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  • Yet another Popper mod...

    At the risk of being repetitive, Hazbean has suggested I post some pictures of his old popper which I have modified. The mods are simple, and very effective. Hazbean suggests that this setup is "better" than his iRoast, but I think that might have something to do with the failures he has experienced lately...

    The basic modification was the addition of a chimney (tin can), followed by the addition of a temperature probe (K-type thermocouple - because they are cheap). What followed that was the addition of a ramp/soak PID controller....

    Adding the PID was interesting - it involves surgery inside the popper to separate the fan from the heating elements. Since this involves stuff that can kill you, Im omitting the details lest Im indirectly responsible for a CSer leaving the community..

    The chimney mod was largely done by Hazbean - the plastic doofer that comes on the popper basically forms a holder for it. Unless youve been roasting without the chimney, in which case it is probably a pile of melted plastic..

    This attachment is a side view of the popper with the thermocouple wire (white) going into the tin-can and the red/black wire providing 28VAC for the fan.


  • #2
    Re: Yet another Popper mod...

    And this is a piccy of the controller. It consists of an Auber Instruments ramp/soak PID, a 28VAC transformer to provide power for the fan and a 25A zero crossing solid state relay.

    Again, Im loathe to post a picture with the lid off - if you know enough to do this mod safely, you already know what to do!!

    All up this modification to the popper was about $120(AUS). But it depends on what bits of kit you have already.

    (The tin-can was free - it came with the popper from Hazbean!)

    This "Franken Popper" set up is a prototype for a less Heath-Robinson lashup I plan on doing soon. Due to extended periods of being ill, this was cobbled together as a proof of concept and it has proved the concept!


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    • #3
      Re: Yet another Popper mod...

      And finally, to get to the reason why this is a good mod.

      It works.

      For example - here is a roast profile I regularly use:
      150C for 2 mins (ramps to 150 and holds there)
      4min ramp to 180C
      2min ramp to 210C
      5min ramp to 230C

      (The temperatures arent exactly as quoted - the compensation map for the thermocouple is out a bit for temperatures < 200C - but this is a controller designed for industrial ovens!)

      You cant do that kind of thing with an un-modified popper. Changing the profile can be done too and the controller has 3 different profiles stored in it. Overall: very effective but not something youd show off to your mother!

      /Kevin

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      • #4
        Re: Yet another Popper mod...


        Appears to be the highest-tech popper I have ever seen.
        Nice work Kevin.

        What volume of beans are you using?
        Do you need to stir them at the start of the roast?

        I would be tempted to see if you can try a profile that is slower again.

        Maybe a prior step of ramp to 100 over the first 3 minutes and adjust the final 230 down to 215-220 odd. That would put your 1st crack at the 10 minute mark and 2nd at 15 ish.


        Interesting to have that level of control on the roast. Do you use an external cooler contraption or just blow with no heat for a while?


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        • #5
          Re: Yet another Popper mod...

          Nice work KJM 8-),

          That "Black Box" definitely has the potential to be an essential and very flexible, portable multi-roaster control if ever I saw one . Cant wait to see the final version in action and some resulting roasts....

          Mal.

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          • #6
            Re: Yet another Popper mod...

            (Sorry for not responding - it was our CFS brigades annual snapper fishing trip this weekend ;D ;D )

            Yes - I can do significantly slower profiles. Ive just been poodle-ing about with it and have used the profile I quoted quite a bit. Slower is very, very easy - fast ramps are really hard to do tho. The popper hasnt got enough oomph. Ive been a bit wary of "baking" the beans rather than roasting...

            The temperatures are entirely notional. The system is uncalibrated - so 230C is more like 227C when you measure the beans. This has always been an issue with me - there is a limit to the rate at which you can get heat into the beans.

            My batch size is 140g. Nominally. The fan cant loft the beans if I put much more than that, and cant loft some beans at 140g at all! 140g is enough for me - kind of. I do about 3 batches on the weekend and it is enough.

            The "sophisticated" box aint all that sophisticated! Its just a controller, SSR and transformer in a "just fits" box (actually a "just doesnt quite fit box" > ). This was actually a quickie lash-up to prove the concept. I did it that way after I first opened the popper and discovered how it was made! I can see a new popper on the horizon - they arent designed to run for the time/temp we need for coffee roasting. This way, I can get another one and bypass the thermal cut out, secondary heater etc and get a replacement up and going for 30minutes work and the loss of only a small amount of blood (damn those things are jaggy inside!).

            Ive attached a picture of the "chimney" mod. Hazbean just used to poke the thermocouple sensor "down the hole". Being an engineer type - I used some wire to hold the probes in place within the bean mass. If anyone does the same, Id suggest putting the wire in a bit higher up the tin can. Believe it or not, the three legged spider to hold the probes actually interferes with the circulation of the beans when they are roasted and expanded fully. Not a lot, but enough to make me keep thinking about changing it.

            Anyway, I hope it gives all us popper hackers some ideas! CoffeeSnobs has been a wonderful source of neat ideas for me - Im just trying to give something back...

            Cheers
            /Kevin

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            • #7
              Re: Yet another Popper mod...

              Andy - (drat! I didnt see the question about cooling!)

              Cooling is a no brainer for me. Things like the iRoast cool down the beans by stopping the heat. I just stop the heat too! Cools down to an indicated 80C in 1 minute (although in the warmer weather, this will be slower). Then I dump the beans into an old aluminium roasting pan. Great heatsink! By the time I walk from the mower shed to the kitchen, the beans are totally cool... So maybe 2minutes from full roast temp to ambient?

              I dont have any idea if the cooling is (a) too fast -or- (b) too slow!!!

              Any words of wisdom on it?

              /Kevin

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              • #8
                Re: Yet another Popper mod...

                According to what Hazel de los Reyes told me, your cooling times are OK.

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                • #9
                  Re: Yet another Popper mod...

                  This is how I fitted the thermocouple in to my B & D Popper. I fitted it inside the popper body, between the black top and the top of the metal roasting chamber, angled down in to the bean mass. I needed to modify the black top slightly for it to fit though.

                  I also recently fitted another thermocouple probe through a hole in the black top, directed straight down in through a drilled hole in the metal casing. Its hard to explain without a photo, but basically the 2nd probe is positioned such that it measures the air inlet temperature just before it enters the roast chamber. This has made it much easier for me to adjust the roast profile via my "black box" controller, as this 2nd probe reacts much faster to my adjustments to the heater controller than the probe in the bean mass does. So, if I adjust the heater controller too high or low, I get an earlier indication and can correct it before the effect shows up in the bean mass. eg. If Im ramping up towards 1st crack, I want to keep the air inlet temp higher than the bean mass temp, otherwise the roast will stall. If the inlet temp drops below the bean mass temp, I can quickly add more heat before the bean mass temp drops.

                  See attached photos:



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                  • #10
                    Re: Yet another Popper mod...

                    and another view:



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                    • #11
                      Re: Yet another Popper mod...

                      Very nice fit-up there Bill! I made use of the traditional "Fencing wire & Bailer twine" approach simply because I didnt want to take the thing apart yet-another-time.

                      Yours will interfere with "bean circulation" a lot less!

                      My next popper will have something similar, I think.

                      Cheers
                      /Kevin

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                      • #12
                        Re: Yet another Popper mod...

                        Andy: I dusted off the laptop and took it out to the mower shed :P This is the modified profile as per your recommendation! But with two stuff ups - I forgot to plug it in initially :-[ and also forgot the calibration is whacked. Its out by 10C initially, tapering to out by 0.8C at 200C.... Kind of hard to "squint" and correct the image, but the general trend is pretty clear.

                        The data points are being sampled full tilt, hence the wee dips when the heating switches off! If I smoothed the data it wouldnt look quite so raggedy-anne. Anyway, this simple mod to the popper does give the control you need, I think!

                        /Kevin

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                        • #13
                          Re: Yet another Popper mod...


                          Very nice control (doesnt need smoothing either)

                          Will be interesting to hear how the different profiles taste.

                          Cooling? Cannot be too fast but a couple of minutes is excellent. The big boys work on "under 6 minutes" but I like room temp under 3 as my target.

                          I was told once that lobbing the roast into a bath (err.. waterless bath with the plug in!) will snap cool near instantly. I have tried with sucess on a big block of stone / marble back in my popper days too.

                          I would love a cubic meter of granite with a hole through it at the snoberry for pass-through cooling a roast.

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                          • #14
                            Re: Yet another Popper mod...

                            Originally posted by Andy Freeman link=1196396976/0#12 date=1197123316
                            Very nice control (doesnt need smoothing either)

                            Will be interesting to hear how the different profiles taste.
                            Well, different profiles do produce different tastes! I use a long, slow profile for my much loved Ethiopian beans and my newly found mega-love Yemenis...

                            Originally posted by Andy Freeman link=1196396976/0#12 date=1197123316
                            Cooling? Cannot be too fast but a couple of minutes is excellent. The big boys work on "under 6 minutes" but I like room temp under 3 as my target.

                            I was told once that lobbing the roast into a bath (err.. waterless bath with the plug in!) will snap cool near instantly. I have tried with sucess on a big block of stone / marble back in my popper days too.

                            I would love a cubic meter of granite with a hole through it at the snoberry for pass-through cooling a roast.
                            You seek the elusive reverse-cycle microwave :P !

                            Unfortunately, I (temporarily) dont need to worry about cooling! Doing a bunch of back to back batches for my Sister has busted the popper!

                            Cautionary tale for popper owners: the fan is a piece of hard plastic (polycarb?) which isnt designed for the heat load we put in. Its fine for a single roast, as long as you leave the fan running (and no heater) so you cool the guts of the machine down... But if you try too many roasts in a row - it gets hot, distorts, hits the metal bits and the metal bits win > Entirely my fault, I knew the fan was plastic! Not being able to touch the outside of the popper should have rung alarm bells!

                            "Bugga".

                            /Kevin

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                            • #15
                              Re: Yet another Popper mod...

                              Bugger......

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