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  • #16
    Re: PID Silvia Sydney

    Thank you all for all the helpful replies

    Mal, did you get your PID here http://www.onetemp.com.au/ ? May I ask which model you got?

    I have an electrician coming over on Saturday to fix some lights, if I can throw it all together by then Ill get him to have a look at it. Then Ill let yall know how it goes, if I live to tell the tale ;D

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    • #17
      Re: PID Silvia Sydney

      Hi again Christian,

      No worries ;D.....

      Basically, PID control has been around in industrial applications in all manner of processes for many decades. Until the "digital" age rolled in, assigning PID control or some variation there-of to these processes was very expensive. As with many other fields that used to be controlled via analogue means, the digital age has realised drastic reductions in all these forms of control, monitoring and acquisition.

      There are many good references to be found by scouting the web for more detailed explanations of what PID is about but in essence, Ill try to condense it down into as brief an explanation as possible.

      The letters in the acronym PID stand for Proportional (Band), Integral and Derivative respectively. Depending on the outcomes required by the process designer (heating an Espresso Machines Boiler to 100deg C for example), it is not always necessary or desirable to activate all parts of the control algorithm to achieve the desired level of control dictated by the process output target(s). It is possible to use P only, PI only, PD only or all three.

      The "P" component basically relates to an error between the Setpoint (the Target) and the actual measured value of the process, usually called the Process Variable. This PV is what is being measured and fed back to the controller, compared to the Setpoint and then the Output of the Controller is adjusted accordingly, i.e. if the PV is under the Setpoint, then the controller output will be calling for an increase; on the other hand, if the PV is above the Setpoint, the controller output will be calling for a decrease. As the name implies, Proportional Control adjusts the output in accordance with the degree that the PV is in error to the Setpoint as a proportion of the error of the PV to the Setpoint.

      You may have noticed that all combinations of control require that in all cases that a Proportional control component must be present before the other levels of control can be employed. This is because that without some level of measurable error in the control loop, it is impossible to implement any kind of closed loop control. An example of Open Loop control is when you want to boil some water in a simple, ordinary electric kettle or jug..... you switch it on and wait until it boils and then switch it off. If you werent there to switch it off, the kettle/jug would just keep boiling away until some form of intervention was introduced.

      The "I" component of control is sometimes also called the "Reset". In a nutshell, the Integral portion of the algorithm looks at the amount of "Steady-State" error between the Setpoint and the PV and by design, will adjust the controller Output such that this error will be minimised or eliminated. In other words, PI control will always drive the output to eliminate any error between the Setpoint and the PV. Integral control is more of a reactive control measure in that it is intended to operate in a predetermined time space, reacting to changes in the PV over time.

      The "D" component of control is monitoring the "Rate of Change" between the Setpoint and the PV. Should the PV begin to drop below the Setpoint, depending on the rate of fall, the Derivative will attempt to adjust the controller Output such that the instant the fall is detected, there will be an Output adjustment to oppose this rate of fall (or rise). It is a pre-emptive control measure in that it attempts to arrest any deviation away from the Setpoint the instant it is detected.

      Heres a good description of how the three components operate together to achieve a high level of control in a typical Heating Application.....http://tinyurl.com/qmbst. Hope Ive helped you out here and not muddied the waters even further. Let me know if you would like to read more information about it and Ill steer you to a couple more sites that have a more thorough explanation . All the best,

      Mal.

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      • #18
        Re: PID Silvia Sydney

        Originally posted by bloop link=1143536728/15#15 date=1144073220
        Thank you all for all the helpful replies

        Mal, did you get your PID here http://www.onetemp.com.au/ ? May I ask which model you got?

        I have an electrician coming over on Saturday to fix some lights, if I can throw it all together by then Ill get him to have a look at it. Then Ill let yall know how it goes, if I live to tell the tale ;D
        Hiya bloop,

        Sounds good ;D. Yep, OneTemp is the supplier I got my hardware from and the rep I talked to was Ron Fowler. If you mention to Ron that you are a member of CoffeeSnobs, he will take good care of you and make sure you get the right hardware at the best prices. The controllers that are worth looking at are this one here....http://www.onetemp.com.au/pdf/HT-BS-1100-en-v2.pdf an OEM Fuzzy Logic controller, and this one....http://www.onetemp.com.au/pdf/sr1_sr3_sr4.pdf. The SR1 is the unit I used. When you talk to Ron, make sure that you ask him to provide you with the ordering information for an SSR Output model and a 25A SSR to suit. Im pretty sure that is what he will recommend to you anyway. Trust this helps ,

        Cheers,
        Mal.

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        • #19
          Re: PID Silvia Sydney

          Good post Mal. A good explanation of an often baffling acronym.
          Some people have claimed that a PID is over-the-top for a small boiler machine. But that speaks for itself -- because it is so small with a very large heating element, some sophisticated control IS desirable.

          Robuso

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          • #20
            Re: PID Silvia Sydney

            An excellent description Mal, thank you

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            • #21
              Re: PID Silvia Sydney

              Thanks Mal, will give them a try.

              Comment


              • #22
                Re: PID Silvia Sydney

                Just an update. Ive ordered a Shimaden SR1 and an SSR from onetemp. Should be coming tomorrow ;D

                Im going to go to Jaycar now and grab the extra bits.

                Hopefully they have a project box that fits the PID.

                Comment


                • #23
                  Re: PID Silvia Sydney

                  Mal, may I ask another question seeing as you have the same controller?

                  1. Where did you get the project box to fit the PID in?

                  2. Did you use a fuse and if so, whats the rating?

                  I was interested in the gooseneck mounting that can be seen here: http://www.digidive.com/coffee/index.html . I checked out goosenecks at Jaycar, but the internal diameter was way too small to fit all the wires in, oh well.

                  Comment


                  • #24
                    Re: PID Silvia Sydney

                    Originally posted by bloop link=1143536728/15#22 date=1144320561
                    Mal, may I ask another question seeing as you have the same controller?

                    1. Where did you get the project box to fit the PID in?

                    2. Did you use a fuse and if so, whats the rating?

                    I was interested in the gooseneck mounting that can be seen here: http://www.digidive.com/coffee/index.html . I checked out goosenecks at Jaycar, but the internal diameter was way too small to fit all the wires in, oh well.
                    Hi again Bloop,

                    No worries mate.....

                    1. I just took my controller with me down to our local Dick Smiths and found a neat little w/proof High Impact Plastic box that fitted nicely .

                    2. Yep, sure did use a fuse.... a Fast-Blow 0.5A fitted into an In-Line Fuse Carrier which I supplied from the downstream side of the Main Power Switch. This way, the controller is only powered up whenever the Mokita is powered up. No messy dual switching, etc to worry about 8-).

                    Yeah, that Goose-neck mod is a real beaut for sure. I also looked at that as a possibility for mine but as you also discovered, its a real tight fit for all the cabling and that coupled with the difficulty trying to find proper end terminators for the Goose-neck for fitting to the Mokita and the controller box, basically turned me off the whole idea. I guess its sort of ok to glue everything together with epoxy or whatever but it just didnt sit right with me.

                    In the end, I opted to go with a length of an appropriately sized piece of Heat-Shrink Tubing to both contain and protect the cables and t/c, and this worked out ok. I then terminated this with a suitable compression fitting on the controller box to keep things water-proof and used the original cable gland on the Mokita for both the original power cable and the new controller cable. I suppose if I had access to an instrument fitting workshop, Id have found more suitable and cosmetically appealing protection for the controller cable than heat-shrink, but one has to make do with what can get hold of.

                    Just thinking about the controller box again, you could probably get a sheet metal shop to knock you up a real nice little s/s box custom made to blend in with the Silvia perfectly. If I ever do this sort of thing again, thats probably the route Ill take so that I end up with a more professional job. As the Mythbusters say, "When will the fun ever stop?" ;D. All the best,

                    Mal.

                    Comment


                    • #25
                      Re: PID Silvia Sydney

                      Congrats, bloop. Sounds like you are well on your way. You wont go wrong if you keep following Mals advice!

                      Mal - I checked the sheet metal shop route for the SS box. Wow, did they want $$$ to make just one of something! Way too pricey for me.

                      So I ended up making box myself (of course I needed buy a bunch of neat tools and to build a spot welder along the way - but thats what projects are for, right?) Cost me lots more in the long run, but now I got all the stuff to make as many boxes as I need.

                      Have fun, bloop! You will absolutely love having the PID.

                      -- JGG

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                      • #26
                        Re: PID Silvia Sydney

                        Hi JGG,

                        Sounds like you might have a ready market to make good use of your hard won tools and equipment .....

                        Re the cost of getting shops to do it for you..... It probably comes down to how busy they are and whether they are actually interested or not. Another avenue to consider though, and I guess some members might think I harp on about it a bit, but you should never overlook your local TAFE Trade Colleges. They are usually more than happy to take on small jobs, always supervised by professional instructors/tutors... you just have to supply materials and pay for consumables. Worth a try if a TAFE College is not far from home

                        Mal.

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                        • #27
                          Re: PID Silvia Sydney

                          There must be some nifty chrome little box in a kitchen wares shop which may do the job -- you know, "used-toothpick holder" come PID enclosure!

                          Of course, insulating terminals will become doubly more important so as not to make the entire machine live.

                          Otherwise, a black plastic box may make a good cosmetic complement to the Silvias brushed stainless steel case and black iron frame.

                          Good luck with the project, Bloop

                          Robusto

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                          • #28
                            Re: PID Silvia Sydney

                            Update 2:

                            The PID didnt come today

                            Toll apparently forgot to drop by onetemp to pick up the deliveries, so Ill have to wait till Monday.

                            I bought a grey plastic project box from Jaycar but the internal dimensions arent quite what it states outside so I dont think itll fit too well. I dont think Ill go for a metal case. The thought of live wires being so close to metal is a bit scary.

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                            • #29
                              Re: PID Silvia Sydney

                              bloop -

                              Having been down this road, I will offer to you that "too big" is much better than "too small" when it comes to your box. Getting PID installed, plus wiring, can be a real PITA, made far worse in confined spots.

                              If for some reason you do end up with a metal box, be sure you ground it directly. This will take away some of the concern regarding a loose live wire (definitely a bad thing). You can easily tap into Silvias ground. Look for a pair of green, or green/yellow, wires fastened to the base of the boiler on the right side, near where the mains enter.

                              -- JGG

                              Comment


                              • #30
                                Re: PID Silvia Sydney

                                Hey all, I got the PID today. All wrapped up nicely in bubble wrap, together with a 40A SSR and a teflon type K thermocouple.

                                The thermocouple wire doesnt seem to be soldered at the end, anyone know if normal lead solder will do the job or does that have too low a melting point?

                                Yep, sure did use a fuse.... a Fast-Blow 0.5A fitted into an In-Line Fuse Carrier which I supplied from the downstream side of the Main Power Switch. This way, the controller is only powered up whenever the Mokita is powered up. No messy dual switching, etc to worry about Cool.
                                Mal, you piggy-backed power off the Mokita? If so did you splice the wire or is there some kind of "double adaptor" attachment available for this kind of job?

                                If for some reason you do end up with a metal box, be sure you ground it directly. This will take away some of the concern regarding a loose live wire (definitely a bad thing). You can easily tap into Silvias ground. Look for a pair of green, or green/yellow, wires fastened to the base of the boiler on the right side, near where the mains enter.
                                Thanks for that JGG, I think Ill go plastic though, as good as coffee is, its not worth getting fried over Oh and after reading up on all this PID stuff, your first post finally made sense to me ;D

                                Ive got to get a few more bits and pieces and hopefully will finish this job by the Easter weekend.

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