Detecting the peak value
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From: Tim Wescott on 30 Jul 2010 11:06 On 07/29/2010 12:01 PM, john1987 wrote: > > > Hi, > Thanks for your response. I need analog or digital solution to > implement it. I have doe search on peak detector on the internet and > found many circuits. But I need something that can do what I mentioned > in the diagram. Ideally with out those capacitor and resistor. If you > can direct me in correct way than I wil be thankful. If it's really a sine wave you could square it up and lock to it with a 4046 or other PLL. Why the objection to the cap? Nothing that you can replace the RC network with is going to be smaller, but there are lots of options that are far bigger. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Jim Thompson on 30 Jul 2010 11:12 On Fri, 30 Jul 2010 08:05:08 -0700, Tim Wescott <tim(a)seemywebsite.com> wrote: >On 07/29/2010 12:03 PM, john1987 wrote: >> I think that I am doing what are suggesting to use the differeniator. >> But is there another analog way to do it meant without using the RC >> circuit. >> >Detecting peaks requires memory of past history of the wave, which means >(in an analog circuit) than you need a capacitor or an inductor. So, >sure you can get rid of the cap -- if you don't mind having an inductor >in there. > >People keep asking you questions like "is your frequency stable", trying >to find ways to make you happy, and you keep responding with "I don't >even want to put up with a capacitor in my circuit". > >What are you really trying to do, and what are your real constraints? >What's the matter with a cruddy capacitor? Trying to find actual end-use intent is one of the bigger problems everywhere. Vagueness drives me nuts. Reminds me, in the early '60's, an Admiral comes to Moto and we get in a closed meeting, only those with secret clearance allowed. This SOB rambles and rambles and rambles... for several hours. I'm taking notes. All of a sudden I say, "You're trying to do... TOP SECRET" :-) After he got over his white faced shock. I showed a simple PLL solution. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Performance only as good as the person behind the wheel.
From: Jim Thompson on 30 Jul 2010 11:14 On Fri, 30 Jul 2010 08:06:44 -0700, Tim Wescott <tim(a)seemywebsite.com> wrote: >On 07/29/2010 12:01 PM, john1987 wrote: >> >> >> Hi, >> Thanks for your response. I need analog or digital solution to >> implement it. I have doe search on peak detector on the internet and >> found many circuits. But I need something that can do what I mentioned >> in the diagram. Ideally with out those capacitor and resistor. If you >> can direct me in correct way than I wil be thankful. > >If it's really a sine wave you could square it up and lock to it with a >4046 or other PLL. Very good solution! An analog phase detector would give you the 90� phase shift, thus the "transitions on peaks" the OP wants. More capacitors than the differentiator, or all-pass, though :-) > >Why the objection to the cap? Nothing that you can replace the RC >network with is going to be smaller, but there are lots of options that >are far bigger. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Performance only as good as the person behind the wheel.
From: Nico Coesel on 30 Jul 2010 12:38 Grant <omg(a)grrr.id.au> wrote: >On Thu, 29 Jul 2010 12:01:20 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: > >> >> >>Hi, >>Thanks for your response. I need analog or digital solution to >>implement it. I have doe search on peak detector on the internet and >>found many circuits. But I need something that can do what I mentioned >>in the diagram. Ideally with out those capacitor and resistor. If you >>can direct me in correct way than I wil be thankful. > >Also see my post in reply to Jim T. > >You can do it in software, but not easily for 100kHz. That's >need DSP techniques, I think? Nope. Just do random time sampling using a simple microcontroller. As long as the S&H can handle 100kHz it's fine. Keep in mind that today's microcontrollers are 32 bit, run at >50MHz and have hardware multipliers and dividers. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: Nico Coesel on 30 Jul 2010 12:42
Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Thu, 29 Jul 2010 12:03:46 -0700 (PDT), john1987 ><conphiloso(a)hotmail.com> wrote: > >>I think that I am doing what are suggesting to use the differeniator. >>But is there another analog way to do it meant without using the RC >>circuit. > >You have an integrator (of sorts). > >I don't know of any way to find a sinusoid's peak without using a >capacitor or a tracking A-to-D. > >This seems to work pretty well... > >http://analog-innovations.com/SED/PeakFinder_2.pdf > >"U1" is a comparator. Clever indeed. Are you working for Elektor these days? :-) -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) -------------------------------------------------------------- |