First roast using computer control of Hottop B2K+

#1: Post by **swisher103** » October 26th, 2015, 9:47 pm

This is my first roast using my computer for complete control of the Hottop B2K+. I am pretty happy with the rate of rise, but I'm a little concerned about the finishing temperature. This is an Ethiopian Yirga. Looking for City +. All feedback, no matter how small, is welcome. Thank you

#2: Post by **Randy G.** » October 27th, 2015, 12:50 am

At the end of the roast you can save the program but also it can save an image file of the graph that would be better to share.
Did you do that roast with the "alarms"?
Let us know how it tastes.

#3: Post by **ajf** » October 27th, 2015, 10:58 am

What temperature is shown when you first switch the roaster on?.

My central heating thermostat is set to 68, yet when I switched my Hottop on (this morning) the bean temperature read 51.8 and the environment temperature read 57.2 I checked the actual temperature with a calibrated thermometer, and the actual temperature was 67.6

Looking at your graph, 1st crack starts at a reported temperature of ~360 while is should be in the region of 390. I have also seen a graph posted by Randy G which shows 1st crack starting at 360, and my own roaster also starts 1st crack at a reported 360.

Looks like the reported temperature is off by 20 - 30 degrees, but at least it is consistent.

Alan

October 27th, 2015, 12:48 pm

Alan,
Great point...I will check that tonight.

#5: Post by **jgbnm** » October 27th, 2015, 1:52 pm

Can't read the numbers. Might be helpful to post them.

Can you use offsets to adjust the temperatures? The actual temps probably matter less than the deltas though.

Is development time being calculated on the end of first crack temp? I'm assuming the drop temp is the last number shown? If you believe in Rao's 20-25% development time as being ideal, this one is kind of long.

Looks pretty good overall. Many would suggest that you try to avoid the upward bean temp flick at the end if you can. Finishing temps maybe a bit low for C+?

Of course, all that matters is the taste...

#6: Post by **Randy G.** » October 27th, 2015, 2:48 pm

ajf wrote:What temperature is shown when you first switch the roaster on?.

My central heating thermostat is set to 68, yet when I switched my Hottop on (this morning) the bean temperature read 51.8 and the environment temperature read 57.2 I checked the actual temperature with a calibrated thermometer, and the actual temperature was 67.6

The thermocouples are not accurate in that low of a temperature range. I don't remember the exact number but it is something below around 80 to 100F. After that they are dependable, or at least to say, repeatable if not "accurate."

October 27th, 2015, 5:37 pm

What???

A K type thermocouple has a range of approximately -270C to 1260C.

Within that range, their accuracy will vary slightly, but in the range used for roasting (0C to 400C) they should be accurate to within 1.6C
See http://www.microlink.co.uk/tctable.html

Swisher's, yours and mine all have a reported temperature that is approximately 17C low at 1st crack temperature (or we don't hit the FC Start button at the correct time), but with mine, the error is consistent from one roast to the next.

I intend to investigate this matter further, and see if I can come up with a way to produce an accurate reading without introducing any adverse side effects. If I can, I will pass the proposed solution on to Artisan.

Alan