BC-2 Purchase, Setup, and First Roasts - Page 4

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

#31: Post by aabud (original poster) »

CarefreeBuzzBuzz wrote: Pressure Resolution 5 Pa
Since what I'm seeing is that a difference of 1 Pa affects the roast, and I'm trying to maintain a 4 pascal pressure, I'm thinking I would want something that has a resolution of something like 0.1 Pa. The Sensirion I referenced has a range of -25 pascals to 25 pascals, and if I interpret the phrase "12 bit resolution"... then Sensirion resolution is better than 0.01 pascal. The manual Magnehelic gauge that I'm finding works for me has a range of 0 to 30 pascals. The 1136's range and resolution just doesn't look like it would work for what I'm trying to do. I know at least a few people are using the 1136's... makes me curious to look at the pressure readings they are recording. Maybe I'm running pressure that's way lower than most?

Team HB

#32: Post by baldheadracing »

Pressure readings are not comparable as, for example, pipe diameter, layout, and fan&damper location directly affect the pressure reading (as does temperature, what phase the coffee is in, the moisture content of the green, decaf or not ...).
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

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#33: Post by okmed »

Thanks Roy. I asked the question because I'm considering the purchase of a BC-2 and was going to pick up a magnehelic locally.
The 0-30 pascal is not available but 0-60 is. I'm thinking that would be good to avoid pegging the gauge when fully opening the damper to clear chaff at the end of a roast but wonder if the resolution would be adequate during roasting. What do you think ?

aabud (original poster)

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

I would prefer the 0-30 over the 0-60, but I think the 0-60 would work - there' plenty of visual distance on my gauge, for example, between a 4 and 5 reading, so if I cut that in half (e.g with a 0-60 scale), I could still comfortably tell the difference. I don't think you have to worry about the pegging unless you're going over the max pressure for the gauge, which is loads higher than the max reading.

Make sure you calibrate the gauge after you install it (it was easy) - the BC-2 Mag gauge instructions (http://nebula.wsimg.com/45199583e3a3b42 ... oworigin=1) omit mentioning that. How to calibrate will be either in the docs you get with the gauge, or you can find them online. As I recall, it was basically open up both ports so there is no pressure differential and then turn a screw on the front until the needle points to zero.

aabud (original poster)

#35: Post by aabud (original poster) »

FYI - That little Sensirion SDP610-025Pa worked like a champ - the readings from it match what I'm seeing on the gauge. I just put a tee in the line, so I've got them both active. I haven't run a whole roast with it yet, but looks like the raw data from the sensor will need a bit of smoothing. Using a damper setting that got me 5 pascals of pressure, the Sensirion bounces around a bit between 4 and 6. The analog itself will twitch also, but not quite as much... I'd say between 4.75 and 5.25. The digital sensor maxes out at 27 pascals (it's the 025pa model), so if you give one of these a whirl, you might need the 100pa or different version if your pressures are higher.

I've got another thread started for the mods I'm doing to my BC-2 so I'll post pics and an actual roast graph when I get one.


#36: Post by Choll »

I've enjoyed your posts here and in your mod post too. I roasted on a Behmor for a dozen years, then got a Huky after lurking around here. The Huky is nice but I just got my own BC-2 a couple days ago. It is quite a bit more roaster than the others. I look forward to learning this new roaster. Thanks again for your posts.

aabud (original poster)

#37: Post by aabud (original poster) »

Welcome to club BC! I came really close to going the Huky route. After you get the BC up and running, I'd be interested to hear how you compare the two.

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#38: Post by okmed »

aabud wrote:Using a damper setting that got me 5 pascals of pressure, the Sensirion bounces around a bit between 4 and 6. The analog itself will twitch also, but not quite as much...
When I was still on the tools we would use a device called a "snubber" to dampen pulsation of gauges mounted on pumps. The snubber was basically an orifice that dampened pressure pulsation. You might try and jury rig your own snubber by soldering the inlet side of your tee and then drill a very tiny hole in the solder for a orifice.

aabud (original poster)

#39: Post by aabud (original poster) »

Interesting idea, and the more I thought about it, the more I liked it, so gave it a go.

First attempt, was with a very small hole, and the resulting pressure reading has a large reduction error (like reading only 10% of the actual pressure). Second attempt was with a bigger hole, and that also reduced the pressure materially( like, by 50%). Even reduced by 50%, the pressure readings were kinda jumpy, so that tells me the issue isn't so much with the pressure itself, but perhaps more in the instrument. For a third experiment, I just tried various forms of kink in the line, and that was a way of sort of varying the restriction... same result.

I've got an improved digital smoothing mechanism on it, which has helped quite a bit - it's usable for recording so I remember what I did, which was my goal.

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#40: Post by okmed »

aabud wrote:The analog itself will twitch also, but not quite as much... I'd say between 4.75 and 5.25.
Did the orifice take the twitch out of the analog reading ?