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 HTC/TC4 - HT - Temperature problem
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| frachlitz |
Posted on 09/05/2014 1:50 AM
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 Newbie  Posts: 16 Joined: March 26, 2014 |
Hi all, I am having a bit of a problem. TL;DR: My temperture cureves in artisan of BT/ET are jumping aroound, and are making the scope fail and loggin stop. The Story: I have a fairly new Hottop BK2, i have now installed two Omega probes in termocouple fitings, and have hocked up the HTC/TC4 boards inside the roaster. But when i try to start loggin in Artisan i can see the values from the probes are jumping all around. Ex. when i see the temp in the roasting chamber is arounf 170c/338f (also messured with a termapen) the probes are jumping all around at 80-80c, and up and down. The last tries i have had an artisan error "Temperature: Index out of rage" which i expect comes as the probes are reporting crazy high or low temps. I have tried using "oversampling" i helps a bit, but the temps are still way off. What to do? (Sorry if i sound a bit down, after 10h modding i was hoping to roast againg, is a bit tired of buying roasted coffee :-).
frachlitz attached the following images:
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| frachlitz |
Posted on 09/05/2014 1:52 AM
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Newbie Posts: 16 Joined: March 26, 2014 |
In the exampe picture, the actual temp was abound 170c (also messures with a termapen trough the bean chute). I am using the probes and fittings a this user: http://homeroaste...post_45922 |
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| JimG |
Posted on 09/05/2014 7:07 AM
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 1 1/2 Pounder  Posts: 834 Joined: October 23, 2008 |
That sounds very frustrating! Hopefully, we can get it sorted out quickly. Best guesses regarding cause: 1. Stray voltages from the grounded thermocouples are making their way into the TC4C. 2. Loose connection of thermocouples in the green terminal blocks. 3. Bad, or too long, USB cable. My money is on #1 above. Consider the following steps: a) Electrically insulate/isolate the thermocouples from the roaster frame, using silicon sleeves or other means. b) Change to thermocouples with ungrounded tips. c) Connect USB to a laptop running on battery power (i.e. no charger connected) d) Run a grounding wire from the roaster frame to the "TCGND" pins on the HTC board. This carries a small risk of damage to the USB port on your computer that is mitigated somewhat by the 10K series resistor that all recent HTC boards have installed. (If this lessens the problem, but doesn't quite solve it, there is a place on the HTC board to add a 2nd series resistor that reduces the protection, but increases the grounding effectiveness). Jim |
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| Randy G |
Posted on 09/05/2014 8:22 AM
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 1/2 Pounder  Posts: 398 Joined: February 17, 2010 |
Try another outlet for the roaster or try a different location (neighbor's house, at work, etc.). Try running the laptop on battery instead of a power supply, or vice versa. Check that the grounding of the wall outlet is correctly wired.
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| JimG |
Posted on 09/05/2014 11:10 AM
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1 1/2 Pounder Posts: 834 Joined: October 23, 2008 |
Yes to all of the above, too. In fact, Randy's post reminded me that grounding the frame of your roaster is another option. My Hottop (KN8828-D) does not have a grounded plug, and the roaster frame is not otherwise grounded. Your's may be similar. Something else to try is to run a wire to a good source of earth/ground that is part of your home electrical wiring. (In the US, the screws that secure the plastic or metal covers on 3-prong outlets are usually directly connected to ground.) Then hold the other end of this wire against something metal on the roaster and observe if the temperature readings change. If they change, then you have confirmed that a ground loop problem is at least part of the issue. If you have any uncertainty about whether the extra wire described above is safely connected to a source of ground, DON'T TRY THIS. Jim |
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| frachlitz |
Posted on 09/07/2014 2:10 PM
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Newbie Posts: 16 Joined: March 26, 2014 |
Thank you all for your time to reply :-) I have been quite a busy weekend, so i am hoping to test the sugestions during the coming week. I will keep you posed regarding the progress. |
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| frachlitz |
Posted on 09/09/2014 10:47 AM
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Newbie Posts: 16 Joined: March 26, 2014 |
So... a little closer.... still far off :-( I have installed a new plug on my HotTop with ground. Reinstalles the termocouples in the HTC/TC4 and change the Baud rate down in artisan. Succes!... Well sort of. Now i see almost correct values. But they differ 10-15c (between ET and BT) with a empty drum, and more than 20-40c from the HT's probe. I tried doing a roast, but the temps are way off, and it seems like they are very slow to respond. I have attached a log (the best i can do in artisan now :-)) with the log - i dropped the beans at around 1-2min (auto charge did not work), but the bean temp almost did not drop. I added the beans at around 130c on the HTs temp, and here tge BT temp from the new probe was around 80-90c!. I ended up with the HT dropping the beans as it reached the max temp (220c??) that was about 1,5min into 1C.... This is not the first time that have happend. The messured temp from the BT probe was about 165c. I dont know what to do now.....   |
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| turtle |
Posted on 09/09/2014 10:53 PM
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 1 1/2 Pounder Posts: 652 Joined: November 06, 2013 |
That is the difference in placement of the probes. Heat rises so the et will usually be a little higher than the lower mounted bt probe And both probes will read differently than your button type sensor too 
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: 2 kilo Chinese drum Grinders: Mazzer Major - 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 |
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| JimG |
Posted on 09/10/2014 4:23 PM
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1 1/2 Pounder Posts: 834 Joined: October 23, 2008 |
I don't have a good theory on why your readings are so low. The ET and BT readings will always be different, as Turtle said. But it seems both readings are a lot lower than expected. The 3 prime suspects are: 1. Thermocouple probes could be too closely tied, thermally, to their mountings. If this is the case, then mostly what you are measuring is the temperature of the rear wall of the roaster. Fix this by insulating the probes, both electrically and thermally, from the roaster. Silicon sleeves are an appropriate solution in many cases. 2. There may still be some stray voltage getting into the thermocouples. You said you changed the plug to be grounded, but did you also connect a grounding wire to the frame of the roaster? Suggest that you measure the AC voltage, using a DMM, between the roaster frame and a ground point in your home electrical system. Ideally, the reading will be zero. If not zero, something less than 2V would be nice? 3. Gremlins. Jim |
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| frachlitz |
Posted on 09/11/2014 1:11 AM
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Newbie Posts: 16 Joined: March 26, 2014 |
Quote Thank you Jim, i will try out a few thing. I don't think its 3 - it has not been wet :-) |
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| frachlitz |
Posted on 09/11/2014 7:00 AM
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Newbie Posts: 16 Joined: March 26, 2014 |
I have now tried a lot. - Checked the fittings, they probes shold be completly shilded from metal in the nylon fitting. - Uploaded the RoastLogger sketch at testet with RoastLogger to rule out it was a software setting. - Then i have tried messureing with them outside the machine, and think i found the problem... They dont messure in the tip -but circa midtway on the housing... So that means almost exactly where the probe is sitting in the fitting.... I have tried makeing a video showing the problem. They are Omega HTTC36-K-116U-2.5 at 31USD pr. pc..... What to do???? |
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| JimG |
Posted on 09/11/2014 10:11 AM
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1 1/2 Pounder Posts: 834 Joined: October 23, 2008 |
I think what I saw in your video is that the probes' response to heat from your fingers is greater in the middle than at the tip? If so, then you have bad thermocouples and Omega should replace them for no charge. This can happen when a "false junction" is created at a point other then the very end of the thermocouple wires, and is a well-known flaw present in poorly constructed thermocouples. A false junction occurs when the insulation on the probes is missing or interrupted and the thermocouple wires become shorted together prior to the ends of the wires. Alternatively, maybe they did not push the tips of the wires all the way to the end of the sleeve. This would also explain what your video seems to show. Nice piece of sleuth work ;-) Jim |
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| frachlitz |
Posted on 09/24/2014 1:50 AM
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Newbie Posts: 16 Joined: March 26, 2014 |
I finaly had a reply from Omega. I was a bit of a long way, as i am based in Denmark, Europe. My request to Omega USA, was farwarded to the UK, and was again forwarded to a brand new danish Omega office. So i was a bit suprised to get a danish speaking person on the phone :-) (This is brand new, i could not order them in europe at the time). So they will produce two new and send to me free. They will create grounded insted, to make sure that the termocouple will stick to the tip. |
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| JimG |
Posted on 09/24/2014 8:41 AM
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1 1/2 Pounder Posts: 834 Joined: October 23, 2008 |
It is particularly important with grounded probes that the entire sleeve of the probe is electrically insulated from the roaster body. Jim |
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