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Understanding changes to Behmor roast profiles

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doublepedro
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Joined: 27 Nov 2009
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Posted Wed Dec 9, 2009, 1:40pm Subject: Understanding changes to Behmor roast profiles

I just started roasting with a Behmor 1600 and have been experimenting with a few roasts where I had to add or subtract time. In the course of this, I noticed that it didn’t seem to make a difference to the roast profiles whether I added/subtracted time before or after pressing “Start” – in either case, the additional time would simply show up in the last leg. This surprised me since somewhere along the line (I don’t recall exactly where) I had picked up the notion that time added/subtracted before the start had a different effect than that added/subtracted after the start. To confirm things, I ran several test runs (no beans) where I carefully noted when the heating element cycled on and off. FWIW, it appears that the Behmor runs at less than full power by cycling the heater elements on/off at a certain ratio – not only can you see the elements brighten or dim but you can also hear the relay click as they are switched on and off. Typically, I observed that it would cycle on for 15 seconds and then off for some other fixed length of time depending on the power level it was trying to achieve (e.g. 15 sec on / 8 sec off for leg 1 of P4 versus 15 sec on / 5 sec off for leg 2 of P4). In the course of this, I noted specific transition points in the cycles which corresponded well to those expected for the initial selected roast profile (e.g. P4 - A) regardless of whether time was added before or after the start. These are summarized below. What this all means in a nutshell is that it appears you can only stretch or compress the entire roast profiles in actual time using the A, B, C, and D buttons. Any change in roast time using the (+/-) buttons only affects the last leg even if you make the addition/subtraction before hitting start. P4 Profile Measurements ¼ lb - P4 – A 8:30 minute roast • From 0:00 to 2:18 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 = 65% duty factor); • From 2:18 to 4:58 into the roast the roaster cycled 15 sec on and 5 sec off (15/20 =75% duty factor); • From 4:58 to 8:30 (end of roast) the roaster stayed on all of the time (100% duty factor). (The expected transition points for leg 1 and 2 are 2:33 and 5:06 according to the profiles given in the manual.) ¼ lb - P4 – A – add 1:30 minute prior to “Start” 10:00 minute roast • From 0:00 to 2:18 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 = 65% duty factor); • From 2:18 to 4:58 into the roast the roaster cycled 15 sec on and 5 sec off (15/20 =75% duty factor); • From 4:58 to 10:00 (end of roast) the roaster stayed on all of the time (100% duty factor). (Note the observed transition points are the same as the unaltered (¼ lb - P4 – A) roast above.) ¼ lb - P4 – A – add 1:30 minute immediately AFTER “Start” 10:00 minute roast • From 0:00 to 2:18 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 = 65% duty factor); • From 2:18 to 4:58 into the roast the roaster cycled 15 sec on and 5 sec off (15/20 =75% duty factor); • From 4:58 to 10:00 (end of roast) the roaster stayed on all of the time (100% duty factor). (Note the observed transition points are the same as the unaltered (¼ lb - P4 – A) roast above.) ¼ lb - P4 – C 10:00 minute roast • From 0:00 to 2:41 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 = 65% duty factor); • From 2:41 to 6:01 into the roast the roaster cycled 15 sec on and 5 sec off (15/20 =75% duty factor); • From 6:01 to 10:00 (end of roast) the roaster stayed on all of the time (100% duty factor). (The expected transition points for leg 1 and 2 are 3:00 and 6:00 according to the profiles given in the manual.) P2 Profile Measurements ¼ lb – P2 – A 8:30 minute roast • From 0:00 to 5:21 into the roast the roaster was on constantly (100% duty factor); • From 5:21 to 7:39 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 =65% duty factor); • From 7:39 to 8:30 (end of roast) the roaster stayed on all of the time (100% duty factor). (The expected transition points for leg 1 and 2 are 5:06 and 7:39 according to the profiles given in the manual.) ¼ lb – P2 – A – add 1:30 minute prior to “Start” 10:00 minute roast • From 0:00 to 5:21 into the roast the roaster was on constantly (100% duty factor); • From 5:21 to 7:39 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 =65% duty factor); • From 7:39 to 10:00 (end of roast) the roaster stayed on all of the time (100% duty factor). (Note the observed transition points are the same as the unaltered (¼ lb – P2 – A) roast above.) ¼ lb – P2 – A – add 1:30 minute immediately AFTER “Start” 10:00 minute roast • From 0:00 to 5:20 into the roast the roaster was on constantly (100% duty factor); • From 5:20 to 7:39 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 =65% duty factor); • From 7:39 to 10:00 (end of roast) the roaster stayed on all of the time (100% duty factor). (Note the observed transition points are the same as the unaltered (¼ lb – P2 – A) roast above.) ¼ lb – P2 – C 10:00 minute roast • From 0:00 to 6:15 into the roast the roaster was on constantly (100% duty factor); • From 6:15 to 9:00 into the roast the roaster cycled 15 sec on and 8 sec off (15/23 =65% duty factor); • From 9:00 to 10:00 (end of roast) the roaster stayed on all of the time (100% duty factor). (The expected transition points for leg 1 and 2 are 6:00 and 9:00 according to the profiles given in the manual.)

shaneo
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Joined: 3 Jan 2002
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Posted Wed Dec 9, 2009, 8:00pm Subject: Re: Understanding changes to Behmor roast profiles

I would suggest to download the "Behmor thing" it models the profiles quite well and help one understand what the changes do. Shane

Posted Wed Dec 9, 2009, 11:55pm
Subject: Re: Understanding changes to Behmor roast profiles

shaneo Said:

I would suggest to download the "Behmor thing" it models the profiles quite well and help one understand what the changes do.

Shane

Posted December 9, 2009 link

Shane - thanks for the suggestion. I actually did that after I noticed that adding time before hitting start wasn't doing what I expected. FWIW, what I expected was the same as what's in the Behmor Thing. At this point, based on direct observation, I think I understand pretty well what *my roaster* is doing (I emphasize "my roaster" since I can't really say for anyone else's roaster unless I sit in front of it and run some tests). However, mine seems to be at odds with what's in the "Behmor Thing" and I haven't been able to get any clarification from Behmor directly.

In the end it really comes down to what the roaster is doing and that is easy enough to observe directly by noting when the roaster modulates the duty factor of the heating elements (i.e. turns them on and off in a periodic fashion).

It would be interesting if someone else with a Behmor would repeat the same observations as in my previous post above. It's slightly tedious but not that bad - just set up a "roast" with an empty basket (add or subtract time prior to the start) and watch/listen for the heater elements to cycle on and off during the roast and note the times for each. You can either record the entire roast cycle (as I did) and end up with a list of about 40 times in the course of a 10:00 minute roast, or if you just check out P2, you can just watch for when the power drops as you enter leg #2 (the elements will start to dim on and off as the power to them cycles 15 sec on / 5 sec off). The time that this occurs will tell you whether time added prior to hitting start showed up in the entire roast or not. In every test I did, it always showed up at the end. Go figure.

yakster
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Joined: 25 Feb 2009
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Posted Thu Dec 10, 2009, 10:07am Subject: Re: Understanding changes to Behmor roast profiles

It was too cold in the garage last night to contemplate testing this out, but it is interesting and should be easily checked. The timings that you cite, they're not countdown timings... did you just use a stopwatch? How old is your Behmor? I'll probably just do one of your P2 roasts with the time adjusted before the start and compare it to BehmorThing. I've got a thermocouple installed below the lower heater and can see the drop in power on the Killawatt (though it's hard to miss by the sights and sounds anyway). From BehmorThing, looks like it's time for me to run a cleaning cycle anyway, so it's good timing. Hopefully I'll be able to do this before the weekend. -Chris

-Chris LMWDP # 272

Posted Thu Dec 10, 2009, 11:05am Subject: Re: Understanding changes to Behmor roast profiles

Chris, Great, let me know what you find. My roaster is brand new (got it Monday from Sweet Maria's). The times I cite are times into the roast based on recorded count down times. Here's an actual example using a 1/4-P3-C roast. Note that the base time is 10:00 minutes for a 1/4-C and then I subtracted 1:30 before pressing start. So, the machine counts down from 8:30 to 0:00 and while it does this I record the count down times when the element switches on/off (see recorded count-down times below). Count-Down Times On Off 8:07 7:52 7:44 7:29 7:21 7:06 6:58 6:43 6:35 6:20 6:15 6:00 5:55 5:40 5:35 5:20 5:15 5:00 4:55 4:40 4:35 4:20 4:15 4:00 3:55 3:40 3:35 3:20 3:15 0:00 FWIW, there seems to be a delay in the initial start-up of the elements. I'm not sure if this is real or if it takes a cycle for the elements to visibly glow so I may end up missing the first cycle. From the above list of recorded count-down times, I then note the times where the cycle period changes (e.g. 6:35 marks the last of the "15 sec on/8 sec off" cycles and the start of the "15 sec on/ 5 sec off" cycles; and from 3:15 on the elements just stayed on). I then subtract these from the the roast length (8:30 in this example) to get the transition points as "times into the roast", namely, 8:30 - 6:35 = 1:55, and 8:30 - 3:15 = 5:15 respectively. Note that these agree better with the transition points expected for the original 10:00 minute 1/4-P3-C profile (2:00 and 5:30 into the roast, respectively) rather than those for an 8:30 minute P3 (1:42 and 4:41 into the roast, respectively). There isn't perfect agreement with either because of the discrete cycle length being used by the roaster to modulate the applied heat. If a longer roast time and/or change was used, the difference in the level of agreement between the two sets of expected transition points would be even greater. -Guy

yakster
Senior Member

Posted Thu Dec 10, 2009, 11:34pm Subject: Re: Understanding changes to Behmor roast profiles

Chris, I ran a test roast / cleaning cycle tonight and confirmed your findings. I've got an older Behmor so I was curious if something had changed, but since I rarely do 1/4 # roasts, I'm starting to think this might be something peculiar to the 1/4 # roast profiles. I want to try this again with a 1# roast to see if I can duplicate your findings there too, but that is an experiment for another day. The profile I chose to test was 1/4 # P2 A with time added before hitting start to make the total roast time 10:00. I took the easy way out and just entered the temps in BehmorThing during the roast and let the computer keep track of the time. The top profile is the profile that I programmed into the Behmor and BehmorThing while running the test, the second leg should start at 6 minutes and the third at 9 minutes. The lower curve is what the profile should look like if you added the time after hitting start as displayed in BehmorThing. The red line is my temperature readings manually entered. A word about the temp readings here. The first hump at 4 minutes is where the afterburner kicks in to prevent smoke. This shows up as a rise in temp and then a gradual drop and there's increased airflow in the roaster when the afterburner is engaged. My thermocouple is taped below the bottom heating element. At five minutes, the temps hit a valley and then start up to a peak at about 5:30. I thought that the second leg started at 5:30 by looking at the roaster and the temps, but it could have started a little earlier. The temps drop during the second leg and then rise again at the third leg. It's clear that the third leg starts at around 7:30 where it would normally start in a striaght 1/4# P2 A profile or a 1/4# P2 A profile with time added after hitting start. -Chris (Click for larger image)

-Chris LMWDP # 272

Posted Fri Dec 11, 2009, 5:53am Subject: Re: Understanding changes to Behmor roast profiles

Chris, Nice! FWIW, I think I first noticed this on a 1lb-P2-A roast that I subtracted 2:00 minutes prior to starting - I saw the elements start to cycle on/off at just under 11:00 left in the roast which wasn't where I had thought it would happen. That motivated me to take a closer look (focusing on the 1/4 lb roasts for brevity). Let me know what you find for a longer roast. Guy

Jnani
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Posted Sat Dec 12, 2009, 10:02am Subject: Re: Understanding changes to Behmor roast profiles

What this all means in a nutshell is that it appears you can only stretch or compress the entire roast profiles in actual time using the A, B, C, and D buttons. Any change in roast time using the (+/-) buttons only affects the last leg even if you make the addition/subtraction before hitting start. So, you figured this out, eh? I believe it says so in the manual somewhere (though not clearly), or maybe I picked up on this forum along the way. You're almost right, in that the +/- buttons do affect the start time (and thus profile) before hitting start, but only the last leg if hit after pressing the start button. The choice of weights or A, B, C, D buttons do not affect the profiles, just the maximum time allowable. The profiles set different temperatures for different percentages of the start time - adding or subtracting time after hitting start only affects the last leg, so I just set the start time and then hit the cool button at the appropriate point in the roast. My next step was figuring out how to fit the roast profiles to different beans by adjusting the start time. I use P4 exclusively now, using a longer start time for lighter roasts, and a shorter start time for darker roasts. That may be counterintuitive, but there's a reason for it, and it works. BTW, last time I checked, Behmor Thing only worked for that inferior platform - Win something...

Posted Sat Dec 12, 2009, 11:07am
Subject: Re: Understanding changes to Behmor roast profiles

Jnani Said:

You're almost right, in that the +/- buttons do affect the start time (and thus profile) before hitting start

Posted December 12, 2009 link

Jnani - Thanks for the comments. The point I am trying to demonstrate is that the above statement is not correct. Based on my observations (and apparently confirmed by yakster), it seems that even if you hit the +/- buttons before the start it only affects the last leg. That point isn't spelled out in the manual one way or the other as far as I can tell.

Jnani Said:

My next step was figuring out how to fit the roast profiles to different beans by adjusting the start time.

Posted December 12, 2009 link

That sounds like good advice and is what I am trying to do. But, in order to do this effectively, I needed to understand what changes to the start time actually does to the profile. This led me to the above conclusion which seems to be different that what is commonly accepted regarding how the Behmor handles time adjustments.

yakster
Senior Member

Posted Sat Dec 12, 2009, 3:07pm Subject: Re: Understanding changes to Behmor roast profiles

I found out that my in-laws are down to about 3 days of decaf left, and I'm running low on roasted myself so that gives me some opportunities for roasting this weekend. I think I'll try a 1# profile with time added or subtracted before hitting start to see what happens with the 1# P2 profile. Before this thread, my understanding of adding or subtracting time before hitting start was that it pushed out all the legs of the roast, each leg was a percentage of the total and you were just changing the total time. Now that I've run a 1/4 # batch with time added before the roast, I'm not so sure. -Chris

-Chris LMWDP # 272

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