Hottop Manual Roast Controls (for Digital Model)

[emckissock]

Re: Hottop Manual Roast Controls (for Digital Model)

Very brief update. My hottop has an interim manual heat control and fan still under hottop control.
16 min roast is now easy (could go faster). One side insulated with a silicone pot holder as I didnt want to block air vents on other side.

Next stage will be to try an arduino microcontroller and add multi thermocouples.
I will shortly be buying a TC4 shield for the interface to thermocouples.
If any other snobs are interested in playing with arduino/catuai/bourbon etc, or are already doing so and want to share experience, parts etc. Let me know. Doesnt need to be on a hottop, could be popper, behmor, coretto, I-coffee, TO,...

[emckissock]

Re: Hottop Manual Roast Controls (for Digital Model)

ALL is good.

Helps to look and understand what is going on rather than just accepting things...

Yeah, with a bit more time Id have done that, but wanted to get it to you quickly, had anyone known what was about to hit QLD, things would have been very different...

Fire blanket from Bunnings is a good start...  Just need to think about what air flow and where is best placed.

L/H side to insulate and reduce losses from teh elements is the first step...

Keep going with yours and many thanks to Yoma  once again...

Maybe not from bunnings, but great thought should fit nicely.

And once again, huge thanks to yoma. It will be sooooo much fun learning how to tweak this so I can manually roast to the profile I want.

[A_M]

Re: Hottop Manual Roast Controls (for Digital Model)

ALL is good.

Helps to look and understand what is going on rather than just accepting things...

Fire blanket from Bunnings is a good start... Just need to think about what air flow and where is best placed.

L/H side to insulate and reduce losses from teh elements is the first step...

Keep going with yours and many thanks to Yoma once again...

[emckissock]

Re: Hottop Manual Roast Controls (for Digital Model)

1: After much mucking about and lost transport...  Finally got it home.

2: Studied the cct and was able to piece back together the bread board which had taken the odd tango step or two during its travels...

Glad you got it, I was about to ask how things were going.

the circuit board stuff ups were probably my doing, only had a brief glance at it before shoving components back in place and I suspect most fell out when I braked suddenly and it took a dive off the back seat. Sorry about that.

Special insulation for between the walls in progress.

What are you using for insulation? Sounds like a good idea.

[A_M]

Re: Hottop Manual Roast Controls (for Digital Model)

BIG Heads up for Yoma [smiley=tekst-toppie.gif]


1: After much mucking about and lost transport... Finally got it home.

2: Studied teh cct and was able to piece back together the bread board which had taken the odd tango step or two during its travels...

3: Have a thermistor that might just replace teh standard HT one (same temp response profile) but can sit into teh bean mass. Existing one in the lid was Open cct.

4: Re set teh unit to standard and tested... Alll OK

5: Stripped all removable bits for soaking and cleaning.

Special insulation for between the walls in progress.

Box with Vero Board x 2 (Fan and Heater) with master slide switch to enable external or standard HT controls on teh drawing board.

[JavaB]

Re: Hottop Manual Roast Controls (for Digital Mode

yoma,

That roast was using Malibar which requires at least 7 days resting so Ill be tasting it soon. The inspiration for this was that Malibar needs a lengthy FC to SC gap for best flavour (based on Corretto experience) and a standard HT just wont do that.......

Yes, Ill be doing more manual roasts. Greg Pullman and I will be exchanging more HT and Gene roasts to see how the results compare. Ill give your suggestion a try - but not with the Malibar as it also benefits from a slow ramp to FC..... however I have many other SO where your method would give better results.....

The HT appears to be a very flexible roaster.... but not as it comes "out of the box"

[yoma]

Re: Hottop Manual Roast Controls (for Digital Mode

Hi JavaB,

Curious to know how your tasting went.
Also, do you plan to try any further manual roasts?
If so, you may like to consider the following diffs.
- Drop in the beans 2mins after the beeps...
   Hottop temp approx. 137C, TC temp approx, 230C
- Use around 220 to 225g green.
This gets to FC in approx. 10min.
Eject approx. 3 to 4min. later.
Ive found getting to FC sooner, allows more time to SC, to develop the flavour without cooking off the oils.

Regards,
yoma.

[JavaB]

Re: Hottop Manual Roast Controls (for Digital Mode

Progress report....

Well prior to fitting the PID control I thought I would try manual control to see what was possible....

Using a triac control (the same could be done with Yomas circuit) I controlled the heater between off and 100% power - this was done since I will be using a SSR to connect directly to the element and not via the main board when I fit the PID.

I used the CS roast monitor - which is excellent as it give a rate of change of temperature display - and a thermocouple in the bean mass to detect the temperature.....

The HT controlled the fan as per usual and beans were loaded on the beep - also as per usual.

The heaters were on 100% until FC - which with 250g of beans arrived at 11 minutes 40 seconds..... The heater was then switched off for a minute until the rate of change dropped to about +2 degrees per minute and then the heaters returned to about 50-60% to maintain about +2 deg per minute..... with a slightly higher value towards the end. SC started at 15min 50 seconds and the beans were dumped... They are of very uniform colour..... but the proof will be in the cup.

The time between FC and SC could easily be made longer if desired. The cracks were louder than with the normal roast and FC really got rolling within 30 seconds from the first crack..... there was also a good gap between the end of FC and the first cracks of second....

So far very pleased. The HT has plenty of heater power but in normal mode this is only used at about 60% from the time the beans are loaded until they are dumped..... using the full power of the heater allows the roast time to FC to be reduced to about 3/5 ths of the normal time.... and with some form of heater control the time between FC and SC can be made MUCH longer.

[yoma]

Re: Hottop Manual Roast Controls (for Digital Mode

Hey JavaB

I have added couple of TCs into the bean mass and agree its a very worthwhile investment.

I may one day boost the power - it may depend on the what element I need / can find.   In my experience it would make that crucial difference to get through 250+g size batches (dont want to push it too far and get a meltdown.

Greg, I will post the circuit details and anything else I can do to assist - just need to find my original notes.

[JavaB]

Re: Hottop Manual Roast Controls (for Digital Mode

Yoma,

Im sure you are right.... it uses the same "environmental" RTD in all versions.

IMHO that is probably one of the most significant weaknesses of the HT (and the Gene....) they both measure the chamber temperature (or air temp).... which doesnt reflect the actual bean temperature.

Surprisingly (using a thermocouple actually in the bean mass).... the HTs indicated temperature is within about a degree from FC to SC.... but before FC it is 10C - or more - higher than bean temperature....

Even a degree is too much.... and a bean mass probe is the only way to go - and dead easy (with the HT) to install one - as long as you are prepared to drill a couple of holes in the stainless steel...... definitely worth the effort!!

[yoma]

Re: Hottop Manual Roast Controls (for Digital Mode

AFAIK, the newer hottop controller(s) still use their next to meaningless temperature sensor which defeats the purpose of all that high priced stuff behind it... garbage in -> garbage out.

The chamber sensor as they refer to it has no bearing to the temperature of the beans.

Id like someone to tell me this is no longer case, because in my experience - the hottop components can easily produce consistently excellent coffee.

[JavaB]

Re: Hottop Manual Roast Controls (for Digital Mode

I guess another alternative would be the B upgrade though its approaching half the cost of the Gene at $US300! Why do they make those things so expensive??

Yep, it is expensive - however it replaces both the simple digital control mainboard and the control panel with what amounts to a couple of interlocked PIDs and SSRs so that you have far better control of all functions. The existing D version is a PWM system of control rather than the almost linear control of temperature and fan speed possible under program control with both the B and especially P variants...

Or you can just fit a ramp/soak PID

[gregpullman]

Re: Hottop Manual Roast Controls (for Digital Mode

Good reasoning JavaB, I guess another alternative would be the B upgrade though its approaching half the cost of the Gene at $US300! Why do they make those things so expensive??

[JavaB]

Re: Hottop Manual Roast Controls (for Digital Mode

Yep, the HT element is 750W and after pre-heat (heater on at 100% until that point) - it seems to be cut back to about 50-60% for the rest of the roast.... hence the longer roast time....

But either with yomas mod or a PID - that could be increased to 100% when required - thereby shortening the roast time.

The big difference between the heat requirements IMHO is that the Gene heats the air - and looses a lot of that heat by exhausting the hot air out of the chamber - only transferring some of the heat to the beans.....

With the HT there is no air movement until the start of FC (the fan cuts in briefly at about 100C - presumably to remove the steam).... so all heat in the chamber stays in the chamber except for a little convected and radiated loss into the atmosphere..... This would appear to be a far more efficient process - therefore a 750W heater is more than adequate especially when you consider they are trying to emulate a drum roaster with a roast time of about 20 minutes.... and they can do that with 60% power to the heater.

I doubt a more powerful heater is actually required with this design.

[gregpullman]

Re: Hottop Manual Roast Controls (for Digital Mode

http://www.roastmasters.com/hottop.html lists the Hottops element as being a 750W unit whereas the Gene has a 1000W element. 750 doesnt seem much considering what its trying to do. This is odd since the Gene has more plastic than the Hottop (apparently) so I wonder if the Hottop could take a more powerful element, supply permitting? Itd be interesting to know how hard the Hottops element is actually getting driven (I think you said something about it having some spare capacity?).

My Gene roast suggests its definitely an on/off setup - the first tick of its thermostat I thought it was the start of FC! ;D From there on it was oscillating up and down with about 2dec C variation as the thermostat clicked in and out. So perhaps more judicious use of the available power (via PWM) could allow for more efficiency than a all-or-nothing setup like the Gene; though one comment about the Hottop seems to be that its roasts are longer which would correlate with a weaker heater element.

Greg