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Koffee Kosmo
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· 08/28/2020 7:15 PM
I have updated my signature and added links to the KKTO roaster build

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Had to make myself another cup of coffee to get through it.

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Connecting my popper to a variable voltage regulator?
ste
Hello there, I have recently started home roasting with a Severin popcorn popper!
I would like to slow down the roasting time, in order to get a better development and possibly a more even roast.
With 130g of beans I can reach a full city + in 7 minutes.

I know I can open it an modify but I am simply too ignorant for that.

So I was thinking to connect the popper to a variable voltage regulator (some call it variable speed router controller, but I think It’s very similar).
With it I would be able to reduce the voltage on a range from 0 to 240V (where I live we reach up to 240V)

Problem is that this would also reduce the air flow and hence the agitation of the beans.

Do you think it could be OK as a solution? Will I have to stir also manually once I decrease the voltage/temperature?

Has anyone used a solution as such?

Would love to hear from you!

Thanks

Stefano
 
mg512

Quote

ste wrote:

Hello there, I have recently started home roasting with a Severin popcorn popper!
I would like to slow down the roasting time, in order to get a better development and possibly a more even roast.
With 130g of beans I can reach a full city + in 7 minutes.

I know I can open it an modify but I am simply too ignorant for that.

So I was thinking to connect the popper to a variable voltage regulator (some call it variable speed router controller, but I think It’s very similar).
With it I would be able to reduce the voltage on a range from 0 to 240V (where I live we reach up to 240V)

Problem is that this would also reduce the air flow and hence the agitation of the beans.

Do you think it could be OK as a solution? Will I have to stir also manually once I decrease the voltage/temperature?

Has anyone used a solution as such?

Would love to hear from you!

Thanks

Stefano


Are you sure it's variable voltage, not just a usual AC dimmer that chops off part of the sine wave? Either way, yes, in principle it should work. Depending on how much you reduce the effective power, you might indeed either have to stir the beans, or just use fewer beans.
 
https://www.tindie.com/products/15798/
ste
Thanks for the comment! Yes it is a variable voltage device which can be used with multiple items, for a maximum of 4,000W input power and with voltage ranging from 0 to 220v.

I’m posting a link hereunder.
I just ordered it for 10 USD, and in a few weeks I will be able to test it!


https://www.amazon.ae/dp/B081PWZ7Y7/r...uFb354W26K
Edited by JackH on 09/05/2020 3:30 AM
 
renatoa
Welcome !

Yep, as mg512, it's a dimmer/chopper, will modify the effective value of A/C, it's not a transformer or a pure sine wave converter.
Will work, but the fan speed will be very low to move the beans, you should start thinking to an alternate stir method, until the voltage regulator will arrive.
I can suggest the flour sifter method, using the popper as heat source instead hotgun. you remove the original popper roast chamber, and place a flour sifter above. All you need to tinker is a stirrer mechanism, check for example this thread:
forum.homeroasters.org/forum/viewthre...ad_id=6345

Incidentally, having a flour sifter around... and a dissected popper, how else Grin I did quickly a mockup of this contraption... they stack pretty nice, eh !? Grin
renatoa attached the following image:
whatsapp_image_2020-09-05_at_121412.jpeg

Edited by renatoa on 09/05/2020 4:24 AM
 
ste
Oh so it’s not a variable voltage device as it’s described on the link where I purchased it!
Thanks for clarifying that.
I understand from your words that a “transformer or a pure sine wave converter” would work better. Can you give me a couple of names which I could check? Can you help me understand how it would be better than the dimmer I ordered? I assume a transformer / sine wave converter would also be more expensive but I would love to check those out online!
An thanks also for the stirring advice, I am going to read your source and in case get back :)
 
renatoa
Please, first check the picture just posted while you are typing Grin

Well, about pure sine, in your specific case, is NOT a requirement !
Both the heater and the fan motor will work ok with chopped sine, no need for pure sine.
So, forget it, was just a futile perfectionism... and absurdly expensive, both solutions, either transformer or converter.
Edited by renatoa on 09/05/2020 4:43 AM
 
ste
I swear I couldn’t see the second paragraph you posted! ????
I can see the photo of the flour sifter on top of the popper, look very interesting but I have no experience whatsoever with the flower sifter. Don’t even know what that is, so I’m gonna have to do some readings to understand what you mean. I also checked the YouTube link on the other thread you posted.
Meanwhile, many thanks for all your input :)
 
ste
That “????” Was meant to be a smiling face. Guess I have to fully understand it works hehehe
 
DrHenley

Quote

ste wrote:
I can see the photo of the flour sifter on top of the popper, look very interesting but I have no experience whatsoever with the flower sifter. Don’t even know what that is, so I’m gonna have to do some readings to understand what you mean.


i.imgur.com/UXXvTuk.gif
Edited by DrHenley on 09/08/2020 11:43 AM
--------------------------------------------------------------------------------
A morning without coffee is like a marriage without a honeymoon.
 
renatoa
Actually, you can use any tin pipe and a round sieve for this job, the innards of a flour sifter are removed, to turn it into a roast chamber...
renatoa attached the following image:
whatsapp_image_2020-09-08_at_210329.jpeg
 
ste

Quote

renatoa wrote:

Welcome !

Yep, as mg512, it's a dimmer/chopper, will modify the effective value of A/C, it's not a transformer or a pure sine wave converter.
Will work, but the fan speed will be very low to move the beans, you should start thinking to an alternate stir method, until the voltage regulator will arrive.
I can suggest the flour sifter method, using the popper as heat source instead hotgun. you remove the original popper roast chamber, and place a flour sifter above. All you need to tinker is a stirrer mechanism, check for example this thread:
forum.homeroasters.org/forum/viewthre...ad_id=6345

Incidentally, having a flour sifter around... and a dissected popper, how else Grin I did quickly a mockup of this contraption... they stack pretty nice, eh !? Grin
 
ste
So I have been using the dimmer and it is pretty good actually. However I’m still not happy with the consistency especially now that I’m try for a city roast.
Today I charged the popper with 100g. Started at maximum voltage of 220. At minute 4 I hit the first crack and reduced the voltage to 180. Then at minute 5 I reduced to 160V. I think the first crack lasted a couple f minutes. At minute 8 I pulled it out. Will share a photo tomorrow with natural light.
Still, how come a hot air popper doesn’t guarantee an even roast despite all that agitation?
Overall happy with the dimmer as it allows me to extend the roast without having to do an intermittent roast with manual stirring, but I am really considering that probably I need to take the chamber out and try the flour sifter method - I would buy one with a crank handle.
But I have 2 questions:
1) will the heat be enough, since the beans will be at a much higher level - out of the chamber.
2) will the sifter help me improve the consistency ?

Thanks!

Stefano
 
ste
And that’s how the roast looks like. Do you also see unevenness and scorching ? I have no idea how to avoid that
 
Gullygossner
I think you've got to much heat if you are hitting first crack at 4minutes.

Try with a lower heat for the first 3-5minutes and then adjust your heat level up to hit first crack around 7-8minutes. This may help the evenness of your roast as it will allow the beans to mix more and slowly come into first crack.
 
ste
Thank you ! I will try that. I am unable to upload a photo but there is not only unevenness, there is also scorching. I have 3 batches like that of 85g each that I need to drink now hahaha
 
renatoa
Conversely, for FB machines your heat dosing should follow closely the profile.
For example, you have below excerpts from a sample roasting I did yesterday:


00:04      28.06 C   CHARGE   19%
04:17      150.2 C   Dry End   54%
08:13      204.2 C   FCs      70%


Near and after FC is the area where you decrease power, else it should increase permanently, to drive the BT progress.
 
ste
Thanks a ton!
Would you mind helping me understand a little bit more?
- what was your batch size?
- your FC starts at minute 8:13. When did you end the roast?
- what are those percentages ?
- So you decrease the power / heat right before entering first crack. Once FC starts you increase the power again. When FC is about to end, you decrease the power. I tough in fact you have to decrease power once you’ve entered FC. Do I get your process right ?

The max capacity of my popper seems to be 130g. At the beginning the beans won’t move much, but as you can imagine they start moving nicely after 2 mins max and they tend to jump out when FC starts.
So far I have charged it with 100g.
I could play it safer and test with 60g.

- do you mind recommending a rough profile for a city roast, which I could test? Batch size: the safest you’d recommend.

Sorry for the many questions - I’m really struggling hahaha.

I wish I could upload a photo of my roast, but I have not idea why it doesn’t work.

Thanks !
 
renatoa
Batch size should not matter, if the roast chamber and power are right for the task. Seems that US poppers are significantly different than China imported EU poppers.
I don't change anything in the roast process if adding 20% more beans.
This is a measure that I am in the right spot of machine capabilities.

You end the task according to your intended roast degree.
For me this was a light-medium roast, stopped 1:30 minute later, at 09:48, 213.60 C, and same 70% power.

% are percents... ratio of maximum power the heater is able to deliver.
100% means connected directly to mains, without any variator.

Decrease/increase is not a rule, I just try to maintain a steadily decreasing RoR
Just as an example, you have below the power changes, before and after FC, until drop, but please take them as very specific to a machine and a roast evolution, tomorrow will be different if outside is 3 degrees colder/warmer, or the wind is blowing.


06:50      186.21      65
06:51      186.44      66
...
07:06      189.68      66
07:07      189.86      67
...
07:22      193.28      67
07:23      193.51      68
...
07:40      197.16      68
07:41      197.40      69
...
07:59      201.51      69
08:00      201.70      70
...
08:12      204.01      70
08:13      204.20   FCs   70
08:14      204.40      70
...
08:22      205.92      70
08:23      206.07      69
...
08:38      207.90      69
08:39      207.97      70
...
08:46      208.41      70
08:47      208.47      71
...
08:55      209.18      71
08:56      209.29      68
08:57      209.39      69
08:58      209.48      70
...
09:47      213.55      70
09:48      213.60   DROP   70
09:49      213.66      70
09:50      213.72      0


Without a setup able to compute and display rate of change evolution, such manual control is a lottery.
Just power control and a thermometer is not enough.

City roast means the above roast should be pushed more, in the 216-220 C degrees range, probably 2-3 minutes after FC. Beware, at 220 C you expect to start hearing second crack !
 
ste
What a fantastic piece of advice! You can teach roasting!
Thanks a lot for the time you put into your description!

So I guess what I need is a thermocouple for BT and ET and a data bridge to a laptop...
Would you have a specific thermocouple to recommend ? Which thickness?
Do you have now a proper roaster, or a highly modified popcorn popper?

Thanks again

Stefano
 
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