Forums

Passive f to 2f converter

Started by George Herold December 10, 2012
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.




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
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 -
On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

>On Dec 10, 10:28&#2013266080;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 &#2013266080;f to 2f &#2013266080;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. &#2013266080; 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. &#2013266080;(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
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.
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.
On Tue, 11 Dec 2012 12:02:48 -0800 (PST), George Herold <gherold@teachspin.com>
wrote:

>On Dec 10, 10:28&#2013266080;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 &#2013266080;f to 2f &#2013266080;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. &#2013266080; 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. &#2013266080;(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
On Tue, 11 Dec 2012 17:44:07 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

>On Dec 11, 4:11&#2013266080;pm, George Herold <gher...@teachspin.com> wrote: >> On Dec 11, 3:51&#2013266080;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. &#2013266080;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? &#2013266080;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? >> >> > . &#2013266080; &#2013266080; &#2013266080; +-----+ &#2013266080; &#2013266080;+-------------+ >> > .AC>----|~ &#2013266080; +|----|A---+ &#2013266080; &#2013266080; &#2013266080; &#2013266080;| >> > . &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; | &#2013266080; &#2013266080;| &#2013266080; &#2013266080;| &#2013266080; &#2013266080; &#2013266080; C| >> > . &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; | &#2013266080; &#2013266080;| &#2013266080;[LED]-> B &#2013266080;| >> > . &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; | &#2013266080; &#2013266080;| &#2013266080; &#2013266080;| &#2013266080; &#2013266080; &#2013266080; E| >> > .AC>----|~ &#2013266080; -|----|K---+ &#2013266080; &#2013266080; &#2013266080; &#2013266080;| >> > . &#2013266080; &#2013266080; &#2013266080; +-----+ &#2013266080; &#2013266080;+-------------+ >> >> > -- >> > JF- Hide quoted text - >> >> > - Show quoted text - >> >> Thanks John, &#2013266080;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.) &#2013266080;So I like the double >> LED idea. &#2013266080;I don't have that much voltage to play with (~ 6 V p-p). &#2013266080;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
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 -
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 -