MNate wrote:True BT is going to be a mystery any way you go. The sight and sound method has a lot of merit. If you want to go the data method the main concern is getting good data that you can foremost use to repeat a roast profile that you liked. Secondarily if you're really good you might be able to see in the data correlations between actions you make and responses in the data. But there I have been really surprised by the two very different approaches discussed above (I'd call them low fan/high heat and high fan/low heat). Controlling the heat with the high fan one was mainly by controlling the fan, and by the low fan one by controlling the heat.

Anyway, you have some fun experimenting ahead of you and probe placement is certainly part of it. And yes, I know someone claimed good readout by placing a probe below the chamber somehow, but I don't think I've heard yet of people talking difference between two probes as a way to figure anything (wait, are you saying difference or differential? Difference being subtracting one from the other, differential being a rate of change sort of thing, right? Math was awhile ago...)

For me though, a probe in the bean mass has been a reliable indicator of bean color/stage and all I really look at now. But hasn't been a good indicator of how well the inside color matches the outside color, but I don't think it is in drum roasters either. That's the real skill!

Agreed on data being useful for repeatability! Since I'm very new to roasting, I was looking at "good" and "bad" curves to see if there's anything i should be looking out for during a roast. One thing that stood out from Rao's example curves was that his ET readings almost always take a dip right before FC, followed by no dip in BT. When there was a dip or crash in BT he says the roast is baked. I think this is disputed.

My understanding of this is that a drum roaster is sensitive to a pre-FC dip in ET because the drum acts as a heat sink and the seconds leading up to FC the beans expand and absorb heat which comes from the heat stored in the drum metal and picked up by the ET probe. The heat is promptly released when the bean cracks.

In the SR800 or any air roaster there's no heat sink to provide this sensitive ET dip reading. I was hoping that placing a probe underneath the bean bed might provide this data. And yes I meant difference between the 2 probes, i.e. the one placed right above the beans and one right below. Any difference in temperature between those two could be attributed to heat absorbed or released by the bean mass as the air travels through it. Heat loss through the glass will be included in this, skewing the data.

I have a theory on why FC crash results in baked beans and FC surge results in burnt flavors, IF Rao's theory is correct. I DM'ed him on IG but based on his response he wasn't amused. I'll do some tests once I get my SR800 and see if it holds water before sharing here.

I'm not sure you'd get anything useful from a ET Probe beneath the bed. The SR800 has an at source probe you can us for reference and interestingly when FC happens I do notice the dip (more on some beans over others) and you see the device temp dip as well. A probe over, I am sure could show some data but what I found is the temp will be severely impacted by your airflow and as beans loft it will release some pockets of air that skews the probes. For comparison, I only have a BT probe but I do use the device temperature for reference as well.

jfjj wrote:The SR800 has an at source probe you can us for reference and interestingly when FC happens I do notice the dip (more on some beans over others) and you see the device temp dip as well.

Thanks for sharing that! If the display temp shows a dip right before FC it means that the metal grate probably stores some heat and allows the probe to respond to the sudden heat absorption by the beans.

jfjj wrote:what I found is the temp will be severely impacted by your airflow and as beans loft it will release some pockets of air that skews the probes

This is the main reason I want to try tracking temperature difference between a probe beneath the beans and one right above. When a fan setting is changed, the amount of cool air entering the device changes dramatically and has a big impact on the probe readings, including BT without actually causing that big of a change at the beans themselves.

yakster wrote:Sounds like you've got a voltage drop problem, which you can confirm with a Kill-A-Watt inline.

How would you confirm/disprove a voltage problem with the kill-a-watt? what numbers are you looking for?

The Kill-A-Watt will measure the voltage at the outlet going to the roaster inline. First you get a baseline voltage with the roaster off, should be around 120 V. It shouldn't drop too far down, if it drops below 110 V that would affect your roasting. With the Behmor, I looked for at least 116 V, plus I had a Variac to boost the voltage to compensate for any voltage drop.

In your case, you could use a Kill-A-Watt to select a good location to roast in, one with the least voltage drop. Other solutions are to run a dedicated 20 A outlet to your roasting location.

I have spent a lot of beans (~20lbs) experimenting with this roaster.
Baseline is -- there is no single roasting strategy that fits all.
There are so many factors that affect the behavior of the beans to the heat: process, density (altitude), bean size, and so on.
So one profile that fits perfectly on washed ethiopian may result in a baked roast on dry brazillian and an underdeveloped roast on colombian.
That is, you need an extra thermometer that probes the bean temperature for profiling if you don't want to waste a pound of beans whenever you want to try a new type of beans.

However, I didn't want to spend hundreds on an artisan-compatible thermometer and drill my machine.
Luckily, I found a lot cheaper alternative at SM: https://www.sweetmarias.com/digital-the ... ouple.html plus https://www.sweetmarias.com/ss-rigid-thermocouple.html.
There is no need for drilling. Just hang the probe on top of the bean agitation and you should be fine.

Yes, you won't be able to do precise ROR control. But you cannot follow drum roaster profiles anyway.
It is impossible to follow a steady ROR decline in this roaster since the heat reaction is a lot faster in air roasters.
So forget about ROR. What you really need to care about is control the dropping temperature, and the ratio of drying, mallard, and development phases.

The temperature reading is specific to the type of probe and the theromometer. The readings align very well with those of SM's guide.
https://library.sweetmarias.com/using-s ... -of-roast/
The drying will end around 320~330F, and FC will begin around 400F while it depends on the type of the beans.
My city roast profile is usually 4:30 drying, 3:30 mallard, and 2:00 development to reach 425f drop temperature.
Control roast level by drop temperature. 435f for city+ and 445f for fc.
The final ambient temperature should be about 20f higher than your drop temp.
Focus on the drop temperature, not DTR. Dry processed coffees tend to crack later so it is OK to have a shorter DTR.
On the other hand, denser beans require longer time / more heat to reach the same roast level so be patient.

Below is my very successful profile for 150g dry-processed nicaraguan.
I have the extension tube and the machine was moderately preheated.
Time Fan/power ET(machine) BT
1:00 9/1 300 210
2:00 9/1 315 270
3:00 8/2 335 295
4:00 8/2 340 315
5:00 7/3 365 335 (DE at 10~20s)
6:00 6/4 395 360
7:00 5/5 420 380
8:00 4/6 450 408 (FC at 40s, 405f)
9:15 4/6 455 425 --> start cooling
4:20 drying, 3:20 mallard, 1:35 develop, 17% DTR

This is a coarse bean that takes the heat very quickly. I tried hard to elongate the drying phase. Your BT will converge to 20F lower than the machine reading. So stay lower than 340f for the drying phase, and 420f for the mallard phase.
If you want a higher roast level, turn the fan down once more and let it develop longer.
The result was a very fruity and sweet light roast without astringency or unpleasant sourness.
Before using the BT probe, I rarely succeeded to produce such light roasted coffee when I tried a new type of beans.
Now I am very confident with my roasting. The cheap thermometer+probe combination really makes a difference.
Hope this helps fresh home roasters like myself.

hwnam831 wrote:I have spent a lot of beans (~20lbs) experimenting with this roaster.
Baseline is -- there is no single roasting strategy that fits all.
There are so many factors that affect the behavior of the beans to the heat: process, density (altitude), bean size, and so on.

Hey, welcome to HB! Nice to have another person willing to put in the effort to learn the FreshRoast, plus being willing to explain your process. It's so true that the different bean types take a different approach... I think I'm just going to find my two or three beans I can make work well and stick with them. At least for a year or two.

I'll be interested to hear more as you progress!

Freddofl wrote:Got my SR800...
Someone reported having placed a thermocouple below the bean bed, just to hey the inlet temperature reading...
If we're able to track inlet air temperature and subtract the ET right above the beans, presumably we would get the heat absorption from the beans...

The Ikawa Pro roasters measure the inlet and outlet temperatures of the airflow then use an algorithm to control their profiles (how it works). I was wondering how we could do something similar with the FreshRoast roasters.

They have a smart phone app with roast profiles. Has anyone looked into this?

I'm new here but not to roasting on the Fresh Roast. I had the 500 years ago and then passed it down to my Son 5 years ago when I bought my Behmor 1600 plus. Before that I was roasting on various vintage poppers like the Poppery and Popper 2 with no mods.

The machine I really want and hopefully get one day is the Artisan 3-e. I listened to the owner on youtube and a light-bulb went off in my head with something he said which I implemented into my roast profiles. He said the only thing you need to do with this machine to control temps is just play with the air flow. This eliminates all of the back and forth between airflow and heat adjustments and gives you a more reliable roast by eliminating so many variables keeping the heat source at a constant temp.

So I thought why not try this with my SR800 / OEM Ext tube and see what kind of results I can achieve. I start off at 9/4 and work my way down to a 4/4 or 3/4 by the end of the roast for city- city plus. this is usually a total roast time in the 8-10 minute range. And the results are the best tasting coffee I have ever roasted. I will try and post some data since I do not use any software or probes. I just use the temp read out from the machine and log that info along with the mark for dry time and 1st crack and drop temp/time.