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snwcmpr
09/18/2019 4:09 AM
JavaBob ... You will get more response if you post a question on the forum rather than the shoutbox.

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09/17/2019 5:50 AM
check out the Hive Roaster!

JavaBob
09/16/2019 4:03 PM
Has anyone used a Leister hot air blower to roast coffee and if so, which model did you use? What was your experience like?

JavaBob
09/16/2019 3:53 PM
Source for customable borosilicate glass cylinders for use as a roasting chamber?

shoron
09/06/2019 7:25 AM
how to make medium raw colored beans to dark ?

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Charge temperature / preheat for popper?
marcov
Most of the profiles you can look up online are for drum roasters and from what I read the charge temperature and the turning point (TP) matter for them.

The very first times I tried to roast with a popper I tried doing pre-heat at about 150C / 300F and forcing to go thru a TP of 90C/195F after about 2 minutes.

However I find it very difficult to do: after charge, the quick variation in temperature is not easy to control so that it results in a round curve with the minimum point at the TP.

I am also seeing logs of people using hot air roaster that just start from room temperature.

So what should I do? For a hot air / popcorn popper style roasting machine, do charge temperature / preheat / TP matter?
 
JitterzZ
Just read this thread (https://forum.hom...post_68203) and a post towards the end by garybt3 gives you a link to his site (https://sites.goo...rybt3/home) He apparently has much experience with popper roasting.
 
renatoa
The TP should not be enforced to a specific value, it is where it is due to the machine construction, and the load.
What is more important to do is to maintain until TP the same power % you had for preheat, and start increasing the power, either manually, either engaging PID, only after TP.

However, there could cases of severe overloading (with beans) or machines with power issues (under powered or great power losses) where TP is significantly dropped under profile, that led to a hard to recover undershoot.
In such cases is necessary a manual compensation/increase of power % during charge, the goal being to raise TP value for a smooth landing on the profile curve.

But all of the above are specific to great inertia machines, of great volumes/mass, where preheat is mandatory, not apply to FB machines where you can reach 100C in a minute.
So I suggest to use a profile starting from ambient temperature, and don't bang the head unnecessary with TP on a popper.
My 2nd cracks Grin
 
BenKeith
As mentioned, sounds like you might be trying for too big of a load.
When I first started 19 years ago (wow, doesn't seem like it) I started with a Poppery and was relegated to approx. 80 gram loads. After tons of modifications, this even included adapting a Hearthware Precision heating and fan unit and making a larger 2,000 watt heating element, I finally got it up to 150 gram load.

What you have to watch out for trying to push it to hard is scorched and tipped beans. If you look at the beans after roasting and see black edges, ends, spots/areas on the beans and even whole beans, then you are over heating them with more heat than the bean can absorb in the drying stage.

I think if you heat to 250F, drop the beans and it drops below 140-150F, you are loading too many beans. I actually have to run my current roaster on 80% heat in a cold garage and still have problems with it hitting 300F in three minutes if I'm not watching it, when I'm looking for 300f in four minutes. If I load too many beans, I have to turn the heat up and then I get scorched, tipped beans.
 
JitterzZ
BenKeith wrote:

As mentioned, sounds like you might be trying for too big of a load.
When I first started 19 years ago (wow, doesn't seem like it) I started with a Poppery and was relegated to approx. 80 gram loads. After tons of modifications, this even included adapting a Hearthware Precision heating and fan unit and making a larger 2,000 watt heating element, I finally got it up to 150 gram load.

What you have to watch out for trying to push it to hard is scorched and tipped beans. If you look at the beans after roasting and see black edges, ends, spots/areas on the beans and even whole beans, then you are over heating them with more heat than the bean can absorb in the drying stage.

I think if you heat to 250F, drop the beans and it drops below 140-150F, you are loading too many beans. I actually have to run my current roaster on 80% heat in a cold garage and still have problems with it hitting 300F in three minutes if I'm not watching it, when I'm looking for 300f in four minutes. If I load too many beans, I have to turn the heat up and then I get scorched, tipped beans.

I was wondering what those spots were on the roasted beans when I used my Nostalgia popper. Thank you.
Can you provide build details on the 2000 watt element that you made? Thank you.
 
marcov
Thanks for the tips.
I guess that for me the easiest thing to do is just to start from room temperature, as renatoa said.

I am attaching an example of a failed attempt at tracking the TP. Coffee resulted flat and quite bitter :(. In presents indeed some dark spots.
marcov attached the following image:
preheat.png
 
Wiz Kalita
Why is your heat and fan going all over the place like that? What I normally do is set the fan to 100% and ramp up the heat slowly and I find that I can track a specific curve quite well that way.
 
renatoa
Same here, the projection (trending) lines are more useful than the profile itself.
I am slowly increasing power aiming the desired DE, then the desired FC.
These two points are enough to replicate any profile better than a PID and setpoints.
Hardly ever need decreasing power, because so is the machine natural curve, being a concave curve, once a point is aimed, rarely overshots.

However, I don't think that restless start of the profile damaged the beans so bad... evolution seems ok from 130C to the end.
Could be old beans or other reason.
 
marcov
Wiz Kalita wrote:

Why is your heat and fan going all over the place like that?

I run that in manual mode and I felt that small variations of the fan allowed me to smooth abrupt temperature changes, that may happen when I quickly change heater levels.


renatoa wrote:
I am slowly increasing power aiming the desired DE, then the desired FC.
These two points are enough to replicate any profile better than a PID and setpoints.

I like this simple approach! Next time I'll try like this.
 
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