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Date: 08 Feb 2007 18:27:55
From: yoma
Subject: Digital Hottop Tweak
A Faster Roast Profile
-----------------------

I've been getting my best roasts out of the Hottop with a 9:00min to 1st
crack, +3:00 to 5:00+ min to 2nd, using the following params:

Coffee: 200g
Program: 21:59
Drop in: 13:30 (Hottop countdown display)
1st crack: ~4:30 ...
Ambient Temp: 15C~23C

As the coffee mass hits 200C (via my own thermocouple), the Hottop
chamber thermistor can be anywhere b/w 190C to 200C.

When it's at the high end (to 200C), then it usually proceeds nicely
into and past the 1st crack, by easing off the heat early rather than later.

I've had some roasts go for up to 3min past the end of the 1st without
getting into the 2nd - with great results.

The problem is when the hottop is at the low end (190C), it tends to
push through the cracks a bit too fast (however still much better roast
than the lame built-in profiles where you drop in the beans at the beep,
shut your eyes, hope for the best).

If anybody tries these roast params. I'd be interested to hear the outcome.


The Tweak
---------

To fine tune (control) the crucial latter stage of the roast, I added a
POT (50k potentiometer in parallel) to the thermistor (hottop
temperature sensor).

If the hottop temperature is at the low end (190C) as it nears the first
crack, I can switch in the POT and dial up the temp. toward 200C which
makes the Hottop controller begin to ease off the heat.

I've also wired in a POT (in series) to be able to dial down the temp.
This could be useful to extend the late stage of a roast it the
temperature is nearing the automatic bean eject.

If anyone's interested I can post the details in separate message,
rather than clutter up this message.


Upgrade
-------
Having established for myself the that built in roast
profiles/controller in the digital HotTop model do a great injustice to
the unit, I was really looking forward to the new upgrade model.

But considering the price, programming complexity (which I attribute
partly to the poor design location/housing of the thermistor), lack of
data logging, inherent temperature monitoring inconsistencies, I think
I'll roll my own...


**Alternative Upgrade Ideas**


1. Thermistor Tweak
--------------------

A very simple (almost trivial) way to tweak the heater during a roast,
as described above.


2. Manual Temperature and Fan Control
-------------------------------------

Simple timer based PWM to drive the heater and fan instead of the built
in PIC controller. Provides a very cheap manual roast mode (can be
switched out of course). No need to muck around with delayed coffee
drop in and fighting the in built profile with the thermistor tweak.

(details available soon)


3. Addition Micro Controller
----------------------------

Make it do what the 8828P should have done.






 
Date: 08 Feb 2007 20:13:52
From: Nick Cho
Subject: Re: Digital Hottop Tweak
I mean, THIS?
http://www.hottopusa.com/news.html


On Feb 8, 11:04 pm, "Nick Cho" <portafil...@gmail.com > wrote:
> Have folks seen this yet?http://www.hasblog.co.uk/?p=185
>
> On Feb 8, 2:27 am, yoma <y...@yoma.net.au> wrote:
>
> > A Faster Roast Profile
> > -----------------------
>
> > I've been getting my best roasts out of the Hottop with a 9:00min to 1st
> > crack, +3:00 to 5:00+ min to 2nd, using the following params:
>
> > Coffee: 200g
> > Program: 21:59
> > Drop in: 13:30 (Hottop countdown display)
> > 1st crack: ~4:30 ...
> > Ambient Temp: 15C~23C
>
> > As the coffee mass hits 200C (via my own thermocouple), the Hottop
> > chamber thermistor can be anywhere b/w 190C to 200C.
>
> > When it's at the high end (to 200C), then it usually proceeds nicely
> > into and past the 1st crack, by easing off the heat early rather than later.
>
> > I've had some roasts go for up to 3min past the end of the 1st without
> > getting into the 2nd - with great results.
>
> > The problem is when the hottop is at the low end (190C), it tends to
> > push through the cracks a bit too fast (however still much better roast
> > than the lame built-in profiles where you drop in the beans at the beep,
> > shut your eyes, hope for the best).
>
> > If anybody tries these roast params. I'd be interested to hear the outcome.
>
> > The Tweak
> > ---------
>
> > To fine tune (control) the crucial latter stage of the roast, I added a
> > POT (50k potentiometer in parallel) to the thermistor (hottop
> > temperature sensor).
>
> > If the hottop temperature is at the low end (190C) as it nears the first
> > crack, I can switch in the POT and dial up the temp. toward 200C which
> > makes the Hottop controller begin to ease off the heat.
>
> > I've also wired in a POT (in series) to be able to dial down the temp.
> > This could be useful to extend the late stage of a roast it the
> > temperature is nearing the automatic bean eject.
>
> > If anyone's interested I can post the details in separate message,
> > rather than clutter up this message.
>
> > Upgrade
> > -------
> > Having established for myself the that built in roast
> > profiles/controller in the digital HotTop model do a great injustice to
> > the unit, I was really looking forward to the new upgrade model.
>
> > But considering the price, programming complexity (which I attribute
> > partly to the poor design location/housing of the thermistor), lack of
> > data logging, inherent temperature monitoring inconsistencies, I think
> > I'll roll my own...
>
> > **Alternative Upgrade Ideas**
>
> > 1. Thermistor Tweak
> > --------------------
>
> > A very simple (almost trivial) way to tweak the heater during a roast,
> > as described above.
>
> > 2. Manual Temperature and Fan Control
> > -------------------------------------
>
> > Simple timer based PWM to drive the heater and fan instead of the built
> > in PIC controller. Provides a very cheap manual roast mode (can be
> > switched out of course). No need to muck around with delayed coffee
> > drop in and fighting the in built profile with the thermistor tweak.
>
> > (details available soon)
>
> > 3. Addition Micro Controller
> > ----------------------------
>
> > Make it do what the 8828P should have done.




 
Date: 08 Feb 2007 20:04:36
From: Nick Cho
Subject: Re: Digital Hottop Tweak
Have folks seen this yet?
http://www.hasblog.co.uk/?p=185

On Feb 8, 2:27 am, yoma <y...@yoma.net.au > wrote:
> A Faster Roast Profile
> -----------------------
>
> I've been getting my best roasts out of the Hottop with a 9:00min to 1st
> crack, +3:00 to 5:00+ min to 2nd, using the following params:
>
> Coffee: 200g
> Program: 21:59
> Drop in: 13:30 (Hottop countdown display)
> 1st crack: ~4:30 ...
> Ambient Temp: 15C~23C
>
> As the coffee mass hits 200C (via my own thermocouple), the Hottop
> chamber thermistor can be anywhere b/w 190C to 200C.
>
> When it's at the high end (to 200C), then it usually proceeds nicely
> into and past the 1st crack, by easing off the heat early rather than later.
>
> I've had some roasts go for up to 3min past the end of the 1st without
> getting into the 2nd - with great results.
>
> The problem is when the hottop is at the low end (190C), it tends to
> push through the cracks a bit too fast (however still much better roast
> than the lame built-in profiles where you drop in the beans at the beep,
> shut your eyes, hope for the best).
>
> If anybody tries these roast params. I'd be interested to hear the outcome.
>
> The Tweak
> ---------
>
> To fine tune (control) the crucial latter stage of the roast, I added a
> POT (50k potentiometer in parallel) to the thermistor (hottop
> temperature sensor).
>
> If the hottop temperature is at the low end (190C) as it nears the first
> crack, I can switch in the POT and dial up the temp. toward 200C which
> makes the Hottop controller begin to ease off the heat.
>
> I've also wired in a POT (in series) to be able to dial down the temp.
> This could be useful to extend the late stage of a roast it the
> temperature is nearing the automatic bean eject.
>
> If anyone's interested I can post the details in separate message,
> rather than clutter up this message.
>
> Upgrade
> -------
> Having established for myself the that built in roast
> profiles/controller in the digital HotTop model do a great injustice to
> the unit, I was really looking forward to the new upgrade model.
>
> But considering the price, programming complexity (which I attribute
> partly to the poor design location/housing of the thermistor), lack of
> data logging, inherent temperature monitoring inconsistencies, I think
> I'll roll my own...
>
> **Alternative Upgrade Ideas**
>
> 1. Thermistor Tweak
> --------------------
>
> A very simple (almost trivial) way to tweak the heater during a roast,
> as described above.
>
> 2. Manual Temperature and Fan Control
> -------------------------------------
>
> Simple timer based PWM to drive the heater and fan instead of the built
> in PIC controller. Provides a very cheap manual roast mode (can be
> switched out of course). No need to muck around with delayed coffee
> drop in and fighting the in built profile with the thermistor tweak.
>
> (details available soon)
>
> 3. Addition Micro Controller
> ----------------------------
>
> Make it do what the 8828P should have done.




 
Date: 08 Feb 2007 16:32:25
From: JulesG
Subject: Re: Digital Hottop Tweak
Quite interesting ! I presently use a iR2 and I am thinking of
upgrading to a more sophisticated unit that can roast more at a time.
You use a thermocouple in addition to the built in temp. sensor. The
HotTop being a rotating drum, how do you install the thermocouple ?
Do you feel that a TC is needed or is the built-in sensor adequate ?



  
Date: 09 Feb 2007 13:27:01
From: yoma
Subject: Re: Digital Hottop Tweak
JulesG wrote:
> Quite interesting ! I presently use a iR2 and I am thinking of
> upgrading to a more sophisticated unit that can roast more at a time.
> You use a thermocouple in addition to the built in temp. sensor. The
> HotTop being a rotating drum, how do you install the thermocouple ?

I 'drilled in' 2 TC's through the bean insertion chute (I'll try put
some pics up somewhere).

> Do you feel that a TC is needed or is the built-in sensor adequate ?

If I had to choose - and couldn't hack my hottop) - I'd sell my hottop
and keep the temperature logger.

The inbuilt sensor is too far removed from the beans. There is too much
variation depending on:

- ambient temperature
- ambient heat loss (significant if you roast outside and there's any
breeze at all)
- mass of the coffee
- type of the coffee
- age (cleanliness) of the filters
- whether it's the first roast in a batch (it measures hotter for
subsequent roasts because it measure the temperature of the chamber wall)

It's impossible to constrain all of the above within the necessary limits.

Unfortunately without the hacks, having your own TC's will at least let
you helplessly watch many a bad roast in progress (with the digital model).

The digital hottop inbuilt profiles are the way they are because of the
sensor location/design. At best the controller tippy toes around like 3
blind mice roastmasters.


The Low Down (IMHO)
-------------------

Having hacked and fought my way through 170 hottop roasts...

The (unmodified) digital model is a not worth it. Maybe it doesn't
matter as much if you're not going to use it for espresso. It's also
probably better than most other home-roasters.

I used to think it was ok and could get some good roasts out of it, but
also too many unacceptable roasts as well.

OTH, if you don't mind doing a little work under the hood, the hottop
can consistently produce phenomenal roasts.


Programmable Model
------------------

They should of replaced the current in-built in chamber sensor with a
new probe into the bean mass. Maybe they will eventually.

Anyhow, no doubt the new model/upgrade will make it a much better
roaster. I think it's consistency may improve to some extent.

And if you look closely at the online programming guide, the operator
can manually override any 'programmed segment' during the roast. This
is how the new $480 controller handler sensor variations.

The thermistor tweak does it for $6 to $12.


  
Date: 08 Feb 2007 18:27:29
From: I->Ian
Subject: Re: Digital Hottop Tweak
On 8 Feb 2007 16:32:25 -0800, "JulesG" <jules.gobeil@videotron.ca >
wrote:

>Quite interesting ! I presently use a iR2 and I am thinking of
>upgrading to a more sophisticated unit that can roast more at a time.
>You use a thermocouple in addition to the built in temp. sensor. The
>HotTop being a rotating drum, how do you install the thermocouple ?
>Do you feel that a TC is needed or is the built-in sensor adequate ?

Built in sensor is off by as much as 70F from the bean temp and
flattens at 1st crack to be completely useless to judge the end of
roast temperature.
http://www.ielogical.com/coffee/HTvsBean.gif

Randy G has instructions for a HT TC installation.
http://home.surewest.net/frcn/Coffee/HowToHottopTemp.html

My Beast
http://www.ielogical.com/coffee/HTFan.jpg