I got a request for a f to 2f converter for our lockin. http://www.teachspin.com/instruments/signal_processor/ (Freq = 3 - 3k Hz. ) (Well a crappy pic, but I wanted to show that it has a filter module. (It stinks signal wise too, the photographer didn't like the second bnc cable from the reference output.)) Passive would be the simplest. I thought of a diode rectifier, and when my boss mentioned that we could send it through the filter, I was sold. I first drew it up with coupling caps, but that wouldn't float. So a transformer was needed. I've got some of these, http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 Triad transformers. (in both 10k and 600 ohm flavors) And it worked great. I hung a 1 k ohm load on the rectifier output of the 10k transformer. (hmm, that might be my problem.) And at some low frequency ~30Hz, all hell broke out, with some jaggedie's during the sine wave. Did I mention I was driving it from an opamp? I was wondering if I should add some source resistance? George H.
Passive f to 2f converter
Started by ●December 10, 2012
Reply by ●December 10, 20122012-12-10
On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>I got a request for a f to 2f converter for our lockin. >http://www.teachspin.com/instruments/signal_processor/ >(Freq = 3 - 3k Hz. ) >(Well a crappy pic, but I wanted to show that it has a filter module. > (It stinks signal wise too, the photographer didn't like the second >bnc cable from the reference output.)) > >Passive would be the simplest. I thought of a diode rectifier, and >when my boss mentioned that we could send it through the filter, I was >sold. > >I first drew it up with coupling caps, but that wouldn't float. >So a transformer was needed. >I've got some of these, >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 >Triad transformers. (in both 10k and 600 ohm flavors) >And it worked great. >I hung a 1 k ohm load on the rectifier output of the 10k transformer. >(hmm, that might be my problem.) >And at some low frequency ~30Hz, all hell broke out, >with some jaggedie's during the sine wave. >Did I mention I was driving it from an opamp? > >I was wondering if I should add some source resistance? > >George H. > > >Transformer saturating? Try using a higher impedance transformer. Another cute way: drive an optoisolator that has back-to-back LEDs, and use a pullup on the phototransistor. You'll get two sinks per cycle. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●December 11, 20122012-12-11
On Dec 10, 10:28=A0pm, John Larkin <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@teachspi=n.com>> wrote: > > > > > > >I got a request for a =A0f to 2f =A0converter for our lockin. > >http://www.teachspin.com/instruments/signal_processor/ > >(Freq =3D 3 - 3k Hz. ) > >(Well a crappy pic, but I wanted to show that it has a filter module. > > (It stinks signal wise too, the photographer didn't like the second > >bnc cable from the reference output.)) > > >Passive would be the simplest. =A0 I thought of a diode rectifier, and > >when my boss mentioned that we could send it through the filter, I was > >sold. > > >I first drew it up with coupling caps, but that wouldn't float. > >So a transformer was needed. > >I've got some of these, > >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 > >Triad transformers. =A0(in both 10k and 600 ohm flavors) > >And it worked great. > >I hung a 1 k ohm load on the rectifier output of the 10k transformer. > >(hmm, that might be my problem.) > >And at some low frequency ~30Hz, all hell broke out, > >with some jaggedie's during the sine wave. > >Did I mention I was driving it from an opamp? > > >I was wondering if I should add some source resistance? > > >George H. > > Transformer saturating? Try using a higher impedance transformer.Hmm I don't really know. Here's a 'scope shot of the input to the transformer. http://bayimg.com/cAhhdaaeB At a slightly higher frequency the step and the jaggedies go away. (Jaggedies look like slew rate limitied oscillations ~2MHz.) I put 100 ohms between the opamp and transformer and that made everyone happy. Of course this is much below the spec for the transformer. (200 to 15 kHz.)> > Another cute way: drive an optoisolator that has back-to-back LEDs, and u=se a> pullup on the phototransistor. You'll get two sinks per cycle.Oh that's nice, then I wouldn't need the transformer. Any hints for an opto-isolater with back to back leds? I see nothing useful in digikeys search function. George H.> > -- > > John Larkin =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Highland Technology Incwww=.highlandtechnology.com=A0 jlarkin at highlandtechnology dot com> > Precision electronic instrumentation > Picosecond-resolution Digital Delay and Pulse generators > Custom timing and laser controllers > Photonics and fiberoptic TTL data links > VME =A0analog, thermocouple, LVDT, synchro, tachometer > Multichannel arbitrary waveform generators- Hide quoted text - > > - Show quoted text -
Reply by ●December 11, 20122012-12-11
On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Dec 10, 10:28�pm, John Larkin ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@teachspin.com> >> wrote: >> >> >> >> >> >> >I got a request for a �f to 2f �converter for our lockin. >> >http://www.teachspin.com/instruments/signal_processor/ >> >(Freq = 3 - 3k Hz. ) >> >(Well a crappy pic, but I wanted to show that it has a filter module. >> > (It stinks signal wise too, the photographer didn't like the second >> >bnc cable from the reference output.)) >> >> >Passive would be the simplest. � I thought of a diode rectifier, and >> >when my boss mentioned that we could send it through the filter, I was >> >sold. >> >> >I first drew it up with coupling caps, but that wouldn't float. >> >So a transformer was needed. >> >I've got some of these, >> >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 >> >Triad transformers. �(in both 10k and 600 ohm flavors) >> >And it worked great. >> >I hung a 1 k ohm load on the rectifier output of the 10k transformer. >> >(hmm, that might be my problem.) >> >And at some low frequency ~30Hz, all hell broke out, >> >with some jaggedie's during the sine wave. >> >Did I mention I was driving it from an opamp? >> >> >I was wondering if I should add some source resistance? >> >> >George H. >> >> Transformer saturating? Try using a higher impedance transformer. > >Hmm I don't really know. Here's a 'scope shot of the input to the >transformer. > >http://bayimg.com/cAhhdaaeB > >At a slightly higher frequency the step and the jaggedies go away. >(Jaggedies look like slew rate limitied oscillations ~2MHz.) > >I put 100 ohms between the opamp and transformer and that made >everyone happy. > >Of course this is much below the spec for the transformer. >(200 to 15 kHz.) > >> >> Another cute way: drive an optoisolator that has back-to-back LEDs, and use a >> pullup on the phototransistor. You'll get two sinks per cycle. > >Oh that's nice, then I wouldn't need the transformer. >Any hints for an opto-isolater with back to back leds? I see nothing >useful in digikeys search function.--- H11AA1, AA2, AA3, AND AA4, but why bother when you can do the same thing by feeding a single emitter device from a full-wave bridge? . +-----+ +-------------+ .AC>----|~ +|----|A---+ | . | | | | C| . | | | [LED]-> B | . | | | | E| .AC>----|~ -|----|K---+ | . +-----+ +-------------+ -- JF
Reply by ●December 11, 20122012-12-11
On Dec 11, 3:51=A0pm, John Fields <jfie...@austininstruments.com> wrote:> On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold > > > > > > <gher...@teachspin.com> wrote: > >On Dec 10, 10:28 pm, John Larkin > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@teach=spin.com>> >> wrote: > > >> >I got a request for a f to 2f converter for our lockin. > >> >http://www.teachspin.com/instruments/signal_processor/ > >> >(Freq =3D 3 - 3k Hz. ) > >> >(Well a crappy pic, but I wanted to show that it has a filter module. > >> > (It stinks signal wise too, the photographer didn't like the second > >> >bnc cable from the reference output.)) > > >> >Passive would be the simplest. I thought of a diode rectifier, and > >> >when my boss mentioned that we could send it through the filter, I wa=s> >> >sold. > > >> >I first drew it up with coupling caps, but that wouldn't float. > >> >So a transformer was needed. > >> >I've got some of these, > >> >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 > >> >Triad transformers. (in both 10k and 600 ohm flavors) > >> >And it worked great. > >> >I hung a 1 k ohm load on the rectifier output of the 10k transformer. > >> >(hmm, that might be my problem.) > >> >And at some low frequency ~30Hz, all hell broke out, > >> >with some jaggedie's during the sine wave. > >> >Did I mention I was driving it from an opamp? > > >> >I was wondering if I should add some source resistance? > > >> >George H. > > >> Transformer saturating? Try using a higher impedance transformer. > > >Hmm I don't really know. =A0Here's a 'scope shot of the input to the > >transformer. > > >http://bayimg.com/cAhhdaaeB > > >At a slightly higher frequency the step and the jaggedies go away. > >(Jaggedies look like slew rate limitied oscillations ~2MHz.) > > >I put 100 ohms between the opamp and transformer and that made > >everyone happy. > > >Of course this is much below the spec for the transformer. > >(200 to 15 kHz.) > > >> Another cute way: drive an optoisolator that has back-to-back LEDs, an=d use a> >> pullup on the phototransistor. You'll get two sinks per cycle. > > >Oh that's nice, then I wouldn't need the transformer. > >Any hints for an opto-isolater with back to back leds? =A0I see nothing > >useful in digikeys search function. > > --- > H11AA1, AA2, AA3, AND AA4, but why bother when you can do the same > thing by feeding a single emitter device from a full-wave bridge? > > . =A0 =A0 =A0 +-----+ =A0 =A0+-------------+ > .AC>----|~ =A0 +|----|A---+ =A0 =A0 =A0 =A0| > . =A0 =A0 =A0 | =A0 =A0 | =A0 =A0| =A0 =A0| =A0 =A0 =A0 C| > . =A0 =A0 =A0 | =A0 =A0 | =A0 =A0| =A0[LED]-> B =A0| > . =A0 =A0 =A0 | =A0 =A0 | =A0 =A0| =A0 =A0| =A0 =A0 =A0 E| > .AC>----|~ =A0 -|----|K---+ =A0 =A0 =A0 =A0| > . =A0 =A0 =A0 +-----+ =A0 =A0+-------------+ > > -- > JF- Hide quoted text - > > - Show quoted text -Thanks John, If I can do it without the brdige and transformer that will be a win. I've got a single ended (is that the right term?) input and output. (Both are referenced to the same ground point.) So I like the double LED idea. I don't have that much voltage to play with (~ 6 V p-p). I guess I'll loose about the same on the LED's or bridge. Oh, but I'll need some voltage to drive the transistor.... but maybe I can use that idea sometime in the future. George H.
Reply by ●December 11, 20122012-12-11
On Dec 11, 4:11=A0pm, George Herold <gher...@teachspin.com> wrote:> On Dec 11, 3:51=A0pm, John Fields <jfie...@austininstruments.com> wrote: > > > > > > > On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold > > > <gher...@teachspin.com> wrote: > > >On Dec 10, 10:28 pm, John Larkin > > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > > >> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@tea=chspin.com>> > >> wrote: > > > >> >I got a request for a f to 2f converter for our lockin. > > >> >http://www.teachspin.com/instruments/signal_processor/ > > >> >(Freq =3D 3 - 3k Hz. ) > > >> >(Well a crappy pic, but I wanted to show that it has a filter modul=e.> > >> > (It stinks signal wise too, the photographer didn't like the secon=d> > >> >bnc cable from the reference output.)) > > > >> >Passive would be the simplest. I thought of a diode rectifier, and > > >> >when my boss mentioned that we could send it through the filter, I =was> > >> >sold. > > > >> >I first drew it up with coupling caps, but that wouldn't float. > > >> >So a transformer was needed. > > >> >I've got some of these, > > >> >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 > > >> >Triad transformers. (in both 10k and 600 ohm flavors) > > >> >And it worked great. > > >> >I hung a 1 k ohm load on the rectifier output of the 10k transforme=r.> > >> >(hmm, that might be my problem.) > > >> >And at some low frequency ~30Hz, all hell broke out, > > >> >with some jaggedie's during the sine wave. > > >> >Did I mention I was driving it from an opamp? > > > >> >I was wondering if I should add some source resistance? > > > >> >George H. > > > >> Transformer saturating? Try using a higher impedance transformer. > > > >Hmm I don't really know. =A0Here's a 'scope shot of the input to the > > >transformer. > > > >http://bayimg.com/cAhhdaaeB > > > >At a slightly higher frequency the step and the jaggedies go away. > > >(Jaggedies look like slew rate limitied oscillations ~2MHz.) > > > >I put 100 ohms between the opamp and transformer and that made > > >everyone happy. > > > >Of course this is much below the spec for the transformer. > > >(200 to 15 kHz.) > > > >> Another cute way: drive an optoisolator that has back-to-back LEDs, =and use a> > >> pullup on the phototransistor. You'll get two sinks per cycle. > > > >Oh that's nice, then I wouldn't need the transformer. > > >Any hints for an opto-isolater with back to back leds? =A0I see nothin=g> > >useful in digikeys search function. > > > --- > > H11AA1, AA2, AA3, AND AA4, but why bother when you can do the same > > thing by feeding a single emitter device from a full-wave bridge? > > > . =A0 =A0 =A0 +-----+ =A0 =A0+-------------+ > > .AC>----|~ =A0 +|----|A---+ =A0 =A0 =A0 =A0| > > . =A0 =A0 =A0 | =A0 =A0 | =A0 =A0| =A0 =A0| =A0 =A0 =A0 C| > > . =A0 =A0 =A0 | =A0 =A0 | =A0 =A0| =A0[LED]-> B =A0| > > . =A0 =A0 =A0 | =A0 =A0 | =A0 =A0| =A0 =A0| =A0 =A0 =A0 E| > > .AC>----|~ =A0 -|----|K---+ =A0 =A0 =A0 =A0| > > . =A0 =A0 =A0 +-----+ =A0 =A0+-------------+ > > > -- > > JF- Hide quoted text - > > > - Show quoted text - > > Thanks John, =A0If I can do it without the brdige and transformer that > will be a win. > > I've got a single ended (is that the right term?) input and output. > (Both are referenced to the same ground point.) =A0So I like the double > LED idea. =A0I don't have that much voltage to play with (~ 6 V p-p). =A0=I> guess I'll loose about the same on the LED's or bridge. > > Oh, but I'll need some voltage to drive the transistor.... but maybe I > can use that idea sometime in the future. > > George H.- Hide quoted text - > > - Show quoted text -Hey, is there an opto with back to back LEDs and just a photodiode output? Or maybe a dual, that I hook up back to back? I found this on digikey... a bit spendie http://www.digikey.com/product-detail/en/PVI5013RPBF/PVI5013RPBF-ND/1828126 But a lot less mass than a transformer! George H.
Reply by ●December 12, 20122012-12-12
On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Dec 10, 10:28�pm, John Larkin ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@teachspin.com> >> wrote: >> >> >> >> >> >> >I got a request for a �f to 2f �converter for our lockin. >> >http://www.teachspin.com/instruments/signal_processor/ >> >(Freq = 3 - 3k Hz. ) >> >(Well a crappy pic, but I wanted to show that it has a filter module. >> > (It stinks signal wise too, the photographer didn't like the second >> >bnc cable from the reference output.)) >> >> >Passive would be the simplest. � I thought of a diode rectifier, and >> >when my boss mentioned that we could send it through the filter, I was >> >sold. >> >> >I first drew it up with coupling caps, but that wouldn't float. >> >So a transformer was needed. >> >I've got some of these, >> >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 >> >Triad transformers. �(in both 10k and 600 ohm flavors) >> >And it worked great. >> >I hung a 1 k ohm load on the rectifier output of the 10k transformer. >> >(hmm, that might be my problem.) >> >And at some low frequency ~30Hz, all hell broke out, >> >with some jaggedie's during the sine wave. >> >Did I mention I was driving it from an opamp? >> >> >I was wondering if I should add some source resistance? >> >> >George H. >> >> Transformer saturating? Try using a higher impedance transformer. > >Hmm I don't really know. Here's a 'scope shot of the input to the >transformer. > >http://bayimg.com/cAhhdaaeB > >At a slightly higher frequency the step and the jaggedies go away. >(Jaggedies look like slew rate limitied oscillations ~2MHz.) > >I put 100 ohms between the opamp and transformer and that made >everyone happy. > >Of course this is much below the spec for the transformer. >(200 to 15 kHz.) > >> >> Another cute way: drive an optoisolator that has back-to-back LEDs, and use a >> pullup on the phototransistor. You'll get two sinks per cycle. > >Oh that's nice, then I wouldn't need the transformer. >Any hints for an opto-isolater with back to back leds? I see nothing >useful in digikeys search function.We use this one: http://www1.futureelectronics.com/doc/CALIFORNIA%20EASTERN%20LAB/PS2805-1-F3-A.pdf What's your signal waveform? What 2f waveform do you need? A true sine-to-sine doubler is an analog squarer and a DC offset. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●December 12, 20122012-12-12
On Tue, 11 Dec 2012 17:44:07 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Dec 11, 4:11�pm, George Herold <gher...@teachspin.com> wrote: >> On Dec 11, 3:51�pm, John Fields <jfie...@austininstruments.com> wrote: >> >> >> >> >> >> > On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold >> >> > <gher...@teachspin.com> wrote: >> > >On Dec 10, 10:28 pm, John Larkin >> > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> > >> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@teachspin.com> >> > >> wrote: >> >> > >> >I got a request for a f to 2f converter for our lockin. >> > >> >http://www.teachspin.com/instruments/signal_processor/ >> > >> >(Freq = 3 - 3k Hz. ) >> > >> >(Well a crappy pic, but I wanted to show that it has a filter module. >> > >> > (It stinks signal wise too, the photographer didn't like the second >> > >> >bnc cable from the reference output.)) >> >> > >> >Passive would be the simplest. I thought of a diode rectifier, and >> > >> >when my boss mentioned that we could send it through the filter, I was >> > >> >sold. >> >> > >> >I first drew it up with coupling caps, but that wouldn't float. >> > >> >So a transformer was needed. >> > >> >I've got some of these, >> > >> >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 >> > >> >Triad transformers. (in both 10k and 600 ohm flavors) >> > >> >And it worked great. >> > >> >I hung a 1 k ohm load on the rectifier output of the 10k transformer. >> > >> >(hmm, that might be my problem.) >> > >> >And at some low frequency ~30Hz, all hell broke out, >> > >> >with some jaggedie's during the sine wave. >> > >> >Did I mention I was driving it from an opamp? >> >> > >> >I was wondering if I should add some source resistance? >> >> > >> >George H. >> >> > >> Transformer saturating? Try using a higher impedance transformer. >> >> > >Hmm I don't really know. �Here's a 'scope shot of the input to the >> > >transformer. >> >> > >http://bayimg.com/cAhhdaaeB >> >> > >At a slightly higher frequency the step and the jaggedies go away. >> > >(Jaggedies look like slew rate limitied oscillations ~2MHz.) >> >> > >I put 100 ohms between the opamp and transformer and that made >> > >everyone happy. >> >> > >Of course this is much below the spec for the transformer. >> > >(200 to 15 kHz.) >> >> > >> Another cute way: drive an optoisolator that has back-to-back LEDs, and use a >> > >> pullup on the phototransistor. You'll get two sinks per cycle. >> >> > >Oh that's nice, then I wouldn't need the transformer. >> > >Any hints for an opto-isolater with back to back leds? �I see nothing >> > >useful in digikeys search function. >> >> > --- >> > H11AA1, AA2, AA3, AND AA4, but why bother when you can do the same >> > thing by feeding a single emitter device from a full-wave bridge? >> >> > . � � � +-----+ � �+-------------+ >> > .AC>----|~ � +|----|A---+ � � � �| >> > . � � � | � � | � �| � �| � � � C| >> > . � � � | � � | � �| �[LED]-> B �| >> > . � � � | � � | � �| � �| � � � E| >> > .AC>----|~ � -|----|K---+ � � � �| >> > . � � � +-----+ � �+-------------+ >> >> > -- >> > JF- Hide quoted text - >> >> > - Show quoted text - >> >> Thanks John, �If I can do it without the brdige and transformer that >> will be a win. >> >> I've got a single ended (is that the right term?) input and output. >> (Both are referenced to the same ground point.) �So I like the double >> LED idea. �I don't have that much voltage to play with (~ 6 V p-p). �I >> guess I'll loose about the same on the LED's or bridge. >> >> Oh, but I'll need some voltage to drive the transistor.... but maybe I >> can use that idea sometime in the future. >> >> George H.- Hide quoted text - >> >> - Show quoted text - > >Hey, is there an opto with back to back LEDs and just a photodiode >output? > >Or maybe a dual, that I hook up back to back? >I found this on digikey... a bit spendie > >http://www.digikey.com/product-detail/en/PVI5013RPBF/PVI5013RPBF-ND/1828126 > >But a lot less mass than a transformer! > >George H.--- Here's the data sheet: http://www.irf.com/product-info/datasheets/data/pvi5013r.pdf Take a look at the response time specs... OTOH, take a look at this: http://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/H11F1,2,3.pdf Wire the LEDs in parallel opposition and the FETs in parallel and Bob's yer uncle! -- JF
Reply by ●December 12, 20122012-12-12
On Dec 12, 12:23=A0am, John Larkin <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:> On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold <gher...@teachspi=n.com>> wrote: > > > > > > >On Dec 10, 10:28 pm, John Larkin > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@teach=spin.com>> >> wrote: > > >> >I got a request for a f to 2f converter for our lockin. > >> >http://www.teachspin.com/instruments/signal_processor/ > >> >(Freq =3D 3 - 3k Hz. ) > >> >(Well a crappy pic, but I wanted to show that it has a filter module. > >> > (It stinks signal wise too, the photographer didn't like the second > >> >bnc cable from the reference output.)) > > >> >Passive would be the simplest. I thought of a diode rectifier, and > >> >when my boss mentioned that we could send it through the filter, I wa=s> >> >sold. > > >> >I first drew it up with coupling caps, but that wouldn't float. > >> >So a transformer was needed. > >> >I've got some of these, > >> >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242640 > >> >Triad transformers. (in both 10k and 600 ohm flavors) > >> >And it worked great. > >> >I hung a 1 k ohm load on the rectifier output of the 10k transformer. > >> >(hmm, that might be my problem.) > >> >And at some low frequency ~30Hz, all hell broke out, > >> >with some jaggedie's during the sine wave. > >> >Did I mention I was driving it from an opamp? > > >> >I was wondering if I should add some source resistance? > > >> >George H. > > >> Transformer saturating? Try using a higher impedance transformer. > > >Hmm I don't really know. =A0Here's a 'scope shot of the input to the > >transformer. > > >http://bayimg.com/cAhhdaaeB > > >At a slightly higher frequency the step and the jaggedies go away. > >(Jaggedies look like slew rate limitied oscillations ~2MHz.) > > >I put 100 ohms between the opamp and transformer and that made > >everyone happy. > > >Of course this is much below the spec for the transformer. > >(200 to 15 kHz.) > > >> Another cute way: drive an optoisolator that has back-to-back LEDs, an=d use a> >> pullup on the phototransistor. You'll get two sinks per cycle. > > >Oh that's nice, then I wouldn't need the transformer. > >Any hints for an opto-isolater with back to back leds? =A0I see nothing > >useful in digikeys search function. > > We use this one: > > http://www1.futureelectronics.com/doc/CALIFORNIA%20EASTERN%20LAB/PS28... >OK thanks,> What's your signal waveform? What 2f waveform do you need? A true sine-to=-sine> doubler is an analog squarer and a DC offset.The input is a sine wave 3-3kHz, ~6Vp-p. The output can be almost anything that has some 2f. The user can send the signal through a filter (with gain =3D to Q) and then the signal becomes the reference input for a switched gain lockin amp. George H.> > -- > > John Larkin =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Highland Technology Incwww=.highlandtechnology.com=A0 jlarkin at highlandtechnology dot com> > Precision electronic instrumentation > Picosecond-resolution Digital Delay and Pulse generators > Custom timing and laser controllers > Photonics and fiberoptic TTL data links > VME =A0analog, thermocouple, LVDT, synchro, tachometer > Multichannel arbitrary waveform generators- Hide quoted text - > > - Show quoted text -
Reply by ●December 12, 20122012-12-12
On Dec 12, 7:36=A0am, John Fields <jfie...@austininstruments.com> wrote:> On Tue, 11 Dec 2012 17:44:07 -0800 (PST), George Herold > > > > > > <gher...@teachspin.com> wrote: > >On Dec 11, 4:11 pm, George Herold <gher...@teachspin.com> wrote: > >> On Dec 11, 3:51 pm, John Fields <jfie...@austininstruments.com> wrote: > > >> > On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold > > >> > <gher...@teachspin.com> wrote: > >> > >On Dec 10, 10:28 pm, John Larkin > >> > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> > >> On Mon, 10 Dec 2012 16:34:05 -0800 (PST), George Herold <gher...@=teachspin.com>> >> > >> wrote: > > >> > >> >I got a request for a f to 2f converter for our lockin. > >> > >> >http://www.teachspin.com/instruments/signal_processor/ > >> > >> >(Freq =3D 3 - 3k Hz. ) > >> > >> >(Well a crappy pic, but I wanted to show that it has a filter mo=dule.> >> > >> > (It stinks signal wise too, the photographer didn't like the se=cond> >> > >> >bnc cable from the reference output.)) > > >> > >> >Passive would be the simplest. I thought of a diode rectifier, a=nd> >> > >> >when my boss mentioned that we could send it through the filter,=I was> >> > >> >sold. > > >> > >> >I first drew it up with coupling caps, but that wouldn't float. > >> > >> >So a transformer was needed. > >> > >> >I've got some of these, > >> > >> >http://www.digikey.com/product-detail/en/TY-141P/237-1118-ND/242=640> >> > >> >Triad transformers. (in both 10k and 600 ohm flavors) > >> > >> >And it worked great. > >> > >> >I hung a 1 k ohm load on the rectifier output of the 10k transfo=rmer.> >> > >> >(hmm, that might be my problem.) > >> > >> >And at some low frequency ~30Hz, all hell broke out, > >> > >> >with some jaggedie's during the sine wave. > >> > >> >Did I mention I was driving it from an opamp? > > >> > >> >I was wondering if I should add some source resistance? > > >> > >> >George H. > > >> > >> Transformer saturating? Try using a higher impedance transformer. > > >> > >Hmm I don't really know. Here's a 'scope shot of the input to the > >> > >transformer. > > >> > >http://bayimg.com/cAhhdaaeB > > >> > >At a slightly higher frequency the step and the jaggedies go away. > >> > >(Jaggedies look like slew rate limitied oscillations ~2MHz.) > > >> > >I put 100 ohms between the opamp and transformer and that made > >> > >everyone happy. > > >> > >Of course this is much below the spec for the transformer. > >> > >(200 to 15 kHz.) > > >> > >> Another cute way: drive an optoisolator that has back-to-back LED=s, and use a> >> > >> pullup on the phototransistor. You'll get two sinks per cycle. > > >> > >Oh that's nice, then I wouldn't need the transformer. > >> > >Any hints for an opto-isolater with back to back leds? I see nothin=g> >> > >useful in digikeys search function. > > >> > --- > >> > H11AA1, AA2, AA3, AND AA4, but why bother when you can do the same > >> > thing by feeding a single emitter device from a full-wave bridge? > > >> > . +-----+ +-------------+ > >> > .AC>----|~ +|----|A---+ | > >> > . | | | | C| > >> > . | | | [LED]-> B | > >> > . | | | | E| > >> > .AC>----|~ -|----|K---+ | > >> > . +-----+ +-------------+ > > >> > -- > >> > JF- Hide quoted text - > > >> > - Show quoted text - > > >> Thanks John, If I can do it without the brdige and transformer that > >> will be a win. > > >> I've got a single ended (is that the right term?) input and output. > >> (Both are referenced to the same ground point.) So I like the double > >> LED idea. I don't have that much voltage to play with (~ 6 V p-p). I > >> guess I'll loose about the same on the LED's or bridge. > > >> Oh, but I'll need some voltage to drive the transistor.... but maybe I > >> can use that idea sometime in the future. > > >> George H.- Hide quoted text - > > >> - Show quoted text - > > >Hey, is there an opto with back to back LEDs and just a photodiode > >output? > > >Or maybe a dual, that I hook up back to back? > >I found this on digikey... a bit spendie > > >http://www.digikey.com/product-detail/en/PVI5013RPBF/PVI5013RPBF-ND/1... > > >But a lot less mass than a transformer! > > >George H. > > --- > Here's the data sheet: > > http://www.irf.com/product-info/datasheets/data/pvi5013r.pdf > > Take a look at the response time specs...Ughh, that is slow. 1 uA into ~200pF, and with Vf=3D 8V, that's more than 1nC so sure more than 1ms response time.... but maybe I can reduce the load resistance (and forward voltage) and make it a bit snappier?> > OTOH, take a look at this: > > http://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/H11F1,2,3... > > Wire the LEDs in parallel opposition and the FETs in parallel and > Bob's yer uncle!Very interesting. I like the circuit apps! But I'll need power to turn the FET on. (not impossible, but not ideal either.) Thanks George H.> > -- > JF- Hide quoted text - > > - Show quoted text -
