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Thread: Alternative popper mod suggestions

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    Alternative popper mod suggestions

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi everyone.
    Im new to roasting. Did a few roasts on the weekend in an unmodified cornelius popper (coffeenelius?). First crack was happening at 2min and second at 4-5min so Im looking at ways to slow it down a bit.

    Im looking at a couple of ideas.
    One is to speed up the fan because its only running at 16V but its built for 24. I think i can increase the voltage across it by increasing the resistance that controls this (thats the resistance across the smaller heating element). So Id wanna add in a variable resistor (potentiometer/rheostat) between the circuit board and the small heating element. Higher resistance here = higher voltage in to the fan.

    I Dont want to burn out the fan so Ill need a constant resistor in there too, in parrellel to the variable one. This puts an upper limit on the extra voltage, whatever I do with the the knob i cant take the fan past 24V.

    Ive done a bit of maths and I need the constant resistor to be 1.5 ohms and able to take 34 watts of power. The variable resistor needs to be able to take 17 watts and needs to give me control between zero and maybe 10 ohms but it doesnt matter if it goes a bit higher.

    Could this work?
    Does anybody have any suggestions where to buy the bits? I could get a gang of 4 resisters (10Watts) for $2 each from jaycar but not the variable resistor. I like to scrounge electrical parts so best of all would be a tip on what to take apart (knobs from electric stoves maybe?)

    Thanks,
    Conan

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    Re: Alternative popper mod suggestions

    Im no electronics expert but from what Ive read the fan and heater circuits are linked.
    Your idea may do something to the heater that you dont want it to.

    I found the easiest way to slow down a roast by introducing more air was to allow as much air as possible in (look underneath) and to let out heat trapped in the body by adding large holes or removing the top half altogether.

    Im not sure if you can remove the top of a cornelius like you can with a Crazy Popper.

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    Re: Alternative popper mod suggestions

    Welcome home to roast.... [smiley=thumbsup.gif]

    Potentiometer control of the fan speed is not the way to go, far better to split from the voltage divider that are the heating element sections and use a suitably rated transformer driven by an electronic ceiling fan controller.

    Lots of info to be found on this site and others by doing a Search... ;)

    Personally though, Id give TGs ideas a go first since this will get the basics taken care of without the need for electrical circuit intervention, and may well be all that you need to do.... 8-)

    Mal.

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    Re: Alternative popper mod suggestions

    adding resistance will lower the voltage across the motor you want to lower the heater resistance so more voltage is across the motor, it basically a voltage divider with the heater running on 220 and the motor on the remainder about 20V,

    if you lower the the heater resistance *by cutting a bit off or shorting part of heater together, *there will be more voltage across the motor , but lowering the heater resistance may also cause the heater to run hotter , its a fine balancing act, both heater and motor have been chosen to work well together as they are, will it cool more or heat more if you alter heating resistance / motor voltage?

    here is a calculator you can try different values to see what you need to do.

    http://www.raltron.com/cust/tools/voltage_divider.asp


    for E *x I = W , *240V x 5A = 1200W Heater
    E = I x R , 240V = 5A x 48R , total resistance.

    E=I x R , 20V = 5A x 4R *Motor

    E=I x R, 220V = 5A x 44R Heater

    just some approx values for example.

    You also have some voltage drop across the full wave diodes to generate the DC for motor , but it can probably be ignored.

    best to use electronic fan and/or heater controller.










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    Re: Alternative popper mod suggestions

    what about separating the two: Fan <-> heat and using a couple of phase angle controllers or triac based power controllers ?

    then you can turn the AC up and down to whatever you need


    how about a phase angle controller on the heat
    and a 600w dimmer (light switch dimmer) on the fan ?

    but if your ordering one P-Angle just get two....

    not really sure if it will work on the fan :D

    seems overkill on a popper but...

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    Re: Alternative popper mod suggestions

    Adding my second crack.
    On my 15year old Black & decker Popper, the resistance wire that drops the voltage for the fan is not used for heating the chamber. As it is not in the air flow path, it has no direct heating effects.
    As you can see in the picture below, I have taken out all the heat safety devices and bridged the contacts.

    The two outer pins are the heaing element, and the inner (not connected) pin is one end of the fan resistance wire.

    I run my heater element on full power, and only vary my fan speed.
    Fan is controlled by a Jaycar 12+12v 5A transformer which is varied by a 400W light dimmer.

    My roasts can be stretched to whatever time I want.

    Have safe fun. :D
    Dan.




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    Mal Dimal's Avatar
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    Re: Alternative popper mod suggestions

    Hi Dan.... :)

    This may be the design of the B&D but with others I have stripped down, they split the heating element and use it as a voltage divider, with one section feeding the fan motor - Anything from 15-28V. Providing advice is OK but if youre going to delve into the nitty gritty, you need to make sure youre dealing with identically designed systems or disaster may follow for the recipient of that advice... :(

    Mal.

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    Re: Alternative popper mod suggestions

    if the heating element is tapped you could rivet the motor contact higher up to increase the voltage of the tap off point.

    best to carefully examine what type of popper circuit you have and then work out what you can do.

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    Re: Alternative popper mod suggestions

    this guy suggested opening the side vent holes *for better airflow.
    have not seen this mentioned before. simple and easy to do, and with better venting of outer case should increase airflow a lot.

    http://sites.google.com/site/garybt3/thepopcornpumper

    internal side vent holes in metal wall of popper.

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 54797D717C100 link=1292323422/6#6 date=1292375336
    Hi Dan.... :)

    This may be the design of the B&D but with others I have stripped down, they split the heating element and use it as a voltage divider, with one section feeding the fan motor
    In all the poppers Ive stripped down, of various makes, they have all been wired the same. They have all had 2 elements, the outer larger diameter wound wire thats in the airflow (as you can see in the above photo), and another smaller diameter wound wire inside the outer one (cant be seen in the photo). The 2 elements are connected together, end to end.

    They all had 3 wires going to the heater (as in the above photo) - lets call them wire A, B & C. Wire A connects to one end of the main heater element. Wire B connects to the other end of the main element and also to one end of the resistor wire for the fan, ie. both inner and outer elements connect at this point. Wire C connects to the other end of the resistor wire for the fan (inner element). To run the main outer heater element only, all you have to do is connect A to one side of 240V and B to the other side of 240V. Current then only flows between A and B, ie. both ends of the outer main heater element. As we leave C unconnected, no current flows between B and C, ie. the resistor wire for the fan does nothing.

  11. #11
    Mal Dimal's Avatar
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    Re: Alternative popper mod suggestions

    Yes mate....

    What you say is correct but the elements are configured as a voltage divider, not as an element with a separate dropping resistor for the fan motor supply; that is the only point I was trying to make. My background is Electrical Engineering by the way..... ;)

    Mal.
    P.S.
    Just dug out a thumbnail sketch made of an early Tiffany Popper. Explains what Im talking about... ;)


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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 4F607B6C79667E6C7B090 link=1292323422/8#8 date=1292411816
    this guy suggested opening the side vent holesfor better airflow.
    have not seen this mentioned before.
    What about my post above?

    Quote Originally Posted by 5D617C676D6C7B6E666D090 link=1292323422/1#1 date=1292332126
    I found the easiest way to slow down a roast by introducing more air was to allow as much air as possible in (look underneath) and to let out heat trapped in the body by adding large holes or removing the top half altogether.
    (not to mention dozens of posts in dozens of previous threads)


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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 14393D313C500 link=1292323422/10#10 date=1292418175
    My background is Electrical Engineering by the way.....
    Yes, I know..... *::)

    I agree with you. Ok, maybe I was wrong to refer to the inner element as the resistor for the fan. Call that element whatever you like though, the only point Im trying to make is that you dont need to use that element. The poppers do run fine on just the outer element. I know because Ive done it, on a few different poppers. Thats all Im saying - if youre powering the fan separately, for heating you only need to use wires A & B for the outer wire coil, you dont need to use C.

    regards,
    Bill

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 1D30343835590 link=1292323422/10#10 date=1292418175
    Just dug out a thumbnail sketch made of an early Tiffany Popper. Explains what Im talking about...
    Yep, that looks like the ones Ive had. So all Im saying is if you are powering the fan separately, you only need connect what you have labelled "main element", you can bypass "aux. elem."

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    Re: Alternative popper mod suggestions

    Yes mate, I knew what you meant but for non-electrical people it is very confusing....

    Mal.

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 0924202C214D0 link=1292323422/14#14 date=1292421574
    Yes mate, I knew what you meant but for non-electrical people it is very confusing....

    Mal.
    Ok. Sorry, I misinterpreted what you said earlier. I thought you were arguing that there was only 1 element, instead of 2 - that your poppers didnt have the extra middle element. Obviously there are 2 elements.

    But I now see that what you were really arguing about was how the fan is wired up in standard form. I dont disagree with you. Thats not what I was talking about, as it doesnt concern me. Since were disconnecting the fan and powering it separately, how the fan was wired as standard isnt really relevant to what were doing here.

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    Re: Alternative popper mod suggestions

    Hey thanks everyone for your advice and ideas. Im sitting here with one of my first coffees in the cup. ::)

    Quote Originally Posted by 724E5348424354414942260 link=1292323422/1#1 date=1292332126
    Im no electronics expert but from what Ive read the fan and heater circuits are linked.
    Your idea may do something to the heater that you dont want it to.
    Youre right Thundergod, there will be a side effect, with the fan jumped up to 24V it will reduce the heating
    power by between 3% and 6% (depending on how much of the heat generated in the new resistors ends up in the airflow). But that will help a little with operation slowdown.

    Quote Originally Posted by 604F54435649514354260 link=1292323422/3#3 date=1292336544
    adding resistance will lower the voltage across the motor you want to lower the heater resistance so more voltage is across the motor, it basically a voltage divider with the heater running on 220 and the motor on the remainder about 20V,
    Increasing the smaller resistor definitely increases the voltage across the fan. Using your numbers and the voltage calculator you suggested (thanks, Ill use that to check the results of my scribbles) increasing the small resistor from 4R to 5R increases the voltage from 20V to 24.5V.

    Quote Originally Posted by 624F4B474A260 link=1292323422/2#2 date=1292332961
    Potentiometer control of the fan speed is not the way to go, far better to split from the voltage divider that are the heating element sections and use a suitably rated transformer driven by an electronic ceiling fan controller.
    Thanks Mal, youre right about my potentiometer plan not being the way to go, it would have given me a weird irregular response when I turned the knob.
    I guess its just an aesthetic thing (safety too maybe), but Id like to do a modification that fits within the unit rather than having wires running around the place. Id also prefer not to hack into the case, Id rather do a proper job modifying the electricals and sealing it back up than opening up the bit with live lethal wires and leaving it open. That said, I might totally replace the original case with something nice and enclosed but with plenty of vents.
    So youve got me thinking of a new plan. Why not put in a constant 1R5, 40W resistor in line with the small resistor element to increase fan voltage (instead of the transformer) and then put a ceiling fan controller in the resulting 25V AC part of the circuit? Id have this new knob sticking out the side of the original case so it looks like it was built that way.
    Only problems are Ive lost a few percent of heating power and I cant switch off the element to use the popper to cool the beans. How important are those two things?
    Thanks again,
    Conan

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 664D4848240 link=1292323422/9#9 date=1292417812
    To run the main outer heater element only, all you have to do is connect A to one side of 240V and B to the other side of 240V. Current then only flows between A and B, ie. both ends of the outer main heater element. As we leave C unconnected, no current flows between B and C, ie. the resistor wire for the fan does nothing.
    Its amazing how similar all these poppers are (except for Dans old one but even it is only slightly different).
    Have many people done this particular modification that Bills talking about, leaving the smaller element out of the circuit? The thing is it reduces the total resistance by about 10% so it must increase the current (and therefore power) by about 10%.
    Do these things burn out if you do that?

    Conan

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 2E222B26262F430 link=1292323422/4#4 date=1292364023
    what about separating the two: Fan <-> heat and using a couple of phase angle controllers or triac based power controllers ?
    Thanks Maheel.
    Might be the way to go. Ill have to do a bit of homework on that. Are those things the same as the ceiling fan controllers people are talking about? How many $$?

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    Re: Alternative popper mod suggestions


    Hes talking about internal vent holes in the metal wall, I read many about more vent holes in the outer case, side and bottom. the photos in the link explain better. may be i missed enlarging the internal vent holes in posts here.




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    Re: Alternative popper mod suggestions

    This has turned into quite a technical discussion.
    My disclaimer - Do not attempt to do anything I have mentioned unless you are competent to do so safely.
    On with the show.
    I have attached my dodgy schematic of my popper, missing a few capacitors that are not important for this topic. For the record, the fan voltage control is totally different to mals and the majority of others by the sounds of things.

    My popper is wired exactly as bill writes in his first post.

    Please disregard my posts if your popper is not like mine.
    I am an electronics hobbyist with a bit of electrical training and a little common sense. (stress little).

    Dan.


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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 76594255405F475542300 link=1292323422/19#19 date=1292449504
    Hes talking about internal vent holes in the metal wall, I read many about more vent holes in the outer case, side and bottom. the photos in the link explain better. may be i missed enlarging the internal vent holes in posts here.
    Sorry, I misunderstood.

    However, I fail to see how that addresses the OPs problem.
    His problem is that the popper is currently running TOO HOT.

    The article clearly states that opening up the roast chamber holes will allow more HOT air in.


  23. #23
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 524D4C5A5C5E3F0 link=1292323422/20#20 date=1292451443
    I have attached my dodgy schematic of my popper
    Have never come across that design before Dan. Just shows how careful youve got to be when proffering electrical advice... Cant be too careful no matter what modifications are planned ;)

    Mal.

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    Re: Alternative popper mod suggestions

    I dont know , I just high lighting what has been done so other here can try and give feedback.

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 202C2D222D6D2C21312A262D430 link=1292323422/18#18 date=1292445862
    Quote Originally Posted by 2E222B26262F430 link=1292323422/4#4 date=1292364023
    what about separating the two: Fan <-> heat and using a couple of phase angle controllers or triac based power controllers ?
    Thanks Maheel.
    Might be the way to go. Ill have to do a bit of homework on that. Are those things the same as the ceiling fan controllers people are talking about? How many $$?
    An ordinary ceiling fan controller works (in conjunction with a transformer) for the fan control. For heat control youd need something like a high power light dimmer - I used a 2000W one, but you shouldnt need one rated quite that high. The poppers are usually rated around 1100-1200W, so something rated to that power should do.

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 333F3E313E7E3F322239353E500 link=1292323422/18#18 date=1292445862
    Thanks Maheel.
    Might be the way to go. Ill have to do a bit of homework on that. Are those things the same as the ceiling fan controllers people are talking about? How many $$?
    you "can" build your own triac based ones for about $10, they are better than fan controllers as they have a nearly infinite range of control (depending on resister selection etc) You have to do your own solder work (pcb boards etc)

    phase angle cost a bit more depending on if you get a "kit" or ready made. (about $50 to $100) *but you also dont have to do the solder work and again gives you "infinite" range of power control. i actually thought that they might make an interesting mod to a KKTO heating system so there would be no cycling


    i have never seen a 2000w light dimmer (actually PMed Bill about it), and the normal ones only run about 600w i thought. Triac and PA can handle any amp / watts you want with the right part specs

    if you look at RS-online, and search for PSR-25 and look at the
    the range of alternatives.

    they are all 240v so get a sparky / electronics mate to build and check for safety etc *

    i have a PSR-25, i also built a working prototype home made triac one but my solder is crap so it looked super dodgy... rather than my normal dodgy
    i can supply a diagram if anyone is interested *on the triac design

    Leeham

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    Re: Alternative popper mod suggestions

    Looks good Maheel, Id like to see a diagram if you feel like putting one up. I might do that when I do the final version of my popper.
    What do I need to take apart to find triacs that can handle power?

    For now Im gonna crack that power control nut with a beautiful old sledgehammer in the form of an big old variac my grandfather gave me. I just have to check the current rating on it when I get it out of storage. (btw I saw a 5A variac on a popular auction site for pickup in footscray if anyone wants big-is-beautiful power control).

    Another cheap option: I stumbled accross infinite switches while researching phase angle control. They control the current with a bimetalic strip inside the switch that gets hot when the current flows. They are in electric stoves like you see in skips every other day, prob is you need to get exactly the right current rating because you cant change them easily by just adding resistors.

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 414D444949402C0 link=1292323422/25#25 date=1292539364
    i have never seen a 2000w light dimmer (actually PMed Bill about it), and the normal ones only run about 600w i thought.
    I wasnt able to find such a high power one either, within Australia, but was able to source one online from an electronics supplier in the UK. Can get ones up to 4000W from the same supplier.

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    Re: Alternative popper mod suggestions

    Ok this is the diagram (simple picture) traic based power controller

    the 1st one i built did not have the 1M resistor and was not 0 - 100% linear. it did range from around 140v to 240v control i was then advised to add the 1M and it should help. I am not sure if i built and tested it with the 1M res

    The BTA26-600B TRIAC could then handle 26 amps, way more than what i wanted at about 2500w. so you could choose a lower amp triac.



    the BTA26-600B TRIAC (or any triac) would have to be mounted to a heat sink or it would quickly blow blue smoke... i used a PC heatsink and fan. You would of course also need to earth it correctly and safely. no earth is shown !! but needed !!

    Isolated triacs are very important as some are not !!! and make the heatsink live !!!!

    there is a 50page thread about power controllers on "homedistiller.org" where more information can be seen on this diagram at about page 30..... other ideas are in the thread

    other smarter than me people here might have some input *:)

    disclaimer, this post is for information only, anyone attempting to build this should consider the risks. no responsibility taken by me or anyone

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    Re: Alternative popper mod suggestions

    Just a note re Bills post above (#27) about dimmers. Earlier this year I needed a 1000W dimmer for heatimg control on my Gene. The only Aus one I could find was $160. So I imported a Varilight dimmer from the UK. This played up at first, but an email exchange with the engineers at Varilight sorted out how to fix it. Basically the heatsinking needed attention. What I did was disassemble it, apply plenty of heatsink compound at appropriate places, especially the contact area between the triac and the supplied heatsinking; then added additional heatsinking, comprising aluminium sheet bent into an S-shape and with finned PC heatsink blocks attached. I left room in my enclosure for a fan, but that hasnt been needed, it has worked fine ever since. With the additional heatsink properly installed, the dimmer easily handles the 1200W of the Gene. Nonetheless, had I known when I bought it that they had a 1500W version for not much more, I may well have bought it (in that design, the triac is separated out from the other components). Anyway, clearly heatsink design is a key aspect of these higher power dimmers (that might be why the Aus designed one is a lot more expensive).

  31. #31
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    Re: Alternative popper mod suggestions

    Large capacity Dimmers (for resistive loads) are available here in Oz, mostly for commercial lighting applications and can be obtained from commercial/industrial electrical wholesalers who supply licensed electrical contractors. One example I can think of is Theatre Lighting.... Building your own would still be the most economical way to do it though and not very difficult for anyone who possesses basic electrical soldering skills....

    Mal.

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 6E677C64636768060 link=1292323422/29#29 date=1292666100
    Earlier this year I needed a 1000W dimmer for heatimg control on my Gene. The only Aus one I could find was $160. So I imported a Varilight dimmer from the UK.
    Yep, they seem pretty expensive in Aus. My 2000W dimmer was only 22 from the UK. Works well, and never had any problems with it.

    http://www.quasarelectronics.com/ci0013-230vac-light-dimmer-module-range-250-4000w.htm

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    Re: Alternative popper mod suggestions

    Interesting link, Bill, thanks. They seem better constructed than the one I got, at least with regard to integration of the heat sink.

    Mal, I tried to find info from commercial sources but no luck. And with the info in this and a couple of other threads around the place Id be more willing next time to have a look at making one up.

  34. #34
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 6168736B6C6867090 link=1292323422/32#32 date=1292846843
    Mal, I tried to find info from commercial sources but no luck. And with the info in this and a couple of other threads around the place Id be more willing next time to have a look at making one up.
    Good idea "hazbean"... 8-)

    Its a relatively simple thing to do but requires special attention paid to the 240V AC side of things to maintain safety standards. Lots of info about this can be found too or ask a sparky to pass his/her critical eye over it before powering up. "Silicon Chip" is an excellent resource for this sort of info....

    Cheers mate,
    Mal.

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    Re: Alternative popper mod suggestions

    Took my popper apart this afternoon. It wasnt easy getting the mains cable out due to the tight cable strain relief, but with a fine screwdriver and suitable application of force, all was revealed.

    I tested one of the triac power controllers I have on the popper as it stands and it works fine for power control. Nice thing is that it will just fit in the case below the main chamber, directly in the inlet airflow and has a heatsink already on the circuit board. I doubt it will be of much use to drop fan speed and heat at the same time, so I need to maintain fan speed and adjust heat output, or separately control fan speed.

    I havent unscrewed the fan from the body yet, but the wiring looks identical to that posted here:
    http://coffeesnobs.com.au/YaBB.pl?action=downloadfile;file=TiffanyPopperSche matic.pdf

    Colours even match. So, it doesnt look like I can just splice in power control for the heater as the two elements are almost certainly in series.
    Time to go hunting for a spare transformer, or perhaps find a suitably rated switchmode power supply for the fan and leave it running full tilt all the time.


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    Re: Alternative popper mod suggestions

    A couple of photos of my lightly modded popper. Note that the power adjustment even has correct power level markings.

    Still to test it out, just need to wait for the rain to stop.




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    Re: Alternative popper mod suggestions

    After looking at a few options like the triac for power control I ended up going with a PID temperature control unit running a seperate 25A solid state relay. Turned out to be a similar price to the triac dimmers mentioned above. I went fishing in the bay of e and got the lot for $42 including postage from hong kong. Cant wait till it arrives.
    Make sure you get a PID unit that gives a DC output for controling an SSR instead of one with a mechanical relay built in that will wear out and break with the fast switching youll need.

    Ive discarded the popper chasis and Ive put the guts of it in the case from an old microwave with the bean chamber poking out through a hole in the top. This microwave popcorn chimera bulky but as well as plenty of room for mods it gives me a work surface on top and a bean storage cupboard in the bit where the food used to cook. I tried using the microwave power control to moderate the heat but it would turn the power off for 8 seconds every 30 seconds on medium high so that was the end of that. :-/

    Anyway, the thing I need help with is where to put the thermocouple. Do I put it in the beans and continually adjust the temperature manually, giving me steps instead of a ramp. (or maybe there is a ramp function in the pid unit?)
    The other option is to put the thermocouple in the hot air stream just under the bean chamber. This would give me good repeatable control of the heat regardless of ambient temperature and Id probably only have to adjust the temperature setting a couple of times in the roast. The disadvantage is Id probably have to buy another thermometer to go in the bean mass.

    Has anybody tried either of these? Ive searched this site and can only find pids used for heat guns and coffee machines, not poppers.
    Oh and before anybody tells me Im wasting my time doing this on a popper, I want the small batch size. ;)

  38. #38
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 333F3E313E7E3F322239353E500 link=1292323422/36#36 date=1294794443
    I ended up going with a PID temperature control unit running a seperate 25A solid state relay. Turned out to be a similar price to the triac dimmers mentioned above. I went fishing in the bay of e and got the lot for $42 including postage from hong kong. Cant wait till it arrives.
    Make sure you get a PID unit *that gives a DC output for controling an SSR instead of one with a mechanical relay built in that will wear out and break with the fast switching youll need.
    At that price, your PID will not have ramp/soak functions. All you will get is a single set point and it may or may not support different thermocouple types, but in practice, most folks here use K-type anyway. I ordered a PID from the USofA fleabay (for my Gaggia classic) as I got it cheaper there than Aus and it still came from Hong Kong anyway. I clearly specified one that handles an SSR, but they still sent me the wrong one with an internal relay - fixed the problem quickly though and I still have the incorrect relay even though I tried to get them to take it back.
    Another issue with the mechanical relay PIDs is that they are often only rated up to 3A (or 720W at 240V).

    Quote Originally Posted by 333F3E313E7E3F322239353E500 link=1292323422/36#36 date=1294794443
    Anyway, the thing I need help with is where to put the thermocouple. Do I put it in the beans and continually adjust the temperature manually, giving me steps instead of a ramp. (or maybe there is a ramp function in the pid unit?)
    The other option is to put the thermocouple in the hot air stream just under the bean chamber. This would give me good repeatable control of the heat regardless of ambient temperature and Id probably only have to adjust the temperature setting a couple of times in the roast. The disadvantage is Id probably have to buy another thermometer to go in the bean mass.
    Im sure others with more experience will chime in soon enough, but you will not get an accurate bean mass temperature in a fluidised bed, the best you can hope for is something between bean and air temp. This will not matter in practice once you have several previous roasts to refer back to, but makes it hard at first.

    I am just about to use my PID with internal relay and a K-type thermocouple to measure temps in my triac controlled popper. I plan on inserting it so the tip is about 1-2cm above the base of the roasting chamber and as close to the centre as possible, this should get me reasonably close to bean mass temp, but I dont know how it will interfere with the movement of the beans.

    Quote Originally Posted by 333F3E313E7E3F322239353E500 link=1292323422/36#36 date=1294794443
    Has anybody tried either of these? Ive searched this site and can only find pids used for heat guns and coffee machines, not poppers.
    Ive definitely seen something on the net about adding a PID to a popper, cant remember where though. I am pretty sure it was a much more expensive set-up with multi step ramp/soak.
    I really dont know that a simple PID will give decent control as the heater is either full on or full off and the proportional bit comes from the on/off times, but it will be interesting to see how it works out.

    I went the triac route as it was free (apart from a couple of hours and that was play/education).

    Im considering options for airflow management and may go for a hairdryer or computer fan as I happen to have both. Of course I could bring out the big guns and use a 1200w vac motor, but then heating would need to be increased too and that kinda defeats the purpose of a small roaster. Im shooting for a 200g maximum batch size with 3-4 mins between first and second crack. Once I get that Ill be happy.


    Incidentally, how do you empty the popper once it is installed in the microwave?


  39. #39
    Senior Member mtee's Avatar
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    Re: Alternative popper mod suggestions

    As well as making technical mods, you can slow the roast down by using a few simple little techniques.

    I increased the quantity of beans to about 115-120g depending on which popper Im using.

    On start up, this amount of beans wont move on their own, so I tilt and jiggle the popper to get the beans circulating. I used to do it for a minute ot two, just until the beans would move on their own, but found doing it for longer (3-4 minutes) slowed down the first crack significantly. I then place the popper on an angle to keep the beans moving and steadily make it more upright as 1st crack approaches.

    Along with drilling the popper base, this has stretched 1st crack from 3-4 minutes to about 6-7 minutes.

    Id be fiddling with fans and heating elements too, if I knew how, but Ill leave that to technically competent.

  40. #40
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 3D353B33312B2B373B33580 link=1292323422/37#37 date=1294827405
    Incidentally, how do you empty the popper once it is installed in the microwave?
    The bean chamber just slides out the top. When the roaster is complete Ill be able to turn off the heat and leave the fan running to cool the beans in the chamber but for the couple of roasts Ive done Ive used a leather glove to lift out the hot chamber.

    Who me?, I like your power control setup. A big knob like that would give you plenty of room to mark preferred power levels.

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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 554C5D5D380 link=1292323422/38#38 date=1294957962
    Along with drilling the popper base, this has stretched 1st crack from 3-4 minutes to about 6-7 minutes.
    Ive been toying with drilling holes in the base too.
    Im thinking about how to do it to stimulate bottom to top bean curculation as well airflow. I might drill holes all over the centre of the base to increase the the amount of beans rising in the centre (seems to be the natural circulation pattern for the beans when they are dry and light but this might get circulation going earlier). The other option is to drill holes all over one half of the base and get the top to bottom circlation going that way (similar to the effect of tilting the popper, so it would work well together with a tilt).

    Interesting what you seaid about the tilt and jiggle technique delaying first crack. I found vigorous stirring with a stick slowed down the cracking once it had started. I guess this moderates the heat by increasing airflow but as well as that makes sure the beans are all the same temperature so you dont have some of the beans getting to 1crack before the others.

  42. #42
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 3F33323D3272333E2E3539325C0 link=1292323422/39#39 date=1294965950

    Who me?, I like your power control setup. A big knob like that would give you plenty of room to mark preferred power levels.
    Actually, I hadnt thought of that but yes that is a good idea.
    I just thought that since I have one, it would be a shame not to put it to good use.

  43. #43
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    Re: Alternative popper mod suggestions

    Since the weather has improved somewhat here in Melbourne and I finished work early, that gave me the chance to sneak into the garage and play with my big knob (see above for picture).

    I did a small roast of 95g of Gambella Sundried full power to first crack at 3:40 (unusually fast for my popper), then down to 800W for a couple mins, back to 900W until 8min 30, then 1050W until I think I heard a snap of second crack at 9min 30 and pulled the roast - very pale CS6/7 so may have misheard. Unfortunately my spare thermocouple was in use for another task so dont know about temps :(

    I have to say Im pleasantly surprised as I was worried that lower fan speed would mean the beans were in contact with the hot metal more than they should be and it might not provide the control I wanted.
    Definitely warrants further testing with a temp sensor installed to keep a gradual ramp up of bean mass temp 1st to 2nd crack.

  44. #44
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 5E5658505248485458503B0 link=1292323422/37#37 date=1294827405
    I clearly specified one that handles an SSR, but they still sent me the wrong one with an internal relay - fixed the problem quickly though and I still have the incorrect relay even though I tried to get them to take it back.
    Another issue with the mechanical relay PIDs is that they are often only rated up to 3A (or 720W at 240V).
    Sounds like you may already know how to overcome this incorrect supply issue but just in case you end up keeping this controller, there is a simple mod to allow it to drive the SSR. You need to ensure that the Input requirements for the SSR are met and not exceeded of course....

    Remove the cover from the controller and locate the +ve feed to the existing Output Relay Coil. Being very careful and with an appropriate DMM, measure the supply voltage to this relay when it is operated. Knowing this information, you can now scale the output voltage to suit the SSR via the use of a Voltage Divider that can be accommodated within the controller case. If you want to ensure absolute isolation of the Output Voltage, very cheap Opto-Couplers are easily acquired and could be inserted between the Relay +ve and Ground. The Output from the Opto-Coupler can then be used to drive the SSR.

    Most likely though, the Relay supply is already isolated in this way and the need for an Opto-Coupler is unnecessary. Never hurts to have more than one iron in the fire, as they say...

    Cheers mate,
    Mal.

  45. #45
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 674A4E424F230 link=1292323422/43#43 date=1295339065
    Sounds like you may already know how to overcome this incorrect supply issue but just in case you end up keeping this controller, there is a simple mod to allow it to drive the SSR. You need to ensure that the Input requirements for the SSR are met and not exceeded of course....

    Hadnt even thought about that, but yes it is obvious now you mention it. I had considered a much simpler fix - use the internal relay to drive a small DC plug pack that then drives an SSR, not at all elegant, but dead simple and would save opening up a PID that might still be requested back (though it has been months now so it is highly unlikely).

  46. #46
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    Re: Alternative popper mod suggestions

    Well my lightly modded popper died last week :(

    Took it apart today and tested without the triac power control - the popper was still fine, which is a good thing. Closer investigation showed that one of the solder pads on the pot mounting had come away from the PCB track. So now I need to source a new 220K Ohm pot.

    Since everything is apart anyway, it is time to install fan speed control as I recently picked up an old stereo amp which had a 135W multi tap transformer that ought to provide enough power for the fan - any thoughts on what voltage to use? I have a choice of 16.5V, 18V, 28V, 33V or 56V. Im thinking of going 28V and avoid running full blast.

    As a comparison Ill take a sound recording of the fan running normally before the mod so I can tell when it is going beyond that level. I also know it can only successfully agitate up to 100g green beans which should be a handy data point.

    Will update here when mods done.

  47. #47
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    Re: Alternative popper mod suggestions

    Quote Originally Posted by 5C545A52504A4A565A52390 link=1292323422/45#45 date=1305457891
    any thoughts on what voltage to use? I have a choice of 16.5V, 18V, 28V, 33V or 56V.* Im thinking of going 28V and avoid running full blast.
    Yep, Id run 28V. 18V will run the fan much slower than standard. I used 30V in a couple of different ones with no problems (thats 30V AC connected to the rectifier on the fan - the DC voltage that actually gets to the fan is somewhat lower than that).

  48. #48
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    Re: Alternative popper mod suggestions

    I agree...

    Most of the motors Ive looked at over the years have been rated at 24V-- and given the losses youll get through the bridge, it should work out fine. Talk about a Frankenpopper, eh... ;D

    Mal.

  49. #49
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    Re: Alternative popper mod suggestions

    For now it will be 28v with option of going 33v if necessary.

    Thanks to a client cancellation, I got an hour tonight to start on this. Have a suitable box for the transformer and controllers. I currently plan on triac power control for both transformer and heat with fan on all the time and heater switchable. One of the triac controllers is bta16 and will use the metal case as heatsink, the other its btb16 and will be isolated fom case and fingers.
    Hopefully I got that the right way round, but will double check everything in due course.

    Im not sure how much power the triacs actually dissipate and whether I should fan cool the casing, or if small heatsinks are sufficient.

  50. #50
    Mal Dimal's Avatar
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    Re: Alternative popper mod suggestions

    Behmor Coffee Roaster
    Pity you couldnt grab two BTA16 Triacs.... You wouldnt have to worry about the (mica) insulation requirement of the BTB16 then.....

    Should work really well in this application though :)

    http://tinyurl.com/6avfmms

    Mal.



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