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Thread: Coffee Roaster Modifications to Air Popper

  1. #1
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    Exclamation Coffee Roaster Modifications to Air Popper

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi Guys,

    New user with not a lot of experience but what I would consider a reasonable bank of electrical knowledge. So I just need a hand to fill in the gaps.

    Currently I have a Sunbeam popper which is 1150W. It has a 24VDC Fan Motor which from what I can research on it (nothing comes up when you search the model) is rated at 2amps. That is on a circuit board with some sort of rectifier to convert the AC-DC which is fine, however what I want to do is install two seperate controllers to slow down the speed of the roast - currently taking 3.5-4 minutes to roast 100g. Too fast in my opinion and the inners of the beans aren't consistent or roasted hardly at all.

    So my plans are;
    To use a Simmerstat or infinite switch to control the heating element which i've found here https://www.sparkydirect.com.au/p/94...ot-mp101-.html - thoughts on this??

    and to run the 24VDC Motor on a seperate control using a full wave rectifier and a speed controller to suit but what I'm confused about is the DC Sinewave after being converted still resembles the drop off of an AC sine wave so I want to make it more of a consistent Direct current using a filter capacitor... but what size do I need and do you have any recommendations on how to set it up?? this is more of a project for me and something I'm enjoying learning about but having trouble with this..

    So conclusion, How can I set up the DC fan using a full wave rectifier to incorporate a switch into the system to control the speed and if there are any other recommendations for a heating element switch too. I also found this too which I would like some advice on; https://www.amazon.co.uk/6V-90V-Puls.../dp/B00CWSO2IY would I be able to use this after the full wave rectifier and capacitor to control the fan speed??

    See photos below of my components I am currently working with. Please ask if there is any more information you need to help!! Thank you!

    Bottom information of roaster
    https://photos.app.goo.gl/P9b8DcD8DzZRtMnJ3 Bottom of popper (Voltage, wattage info etc)
    https://photos.app.goo.gl/dpBXbOTJ3EQ9hGbl2 Heating element
    https://photos.app.goo.gl/rf2Sr6ncMMBGDIIA3 Fan Motor P1
    https://photos.app.goo.gl/3DgWo8zg0oBQOu453 Fan Motor P2

  2. #2
    Senior Member Jackster's Avatar
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    Yes, i have a opinion. Im not a sparky though.
    Why use a simmerstat when you can have a full digital thermostat for similar price, or less.
    I cant link to ebay. But paste this item number into ebay...you can get similar cheaper without a case..
    172969894344

    For the fan...
    282694405870
    Just disconnect the dc and wire the speed controller in. I chose one with a remote knob, and a couple of heatsinks.

  3. #3
    Senior Member Jackster's Avatar
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    oops, thermostat only goes up to 110...if you change the thermocouple, will that increase its range. Preferably by a fixed offset...

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    Quote Originally Posted by Jackster View Post
    Yes, i have a opinion. Im not a sparky though.
    Why use a simmerstat when you can have a full digital thermostat for similar price, or less.
    I cant link to ebay. But paste this item number into ebay...you can get similar cheaper without a case..
    172969894344

    For the fan...
    282694405870
    Just disconnect the dc and wire the speed controller in. I chose one with a remote knob, and a couple of heatsinks.
    Thank you very much for your reply Jackster. My problem is the dc motor is running off aboard that the heating element also runs into Im just not sure I can disconnect the motor without somehow providing it with another power supply such as the rectifier I mentioned. Could I wire that fan speed controller somehow directly into the board?

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    Senior Member deegee's Avatar
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    Thanks deegee - from your experience, how do I go about wiring them up though? Do I need to remove the board that the dc motor and all the wiring goes to to power them separately? Could you show me some photos of yours?? Inside if that’s okay

  7. #7
    Senior Member deegee's Avatar
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    I have done this with Black & Decker, and Tempo poppers which were easy to work on, but they died or were given away.
    Sorry but I didn't take pics during construction, and my current unit is based on a Breville, which is a real PITA to dismantle.
    But all that any pics would show is the motor with no board, and a bunch of wires.

    On most of the poppers I have seen, the PCB is soldered diectly onto the motor terminals.

    To split the fan off, I un-soldered the PCB from the motor and removed it. This is a neat simple job, but did require rejoining the neutral wires and capping the low voltage active that originally powered the fan.
    With most of these units, it was easy to remove the board from the motor, connect the output from the DC power pack via the pot to the motor, and the output from the SCR to the coils, so that's how I did it.


    If the design of the Sunbeam makes this method difficult, maybe you should have a look at post #22 in this thread :- http://coffeesnobs.com.au/roasters/2...-question.html

    Cheers, deegee.

  8. #8
    Senior Member Yelta's Avatar
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    I know the electrical advice is well meant, however would suggest unless your a qualified electrician you leave this type of modification to the experts.
    Dimal likes this.

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    Mal Dimal's Avatar
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    I agree Yelta...

    Mal.

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    Thank you for your advice. I have a few friends who are electricians. So before anything is plugged in or turned on I’ll be getting them to check everything out or maybe wire it up for me. This is more of a project to enjoy and I have no intention of putting myself in harms way. Thank you for your advice and concern! I’ll let you know how I go �� quick question again, wiring the complimentary up to a few switches. Any recommendations on how to go about this?

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    G'day guys. Update for you. I've met with a great guy from my local town and together we've put together the below. The digital display down the bottom is for the % of speed the fan motor is running at. the two knobs are varying points for the fan and the heater and then switches just isolate the fan or the motor. Anyway test run tomorrow night so will let you know how we go! Thanks for the suggestions.

    So I went with a PWM and an SCR controller for the fan and heating coil and both work amazingly well - plus a 24vDC power supply that my local guru built for me. Amazing venture and super excited for it's maiden voyage tomorrow.

    https://photos.app.goo.gl/yTvkhjf7GQegTWXZ2
    https://photos.app.goo.gl/insm7WenNy67ZeEm2
    Dimal likes this.

  12. #12
    Mal Dimal's Avatar
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    Nicely done mate...
    All safety certified by your Electrician friend I hope...

    Mal.

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    A bit late on the update on the roasting. I did do a batch the following night after completing the project and it worked a treat!! managed to drag the roast time for 3.5 to 4 mins - 12-14 minutes!! Was super happy with it and can't wait to get a temperature logging setup so I can mimic the roast on my Coretto roaster which I am currently in the midst of building as well. Thanks for your help guys!
    IMG_2537.jpg

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    And lastly my latest addition to my setup. I wired and programmed an Arduino Nano with a max6675 board to monitor temp in artisan. Long long process but I did it with the help of countless forums and determination. The end result? First couple of roasts looked like this. 1CD2B39D-5BDC-42EF-83E1-BF212F4A0C82.jpeg8ABCBEFE-C5D3-453C-B23A-CE31E19A4B88.jpeg
    First one is halfway through a PNG with a lot of learning as you can tell. Second is Swiss water decaf that didn’t turn out too bad!! Either way I’m stoked. Just wanted to share my joy!

  15. #15
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    pulled my target popper to bits today and noticed it is using the heating element as a big voltage divider for the fan, which pretty much sucks as like you found you need a 24v supply, I put it vack together while I think about it some more, forgot to measure motor current, any idea what the fan needs ?
    Going by the resistance I thoght they were over volting the fan quite a bit, 47R total and 7R for the fan portion, about 1:7 divider which puts it at around 37.4v rms to the full wave rectifier, but you multiply that by 2/pi (0.636) and end up with 23.8v for the motor ignoring diode drops and motor current across the heater.
    Considered being lazy and just chopping the power but its going to lower the fan speed as well and end up with much the same temperature.
    So I will probably end up going much the same route as you, perhaps use an esp32 or esp8266 to give me a wifi enabled version.

  16. #16
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    I did some experiments with a thermocouple in the beans and a PID controller which ends up cycling power on for 4 seconds and off for about 6 seconds, so being lazy decided the temp control is not that important so long as it does not go crazy at the beginning. Found that with PID control with no ramp I still needed to bring the temperature up in a few stages anyway.
    So with all that in mind I made a little triac controller with a PIC10F220 that simply turns the power on for 4 seconds, off for 6. I can add temp control etc later or a cutoff timer but for my needs suspect it is not required.
    Takes around 9:30 for a medium roast and 12:30 before second crack.

  17. #17
    Senior Member Jackster's Avatar
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    Both of you have done great work that is beyond my skills. Awesome jobs!
    Who would have thought a pid popper....

    I did find some small hard drive transformers. Good for 2a at each of 5v and 12v. Pretty handy to run 5v sensors, and 12v computer fans...they were on ebay for few dollars.

  18. #18
    Senior Member Jackster's Avatar
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    After reading the 2008 thread, i see this has been going on for some time.
    I might have to get one of these poppers yet.
    Inspiring stuff!

  19. #19
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    Behmor Coffee Roaster
    Thermocouples arrived today so made a logging device that dumps the data to an MQTT server every 5 seconds, then pulled the data and plotted it. time scale in minutes
    This was my first test run with the 4 seconds on, 6 seconds off technique on the el cheapo target popper and it seems quite reasonable from a quick web search.
    Attached Images Attached Images



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