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Enhancing My HotTop (5 of 5) ľ Advanced Modifications
snwcmpr
Thanks Ginny.
Like I said, all I have is a bean probe. I have hearing loss, so I rely on the temp.
I measure (weigh) my beans for brewing, but that's about it. That gives me repeatability.
I will say ... all I know about roasting, what little I do know, 90% I got here.
Thanks,
Ken
--------------
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
Barrie

Quote

ginny wrote:


I do not believe you need to mod the hell out of a roaster to get a great bean to brew.

party


Your point is well taken, Ginny, but there is a whole group of people who both enjoy coffee that they have brewed, and enjoy fiddling with machines and electronics. I don't think they are mutually exclusive but, then, perhaps that is what you just said. coffee drink
Barrie (San Diego, CA)
"So much to learn, so little time."
Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).
ginny
Barrie:

There is nothing wrong with mods on anything, period. We have this site for anyone to post up their mods to help other users do the same...

I am/was only suggesting that simply out of the box the Hot Top is a great little roaster.

ginny

greenman
Edited by ginny on 11/16/2013 12:14 PM
RAG

Quote

ginny wrote:
.....
I am was only suggesting that simply out of the box the Hot Top is a great little roaster.

ginny

First and foremost I have to agree with ginny.

Couple of things.
The RAF mod is first. Not only does this prolong hottop life, it adds control to the roast process. Fan to heat control in FC becomes tweakable and more immediate along with the added benefit of removing heat, chaf, and goo from the electronics area.

I added an insulated firewall to further isolate the chamber heat from the roaster internals (not sure this was needed).

I added a diode just after the bean cooling fan so that I can switch the fan and bean rotor motor on without activating the main fan, but still allow the normal design function of both fans being on the same circuit for normal operation.
So now I have a switch that turns on only the bean fan and motor by grounding the yellow wire (U2p5) and the bean tray fan. Normal operation is whenever the main unit fan is off, the bean tray fan is off. I figured if doing back to back, I may want to cool beans, while not activating main chamber fan.

The 165 override I did with a DPDT switch between the regular thermocouple and some left over thermo wire I used to make a junction to monitor the motor area.
This provides a very dangerous heater on switch. It also allows roasting to any level and a hard on heater at any point in the roast cycle, while monitoring internal temperatures.

So roasting and these mods are not for the faint of heart.

Thanks Ciel and others for the motivation.
snwcmpr
Well, some people drive cars the way they are made. If they don't like them, they get another one.
Others modify the car to make it what they want.
No right or wrong, just different.
All I did was add a temp probe to the HT. When I got another roaster, that I like better, I put the HT on the shelf.

Ken in NC
--------------
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
ginny
Share solution-oriented experience and learnings freely.

the above is from our What We Are About on the front page and I am placing it here because I see a trend of machine bashing happening. not simply regarding Hot Tops but other roasters as well.

many members take hours of time and energy posting their respective ideas and mods they have done on any given roaster for other members who want to venture down that road...

while I have never been shy about saying that all of these home roasters are GREAT straight from the box I clearly respect anyone who does creative and cool things with their roasters...

if anyone feels they must bash their roaster start your own thread and do it but please do not roaster bash in threads that are designed to help other move beyond stock. not fair to anyone.

thanks in advance,

ginny
turtle
I wanted to thank Ciel for their time, for not only testing, but posting all of the mod and customization info that they have amassed about their Hottop home roaster.

I know that I will be using many of their ideas.

Last night I finished wiring in switches for the main fan and bean cooler motors as well as the temp sensor interrupt for "hot start" back to back roasts.

I am sure that I will use these additional functions numerous times starting with today's roast.

i1066.photobucket.com/albums/u414/turtle-web/food/coffee/Hottop/mods1_zpsa8f467d5.jpg
ciel-007
Cracking the ô165F Barrierö: A FOLLOW-UP

The modification, as described earlier, was designed to work on older Hottop models (i.e. KN8828B, KN8828P, KN8828B-2, KN8828P-2...) which have a large button shaped Temperature Sensor inside the roasting chamber. Given the nature of its design, that modification could theoretically be called the "OPEN CIRCUIT" method of tricking the Hottop Control Panel into reading "0"F at Startup.

This Follow-Up is directed towards those who have attempted to "Crack the 165F Barrier" on the newer Hottop models (i.e. KN-8828P-2K and KN-8828B-2K) which have a thin K Thermocouple in the roasting chamber. I have two questions for you:

(1)Would it be possible for 2K Hottop owners to tell us if the PHOTO that was used earlier (shown below) is representative of the manner in which the new K Thermocouple leads connect to the new 2K Hottop Control Panel? If not, would it be possible to post a photo that does?

(2) More importantly, would it be possible for 2K Hottop owners to tell us if the electrical DIAGRAM that was used earlier (shown below) provides a circuit that actually works on the new 2K Hottop roasters? It is my understanding that thermocouples generate tiny changes in voltage (micro-volts) when the temperature varies. In that event, the OPEN CIRCUIT method (shown in that DIAGRAM) should theoretically be able to interrupt that tiny voltage flow, and thus trick the Control Panel into accepting that the temperature in the Hottop roaster is actually close to "0" F at startup. Alternately, it might also be theoretically possible to trick the new 2K Control Panel into reading 0 micro-volts by using a SHORT CIRCUIT method. That would involve using a Momentary Button Switch (that is normally open) and connecting it across the two K thermocouple leads; thus, when the button switch is pushed, the resulting short would reduce the micro-voltage to "O", and trick the Control Panel onto reading "0" F.

Since I do not own a 2K roaster, I am unable to compare the Open Circuit and Short Circuit methods for Cracking the 165F Barrier on the new Hottops. Is there a 2K owner out there, who is brave enough to test both methods, and to tell us if one, both or neither of those methods work on the new Hottops?

Ciel
ciel-007 attached the following images:
1_thermal_sensor_cable_1.jpg 2_momentary_switch_diagram_1.jpg

Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK´┐ŻNIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
JimG
I can confirm that the open circuit does not work. Like many other thermocouple instruments, the HT K control boards have open circuit detection. The board will shut down the roaster right away if open circuit is detected at power up. I don't know what happens in the event of open circuit detect at other times, but my guess is immediate shutdown (not good).

Short circuit does work, however. I have never set up a switch to create the short, but a small loop of plain copper wire can be safely substituted for the thermocouple (done this several times). Electrically this is equivalent to closing a shorting switch.

The result is that the HT believes the roasting chamber is the same temperature as the control board, essentially ambient temperature or a bit higher.

I've used the wire loop trick several times for troubleshooting and testing on a P-2K board, and I am pretty sure it will work equally well on B-2K boards.

Regarding switch installation details: if you add copper wire to extend the thermocouple leads there is likely to be some loss of accuracy in the temperature readings because you would be moving the "cold junction" away from the circuit board. Ideally one should use type K wire to extend the TC leads.

The wires to the shorting switch can be copper.

The caveats are:

1. While I have tested the effects of both open and short circuits on a P-2K board, I have never used this to break the 165F barrier. I have done the testing in a controlled test bench environment.

2. Why the heck do you want to do this anyway? Grin. I am perfectly happy to give the roaster a few minutes to rest between roasts. Roflmao

Jim
Edited by JimG on 05/10/2014 8:20 PM
ciel-007
Cracking the ô165F Barrierö: A FOLLOW-UP

Quote

JimG wrote:

I can confirm that the open circuit does not work...
Short circuit does work, however. I have never set up a switch to create the short, but a small loop of plain copper wire can be safely substituted for the thermocouple...
While I have tested the effects of both open and short circuits on a P-2K board, I have never used this to break the 165F barrier...


Jim, thanks for this valuable follow-up. Recognizing your long standing expertise in the field of electronics, I welcome your explanation (and caveats) as to why the "Short Circuit" method should work on the new Hottop 2K models - in contrast to the "Open Circuit" method which works on earlier B and P Hottop models.

I look forward to the day when a 2K Hottop owner will post photos of a modified roaster actually "Cracking the 165F Barrier" with the appropriate switch design.

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK´┐ŻNIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
JimG

Quote

ciel-007 wrote:
... I welcome your explanation (and caveats) as to why the "Short Circuit" method should work on the new Hottop 2K models - in contrast to the "Open Circuit" method which works on earlier B and P Hottop models.


The earlier models use a thermistor. This is a sensor whose resistance changes with temperature. The relationship between resistance and temperature is known, so measuring the resistance is equivalent to measuring the temperature.

To measure the resistance at any point in time, the circuitry on the control board passes a known current through the sensor and measures the resulting voltage drop. If you short circuit this sensor, you end up measuring 0 ohms resistance, which puts the temperature off the chart!

Probably there is circuitry which limits the current in the event of a very low, i.e. 0, thermistor resistance. So I don't think there is too much risk of damaging the control board by shorting the pins on the P or B, but I would not try it just in case.

The newer models (B-2K, P-2K) use thermocouple sensors. Instead of changing resistance with temperature, TC's actually generate small voltages, under 10 mV, when one end is hotter than the other end.

The circuitry to read a thermocouple is entirely different. The control board has a very high input impedance op amp that reads and amplifies the very low mV voltages that are generated by a thermocouple. A reading of 0 mV, which is what you get with a shorting loop in place of a TC, simply means there is no voltage being generated by the sensor. This condition is not unusual and occurs whenever the sensing tip of the TC is at room temperature.

Most thermocouple instruments also pass a very low current through the TC at all times and have circuitry that can tell if this current has been interrupted. The current is too small to generate even mV voltages across the TC leads, so it does not mess up the readings. But if the TC is broken or missing, then the current does not return to the instrument and it knows there is a problem.

I am not sure why an open circuit does not cause a similar problem on the earlier models. Perhaps it would if you left the switch open for a long enough duration?

Jim
ciel-007
Cracking the ô165F Barrierö: A FOLLOW-UP

Jim, I am grateful to you for taking the time to explain the evolution that has taken place in the complex Hottop thermal circuitry over the years - that's much appreciated!


Quote

JimG wrote:



I am not sure why an open circuit does not cause a similar problem on the earlier models. Perhaps it would if you left the switch open for a long enough duration?


Jim, I believe that you are correct (as usual) in your statement. In my attempts to "crack the 165F barrier", I conducted a number of experiments. In earlier trials, I used a toggle switch to open the thermal circuit. I was mystified by the fact that opening the circuit in that manner did not work consistenly. Jim, you have just now provided an explanation as to why it did not.

During my experiments, I eventually realized that success with this tentative modification depended on my ability to activate the toggle switch very quickly. I thus abandoned the toggle switch in favor of an intermittent button switch; with an intermittent button switch, it is easy to open the circuit for only a brief moment, and thus successfully trick the thermal circuitry into allowing the roaster to start-up at higher temperatures.

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK´┐ŻNIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
JimG
Another approach for the earlier thermistor-based boards would be to use a switch to swap in a resistor rather than leave it open circuit.

To determine the correct size resistor, use a DMM to measure the resistance across the sensor leads with the sensor at room temperature and unplugged from the control board.

This approach should eliminate the timing issue.

Jim

PS - I am still not sure I think that tricking the roaster this way is a good idea Grin
ciel-007
Photos of the 2K Control Panels & Cables

It is likely that some of the above mods for the older B and P Hottops may not work as originally intended on the newer roasters. In order to help identify which mods might possibly require some tweaking, additional information about the 2K roasters would be appreciated.

Would it be possible for the owner of a KN-8828P-2K and the owner of a KN-8828B-2K roaster to post photos of the back of their Control Panel (including the Main Control Cable, the Chaff Tray Safety Switch Cable, and K Thermocouple Cable)?

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK´┐ŻNIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
ciel-007
Hottop Struggling - Variac Needed!

Before deciding to buy a Hottop, I remember reading a number of claims made by the manufacturer. Here are two that specifically come to mind:
-Hottop claimed that its roaster provides:
"750 watts of roasting power" .
-The manufacturer also claimed:
" not sensitive to voltage, no variac needed ".

If memory serves, the above claims may possibly date as far back as 2007 or so, when the B and P models were introduced. Those claims encouraged some Hottop re-sellers to advertise the roaster with words such as:
"Not sensitive to the line voltage... no voltage regulator (such as a Variac) is needed... to maintain proper voltage"
or perhaps words along the lines of:
"these new Hottop models are voltage compensated".

I had not given much thought to those claims until recently, when I read several posts by Miroslav (Smico). In his posts, Miroslav explains how he uses a Variac to improve the roasting performance of his Hottop.

http://homeroaste...post_50479

http://homeroaste...post_49882

After reading Miroslav's posts, I thought it might be interesting to take a closer look at Hottop's claims. In order to do that, I first had to find my Variac (an old Superior Electric Powerstat - Spec BP57515) that had been quietly gathering dust in a remote corner of my workshop. Next I had to go out and buy a brand new Kill-A-Watt (model P4400) monitor. I was now ready to power up my faithful Hottop (KN-8828B-2) and to take a closer look at the manufacturer's claims.

I normally use the same 120vac circuit when I roast in my workshop. During the week, this dedicated outlet undergoes typical voltage fluctuations that may range from 119vac to 123vac (with no load applied). That represents a relatively small (under 2%) voltage fluctuation from the mean. Given the above Hottop claims, one would not expect the roasting process to be affected in a meaningful way by those minor voltage fluctuations. Here is what my instruments revealed under two different roasting scenarios.

Roasting on a High Voltage Day:
There are days when the outlet I use to roast provides a voltage of 123vac. When the Hottop is set to roast at full power, the Kill-A-Watt monitor shows 121VAC under load, and the total power consumption appears as 735 watts.

Roasting on a Low Voltage Day:

There are days when the outlet I use to roast provides 119vac. When the Hottop is set up to roast at full power, the Kill-A-Watt monitor shows 118vac under load, and a total power consumption 711 watts. In order to force my Hottop to output the manufacturer's claimed roasting power 750 watts, I need to boost underload voltage to 122vac with the Variac.

Conclusions:
What might one to conclude from the above trials?

1.0 - One possible conclusion might be to reject the above results on the grounds of measurement error. In other words, my Hottop is roasting according to the manufacturer's claims, but that the Kill-A-Watt monitor I used gave me inaccurate readings. I am inclined to dismiss that tentative conclusion given the fact that tests conducted by Consumer Reports (and others) have stated that the P4400 monitor provides "accurate" results.

2.0 - A second conclusion might be that claims advanced by the manufacturer may be optimistic. I find this conclusion attractive for two reasons:

2.1 - In regard to the first claim, my KN-8828B-2 did not provide the manufacturer's advertised roasting power even on a High Voltage Day. On a high voltage day (121vac under load) when my outlet was actually exceeding the norm (120vac) for which my Hottop is designed, my roaster fell short of the claimed roasting power by 15 watts.

2.2 - More importantly, in regard to the second claim, I did not find any evidence that special circuitry might be at play to compensate for low outlet voltage. Quite to the contrary, a mere drop of two volts (118vac) below the norm (120vac) resulted in roasting power (711 watts) that was 35% below the manufacturer's claimed wattage. In other words, my Hottop roaster is sensitive to small voltage fluctuations.

3.0 - Given that the above results are based on a single, aging KN-8828B-2 roaster, I would encourage other Hottop owners to post their results following similar trials. It would be nice to document situations where Hottop roasters meet, or exceed, the manufacturer's claims in terms of roasting power and voltage compensation.

Recommendation:
Should the second conclusion above be confirmed by others, then a case might possibly be made for one further Hottop enhancement; perhaps a recommendation along the following lines:

Hottop Struggling - Variac Needed!

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK´┐ŻNIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
Barrie
Fern,
I have posted my experience with my new variac, KAW, and a 2BK HT with about 500 roasts on it, and have reported
1. That with the voltage adjusted to 120 the KAW indicates 740 watts. Michael says that for some years they have been using elements rated at 740w, not the 750 stated on the website that he says is in error.
2. Small changes in voltage produce large changes in wattage.
3. My line voltage is typically about 118-120, and the wattage during the HT preheat phase is typically ~711. To increase it to 740 I need to increase the voltage to 120 or a little above. On the other hand, to handle large loads with a workable RoR I need to increase the wattage away above the rated level. I have already posted a question to Miroslav, who does this regularly, as to what the effect might be on the element? So I would add to the questions arising from your own experience what effect the prior use of elements regularly used above their rated max. wattage level might be on performance?
Edited by Barrie on 05/23/2014 7:35 PM
Barrie (San Diego, CA)
"So much to learn, so little time."
Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).
smico

Quote

ciel-007 wrote:
-The manufacturer also claimed:
" not sensitive to voltage, no variac needed ".


Ciel,
I still think that their claim is correct, but only if you never use 100% power. See my explanation from an old GCBC post below...


Quote

smico wrote back in 2012:


My 2 cents on the voltage variation and need for variac with HT...

I bet that HT implemented constant power to the heaters. They can not increase voltage, but instead, as the voltage drops few volts, they add few more cycles to go through to the heater to increase effective current, and keep power constant at chosen power level.
For example, if you are at 90 power level 54 out of 60 cycles are let through to the heater. If voltage drops 5 percent to 114 V, controller will let 5 percent more cycles: 57 cycles to go through to the heater to compensate for voltage drop.
Of course, this does not work at 100 percent power level as there are no spare cycles, and only variac will help there.

I roast small batches and never use full power, so my roasts are not very dependent on voltage. My voltage swings from 113 to 119 and I have killawatt, but I don't look at it any longer.

Having said that I will get variac for myself as I will soon have need to roast 300g +. But for smaller batches, I found no major impact of the voltage swings.

Cheers,

Miroslav

Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario
ciel-007

Quote

smico wrote:

... as the voltage drops few volts, they add few more cycles to go through to the heater to increase effective current, and keep power constant at chosen power level.



Miroslav, I'm not sure that I understand how varying cycles might affect power output in a Hottop. Can you expand on this?

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK´┐ŻNIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
smico
AC 60 Hz has 60 full cycles per second.

50% power on Hottop is achieved by blocking 30 out of 60 cycles per second.

If incoming voltage drops a bit, HT controller will let more than 30 cycles through to keep the power constant.
If incoming voltage increases, HT controller will let less then 30 cycles through to keep the power constant.

This works until you don't block any more cycles and reach 100% available power. At that point variac is your only option.

Ciel, is that clear now or I need to add some diagrams. You can look up zero-crossing power control. Another type is phase angle control.

Cheers,

Miroslav
Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario
ciel-007

Quote



smico wrote back in 2012:

... as the voltage drops few volts, they add few more cycles to go through to the heater to increase effective current, and keep power constant at chosen power level...

... Of course, this does not work at 100 percent power level as there are no spare cycles, and only variac will help there...




Miroslav, at your suggestion, I did some reading about "zero crossing power control". More importantly, I re-read your 2012 GCBC post.

The source of my question was the result of my mis-reading your 2012 post. In my perusal of you words, I had missed the most important phrase of all:
"this does not work at 100 percent power"

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK´┐ŻNIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
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