Algorithm and voltage monitoring
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From: Grant on 26 Jul 2010 20:00 On Mon, 26 Jul 2010 14:37:18 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi, > >I am monitoring the voltage across the resistor and needs to maintain >it steady at set point value. Let's suppose if the set point value is >100 volts peak to peak and if the voltage goes below this value or >above this value than I have to make MOSFETS turn ON and OFF using >pulse width modulation to keep the voltage steady. > >Right now, I am reading the voltage across the coil and doing “if >else” statements to see whether the voltage is right and make >adjustments accordingly. This is not easy for me to describe. Firstly, precision of your description, you mention monitoring voltage across a resistor and reading voltage across a coil. Too sloppy. You need more discipline in describing what it is that you're doing. Quite likely I recognise that because I have similar problem? :) > > >My question is > >Is this algorithm of using “if else” algorithm is enough or should I >be controlling the voltage using like control algorithm like PID >controller etc. Enough for what? You don't describe your system, put up a circuit, and are a bit too vague. You know what the three terms PID are? What each does? You don't mention timing, so at the moment you're asking if proportional control is enough? It may be, but you've not stated what the controlled process is, whether you need to seek to setpoint accurately (I), and whether you need to control the approach towards that setpoint (D). And, is there a problem with system stability or response now? Have you built the system, or planning it? Grant.
From: Tim Wescott on 26 Jul 2010 20:07 On 07/26/2010 04:37 PM, john1987 wrote: > Hi, > > I guessed that I should have asked this question in the beginning that > what advantage the PID would have over just if else implementation? It'll actually work far more often. -- 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: Tim Wescott on 26 Jul 2010 20:14 On 07/26/2010 02:37 PM, john1987 wrote: > Hi, > > I am monitoring the voltage across the resistor and needs to maintain > it steady at set point value. Let�s suppose if the set point value is > 100 volts peak to peak and if the voltage goes below this value or > above this value than I have to make MOSFETS turn ON and OFF using > pulse width modulation to keep the voltage steady. > > Right now, I am reading the voltage across the coil and doing �if > else� statements to see whether the voltage is right and make > adjustments accordingly. > > > My question is > > Is this algorithm of using �if else� algorithm is enough or should I > be controlling the voltage using like control algorithm like PID > controller etc. Depending on what "make adjustments accordingly" translates to, you're working on something that might work. Do a PID, get it right, and you'll be working on something that _will_ work. Assuming, of course, that all the rest of the system is right -- but if the rest of the system is screwed up, then some oddball hybrid bang-bang controller is going to have less of a chance at it than even a simple PID controller. While it lasts: dpm1480.pbworks.com/f/PID%20without%20a%20PhD.pdf. eetimes.com has moved things around; they've put all the interesting stuff behind an email harvester. Dang!! -- 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: Martin Riddle on 26 Jul 2010 20:38 "Tim Wescott" <tim(a)seemywebsite.com> wrote in message news:iJKdnWYsC-kvudPRnZ2dnUVZ_i2dnZ2d(a)web-ster.com... > On 07/26/2010 02:37 PM, john1987 wrote: >> Hi, >> >> I am monitoring the voltage across the resistor and needs to maintain >> it steady at set point value. Let�s suppose if the set point value is >> 100 volts peak to peak and if the voltage goes below this value or >> above this value than I have to make MOSFETS turn ON and OFF using >> pulse width modulation to keep the voltage steady. >> >> Right now, I am reading the voltage across the coil and doing �if >> else� statements to see whether the voltage is right and make >> adjustments accordingly. >> >> >> My question is >> >> Is this algorithm of using �if else� algorithm is enough or should I >> be controlling the voltage using like control algorithm like PID >> controller etc. > > Depending on what "make adjustments accordingly" translates to, you're > working on something that might work. > > Do a PID, get it right, and you'll be working on something that _will_ > work. Assuming, of course, that all the rest of the system is > right -- > but if the rest of the system is screwed up, then some oddball hybrid > bang-bang controller is going to have less of a chance at it than even > a simple PID controller. > > While it lasts: dpm1480.pbworks.com/f/PID%20without%20a%20PhD.pdf. > > eetimes.com has moved things around; they've put all the interesting > stuff behind an email harvester. Dang!! > Nope, dead link ;( and not even a half hour. Cheers
From: Dave Platt on 26 Jul 2010 21:02
In article <i2l9r8$hvn$1(a)news.eternal-september.org>, Martin Riddle <martin_rid(a)verizon.net> wrote: >> While it lasts: dpm1480.pbworks.com/f/PID%20without%20a%20PhD.pdf. >> >> eetimes.com has moved things around; they've put all the interesting >> stuff behind an email harvester. Dang!! >> > >Nope, dead link ;( >and not even a half hour. Worked for me here just a moment ago... -- Dave Platt <dplatt(a)radagast.org> AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |