BC-2 Purchase, Setup, and First Roasts - Page 3

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
aabud (original poster)

#21: Post by aabud (original poster) »

I connect to my BC-2 via USB, but mine also came with a blue-tooth dongle and instructions on how to connect that way. I didn't really consider the BT as my experience with other BT devices connecting to my laptop hasn't been stellar, and dropping a connection mid-roast was something I wanted to minimize.

I've roasted quite a few 200-250g batches and think they're fine. I'm used to FC around 197C, and found I'd hit it in these small batches at a temp reading of 190-192C... so I figured maybe that was probe not being in great contact with the beans. However, I've also had a couple of one pound batches go off early (194C), so jury is still out. The temp curves otherwise seem normal on the small batches.

They offer a double wall on the BC-2 (extra cost...quite a bit as I recall), though they told me 99% of people buying the BC-2 go with single wall. I didn't want double wall because of the extra warm up time.

I considered an Arc 800g briefly before narrowing it to BC-2 vs. Mill City. I think I felt like the BC-2 has a bit more capacity and I liked the looks and layout of controls a little better also. In the end, there was a BC-2 available, which probably was as much a deciding factor as anything. All three are great roasters, I imagine.

luvmy40

#22: Post by luvmy40 »

I love living vicariously through others! I want a small commercial drum roaster so bad I can taste it! There's just no way I could justify the cost. I'm getting excellent coffee with my SR800 and I rarely need more than 2 lb./week.

Any way, the reason I posted up here is to share a very small thing, though it is actually quite large.

https://www.sciplus.com/giant-funnel-47647-p

This funnel is perfect for dumping beans from my cooling tray to the gusseted bags. I cut the spout to about half the length to increase flow and stop the occaisional jam.

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aabud (original poster)

#23: Post by aabud (original poster) »

After experiencing some inconsistency in a couple of roasts, I now take back what I said regarding "not being sure the air gauge upgrade was worth it"... it is. And you have to calibrate that thing after you install it though to make it useful.

I have been surprised on two levels...

One... the impact on a roast of even a small change in air pressure. For better or worse, I've been managing repeatability by using temperature points to time gas pressure changes - e.g. after my between batch ritual, I soak for 90 seconds, then 3.5 gas until 140C, then 2.0 gas until 160C, etc. I get a really nice roast at 4 pascal pressure all the way through, but a pretty ugly one at 5 pascal pressure.

Two... the setting on the damper dial does not correspond to a certain pascal pressure very precisely. A certain specific setting might vary from 3 to 7 pascals - plenty enough variation to mess with my roast curves. I don't know if there's a little play in the mechanism or it's dynamics of the roaster, but I trust the gauge reading.

My consistency has returned now that I actively manage the damper to a specific air pressure gauge reading, which means adjusting it at the beginning of the roast and maybe once or twice during the roast to maintain the same pressure. Some day I may experiment with increasing air flow later in the roast, but I'm not there yet :-)

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CarefreeBuzzBuzz

#24: Post by CarefreeBuzzBuzz »

aabud wrote:......

Two... the setting on the damper dial does not correspond to a certain pascal pressure very precisely. A certain specific setting might vary from 3 to 7 pascals - plenty enough variation to mess with my roast curves. I don't know if there's a little play in the mechanism or it's dynamics of the roaster, but I trust the gauge reading.
.......
I thought the new BC2's had a variable fan and the damper? If that is so, have you tried the fan dial? Also if you have a Phidget 1136 you can also measure air pressure and log it into Artisan as an Extra Device so that you have LCD readings. Trick is to set an Alarm to Tare the fan at the start of each roast.
CarefreeBuzzBuzz
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aabud (original poster)

#25: Post by aabud (original poster) »

Buckey recommends leaving the fan at 100% and controlling air with the damper, which is what I'm doing. My issue isn't controlling the air, the damper and fan work fine for controlling... the issue I ran into is that a given fan setting and a given damper setting don't produce a consistent pressure, roast to roast. I need the Magnehelic gauge to know what to set the damper/fan for each roast, because I can't rely on a specific fan/damper settings to produce a specific pressure.

If I've got the unit straight here... I'm seeing 1 pascal make a big difference. I'm concerned about the accuracy of that Phidget, which I think is plus or minus 2 kpa (2000 pascal). If I read the specs right on the gauge, it's accurate to 2% of it's scale, so around plus or minus 0.06 pascal (0-30pa x .02).

I do like the idea of recording the pressure and being able to set an alarm if it varies too much from what I want.

Could be that I'm working on a roasting profile that has too low a pressure/too low a gas volume, and that's making me too sensitive to pressure. So maybe I'd be better off with higher pressure and higher gas volume... I kinda got started down this path because I hit a roast I really liked and stumbled on this issue in trying to repeat it.

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CarefreeBuzzBuzz

#26: Post by CarefreeBuzzBuzz »

aabud wrote:Buckey recommends leaving the fan at 100% and controlling air with the damper, which is what I'm doing.
I would try both ways honestly. Leave the damper open and try just the fan to test variability. You already have the gauge, do you think its accurate and repeatable itself? Are the marking discrete enough to be repeatable and record into Artisan with Events. The original gauges that MCR had on the 500 grams units were not, but I don't know what they are doing now. Can you post an image of yours?
CarefreeBuzzBuzz
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aabud (original poster)

#27: Post by aabud (original poster) »

Tried controlling via a wide open damper and instead using the fan speed dial, and I would judge that to be much worse - damper dial changes produce much more linear and stable pressure gauge readings than does the fan speed dial. It "feels" to me like there's not much torque in that fan motor at reduced settings and it struggles to maintain a consistent RPM - just saying that base on how it sounds. There was also a big lag in gauge readings as relates to fan speed dial changes.

Bottom line - I'm glad I have a nice, accurate, low end (0-30 pascals) pressure gauge to use to manage air flow - I didn't realize how necessary that was for my roasting until recently.

I found a pressure differential sensor (Sensirion SDP610-025Pa) that's similar in range and accuracy to the Dwyer Magnehelic gauge I have, so have put that on my mod list for tracking pressure. I'm Arduino based for mods and this sensor so should be usable.

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CarefreeBuzzBuzz

#28: Post by CarefreeBuzzBuzz »

I am not sure you have the 1136 correct.

Its range is plus or minus 2kpa with an max error of 6.5%.

Product Specifications

Sensor Properties
Sensor Type Gas Pressure (Differential)
Controlled By VoltageRatio Input
Sensor Output Type Ratiometric
Pressure Differential Min -2 kPa
Pressure Differential Max 2 kPa
Case Pressure Max 75 kPa
Pressure Resolution 5 Pa
Measurement Error Max ± 6.5 %
Warm-up Time 20 ms
Response Time Max 1 ms
Electrical Properties
Supply Voltage Min 4.8 V DC
Supply Voltage Max 5.3 V DC
Current Consumption Max 10 mA
Output Impedance 1 kΩ
Output Voltage Min 500 mV DC
Output Voltage Max 4.5 V DC
Physical Properties
Operating Temperature Min 10 °C
Operating Temperature Max 60 °C
Recommended Tubing Size 3⁄32″
CarefreeBuzzBuzz
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Artisan Quick Start Guide
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okmed

#29: Post by okmed »

Roy, what is the pascal reading on your magnehelic gauge when the damper is wide open and the motor is at full speed ?

aabud (original poster)

#30: Post by aabud (original poster) » replying to okmed »

Easily pegged on the high end of the 30 pascal gauge. From memory, I think it pegs around 7 or 8 on the damper's 10 scale (with full speed fan.