Kaffelogic community

Hi,

Firstly, brilliant product - well done! My taste buds thank you, my kidneys have packed up and left the building...

Just a quick question around the roast end time and calculation of development%.

During roast I've marked first crack, then stopped roasting process at indicated development% of 25% indicated on the front panel of the Nano7.

When looking at the log file (attached) in management studio, the first crack time is 5:13:872 and development% as 25.0217%.

Looking at the roast profile curve and log tabs the mean temperature and power appear to drop at around 6:56-6:57.

Subtracting the FC time (5:13.872) from where I'd presume roast ended (6:57) I get a difference of 1:43.1

Working out the development% I get (1:43.1 / 6:57) * 100 = 24.72%

To get the development% indicated in the log file of 25.0217%, the end time would need to be something around 6:58.6, which is a 1.5-2.0 seconds after the graphed temperature and voltages drop?

This is just a matter of curiosity for me - I'm logging in Excel and the difference in my calculated development time disagrees with time in the log, but agrees with the Tools | Calculate Development function if I plug numbers (as best I can extract from graphs) into that...

Is there something I can look for in the log file which gives an end time that will allow my calculated development% to agree with the development% in the log?

I'm sure it makes no practical difference in the real world, but it makes my OCD hurt...

Cheers,
Nick

Interested in the fact you got first crack at temperature of 200.4C (read from your log). I've never heard it that early on a range of beans; 206 unusually and normally 210 and above.

Your curve following error is above the line like mine. Some of my lines are 5 degrees off at the end. That makes 226 become 231. Is there a case for a small Integral factor in the controller? I ask from a position of experienced ignorance.

Hi, I'm always seeing (on a variety of beans) FC of 200-209degC, with average of about 204.

I've had a variety of beans through it while playing to find what I like - Ethopian, Columbian, Ugandan.

I generally do a run with the chamber empty first to mitigate any outside temperature (i.e. a freezing kitchen in the morning... , then run a batch through.

Just done some Ethopian Guji this morning, 2 x 100g batches, both had FC of about 199degC. Previous batches a couple of days ago had FC of around 201degC. I did that previous batch mid afternoon when ambient temperature was a little warmer (i.e. kitchen not quite so freezing), but that's the only difference.

I'm no expert, but my reading suggests anything from around 196degC for first crack wouldn't be unexpected?

Just looking back through a couple of older logs, temperature tracks above the profile earlier on, but tends to hit it later in the process if I'm doing a medium-dark roast. But I'll look at that more closely.

resulted level 0,7 seem to be to early stop to me but I think that depends on what you define the FC. I'm stiil confused but if I pick very fist single pop, some case I hear it early as Nutta. Some sat pick 3rd pop or start of multiple in short period may be that is beginning of RFC.

I never close look at the numbers but I have some few degrees off at end as well, especially doing multiple batch in sequence, But result is quite acceptable.

Sorry, it's not answering your point of question, but Chris may jump in for inside view.

Yes, 0.7 was early, but working my way through a range of DTRs (20%, 25%, 30%, 35%, 40%) to see what effect that has for a particular bean on the standard Nano7 profile.

First crack picked as the first cluster of cracks, ignoring the first few isolated pops.

I'm very interested in your findings for that comparisons.

Nutta wrote: ↑Sat 06 Jul, 2019 2:19 pm To get the development% indicated in the log file of 25.0217%, the end time would need to be something around 6:58.6, which is a 1.5-2.0 seconds after the graphed temperature and voltages drop?

Your calculations are spot on. The one final thing you need is to know that the mean_temp line is a 7 sec rolling mean. This is done to provide smoothing to the curve, and you can see the unsmoothed curve using the "Show options" checkbox and selecting the temp line. The temp line is actually a 0.5 sec rolling mean, but it demonstrates the principle nicely and is less noisy than the spot_temp line which is a raw thermocouple reading.

A 7 second rolling mean will start dipping 3 secs earlier than a 0.5 sec rolling mean. The whole thing is made a little more difficult for you because the log graph information is shown rounded to the nearest second, but nevertheless you can see from the temp line that the roast end was actually at 6:58 to the nearest second. Allowing that we are looking at a 0.5 sec rolling mean this is in exact agreement with your calculations.

The take home message is that if you want to get the roast end time to the nearest second, look at the spot_temp and temp lines.

Nutta wrote: ↑Sun 07 Jul, 2019 10:57 am I generally do a run with the chamber empty first to mitigate any outside temperature (i.e. a freezing kitchen in the morning... , then run a batch through.

I'm interested in whether you do this because you have found it helps? The Kaffelogic is designed to compensate for any variation in ambient temperature: in a colder room it delivers extra heat, and extends the profile it is following back to the lower temperature. This all happens 'under the bonnet' so the user doesn't really see it. The adjustments are removed when you view the log so that one log can be compared to another. That's the theory, but I think there may still be some stored heat in the chamber that needs to be compensated for. So I'm keen to hear whether your roaster works ok in a freezing kitchen without doing the run with empty chamber.

Angela wrote: ↑Sat 06 Jul, 2019 10:13 pm Interested in the fact you got first crack at temperature of 200.4C (read from your log). I've never heard it that early on a range of beans; 206 unusually and normally 210 and above.

Your curve following error is above the line like mine. Some of my lines are 5 degrees off at the end. That makes 226 become 231. Is there a case for a small Integral factor in the controller? I ask from a position of experienced ignorance.

I have answered your question with a separate post https://kaffelogic.com/community/viewtopic.php?f=6&t=36 (this keeps me from getting off topic on this post )