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

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    Senior Member deegee's Avatar
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    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 190C 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 at 12:24 PM. Reason: Updated rewrite by OP

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    Senior Member smokey's Avatar
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    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?

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    Senior Member deegee's Avatar
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    Quote 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
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    Senior Member smokey's Avatar
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    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 at 05:15 PM.

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    Senior Member deegee's Avatar
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    Quote 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.
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    Senior Member smokey's Avatar
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    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.

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    Senior Member deegee's Avatar
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    Quote 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.

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    Senior Member smokey's Avatar
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    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.

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    Senior Member deegee's Avatar
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    Quote 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.

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    Senior Member smokey's Avatar
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    deegee, I had a laugh, my log-in name reflects my coffee roasting experiences very well

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

    regards

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    Hey folks,

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

    Here's a photo:
    image.jpg

    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?

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    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.

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    Mal Dimal's Avatar
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    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...

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    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.

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    Another question: if i was to start by only controlling the fan via a power supply would it be possibly to just remove the pcb from the terminals of the fan, connect the fan to the powersupply and leave the pcb alone so that the original switch of the popper would only control the heat? Or is the circuit broken due to the motor not being in place any more?

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    Mal Dimal's Avatar
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    Yes, that would be Ok...

    Just need to make sure you don't exceed the maximum rated voltage of the Fan Motor. It does vary a bit from one manufacturer to another but as a ballpark, I wouldn't go higher than 24V DC.

    And yes, the Jaycar Kit option is a much safer way to go...

    Mal.

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    I've been toying with the idea of wiring an ssr or a relay into my heating circuit and dc fan supply. So that the heating circuit is open unless there is power to the fan. Are there any issues with overheating the ssr, or with having two ssr's in series? Also, would I be better off wiring the fan in series or parallel with the fan (on the low voltage side)?

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    Mal Dimal's Avatar
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    I kind of get what your driving at there Mr. Jack but if you used either two relays or SSRs, the connection arrangement is called Cascade Logic - Where downstream relays only energise when the direct upstream relay is powered up. Simple but effective for a simple case such as this. A better explanation of what you're trying to achieve and what you already have in your current design would help...

    Mal.

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    Apologies. I have a PID controller controlling the heating element in my popper via an SSR. I am powering the fan via a 19V 4A laptop power supply. I think it would be a useful safety feature if the heating element loop was only active when there is power to the fan. So I was thimking of wiring the low voltage side of a second ssr, into the fan circuit, with the 240V side in series with the existing SSR.

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    Senior Member deegee's Avatar
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    Quote Originally Posted by pmilevski View Post
    hi deegee, where on ebay did you buy the variable SCR from? I have looked abut cannot source one.

    regards
    Hello pmilevski, I got mine online from Fleabay, there are lots of them on there. Log on and search "scr voltage regulator".

    Just make sure that you get one suitable for at least 220 volts and at least 2000 watts. I'm using 3800 watt units on a couple of poppers. They are well over-rated for a 1200 watt popper, but I like that. In use the heat sinks hardly even get warm.

    Sorry for the slow reply, but I haven't been here on site much recently. There has been so much off-topic crap that I have not been inclined to visit. It's bad enough when it is in the off-topic section, but when other threads are hi-jacked for tedious arguments on religion, politics, or alternative life styles, I tend to vote with my feet. ( or in this case, my keyboard ).
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    I've been toying with the idea of wiring an ssr or a relay into my heating circuit and dc fan supply.
    I used a relay in the fan circuit in my modified popper to control power to the SSR, its not ideal as power to the fan can be available but the fan may not be working.
    See this thread from a couple of years ago: Manual Popper Controller

    Here is a bit more info on how it was done.


    Gary
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    Man these are looking good. Giving me more ideas! Just got given a crazy popper to test out too so will have to see which gets the mods done to it. Crazy popper seems much weightier than the other Moda popper from The Warehouse.

    @deegee: I hear that. I lurk most of the time here but threads like these deserve the praise and anyway to further the knowledge makes it worthwhile. Thanks a bunch too everyone involved for the help! I will hopefully make some progress and report back soon.

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    Junior Member bernardrooney's Avatar
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    I use one of those low watt target poppers. To pick up the heat I have a simple air recirc, which is basically a 50 ml perforated flexi pipe that runs from the top of the popper down to a chamber (ice cream bucket) underneath the popper, which thus sucks air through the base. I can tweak the temp by simply raising or lowering the popper from the chamber beneath thus allowing mixture of cool and warm (drier) air. Its hit and miss and guess work you understand.

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    Ok here is my current plan regarding dc fan control:

    Use grimsby's approach mentioned in this thread Crazy Popper Mod Question to simply split the fan control. Then wire from the motor poles to a 5ohm 15w pot which then leads to one of these 2.5mm DC Connector - Jaycar Electronics so that a power supply can be introduced without butchering my partners laptop 19v 4.74a power supply. Sounds good?

    I have been given a free crazy popper which has a way more powerful fan than the other Moda POS I have and seems mUCH sturdier too.

    So then i assume that heater control will come from flicking the crazy's on/off switch which will still work regardless of the pcb tracks being split from the motor leads. This could lead to heater control safely being applied with a 240V 10A Deluxe Motor Speed Controller Kit - Jaycar Electronics if I was so inclined for further and safer control.

    Anyone out there see any glaring errors or ways this can be improved? Mal, I am certainly hoping you'll chime in!

    Cheers,
    Marc

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    Senior Member deegee's Avatar
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    Hello Marc, Yes that should work. If the jaycar connector mates with the output lead on the laptop power supply, it should do the job.

    I recently built another popper/roaster with split fan and heater circuits. To power the fan I bought a S/H Dell 90 watt (4.6 amp) laptop power for less than $20 including postage.

    To split the fan off from the rest I un-soldered the PCB from the motor and removed it. This is a neat simple job, but does involve rejoining the neutral wires and capping the low voltage active that feeds the fan, so you may not want to go that way.

    The Jaycar controller sounds like a simple & safe way to control the heat, but it is rather exy for a popper project.

    Cheers, deegee.

    PS have to go out now, will not be back on line until this evening.

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    Hell yes. Off to jaycar tomorrow then! Are you still using the same scr for your heating?

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    Senior Member deegee's Avatar
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    Quote Originally Posted by marcism View Post
    Are you still using the same scr for your heating?
    Yes - on the new unit I used the same make/model SCR as the first one (in pic above).

    When I first got the original SCR and found that it worked really well, I ordered two more - they were only about $8 each. One of them has since been used in a unit that I built for a friend a few months ago, and the second went into my latest roaster. The original one is still working fine, but the fan bearings are sounding a bit tired.

    Since I already had a spare popper, and a spare SCR, I bought a power supply (about $15) and a Pot ($10) so I could have a complete roaster built and ready to go if the old one died suddenly.

    I also tried using a PWM controller instead of a pot to vary the fan speed, but I stayed with the 5 ohm pot as it allowed me to make smaller adjustments more easily.

    You may need a knob for the pot. I prefer the Jaycar ones with the numbers 1 to 10 around the flange.

    You need to be aware that most laptop chargers have an overload sensor, and if connected straight to a popper fan with no other resistance in series with it, the charger may power off to protect itself. It seems to be a borderline situation, and will depend on the charger, and the resistance of the fan in your popper.

    I have three different popper fans and two different chargers - some combinations will work happily without any extra resistance in circuit, but other combinations need a couple of ohms in series with the fan, or the charger safety will trip.

    Which brand of popper is the one shown in your pic above ??. Some of the innards look very familiar - just like a Black & Decker or a Tiffany, but some other bits look different to any popper that I have seen inside, and so does some of the wiring.

    Cheers, deegee.

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    Above is a Moda brand popper from the warehouse here in NZ but i was given a crazy popper which has the same guts again but seems much better quality.

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    What's not to love about combing my love of coffee and my desire to be Macgyger, did some more playing about with the popper this afternoon. And thinking about doing away with the new whole case and coming up with a new box to build around it.
    I will be about to vary my fan speed easy enough via my variable desktop power supply.
    So just need have some control over the heating element and a decent way to measure the temp

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    Also has anyone entertained the potential of using one of these units? [IMG]http://www.directbuy.com.au/images/Popcorn%20(1)-3.jpg[/IMG]

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    Senior Member deegee's Avatar
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    Quote Originally Posted by cloudwarrior View Post
    I will be about to vary my fan speed easy enough via my variable desktop power supply. So just need have some control over the heating element and a decent way to measure the temp
    Hello CW, apologies for the slow response, I haven't been on line much recently.

    Here are some pics of the SCR, the digital thermometer, and the probe that I am using on my popper rigs to monitor them.
    They are all available on Ebay at bargain prices. Sorry, but the rules won't let me paste links here.

    As you can see in the third & fourth pics I have also put one on my Classic for more accurate temp surfing.

    3800watt SCR.jpegThermometer & Probe.jpgThermometer on Gaggia.jpgPB180002.jpg

    As I said at the top of this thread I have done a lot of research into poppers, but I have never seen anyone using or even suggesting the fancy popper in your other post. I doubt that they would be suitable for coffee and they are much dearer too.

    Cheers, deegee.

    PS the one on the Classic uses a simple bead type TC not a probe.
    Last edited by deegee; 7th May 2014 at 04:42 PM. Reason: See PS
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  33. #33
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    Quote Originally Posted by deegee View Post
    Hello CW, apologies for the slow response, I haven't been on line much recently.

    Here are some pics of the SCR, the digital thermometer, and the probe that I am using on my popper rigs to monitor them.
    They are all available on Ebay at bargain prices. Sorry, but the rules won't let me paste links here.

    As you can see in the third & fourth pics I have also put one on my Classic for more accurate temp surfing.

    3800watt SCR.jpegThermometer & Probe.jpgThermometer on Gaggia.jpgPB180002.jpg

    As I said at the top of this thread I have done a lot of research into poppers, but I have never seen anyone using or even suggesting the fancy popper in your other post. I doubt that they would be suitable for coffee and they are much dearer too.

    Cheers, deegee.

    PS the one on the Classic uses a simple bead type TC not a probe.
    thanks for the reply guru
    actually ordered my SCR & thermometer today also using a gaggia classic at home.
    the fancy popcorn machine was a free bonus with my last TV purchase, so no real outlay of i decide to play with it. my personal theory is that it would stir the beans too slow and may not be hot enough,on account of it using oil during the popcorn popping


    this is what i will be relocating my popper into once all the parts arrive

  34. #34
    Senior Member deegee's Avatar
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    Hello CloudWarrior, That box looks like a neat job. I usually build mine on an open "breadboard" layout, with the various components held in place with velcro so they can be easily changed or moved around.
    If you already have one of those popcorn makers, it would be interesting to give it a try - with a minimum batch of beans - so not too much is wasted if it is a fail.

    Cheers, deegee.

  35. #35
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    Grabbed a pot for the DC fan supply yesterday, and will be installing it tonight. It's the final piece to add for my fully modded popper.
    What I need to know now is what type of roast profile I should be aiming for. Also some ideas on mounting the thermometer lead?

    At the moment it's attached through a wooden ruler and dangling into the moving beans

  36. #36
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    Quote Originally Posted by cloudwarrior View Post
    Grabbed a pot for the DC fan supply yesterday, and will be installing it tonight. It's the final piece to add for my fully modded popper.
    What I need to know now is what type of roast profile I should be aiming for. Also some ideas on mounting the thermometer lead?

    At the moment it's attached through a wooden ruler and dangling into the moving beans
    G'day mate...

    WRT profiles, you're going to find that with your setup, they probably aren't going to be directly transposable. That being said, with most popper roasters, it would be a safe ballpark to aim for a steady profile up to 1st-Crack happening at around 8 minutes or so, slow the ramp down then such that the first couple of snaps of 2nd-Crack happen around the 12 minute mark then stop and immediately cool.

    From there and keeping good records, you should be able to dial-in the profiles so they are much more to your liking, in the cup.

    For the t/couple cable and bead - I just used an appropriately bent up coat-hanger and then secured the cable to the vertical section using short pieces of copper strands from a piece of waste electrical cable. The t/c bead was allowed to extend just proud of the end of the coat-hanger wire so that it wasn't influenced by this. Worked well and survived the years Ok.

    Mal.

  37. #37
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    Agree with Mal re profiles - a good place to start.

    My current go-to profile is up to 120C in just over 1 min (usual caviet re temps - all approx and vary a few degrees on each setup), then steady ramp to 150C at about 4 mins or until drying is over, then aim for start of first crack (200C) at around 8 mins, gentle ramp to start of second crack at 12 mins, although I usually stop just before second. As Mal says, after a bit of roasting you'll get to know your preferences.

    I have found that keeping the airflow as low as possible (while maintaining enough agitation for even roasting) produces nicer results for me. So I keep reducing the fan all through the roast as the beans get lighter.

    My temp probe is 50mm long (k-type TC) and mounted on the bottom of the chamber on the central axis pointing up. It pokes out the top of the bean mass at the start, but has usually disappeared once drying is finished and the beans start to expand. I did a few experiments when I first made this set-up and found it gives a pretty good measure of the bean temp throughout the roast.

  38. #38
    Senior Member deegee's Avatar
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    Quote Originally Posted by cloudwarrior View Post
    Grabbed a pot for the DC fan supply yesterday, and will be installing it tonight. It's the final piece to add for my fully modded popper.
    What I need to know now is what type of roast profile I should be aiming for. Also some ideas on mounting the thermometer lead? At the moment it's attached through a wooden ruler and dangling into the moving beans
    Hello again CW
    When you first try the pot, keep checking that it is not getting too hot. I burned one out recently. At first I thought it must have been faulty, but then I realized that the latest power supply I was using had more grunt than the ones I had used before. Getting warm is OK, but if it starts to get hot, you will need to lower the supply voltage by a few volts, or put a 2 - 3 ohm fixed resistor in series with the pot. I used three 6.8 ohm 10 watt resistors in parallel to get a combined resistance of about 2.3 ohms and with three of them sharing the load, they get warm, but not hot and now the new pot does the same.

    The best kind of thermometer lead is a probe type and you should try to get one for the future. They are cheap and allow you to mount through the case of the popper from whatever direction or angle you want. ( Pics 1 and 2 )

    I also agree with Mal and Pete re the profiles. Those are good times to aim for. Later on you can try going a bit longer.

    Pic 3 is an actual profile, and fairly typical of a medium-long roast for me. But sometimes I ramp it up a bit faster, or stretch it out a minute or two longer.
    Cheers, deegee.
    Probe 2.JPGBreville. (3).jpg Sulawesi Stopped Just before 2C.png

  39. #39
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    cheers guys,
    ran into a small problem last night with the laptops supply

    You need to be aware that most laptop chargers have an overload sensor, and if connected straight to a popper fan with no other resistance in series with it, the charger may power off to protect itself. It seems to be a borderline situation, and will depend on the charger, and the resistance of the fan in your popper.
    even adding some extra resistance wouldn't get it up and running, adding up having to use another laptop supply with a lower overall voltage unfortunately

  40. #40
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    I need to replace the fan motor.Does anyone have an idea what the ideal specs. for a replacement motor might be?
    I would appreciate your input.

  41. #41
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    Probably easier to buy a new popper. It's not easy to remove the fan from the motor without damaging it.

    I have run 2 popper motors in parallel from a 24V HP (if memory serves) laptop supply, no worries. Takes a second to get going though.

    I vaguely remember the motors being 19V...

  42. #42
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    Thankyou for your reply.
    I had to replace the fan some time ago and that proved to be very effective.
    Instead of buying a new popper,I would prefer to just replace parts.
    However, if I can find a replacement popper for $5.00 again .......

  43. #43
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    Check your local op shops, I've seen them in most salvos stores etc

  44. #44
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    Hey deegee, this is exactly what I was looking for. I came across those very same 'el cheapo' Chinese SCRs on eBay for like $2.49. I was very skeptical but I see you've put one into service with what looks like the exact same machine I have except that mine is 110V. I imagine these probably work well with 110V. It's always nice to have some verification before trying such a mod and yours is the only such mod I have found on the net. One other forum post paid lip-service to the idea but not one single detail. Thanks.

  45. #45
    Senior Member deegee's Avatar
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    It's time for another update of my O.P. I have been intending to do this for a while now, and Paco's post has prompted me to do it.

    I've been roasting for a while now with a new modified popper that I'm calling Mark 3. It has split heater & fan circuits, a variable SCR for heater control and a pot to vary fan speed, same as the first two. No major changes there, but I learned a few more things while building & testing it.

    The output voltage of the SCR is controlled by a rheostsat that rotates through about 300 degrees of angle. Mk 1 was fitted with a knob graduated from 1 to 10, and those numbers were used as a guide to control temperature. A typical roast would start at 4 or 5 on the dial and then be increased by half a graduation per minute, which got me the roast profile I wanted.

    Mk 2 was set up the same way and given to a friend, who followed a fairly similar routine, which worked OK for him, though we both found that we had to adjust our routines with the seasons, to allow for different ambient temperatures.

    On Mk3, I used the same type SCR, and tried the same routine, but results were so different that I hooked up a multimeter and took some readings. The output voltage profile of the new SCR is quite different from the first one, so my previous routine no longer worked with the new rig. It gave a much different roast profile.

    So both Mk1 and Mk3 have been fitted with digital voltmeters. I can now increase the heat more accurately with either of them, and I can get the exact time/ temperature profiles I want.

    I also learned the hard way that not all laptop chargers are equal. The unit I used on the new rig has more grunt than the old HP power pack used on Mk1. Fan speed was great, but it burned out the control pot. Had to put a 2 ohm fixed resistor in series with the pot to keep it from overheating. Mounting the pot in a small box with no ventilation didn't help either. They need airflow to avoid over-heating.

    The voltage rating and the current drawn by the fan probably varies with the make/model of popper too. So, a 5 Ohm- 15 Watt pot may be OK for some popper / power supply combinations as long as the pot is ventilated, but others will need the extra resistance.

    I also tried using a PWM to control the fan speed and it worked. No overheating problems with one of these. BUT - the useable range of adjustment was less than a quarter turn of the knob. Even a small tweak of the knob changed the fan speed a lot. So for finer control the pot/rheostat is still the better option here - with ventilation and extra resistance if necessary .

    Lately I have found that I don't vary the fan speed during the roast as much as I used to. Now I set the speed at the start to suit the quantity of beans and the ambient temperature, then control the roast profile with the SCR. So if the pot burns out again I will be giving the PWM another try.

  46. #46
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    Quote Originally Posted by deegee View Post
    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.
    Can you tell me the part number of the SCR chip on this? Can you also sketch out the schematic of the unit? I need to probably modify it for 120V AC and the sellers do not supply enough technical data.

  47. #47
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    Quote Originally Posted by deegee View Post
    So both Mk1 and Mk3 have been fitted with digital voltmeters. I can now increase the heat more accurately with either of them, and I can get the exact time/ temperature profiles I want.
    Why not add either a dial thermometer or a thermocouple and go by the actual temperature? That's what I plan to do.

  48. #48
    Senior Member deegee's Avatar
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    Quote Originally Posted by PacoH View Post
    Why not add either a dial thermometer or a thermocouple and go by the actual temperature? That's what I plan to do.
    Maybe I haven't made it clear in this thread, but all my poppers have thermocouple probes and digital thermometers (see post 32 above)
    and have had them since I first started roasting with poppers.

    The SCR's I use have a part number x4.cn on the PCB, but I don't think you will find them on ebay from that. I cant see any number on the chip.

    If you search within ebay for - SCR motor speed control - you will get a lot of hits. Most of them are for 220V but a few are rated 110-220V. They are a 2000 watt unit with four terminals. Two are marked power in and two are power out. A search for - AC110-220V 2000W SCR Voltage Regulator Dimmer Motor Speed Temperature Controller - will find them.

    The ones I use are rated as 220V 3800 watt and look like the ones in posts #3 & #21. They only have two terminals and the unit is simply inserted in the live wire. in series with the heater coils, but I don't know if they would work on 110V.

    Sorry, but I don't have a schematic for either of these units.
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  49. #49
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    Quote Originally Posted by deegee View Post
    Maybe I haven't made it clear in this thread, but all my poppers have thermocouple probes and digital thermometers (see post 32 above)
    and have had them since I first started roasting with poppers.
    It's hard to see anything in those tiny thumbnails and clicking on them, I don't see any of what you mention attached to a popper other than one image that shows some kind of narrow probe inserted into the wall of one. It doesn't seem to have a display attached to it. But then why do you need to monitor voltage? You said it changes from unit to unit and from popper to popper and is only a relative quantity. Temperature is a more 'absolute' quantity. It takes everything into consideration. Fan flow, heater current, dimensions of the popper tube, bean density, etc. Temperature's what's important to monitor when you do a profile.

    If you search within ebay for - SCR motor speed control - you will get a lot of hits. Most of them are for 220V but a few are rated 110-220V. They are a 2000 watt unit with four terminals. Two are marked power in and two are power out. A search for - AC110-220V 2000W SCR Voltage Regulator Dimmer Motor Speed Temperature Controller - will find them.

    The ones I use are rated as 220V 3800 watt and look like the ones in posts #3 & #21. They only have two terminals and the unit is simply inserted in the live wire. in series with the heater coils, but I don't know if they would work on 110V.
    Yeah, I know. But since there is zero technical specs available, they are all black boxes to me. If I had the chip's identity I could find out all I need to know about how they would need to be configured. I asked several sellers if they had specs and they said no. The one that does mention 110V, 'AC 110v 220V 2000W SCR Voltage Regulator Dimming Speed control Thermostat motor', then goes and lists the Input Voltage: AC 220V. I asked the guy about this and he swears you can input 110V without modifying the circuit. If that's the case then any of the 220V 3800W units would probably work too. And they may very well work as is, but I'm an engineer so it is very foreign to me to accept a component without having the exact specs in front of me. That's why I ask. And BTW all these units have 2 inputs and 2 outputs.

    Sorry, but I don't have a schematic for either of these units.
    I was hoping you'd draw up a sketch with values. There aren't many components on that board. That way I could reverse engineer the specs of the SCR. Otherwise I have to go on blind faith. Not something any engineer wants to do ever.

  50. #50
    Mal Dimal's Avatar
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    Quote Originally Posted by deegee View Post
    I also tried using a PWM to control the fan speed and it worked. No overheating problems with one of these. BUT - the useable range of adjustment was less than a quarter turn of the knob. Even a small tweak of the knob changed the fan speed a lot.
    G'day deegee...

    Probably only requires a change to the voltage scaling into the PWM control circuit. If you could send me a copy of the circuit being used, or a link to it, I might be able to make a couple of suggestions; should you wish to continue pursuing the option of PWM Control of the fan speed. It's an ideal method to use for this purpose, probably down to about 20% of the fan's nominal full speed...

    Mal.

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