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Breaking the 165F Barrier
Rallen
Hey there!

In my own HotTop, I have simply added a momentary switch to one of the cables from temperature sensor, in order to be able to disable it and roast back-to-back without waiting for the cool down.

Last weekend, I tried doing the exact same thing in a friends KN-8828B-2-K roaster. Unfortunately, it turned out that his newer model has a built in security feature that reads max temperature when nothing is received from the sensor. Because of this, the mod doesn't work.

We still want the roaster to roast back to back, so I am now working on another solution using a DPD switch, to change between measuring the real temperature in the chamber and measuring "something else" that is lower than the desired 165F.

I can't quite figure out what this something else should be. I have thought of two possibilities; either placing a similar sensor away from the chamber and forcing the machine to read this while starting the next roast, or faking the reading somehow.

Can someone please tell me what kind of sensor I am dealing with? RTD, TC or something else?

Would it be possible to fake the reading by sending the right voltage or resistance on the alternative connection, or should I just add a similar sensor in a cooler place?

Thanks already!
turtle
This is what has kept me from updating my B model to a B-2K model.

Still waiting to see what the work around is as I do like being able to back to back roast in a hot roaster
Mick - "Drinking in life one cup at a time"
"I'd rather be roasting coffee"

Roaster 1: San Franciscan SF-1
Roaster 2: Hottop B-2K+
Roaster 3: Behmor 1600 +
Grinders: Modified Super Jolly - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
JimG
I don't necessarily suggest the following is a good idea.

The following will not work on a non-K Hottop roaster.

But, notwithstanding the above, there is an easy solution to your problem. Simply short the input terminals of the sensor together with a piece of copper wire. This causes the control board to read a 0.0mV signal coming from the type K thermocouple. This will trick the control board into measuring ambient temperature in the roast chamber. I can imagine that some kind of switch could be rigged up to make this happen.

(A similar thing could be done with non-K roasters that have button-style NTC sensors. The idea would be to measure the resistance of the OEM sensor at, say, 70F. Then temporarily substitute a discrete resistor of that value in place of the NTC sensor, again using some kind of switch).

Reminder: I don't necessarily think this is a good idea limb

Jim
ginny
I am curious as to the actual wait time between using it the "regular" way and adding a swicth to use it right away...

how much time are you going to save by forcing the HT to do back to back?


thanks in advance,



ginny
Barrie
In addition to the mod I imagine one needs to put $110 aside for an earlier replacement of a regularly over-heated motor. Grin
Barrie (San Diego, CA)
"So much to learn, so little time."
Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).
turtle

Quote

ginny wrote:

I am curious as to the actual wait time between using it the "regular" way and adding a swicth to use it right away...

how much time are you going to save by forcing the HT to do back to back?

thanks in advance,

ginny


I've never timed the wait for a complete cool down as my first roast EVER was after I modified my B model with the temp safety interrupt (did the mods before my first roast with the machine).

It is not so much the time but the convince. As soon as the cool down cycle ends my old B model reads around 285-325 With the button mod interrupt I can start a new batch at any time (add fresh beans directly into the roaster @ 300 +/-) as well as keep the previously roasted beans in motion in the cooling tray. I can start my 2nd or 3rd etc batch while cleaning up the first roast.

Without an interrupt to the 165 safety cool down temp I would be reading a book, tapping my foot, or in general wasting time waiting on a dumb machine to come to the conclusion that it is safe to be a dumb machine.

I think that the cool down safety is a good idea and I am sure it is necessary to protect the manufacture but once you know what is happening it is more a hindrance than a good idea.

For me I will stick with the old style non K type B model as it is much easier to trick it into thinking it is a "real" coffee roaster and not a home appliance.

Don't get me wrong. I really, really, really, LIKE my B model roaster and could not imagine roasting coffee in anything else. No I don't want a gas fired 1 kilo batch roaster or anything larger or smaller. It is just fine for me and I will live with its quirks.
Mick - "Drinking in life one cup at a time"
"I'd rather be roasting coffee"

Roaster 1: San Franciscan SF-1
Roaster 2: Hottop B-2K+
Roaster 3: Behmor 1600 +
Grinders: Modified Super Jolly - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
Randy G
The wait between roasts. Here is some data I gathered the other morning:
I did an empty test without beans. Here is the data:
------------ --------------- temperature Time
------------ ------------ ("B-2K" display) (stopwatch)
EJECT at end of roast ---------- 428F. ------ 0:00
End of cool cycle ---------------- 332 --------- 5:00
Re-Start (auto cool begin)*1 -- 325 --------- 5:30
Auto cool down ends ------------163 -------- 13:15
Add beans Signal --------------- 167--------- 14:28

YMMV, but this should give you some idea, all FWIW, of course.

Life's too short to drink bad coffee.
smico

Quote

Barrie wrote:

In addition to the mod I imagine one needs to put $110 aside for an earlier replacement of a regularly over-heated motor. Grin

To control for that, I added additional cheap thermocouple and plot temperature of the motor in Artisan. When temperature of the motor drops to 60C I start the new roast to keep max temp under 80 to 85C.
Time saving averages around 0.34 seconds per roast :)
But it adds up.
Edited by JackH on 02/27/2014 3:06 PM
Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario
smico
Oh boy, my spelling doesn't work today.
Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario
Rallen
Thanks for the suggestions and comments to all of you! I am well aware that it might shorten the life of the motor, but I find that its really worth it. Personally, I am using a HotTop from '06 which I bought about a year ago. In the time i've owned it, I have never done less than 3 roasts in a row. The motor and everything else still works like a charm!

Quote

JimG wrote:

But, notwithstanding the above, there is an easy solution to your problem. Simply short the input terminals of the sensor together with a piece of copper wire. This causes the control board to read a 0.0mV signal coming from the type K thermocouple. This will trick the control board into measuring ambient temperature in the roast chamber. I can imagine that some kind of switch could be rigged up to make this happen.


If this truly works, It'll be the perfect fix for the problem. I had actually thought about shorting the wires, but I suspected that it would just have the same effect as disconnecting them - no measurement, and a reading of max temp.
Are you sure this won't simply do the same? :-)
JimG

Quote

Rallen wrote:
Are you sure this won't simply do the same? :-)

I need to stress that this only applies to the K roasters!

Shorting the two pins of the sensor connector together yields exactly the same effect as a thermocouple whose temperature is the same at the "hot" junction and the "cold" junction. Both cause the control board to read 0.0mV across the input pins.

Jim
Rallen

Quote

JimG wrote:

Quote

Rallen wrote:
Are you sure this won't simply do the same? :-)

I need to stress that this only applies to the K roasters!

Shorting the two pins of the sensor connector together yields exactly the same effect as a thermocouple whose temperature is the same at the "hot" junction and the "cold" junction. Both cause the control board to read 0.0mV across the input pins.

Jim


Thanks. That sounds reasonable!! I was planning to hook it up with a DPD switch with one of the positions simply shorted. But then I thought.. What would happen if I hooked it up to a momentary switch like this?

b.imgdrp.com/lZoi.png

I guess it would allow the current to pass trough in normal use, and successfully short the wires when pushed. But what about the other way around? Will it harm the sensor to be shorted at the same time?
JimG
Should not hurt anything. Best if you use type K wire, though, from the new switch back to the input pins. And don't count on being able to solder the type K wire Roflmao


A thermocouple is nothing more than a dumb old piece of wire made by joining two lengths of different alloy wires. It generates a tiny voltage (<50mV) when the junction of the 2 alloys gets hot. When you short the "cold" ends together, a small current will start flowing around what is now a loop. But I mean small.

On the control board side, the circuitry to read thermocouples is pretty passive. Usually it is just a very high input impedance op amp, or something similar. So it doesn't care a bit if there is a short across the input terminals. It just assumes the hot end is not very hot, and goes on its merry way.

Jim
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