Coffee Bean Roaster Help

Discussion in 'General Electronics Chat' started by james211, Jan 14, 2014.

  1. james211

    Thread Starter Member

    May 29, 2012
    210
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    I know this is random, but I need a bit of help.

    So I have this schematic to modify my roaster (actually a popcorn popper) but I would like to try and do it a bit different. Mostly for cosmetic reasons. I've attached two schematics, one is the schematic of the actual machine, the other is the schematic from a guy who created a simple mod to make the fan speed variable and the heat element turn on and off. Both use basic switches / dimmers from home depot.

    What I would like to do is create this using two dimmers (rheostat or potentiometer) one might find at mouser or digikey to control the fan speed and the intensity of the element. I'd settle for an on and off switch for the element if that's the way it needs to be. Mostly the reason for this project is because project boxes look better than four gang electrical boxs do. With that in mind, how could I go about this? Any help would be appreciated!! This site has never let me down.

    My next task will be to control components via Arduino!!

    So here is the site for the mod:
    http://popperyii.blogspot.com/2011/01/completing-hiros-journey-poppery-ii-mod.html

    Two schematics attached
     
    Last edited: Jan 14, 2014
  2. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,031
    As I understand this, the dimmer is used only to control the speed of the fan, driven by a DC motor with the rectifier built in: "MODEL HR 355OU 20.5 VOC 1.78 A MAX".

    You want a smaller, cleaner approach to controlling the fan speed, with an eye towards control by Arduino in the future. The built-in method of controlling the fan is by dropping the AC supply voltage with a heater coil. Your mod will replace that.

    Does this all sound right?

    I predict the motor control experts around here can give some good ideas.
     
  3. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    You hit it on the head!!
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
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    Why not use the dimmers on the secondary sides? technically much better idea.
    Max.
     
  5. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    I'll be honest...I don't know what you mean Max...
     
  6. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    a dimmer is much simpler than an arduino, no programming or interfacing to scr's or triacs. just a knob and a triac circuit. the heating element can be ran with a dimmer too, reistive heating elements are just like light bulbs to them.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The dimmers are shown on the primary (input) side of the transformers, what I meant was connect them on the secondary (output) side.
    Max.
     
  8. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Thats was kind of what I was thinking Max. But what I don't know is what kind of a dimmer to buy? I want ones that can be surface mounted, not typical home dimmers that have a decorative plate. Does that make sense? Also, wouldn't I need a different type of dimmer for the fan and element since the element gets straight 110V and the fan is getting 25V?
     
  9. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    Is this an air-popper ? is it primarily plastic ?? looking closer, I thought so...,

    These are engineered to have X amount of air blown through at X temperature to do its assigned task... slowing the motor or juicing up the heat element sounds like a fire hazard from here... my kid smoked ours just by overloading it with popcorn !!

    I read far enough in your link to find this :

    NOTE: The following is for INFORMATIONAL PURPOSES ONLY, it is not a recommended mod to your popper as it defeats both thermal safety mechanisms.
    This popcorn popper is designed to operate at approximately 300 degrees F to pop popcorn.
    Coffee is roasted when the beans' temperature rises to 435-450 degrees F. The roaster may not roast properly with these safety mechanisms in-place.

    Not wanting to be a killjoy, I would strongly recommend against this endeavor !
     
  10. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    I saw your post Packrat, many people have done these Mods without issues. Right now without any modifications (I have not displaced the safety mechanism) the unit gets to 450 degrees, I don't need it any hotter than that. The purpose of having the fan and heater on separate controls is simply to make it cooler or to have no heat at all, only fan.
     
  11. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    OK... as long as you don't remove the safety, and you are comfortable with the setup, the only remaining redflag I would insist on, is please don't run the thing unattended...
     
  12. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Awww hell now! The beans only take about three minutes to roast, any longer and I'd ruin my beans! ;)

    I do appreciate you shouting out though.
     
  13. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    Just wanted ya to know, we on AAC got your back if necessary...:D
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    In all probability the timing will be OK on the lower voltage.
    It would be cheap and trivial to try, if you want to custom mount them, just remove the plate and drill a 3/8" hole for the shaft and mount to your panel or?
    The up side is they will be at lower (safer) potential.
    Max.
     
  15. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Does this mean I could buy two identical dimmers, rated for higher voltage, and they will work fine for both the fan and the element?

    So one dimmer would be behind the transformer, and the other would be inline with the 110V line, correct?

    Also, I was looking on mouser and I couldn't seem to find anything under dimmers. Am I looking in the wrong place?
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If it works as I mentioned, do not place any on the primary (transformer input side).
    Only the secondary.
    H.D. have all kinds, there are also heavier duty style for Universal AC motors (power tools).
    Max.
     
  17. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Max,

    My apologies for asking stupid questions, but doesn't the element need the full 110volts?
     
  18. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes if you want to control the element, I was referring to your schematic and dimmers controlling the fans, the schematic did not show any heater control that I could see?.
    Max.
     
  19. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Correct, the schematic did not show that, I thought I had mentioned that earlier in the post. No worries there. What kind of a dimmer would I need if I wanted to control the element as well?
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
    2,369
    What is the wattage of the element you want to control?
    Max.
     
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