Peter J. Kootsookos wrote:>>I just checked; your sense is listed. The Century Dictionary lists the >>sense I used after yours. I don't follow horse races, but I believe that >>my sense is universal among those who do. >> > > I'd go with your meaning, Jerry... but then my father was into race horses.Nice to know we're all correct. I know nothing about horses, and I suspect I'll stay that way :-) Patience, persistence, truth, Dr. mike -- Mike Rosing www.beastrider.com BeastRider, LLC SHARC debug tools
DSP vs. PLCs for control equipment
Started by ●August 21, 2003
Reply by ●August 21, 20032003-08-21
From what I gather, it seems that the two means of electronically controlling something are DSP and PLCs. What exactly are the merits of one over the other? In what types of applications are PLCs better, and in what types of applications is digital signal processing superior? What drawbacks does DSP contain that have prevented it from replacing PLCs? Jason Hsu, AG4DG usenet@@@jasonhsu.com
Reply by ●August 21, 20032003-08-21
From what I gather, it seems that the two means of electronically controlling something are DSP and PLCs. What exactly are the merits of one over the other? In what types of applications are PLCs better, and in what types of applications is digital signal processing superior? What drawbacks does DSP contain that have prevented it from replacing PLCs? Jason Hsu, AG4DG usenet@@@jasonhsu.com
Reply by ●August 21, 20032003-08-21
Jason Hsu wrote:> > From what I gather, it seems that the two means of electronically > controlling something are DSP and PLCs.That's an exceedingly limited view.> > What exactly are the merits of one over the other? In what types of > applications are PLCs better, and in what types of applications is > digital signal processing superior? What drawbacks does DSP contain > that have prevented it from replacing PLCs?Most PLCs -- I assume the common meaning, Programmable Logic Controller -- measure their world and change their control signals at zero crossings of the power line: 100 or 120 times per second. They are designed to work in a factory environment, taking into account the electrical noise and the skills of the workers there. (Most are programmed with Ladder diagrams, originally developed for relays.) PLCs contain general-purpose processors. I could build one with a DSP instead, but most of the DSP's special facilities would be wasted and some of the general-purpose processor's would need to be provided with additional hardware. One doesn't normally use a team of thoroughbreds to pull beer wagons.> > Jason Hsu, AG4DG > usenet@@@jasonhsu.comJerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 21, 20032003-08-21
Mike Rosing wrote:> > Jerry Avins wrote: > > additional hardware. One doesn't normally use a team of thoroughbreds to > > pull beer wagons. > > Depends on the type of thoroughbred. Budweiser Clydesdales are thoroughbred. > While they aren't bred for running races, they are used to pull beer wagons! > > Same point tho - pick the right horse for the job. > > Patience, persistence, truth, > Dr. mike > > -- > Mike Rosing > www.beastrider.com BeastRider, LLC > SHARC debug toolsYou're plain wrong if I'm right. A thoroughbred is a particular breed of horse, as is a Clydesdale, a trotter, or a quarter horse. They're all purebreds, but that's not the same thing. [time passes] I just checked; your sense is listed. The Century Dictionary lists the sense I used after yours. I don't follow horse races, but I believe that my sense is universal among those who do. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 21, 20032003-08-21
Jerry Avins <jya@ieee.org> writes:> I just checked; your sense is listed. The Century Dictionary lists the > sense I used after yours. I don't follow horse races, but I believe that > my sense is universal among those who do.I'd go with your meaning, Jerry... but then my father was into race horses. Ciao, Peter K. -- Peter J. Kootsookos "Na, na na na na na na, na na na na" - 'Hey Jude', Lennon/McCartney
Reply by ●August 22, 20032003-08-22
Oops! I forgot to ask about DCS! What are the advantages and disadvantages of DCS as compared to DSP and PLCs? Jason Hsu, AG4DG usenet@@@jasonhsu.com
Reply by ●August 22, 20032003-08-22
Jason Hsu wrote:> > Oops! I forgot to ask about DCS! > > What are the advantages and disadvantages of DCS as compared to DSP and PLCs? > > Jason Hsu, AG4DG > usenet@@@jasonhsu.comBeats me! What's a DCS: Digital Control System? That could be practically anything. Look here: the best way to control something depends on what you want to control. It depends on other things too, but when you have two pieces to fasten, what to fasten them with is a sensible quest. Less sensible is asking what to do today with this butt welder. (Snicker all you want!) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 23, 20032003-08-23
"Jerry Avins" <jya@ieee.org> wrote in message news:3F46571F.35B04C84@ieee.org...> Jason Hsu wrote: > > > > Oops! I forgot to ask about DCS! > > > > What are the advantages and disadvantages of DCS as compared to DSP andPLCs?> > > > Jason Hsu, AG4DG > > usenet@@@jasonhsu.com > > Beats me! What's a DCS: Digital Control System? That could be > practically anything.Jerry, A DCS (Distributed Control System) is an integrated system including ALL functionality from power supply to operator chairs and everything in between. They are big, expensive and are used on big projects such as oil refineries, etc. They originated in the world of analog control but now can do just about anything so long as high speed is not a requirement. (Typically 1/4 second top scan rate.) A typical system costs about $2,000,000 US. (How are DCSs like the Titanic? They are big, expensive and everyone wants them to go faster.) A PLC is a collection of I/O modules and a logic processor. They inherited the world of relay control but today have much of the analog functionality of a DCS as well. Everything from power supplies to cabinets to operator interface must be bought separately. Buying a DCS is like buying a bus. Buying a PLC is like buying an engine. There is no typical PLC price. They range form $200 to $1,000,000. I have no idea what a DSP is. I've been in process control for 25 years and I've never heard the term. Web search tells me it means digital signal processing. If that is what you mean then your question is like asking, "What are the advantages and disadvantages of batteries as compared to lawn mowers?" But keep prodding this thread. It will go on long time since the DCS vs. PLC split is once that commands strong loyalties. With luck you will even learn something through all the snow. Walter.
Reply by ●August 23, 20032003-08-23
Walter Driedger wrote:> > "Jerry Avins" <jya@ieee.org> wrote in message > news:3F46571F.35B04C84@ieee.org... > > Jason Hsu wrote: > > > > > > Oops! I forgot to ask about DCS! > > > > > > What are the advantages and disadvantages of DCS as compared to DSP and > PLCs? > > > > > > Jason Hsu, AG4DG > > > usenet@@@jasonhsu.com > > > > Beats me! What's a DCS: Digital Control System? That could be > > practically anything. > > Jerry, > > A DCS (Distributed Control System) is an integrated system including ALL > functionality from power supply to operator chairs and everything in > between. They are big, expensive and are used on big projects such as oil > refineries, etc. They originated in the world of analog control but now can > do just about anything so long as high speed is not a requirement. > (Typically 1/4 second top scan rate.) A typical system costs about > $2,000,000 US. (How are DCSs like the Titanic? They are big, expensive and > everyone wants them to go faster.) > > A PLC is a collection of I/O modules and a logic processor. They inherited > the world of relay control but today have much of the analog functionality > of a DCS as well. Everything from power supplies to cabinets to operator > interface must be bought separately. Buying a DCS is like buying a bus. > Buying a PLC is like buying an engine. There is no typical PLC price. They > range form $200 to $1,000,000. > > I have no idea what a DSP is. I've been in process control for 25 years and > I've never heard the term. Web search tells me it means digital signal > processing. If that is what you mean then your question is like asking, > "What are the advantages and disadvantages of batteries as compared to lawn > mowers?" > > But keep prodding this thread. It will go on long time since the DCS vs. > PLC split is once that commands strong loyalties. With luck you will even > learn something through all the snow. > > Walter.Walter, I'm here to learn, and I thank you. I also like to teach when the subject is at a low enough level. I'm a retired engineer dabbling in a new field. When I taught silversmithing (shanghaied by well-meaning neighbors), the course description included the line, "A course for beginners taught by an amateur." I write this from comp.dsp, where people who do DSP or use DSPs meet to ask and answer questions and to shoot the breeze. DSP stands either for digital signal processing -- done with machines from 8080s to Crays -- or for digital signal processor, a computer chip especially adapted for certain algorithms that signal processing commonly needs. Single-cycle multiplies and MAC using circular buffers, bit-reversed addressing for FFTs, zero-overhead loops, multiple DMAs working with dual-ported RAM so data and code can be moved into fast RAM while calculations go on, ann more goodies. That's hardly an exhaustive list. Naturally, there's a price for these goodies. Money aside, they don't have the usual array of peripherals found in most microcontrollers. There's a DSP in every cell phone, modem, GPS, sound card, and more. There's one in the base and another in the handset of a cordless phone. One reason new fax machines can be so cheap is that the same DSP that plays modem also controls the printing process. They make nifty toys. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
