Is there an available Phidget that pairs with a digital K-type thermocouple, that I can use with Artisan? - Page 2

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

#11: Post by jtferraro (original poster) »


I checked and the tip of my TC seems to still be in good shape - insulation is in place. I think only the very tip is exposed.

Gotcha re: what attributes to accuracy in TCs. Makes sense - thanks. One issue I've noted with my inexpensive TC is that if the wire is bent or if you move it too much while it's reading the temperature of the beans chamber, it really jumps around and reports incorrect temps. I have to set it and leave it alone, at least until the end of the roast.

Yes, after a few orders from Sweet Maria's, I've gone back to slightly more affordable Nicaraguan greens from Primos (I still have 2 lbs. of SM though, but they're both espresso blends - one being a holiday varietal they recently sent, called 'Polar espresso').

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#12: Post by civ »

jtferraro wrote: ... tip of my TC seems to still be in good shape ...
Make sure it does not touch any metal parts or the element.
jtferraro wrote: ... issue I've noted with my inexpensive TC ...
That will happen regardless of what type/quality of TC you have. 8^D
This has already been argued and explained quite well here at HB so I'll try to make it short.

Take into account just what it is you are attempting to measure.
ie: the temperature of a mass of coffee beans moving around in a fast/random manner inside an enclosed space.

It is not like when you put a thermometer inside a glass of water to measure it's temperature as it is heating up.
The water molecules move around faster and faster as the temperature rises while countless zillions touch the TC at the same time evey micro-second.

The probe is immersed in the water and this immersion makes the TC generate a very steady analog signal to send the thermometer.
Depending on the thermometer's design/circuit/speed etc., it will interpret and calculate a number to show on the LCD.

This is not the case with the beans, where only a very small number of them touch the TC every second.
ie: think of the tip of a ball point pen touching a basketball once every so often.

So what you are getting is just a general idea of the beans' badly calculated average temperature.

Not to mention that at the start of the roast, you are only measuring the hot air inside the roasting chamber.
You are only getting a real-ish bean temperature once you are past the turning point.

To get a proper reading the TC has to be kept still in the same (carefully selected) place.

It has to be kept still so whatever happens to it will happen (mostly) in the same manner throughout the roast.
And in the same place to be able to have consistency throughout every roast.

There's a lot more to read about this here at HB.
I hope my screed at lesast puts it all in perspective for you.
jtferraro wrote: ... back to slightly more affordable Nicaraguan greens ...
You may want to consider purchasing the least expensive 'comfort beans' you can get from quality purveyors.
And stick to the same bean till you have achieved roasts you can faithfully achieve consistency with.
One less variable in a hobby with far too many of them really helps a lot.

A higher quality or more expensive* bean will not get you better results, you get there with enough patience and practise.
Using those beans to learn how to roast will probably make your wallet thinner faster.
* not the same thing

Sure, you can learn how to drive in a Maserati or a Rolls Royce but it will cost you a fortune in petrol and insurance.

From the very start I made it a point to drink everything I roasted unless it was really very bad.
It's been a sure fire way to always pay attention to what I was doing and keep from getting carried away with roasting another batch without previously considering all aspects of what went on with the last one, one double from a badly roasted batch at a time.

You really learn a lot that way. 8^D
It's the amateur roaster's eat your own dog food method to success.



jtferraro (original poster)

#13: Post by jtferraro (original poster) »

Thanks for the info on how to obtain more accuracy with the TC. Since mine is the K type and not 'hard mounted', it moves around within the roast chamber. That said, if it's working properly, it appears very accurate...or at least very consistent and that's primarily what I'm looking for. BTW, I don't often go to 2nd crack, so was wondering at what temperature ranges I should expect it (potentially as a means to mitigate and, rather, draw the roast out longer via DEV phase).

The green beans I've been using seem cheap enough and like you, I always try to drink everything I roast! I'm onboard with eat your own dog food

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#14: Post by civ »

jtferraro wrote: Thanks ...
You're welcome.
jtferraro wrote: ... is the K type and not 'hard mounted' ...
TC type and mounting methods are not related.

There are a lot of different types of TCs, made from different alloy combinations, each with it's own range and use.
The K type is an inexpensive general use therrmocouple, made from chromel/alumel alloys and can cover a −200 °C to +1200 °C range.
Perfectly suited to the use we are giving it.

But you definitely need to keep it from moving around.
ie: keep it in the same place throughout the roast and in every roast.
That is where you will get consistency from, otherwise your readings will not be useful.

Find a way (there's a lot on HB and the web on popper roasters) to fix a stiff wire going down into the chamber and tie the TC to it.
Or maybe through a small hole from below/the side.
Adjust it so it is far away from the heating element but in the midst of the beans moving around.
jtferraro wrote: ... at what temperature ranges I should expect ...
You may want to to do some reading on roasting phases, times and temperatures.
It's rather out of my league to explain all that, I may end up confusing you.



jtferraro (original poster)

#15: Post by jtferraro (original poster) »

Yes, I realize TC type and mounting methods are unrelated but I typically see rigid types mounted and 'flexy' types often not mounted. That said, I have a lot to lean about all the different types and alloy combinations. I think it only moves around in the beginning, as the beans are spinning about the chamber, but once the beans start bouncing vertically, it seems to maintain its position. The temp readings seem stable - gradually increasing and decreasing once I turn off the heating element, then increasing again once I turn it back on. I guess it makes sense though to completely lock it down - so thanks for the suggestion re: fixing a stiff wire down the chamber and tying the TC to it. I believe my latest popper, a 1400w OG Pumper, actually has a hole in the butter tray that may lead to the heating element, in which I can affix the TC, but I have yet to experience roasting with it and I fear said hole will exclusively lead to the heating element, not where the beans mass is, at the base of the chamber. We'll see...

OK, I'll look up what temperature ranges & times are most often associated with 2nd crack. I've definitely roasted to the start of 2C before, but it was prior to receiving the TC, so I don't specifically know what temps are associated with it. Perhaps it's simply 'X amount of time post 1C', assuming temps don't increase, or some kind of formula is applied to compensate for temps increasing? At any rate, I'll let you know what I find out from my experiences.

Thanks again CIV,