3ish >> packages and 8N resistors. >> >> Fun. > > I poked around the available shift registers @ Digikey. Alas, bi- > directionals are 4 bits only. > > So, my best low chip stepped addition(s) are these: > 74HC154 > .------. > | 0|---[R0]--. > | 1|---[R1]--+ > | 2|---[R2]--+ > | 3|---[R3]--+ > | 4|---[R4]--+ .------. > | 5|---[R5]--+ | X | > | 6|---[R6]--+-->|+/- 1 |--> to filter > | 7|---[R7]--+ | | > | 8|---[R8]--+ '------' > | 9|---[R9]--+ ^ > | 10|--[R10]--+ | > | 11|--[R11]--+ | > | 12|--[R12]--+ | > | 13|--[R13]--+ | > | 14|--[R14]--+ | > | 15|--[R15]--' | > | | | > | ABCD | | > '------' | > |||| | > .----. | > |XOR |<-. | > '----' | | > |||| .-' | > |||| |.---------------' > |||| || > .---------. > | ABCD EF | > 64x clk -|> | 6-bit Counter > | | > '---------' > > You could go to 32 steps by dropping the +/-1 stage and save a chip, > naturally. > > > Or you can extend an 8-step DAC to get a 32-step sine, as suggested > before... > > 'HC4051 > .-----. > v7-----|0 | > v6-----|1 | .-------. > v5-----|2 | | X | > v4-----|3 Y|----| +/- 1 |--- > v3-----|4 | | | > v2-----|5 | '-------' > v1-----|6 | ^ > v0-----|7 | | > | ABC | | > '-----' | > ||| | > .---. | > |XOR|<-. | > '---' | | > ||| .-' | > ||| |.-------' > ||| || > .-------. > | ABC DE| > 32x clk -|> | 5-bit Counter > | | > '-------' > > The neat thing about these sine-weighted DACs over straight linear > DACs is that, theoretically, the steps can be exact. 0.1% resistors > puts you competitive with 10-bit linear DACs, with a lot less hassle. > > -- > Cheers, > James ArthurAgreed about the little RC DACs--they're cute. There's an old arbitrary waveform generator, the Exact 202, that has an array of 10-turn panel pots, one for each point in the waveform I wonder if they used this trick or had a bunch of analogue switches? There's the 74HC299, which is an 8-bit universal shift register, and among its other talents it can shift both directions. That plus an HC74 dual D flipflop will make it do the back and forth one-shuttling trick. One half of the HC74 is an RS flipflop that switches the shifting direction--set on Q8 of the right-hand end (an auxiliary FF--see below), reset on Q0 of the left-hand end. Getting rid of spurious sequences is always the trick with this sort of gizmo. Clocking the 1 off one the end of the register into the other half of the HC74 makes this easy--connect its Q output to the appropriate serial input, AC couple its Qbar output into the Rbar (master reset) inputs of the shift registers, and use a mickey-mouse logic one-shot on its S' input, so that it sets itself asynchronously if it doesn't see a one-state every so often. (Diode from Q to Sbar, RC from Sbar to ground.) If RC-coupling logic is too gross, we could use an HC123 dual one-shot package. (It's also possible to use gates to form the reset and do the RC-coupling thing on the gate package to make a missing pulse detector. So assuming I haven't missed anything too horrible, using symmetry, you can make a 16N+1 step sine wave with N shift registers, one D flipflop package, and a bit of M2L or a one-shot. If an even-order approximation is important, we could take the DFF's input one stage early and get 16N instead. Cheers Phil Hobbs (Who has wasted too much time on this exercise, but enjoyed it.)
Reply by ●October 19, 20112011-10-19
On Oct 19, 11:47=A0am, dagmargoodb...@yahoo.com wrote:> On Oct 19, 10:20=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > > > On Oct 18, 11:49=A0pm, dagmargoodb...@yahoo.com wrote: > > > On Oct 18, 11:15=A0am, George Herold <gher...@teachspin.com> wrote: > > > > Well I stuck a switch cap filter on the output. (LTC1063, I know on=ly> > > > 50kHz, which doesn=92t =91meet my spec', but I had one lying around=.)> > > > > I clocked it at 16 times the stepped sine wave so the 3dB point was > > > > 1.6 times the fundamental. =A0Here=92s the spectrum before the SC. > > > > >http://imageshack.us/photo/my-images/404/sc1s.png/ > > > > > And after it.http://imageshack.us/photo/my-images/6/sc2h.png/ > > > > > The second harmonic goes up more than 10dB! =A0And there is all thi=s> > > > other =91fluff=92 at low frequency. =A0Some new peak stands up at 2=.5 kHz.> > > > I moved the 3dB point up to 3.2kHz and the 2nd harmonic was a few d=B> > > > better... the weird signal at 2.5kHz moved out to 5 kHz? =A0Not sur=e I> > > > like switched cap filters. =A0We used the same SC on a different pr=oject> > > > and it also added =91out of band=92 curd... at similar levels. > > > > > I=92ll try an analog multi pole Butterworth. =A0 Maybe a Sallen-Key=.> > > > > George H. > > > > I've got two articles in the hard drive vault that use a squarewave > > > into a switched cap filter, overclocked >100:1, to generate a > > > sinewave. =A0The first architecture is fixed 1kHz: > > > =A0 =A0TLC555 =3D=3D> 19kHz RC-lowpass =3D=3D> MF6CN100 (Nat'l Semi),=claims> > > harmonics are 60dB down. > > > > The 2nd generates squarewaves with a uC. =A0That drives a 64x > > > overclocked MAX292 (8th-order Bessel directly). =A0"Clean" sinewave i=s> > > all they say. =A0They run the MAX292 bipolar off +5v, using a 10k-10k > > > divider for a virtual rail. =A0Funky. > > > > I could e-mail you the articles if interested, but they _really_ don'=t> > > say much more than what I already wrote. > > > > 1) Simple circuit generates clean sine waves, EDN, June 19, 1997, pg. > > > 99 > > > 2) Microcontroller-based Sine Wave Generator Has Crystal Accuracy, > > > Electronic Design, Dec. 14, 1998, pg. 74 > > > Gee thanks, but please don't bother. =A0I'm now looking for a VCO to > > drive the whole chain. =A0I was going to try the VCO in one of the 4046 > > PLL chips.. they are cheap enough. =A0But I also found this > > 'synchronous' V-F converter. =A0AD7741 =A0it comes in an DIP which is > > nice. > > > George H. > > Don't worry about all the chit-chat--none of it obligates you, we're > just playing. =A0You're already on a pretty good path. > > -- > Cheers, > James Arthur- Hide quoted text - > > - Show quoted text -Big Grin! No it's my great pleasure! Some one sent me "two tramps in mud time" yesterday. http://www.etymonline.com/poems/tramps.htm The last few lines keep tripping through my head. (My 'excuse' for doing electronics.) George H.
Reply by ●October 19, 20112011-10-19
On Oct 19, 10:47=A0am, George Herold <gher...@teachspin.com> wrote:> On Oct 19, 10:05=A0am, dagmargoodb...@yahoo.com wrote: > > > > > On Oct 18, 11:15=A0am, George Herold <gher...@teachspin.com> wrote: > > > > On Oct 17, 10:02=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > On Oct 16, 11:43=A0pm, dagmargoodb...@yahoo.com wrote: > > > > > > On Oct 16, 6:09=A0pm, "k...@att.bizzzzzzzzzzzz" wrote: > > > > > > > On Sun, 16 Oct 2011 10:42:48 -0700 (PDT), dagmargoodb...@yahoo.=com wrote:> > > > > > >On Oct 16, 8:55=A0am, "k...@att.bizzzzzzzzzzzz" wrote: > > > > > > >> On Sun, 16 Oct 2011 06:25:38 -0700 (PDT), dagmargoodb...@yah=oo.com wrote:> > > > > > >> >So, we've got several versions: 10 steps with one chip, 16 =steps with> > > > > > >> >three chips, or 32 steps for five chips. Or, as always, you=could use> > > > > > >> >a PIC :-) > > > > > > > >> Or an 8-bit counter (e.g. '579), ROM, and DAC. =A0256 steps,=three chips. ;-)> > > > > > > >> The synchronous counter is the limitation, here. > > > > > > > >Hey, how about two 'HC4017's, driven out-of-phase. =A0Clock on=e rising,> > > > > > >one falling. =A0That's 20 steps, two chips, dirt-simple. > > > > > > > An FPGA. =A0Hundreds of steps, one chip. =A0Pick your poison. ==A0;-)> > > > > > Come to think of it, I suspect staggered 'HC4017's doesn't work. ==A0Each> > > > > output of "B" would straddle (be active during) two output states=of> > > > > "A", and the simultaneous equations fail. =A0You'd need to buffer='em so> > > > > you could enable just one 'HC4017 at a time, which is messy & tak=es> > > > > more chips. > > > > > > So, it's either one 'HC4017, or a PIC. =A0(Or a 555, details left=as an> > > > > exercise for the student.) > > > > > > -- > > > > > Cheers, > > > > > James Arthur > > > > > Dat's OK James, =A0I'm still pondering your idea of multiple > > > > switching... using each resistor four times during a cycle. =A0(I'm=a> > > > bit slow so it takes me a while to digest what you are suggesting.)==A0I> > > > must admit that the symmetry is appealing. > > > > > George H.- Hide quoted text - > > > > > - Show quoted text - > > > > Well I stuck a switch cap filter on the output. (LTC1063, I know only > > > 50kHz, which doesn=92t =91meet my spec', but I had one lying around.) > > > > I clocked it at 16 times the stepped sine wave so the 3dB point was > > > 1.6 times the fundamental. =A0Here=92s the spectrum before the SC. > > > >http://imageshack.us/photo/my-images/404/sc1s.png/ > > > > And after it.http://imageshack.us/photo/my-images/6/sc2h.png/ > > > > The second harmonic goes up more than 10dB! =A0And there is all this > > > other =91fluff=92 at low frequency. =A0Some new peak stands up at 2.5=kHz.> > > I moved the 3dB point up to 3.2kHz and the 2nd harmonic was a few dB > > > better... the weird signal at 2.5kHz moved out to 5 kHz? =A0Not sure =I> > > like switched cap filters. =A0We used the same SC on a different proj=ect> > > and it also added =91out of band=92 curd... at similar levels. > > > > I=92ll try an analog multi pole Butterworth. =A0 Maybe a Sallen-Key. > > > > George H. > > > Ideas: I'd suggest you aren't clocking the LIC1063 fast enough, and > > need a small anti-aliasing pre-filter. =A0(Doesn't it need 100x anyhow?=)> > SC clocked at 160kHz (1.6kHz corner), =A0stepped sine clocked at 10kHz, > output at 1kHz. =A0Clocking the SC faster helped a bit...I thought the LTC1063 needs a 100x clock (f_cutoff =3D f_clk/100)? So, for a 1KHz output, the 4017 should be clocked at 10Khz, and the filter at 1MHz. No, wait, 100kHz--my mistake. That's only 10x the DAC clock rate. Hmmm. Kind of tight.> > Choosing the filter clock frequency as some integer multiple of the > > DAC clock rate will kill most of the intermodulation products. > > I am clocking everthing from the same source.Good. (I think.)> =A0I mumble, "inter modulation distortion". =A0But I really don't know > what that means. > (OK, sure freq. X mixes with freq. Y and you get a little sum and/or > difference at the output. But how does it happen?)All this chopping and sampling produces mixing products. So, for example, the 9th and 11th harmonics get mixed, producing 2nd and 20th harmonics. The combinations are infinite.> I was wondering if I choose some prime number divider if that would > help? =A0Run the SC at say 17 times the clock to the stepped sine.You could spread them out with spread spectrum techniques (modulate the filter clock), but I'm not sure that helps...depends who's generating how much of what.> I'll see what a little pre-filtering does.Should cut down on lots of high-order mixing products. It's cheap-- worth doing. -- Cheers, James Arthur
Reply by ●October 19, 20112011-10-19
On Oct 19, 12:25=A0pm, George Herold <gher...@teachspin.com> wrote:> On Oct 19, 11:47=A0am, dagmargoodb...@yahoo.com wrote: > > > > > On Oct 19, 10:20=A0am, George Herold <gher...@teachspin.com> wrote: > > > > On Oct 18, 11:49=A0pm, dagmargoodb...@yahoo.com wrote: > > > > On Oct 18, 11:15=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > Well I stuck a switch cap filter on the output. (LTC1063, I know =only> > > > > 50kHz, which doesn=92t =91meet my spec', but I had one lying arou=nd.)> > > > > > I clocked it at 16 times the stepped sine wave so the 3dB point w=as> > > > > 1.6 times the fundamental. =A0Here=92s the spectrum before the SC=.> > > > > >http://imageshack.us/photo/my-images/404/sc1s.png/ > > > > > > And after it.http://imageshack.us/photo/my-images/6/sc2h.png/ > > > > > > The second harmonic goes up more than 10dB! =A0And there is all t=his> > > > > other =91fluff=92 at low frequency. =A0Some new peak stands up at=2.5 kHz.> > > > > I moved the 3dB point up to 3.2kHz and the 2nd harmonic was a few=dB> > > > > better... the weird signal at 2.5kHz moved out to 5 kHz? =A0Not s=ure I> > > > > like switched cap filters. =A0We used the same SC on a different =project> > > > > and it also added =91out of band=92 curd... at similar levels. > > > > > > I=92ll try an analog multi pole Butterworth. =A0 Maybe a Sallen-K=ey.> > > > > > George H. > > > > > I've got two articles in the hard drive vault that use a squarewave > > > > into a switched cap filter, overclocked >100:1, to generate a > > > > sinewave. =A0The first architecture is fixed 1kHz: > > > > =A0 =A0TLC555 =3D=3D> 19kHz RC-lowpass =3D=3D> MF6CN100 (Nat'l Semi=), claims> > > > harmonics are 60dB down. > > > > > The 2nd generates squarewaves with a uC. =A0That drives a 64x > > > > overclocked MAX292 (8th-order Bessel directly). =A0"Clean" sinewave=is> > > > all they say. =A0They run the MAX292 bipolar off +5v, using a 10k-1=0k> > > > divider for a virtual rail. =A0Funky. > > > > > I could e-mail you the articles if interested, but they _really_ do=n't> > > > say much more than what I already wrote. > > > > > 1) Simple circuit generates clean sine waves, EDN, June 19, 1997, p=g.> > > > 99 > > > > 2) Microcontroller-based Sine Wave Generator Has Crystal Accuracy, > > > > Electronic Design, Dec. 14, 1998, pg. 74 > > > > Gee thanks, but please don't bother. =A0I'm now looking for a VCO to > > > drive the whole chain. =A0I was going to try the VCO in one of the 40=46> > > PLL chips.. they are cheap enough. =A0But I also found this > > > 'synchronous' V-F converter. =A0AD7741 =A0it comes in an DIP which is > > > nice. > > > > George H. > > > Don't worry about all the chit-chat--none of it obligates you, we're > > just playing. =A0You're already on a pretty good path. > > > -- > > Cheers, > > James Arthur- Hide quoted text - > > > - Show quoted text - > > Big Grin! =A0No it's my great pleasure! =A0Some one sent me "two tramps i=n> mud time" yesterday. > > http://www.etymonline.com/poems/tramps.htm > > The last few lines keep tripping through my head. > (My 'excuse' for doing electronics.) > > George H.Whose poem this is I think I know, he's nowhere near to see me though; he will not see me reading here his dusty works by monitor's glow... Very appropriate. Lumberjacking has been heavy on my mind, with an eye to a neighbor's ancient mighty oak, felled by tropical storm Lee. A heavy, heavy timber atop the carport it crushed, in need of cutting, hauling, and splitting. Firewood and warmth for years. I've been jammed up, soon to be free, and alas, someone beat me to it yesterday, probably for pay. Shucks. -- Cheers, James Arthur
Reply by ●October 19, 20112011-10-19
On Oct 19, 4:34=A0pm, dagmargoodb...@yahoo.com wrote:> On Oct 19, 12:25=A0pm, George Herold <gher...@teachspin.com> wrote: > > > > > > > On Oct 19, 11:47=A0am, dagmargoodb...@yahoo.com wrote: > > > > On Oct 19, 10:20=A0am, George Herold <gher...@teachspin.com> wrote: > > > > > On Oct 18, 11:49=A0pm, dagmargoodb...@yahoo.com wrote: > > > > > On Oct 18, 11:15=A0am, George Herold <gher...@teachspin.com> wrot=e:> > > > > > Well I stuck a switch cap filter on the output. (LTC1063, I kno=w only> > > > > > 50kHz, which doesn=92t =91meet my spec', but I had one lying ar=ound.)> > > > > > > I clocked it at 16 times the stepped sine wave so the 3dB point=was> > > > > > 1.6 times the fundamental. =A0Here=92s the spectrum before the =SC.> > > > > > >http://imageshack.us/photo/my-images/404/sc1s.png/ > > > > > > > And after it.http://imageshack.us/photo/my-images/6/sc2h.png/ > > > > > > > The second harmonic goes up more than 10dB! =A0And there is all=this> > > > > > other =91fluff=92 at low frequency. =A0Some new peak stands up =at 2.5 kHz.> > > > > > I moved the 3dB point up to 3.2kHz and the 2nd harmonic was a f=ew dB> > > > > > better... the weird signal at 2.5kHz moved out to 5 kHz? =A0Not=sure I> > > > > > like switched cap filters. =A0We used the same SC on a differen=t project> > > > > > and it also added =91out of band=92 curd... at similar levels. > > > > > > > I=92ll try an analog multi pole Butterworth. =A0 Maybe a Sallen=-Key.> > > > > > > George H. > > > > > > I've got two articles in the hard drive vault that use a squarewa=ve> > > > > into a switched cap filter, overclocked >100:1, to generate a > > > > > sinewave. =A0The first architecture is fixed 1kHz: > > > > > =A0 =A0TLC555 =3D=3D> 19kHz RC-lowpass =3D=3D> MF6CN100 (Nat'l Se=mi), claims> > > > > harmonics are 60dB down. > > > > > > The 2nd generates squarewaves with a uC. =A0That drives a 64x > > > > > overclocked MAX292 (8th-order Bessel directly). =A0"Clean" sinewa=ve is> > > > > all they say. =A0They run the MAX292 bipolar off +5v, using a 10k=-10k> > > > > divider for a virtual rail. =A0Funky. > > > > > > I could e-mail you the articles if interested, but they _really_ =don't> > > > > say much more than what I already wrote. > > > > > > 1) Simple circuit generates clean sine waves, EDN, June 19, 1997,=pg.> > > > > 99 > > > > > 2) Microcontroller-based Sine Wave Generator Has Crystal Accuracy=,> > > > > Electronic Design, Dec. 14, 1998, pg. 74 > > > > > Gee thanks, but please don't bother. =A0I'm now looking for a VCO t=o> > > > drive the whole chain. =A0I was going to try the VCO in one of the =4046> > > > PLL chips.. they are cheap enough. =A0But I also found this > > > > 'synchronous' V-F converter. =A0AD7741 =A0it comes in an DIP which =is> > > > nice. > > > > > George H. > > > > Don't worry about all the chit-chat--none of it obligates you, we're > > > just playing. =A0You're already on a pretty good path. > > > > -- > > > Cheers, > > > James Arthur- Hide quoted text - > > > > - Show quoted text - > > > Big Grin! =A0No it's my great pleasure! =A0Some one sent me "two tramps=in> > mud time" yesterday. > > >http://www.etymonline.com/poems/tramps.htm > > > The last few lines keep tripping through my head. > > (My 'excuse' for doing electronics.) > > > George H. > > Whose poem this is I think I know, > he's nowhere near to see me though; > he will not see me reading here > his dusty works by monitor's glow... > > Very appropriate. =A0Lumberjacking has been heavy on my mind, with an > eye to a neighbor's ancient mighty oak, felled by tropical storm Lee. > A heavy, heavy timber atop the carport it crushed, in need of cutting, > hauling, and splitting. =A0Firewood and warmth for years. =A0I've been > jammed up, soon to be free, and alas, someone beat me to it yesterday, > probably for pay. =A0Shucks. > > -- > Cheers, > James Arthur- Hide quoted text - > > - Show quoted text -Ahh, well that was exactly why it was sent to me. Unlike Robert F. I do all my wood splitting in the autumn. I've got a lot of dead and dying Ash in my woods, which splits with a 'snap'. (hydraulically*) And then some big ole dead Elm, which is just about the stringiest, nastiest wood I know. Once they are mostly split with the machine, I still sometimes have to get out the axe to finish the job. I should finish my pile this weekend, then I just have to stack it. The 'problem' with wood is you have to move it three (or more) times before it ends up in the stove. George H. *Once you use hydraulics you're ruined for life. And thanks for the poem.
