Announcement

Collapse
No announcement yet.

UPDATED 12/11/2013 - Popper Roasting - Tips, Tricks & Mods

Collapse
This is a sticky topic.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • UPDATED 12/11/2013 - Popper Roasting - Tips, Tricks & Mods

    I have been collecting and testing different popper mods & tips for a couple of years now.
    Most of what I have found is available here on C.S. - but it is scattered all over the site.
    From time to time we get queries about this, so I've put all the info I have found into this post.

    The web has lots of details on how to use these ideas, just use your favourite search engine.

    DISCLAIMER :- If you choose to make use of any of this information, you do so entirely at your own risk.
    I accept NO responsibility for your actions.

    Popper Basics.

    Most poppers are rated at 1200 or 1250 watts. A few models are different, but they are less common.
    Some are rated 220-240 volts and 1100-1200 watts, i.e. 1100w on 220v, and 1200w at 240 volts.
    The only exception that I know of is Target's "own brand" popper rated 220 - 240 volts and 900 watts.
    Most poppers have a small chamber and a small bean mass. They have a fixed heater wattage, and single fan speed, so ambient air temperature is a MAJOR factor.
    All of the 1200w units will run a bit too hot, and roast too fast even in cool weather, and in warm or hot weather they run much too hot and roast too fast.
    On the other hand, the Target 900W is a little under powered for cool weather roasting, and might not even reach crack temperatures when it's colder.
    The best popper(s) for you will depend on whether you live in the far north, the deep south, or somewhere in between.

    A simple solution is to have two, a 900w unit for Summer and a 1200w for Winter, with a few mods.
    If I was going to do it this way, I'd use a Target in summer and a Breville in winter.

    To get the best from your popper, here are some things you can do:

    Almost all poppers have a top section designed to eject the corn as it pops.
    This is no good for roasting coffee - throw it away. You need a tin can "chimney" instead.
    This is really an extension of the roast chamber, tall enough to keep the beans from jumping out.
    A good chimney is a red or pink salmon can. The 415 gram size is the right size for most poppers.
    Stand the popper on a sloping surface, so it's slightly tilted, for better agitation & turnover of the beans.
    Poppers have a thermostat that trips if they get too hot. It may have to be disabled to reach crack temps.

    Mods / Tips to slow down a popper in warm weather.

    Use a 900 watt popper in warm or hot weather. Blow air over and around the popper with a fan.
    Use a chimney that is just tall enough to keep the beans from escaping, or make one from metal mesh.
    For the first few minutes, vigorously stir the beans - this will increase the airflow and slow the roast a little.
    Roast during the cooler part of the day, and do small batches. (say 60 to 80 grams max).
    Enlarge the vents in the bottom of the chamber, and seal the chamber/fan housing joint to increase airflow.
    Remove the top section of the case, & run the popper "topless" with an external fan blowing on it.
    WARNING :- Running "topless" is not safe with some makes/models. If in doubt - - Don't do it.
    On poppers with a one-piece case, drill lots of holes - but only in the upper section away from the electrics.
    Or cut large holes in front and back, or both side panels, and use an external fan to force air through.
    Toward the end of the roast you may have to switch the external fan off to reach crack temperatures.
    Any of these things will only make a minor change - you will need to combine several to be really effective.

    Myth-buster :- Extension leads will NOT drop enough voltage to make a difference, unless they are faulty, or very light-duty leads 100+ meters long. A typical extension cord (with 2.5 mm conductors) causes a voltage drop of 25mV per amp of current, per meter of length. A 1200 watt popper will draw 5 amps, which = 0.125 volts per meter or just 1.25 volts drop for every 10 meters of extension lead.

    Mods / Tips for cold weather.

    Use a 1200 watt popper in cool or cold weather.
    Roast in a warm location at the warmest time of the day.
    Fit a taller chimney, and/or partly restrict the outward airflow with a cover of some kind.
    Roast larger batches of beans, say 100 to 125 grams. This holds more heat in, but will need stirring.
    Stir the beans gently, just enough to keep them turning over, but no more than that.
    If you have removed the top half of the popper's outer case for summer, put it back on in winter.
    If you have drilled or cut holes in the case, wrap something around it to insulate it.
    Run the popper in a box, open at the front, but closed at the top ,so that some of the hot air is recycled.
    Block the air intakes in the base, & drill holes in the top of the case, so warm air is sucked in at the top.

    Each of these things will make a small change - you will need to combine several to be really effective

    MAJOR ELECTRICAL MODS ( For tech types only )

    WARNING :- Unless you have the know-how to do this safely, it may kill or maim you.
    If you are in any doubt - PLEASE - Don't Do It !!.


    The best popper is a 1200 watt unit, with PID or SCR heat control, & variable DC power to the fan.
    This will allow full and independent control of both the heat and the airflow.

    A variable SCR is cheap, ( less than $10 on Evilbay). It's also simple, and effective.
    If you install it in the heater circuit without slowing the fan, it's the most effective single mod you can do.
    If the SCR is also combined with an external power supply to the fan, with speed control, it is even better.
    To get the best from these mods you really should fit a temp probe & multimeter or digital thermometer.

    Poppers have two heater coils, the main/primary coil, and a small secondary to provide low voltage for the fan.

    A few have the coils in parallel with one another, and the fan rectifier in series with the secondary.
    This type is easier to work with and you can use plan A or B.

    Plan A :- Install an SCR in series with the main coil only, so it does not affect the secondary coil & fan.
    The heat can now be turned up or down while the fan speed and airflow remain unchanged.

    BUT - most poppers have their heater coils in series, with the fan rectifier across the secondary.
    This type is a little bit harder, and you will need to go to Plan B.

    Plan B :- Power the fan from an external power source, and install the SCR in series with the heater coils.
    A laptop power supply will give 18-19 V of smooth DC. This will boost fan speed and agitation of the beans.
    With the increased airflow, even a 1200 watt unit might struggle to reach crack temps in cooler weather.
    Solution - insert a 5ohm 15W pot in series with the fan, & increase temps by slowing the fan as needed.
    These are about $10 from Jaycar or Fleabay, and probably available from other component shops.
    A suitable PWM speed controller should also work, but I have not tried one of these (yet).

    It will take some trial and error to get the roast profiles you want, & ambient temperature will still be a factor.
    A routine that works in warm weather will be different when it's cool, just use the controls to compensate.
    I usually adjust the heat or fan at 1 minute intervals. I have tried shorter times, but this works well for me.

    My usual method in warm to hot weather. ( It's sub-tropical where I live )
    I usually do 125 grams of greens, but have done up to 150 grams. Even with the fan on full speed, I stir the beans occasionally for the first few minutes. I start with the voltage at about one third, increasing it in small steps each minute, so it's up to full power in about 8 to 12 minutes. On my current set-up the temperature is now above 190°C and getting close to first crack. Now I reduce the fan speed a little to reach first crack, then gradually reduce it further until the roast is at the level I want. When the roast level is right, switch the heater off and fan to full speed to cool the beans. Mine are cool within 2/3 minutes.
    This needs a tall chimney, or the beans will be blown out over the top. I add a second can before I crank the fan up.

    I usually start with the voltage setting a bit higher when it's cool, and when it's cold, I also run the fan a little slower right from the start.

    Posts 2 through 9 were made prior to the updated rewrite being posted.
    Last edited by Javaphile; 13th November 2013, 02:24 PM. Reason: Updated rewrite by OP

  • #2
    deegee, thanks, that really helpful, I am in the process of making my own popper roaster and have a few questions.

    1. Re the scr variable, I was thinking I could use a 240 vlt light dimmer switch?
    2. fan, is it critical to have the fan speed variable as well?

    I ask this because I want to play around with roasting until I get to know a bit more about my set up, if I need a fan controllerI should find out soon enough.

    Do you have any pics that will help me?

    Comment


    • #3
      Originally posted by smokey View Post
      1. Re the scr variable, I was thinking I could use a 240 vlt light dimmer switch?
      2. fan, is it critical to have the fan speed variable as well?
      Do you have any pics that will help me?
      Hello Smokey.

      A fan with speed control is best, but not essential, so you can manage without it.

      I have seen a couple of posts somewhere, saying that a dimmer switch will work, but I could not find any that would handle the wattage. Poppers are mostly 1200 - 1250 watts, so I would want something that would handle at least 1500 watts to have some safety margin.
      Last time I looked was a couple of years ago, so this could have changed, but maybe not, because very few lights exceed 150W.

      Relatively cheap SCR's ( less than $10 ) will handle up to 4KW. Most claim to be variable from about 10V up to full supply voltage. In reality the ones I have used will output from about 20v to about 230V when connected on a 240V supply, but this is OK. The main downside is waiting 3 or 4 weeks for them to arrive from China or Hong Kong.

      Whatever you use must be inserted in series with the heater coil(s) ONLY, so it does NOT also affect the fan speed. If you just put it in the poppers power supply, reducing the heater voltage will also slow the fan and the nett result will be little or nothing. On most poppers this is not easy, because some of the connections are rivetted on the coil plate, which is fragile and easily damaged. ( See pic 1.)
      It's much easier to cut out the wires to the fan and connect it to an external supply, in which case it is also easy to put a pot in the circuit to control the fan speed.

      The other pics are of an SCR and an early prototype B&D popper with SCR and fan control. The SCR is in the lower box, and the pot for the fan is above it. ( Pics 2 and 3.)

      I have to go out shortly, and will not be back online til late tonight, or maybe tomorrow. If I know what other pics you want, I could take a few shots and post them for you.

      Cheers, DG
      Attached Files

      Comment


      • #4
        Thanks, your detailed explanation and pics helps a lot. I'll post when I set it up.

        Just one question, whats a pot? For the fan, where can I get one etc?
        Last edited by smokey; 5th November 2013, 07:15 PM.

        Comment


        • #5
          Originally posted by smokey View Post
          Just one question, whats a pot? For the fan, where can I get one etc?
          "pot" is tech shorthand for "potentiometer" which is a variable resistor with three terminals ( see pic )
          In this case we are only using two teminals, so to please the purists, we are using it as a rheostat.
          The one we need here is a 5-Ohm 15-Watt Wirewound Potentiometer.
          They are $9.95 from Jaycar Electronics, FleaBay, and probably from other electonics component suppliers.
          Inserted in series with the fan, it will vary the fan speed between about half and full speed.
          Attached Files

          Comment


          • #6
            deegee, thanks, now I get the picture, how do you increase the fan speed... by adding a power source I suspect. When I get my popper I will be asking more questions, thanks heaps.

            Comment


            • #7
              Originally posted by smokey View Post
              deegee, thanks, now I get the picture, how do you increase the fan speed... by adding a power source I suspect. When I get my popper I will be asking more questions, thanks heaps.
              Yes, as I mentioned in Part 2 of the OP above, I used an old laptop PC power supply.

              The section on electrical mods was written for people with technical training / experience and assumes they will understand the tech terms.

              I don't mind helping you with this - - but - - I am becoming concerned that you do not have much technical experience.

              These mods involve working with mains voltages, and can be dangerous.

              Do you know someone with electrical know-how who could help you with this??.

              If not, I strongly suggest that you stick with the mechanical mods suggested in the earlier part of the post.

              Comment


              • #8
                Hi deegee, re your concerns, I agree, I have been thinking seriously about what I will do, and I have a friend who is an electrician.

                I used my new popper today, 1/4 cup green decaf beans, it runs at 1200 W, it got to FC by 2 minutes and it just continued to roll into SC and was all over by 3:50. I had to pull it due to the smoke, and it set off my fire alarm too.

                Yep, I did it in the kitchen, it was a cold day, I won't be doing it in the kitchen again, way too smelly and when the missus gets home I am in for it.

                Phew, what a ride! Way too hot, way too fast.

                Now to consider your instructions re wiring the speed controller to the heater element and inviting my friend over for a bbq and play.

                Comment


                • #9
                  Originally posted by smokey View Post
                  Hi deegee, re your concerns, I agree, I have been thinking seriously about what I will do, and I have a friend who is an electrician.

                  I used my new popper today, 1/4 cup green decaf beans, it runs at 1200 W, it got to FC by 2 minutes and it just continued to roll into SC and was all over by 3:50. I had to pull it due to the smoke, and it set off my fire alarm too. Yep, I did it in the kitchen, it was a cold day, I won't be doing it in the kitchen again, way too smelly and when the missus gets home I am in for it. Phew, what a ride! Way too hot, way too fast.

                  Now to consider your instructions re wiring the speed controller to the heater element and inviting my friend over for a bbq and play.
                  Hello Smokey, Glad to hear that you have a sparky to help you with the project. I will be happy to help with circuit diagrams and pictures.

                  As for the smoke - you must have had a premonition when you chose your log-in name ???

                  I've been there and done that - set off the alarms. I now roast downstairs in the workshop & storage area.

                  I have added a post to your other thread with a few pics of some things you can try with your target popper.

                  Comment


                  • #10
                    deegee, lol, my log-in name reflects my coffee roasting experiences very well

                    Comment


                    • #11
                      hi deegee, where on ebay did you buy the variable SCR from? I have looked abut cannot source one.

                      regards

                      Comment


                      • #12
                        Hey folks,

                        Just wondering iif anyone can give some tips regarding my popper.

                        Here's a photo:
                        Click image for larger version

Name:	image.jpg
Views:	1
Size:	277.5 KB
ID:	736761

                        Is it possible to just do away with all that stuff on the motor and attach the + and - to a DC dimmer set up and then only use the large coil with a switch attached?

                        Comment


                        • #13
                          So i think my course of action will be this: find an old power laptop supply and remove the pcb connected to the motor and go straight to the motor terminals via a pot to vary the speed there. Then take one of these Mains Motor and Lamp Controller - Jaycar Electronics and connect that sucker straight to the main heater coil.

                          My question is, does this make sense? It makes sense in my head however I am sure I am missing some technical aspects. I have done some electrical work in the past namely with low voltage DC and if I go for this then I will absolutely be having it checked before turning it on.

                          Comment


                          • #14
                            G'day mate...

                            Yes, that would work Ok but you will need to find a higher rated 240V AC controller for the heating element. They're typically rated at over 1,000W so the 600W rated unit won't be up to it (have to take note of the Continuous Rating, not the Maximum). Pretty sure Altronics used to have 10Amp continuously rated kits on the market a while ago; might be worth checking to see if they (or someone else) has one.

                            The Jaycar unit might be amenable to modification to increase its output rating but if you're not 'au fait' with 240V AC electronics, best to go with something that's up to the job from the outset. Always remember though, 240V can and DOES KILL. Take every precaution and if you are at all unsure, pay a professional to do the job for you...

                            All the best,
                            Mal.

                            Edit:
                            Turns out that Jaycar do have one...

                            Comment


                            • #15
                              Jeez not cheap is it. Thanks for the tip. Will have to do some more thinking as budget constraints are a concern too.

                              Edit: I guess however from a safety point of view it makes this a whole lot safer though.

                              Comment

                              Working...
                              X