jbruce12000
Error: short circuit to ground only at higher temperatures
Almost there! After an auto-tune the result of calculations were entered in config file, ran the " test 200-250 " almost perfectly. Next was a Bisque Fire test. I volunteered a few pots to be Bisque fired. Entered a custom profile and hit START. All went well all the way up to about 1100'F. It stopped the profile ( Run complete ) a couple of times. The third time it fired well to about 1600'F . I was getting " Error - Problem reading temp, short circuit " repeatedly. Shortly after, it announced " Run complete " while the Pi's screen was covered with " Problem reading temp, short circuit " I understand that the thermocouple and it's cable must be well insulated from circuit ground. I am sure, I have done all needed to be done about that issue. Why the system started acting up in higher temperatures? And what is causing the " short circuit "?
This seems to be an issue for several users. I think that there are several possible causes.
- Thermocouple shorting to itself or to ground.
- The pi board uses pins to make the connections . These are not a very reliable connection method. I don't know a better way but the quality of the pin wire combos varies. I found after some intermittent problem that using new pins with good wire stopped the problem.
- RFI the pi board is susceptible to RFI from.any source. In kiln areas it could be any motor that has brushes, relays, electronics of any type . Very hard to pin down. One solution is to put a capacitor across the thermocouple leads. 0.1 uF ceramic works fine.
- A problem within the pi board itself. They are made by many sources. Cheap enough to replace.
- The code is being misread due to code problems . Try reinstalling it might help
- The.power source for the pi might be electrically noisy . Try a different one. You may never resolve the uncertainty so plan for it. I have not had these problems and use my phone to watch the firing. Usually I am asleep during the firing so wouldn't know what happened until opening time. I have considered making a independent monitor but so far after hundreds of firing no failures due to the pi system. I still think an Arduino based system would be more reliable but not don't it yet..may be later this year and I will release it as freeware.
On Tue, Jul 22, 2025, 8:44 PM TinMaan @.***> wrote:
TinMaan created an issue (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225
Almost there! After an auto-tune the result of calculations were entered in config file, ran the " test 200-250 " almost perfectly. Next was a Bisque Fire test. I volunteered a few pots to be Bisque fired. Entered a custom profile and hit START. All went well all the way up to about 1100'F. It stopped the profile ( Run complete ) a couple of times. The third time it fired well to about 1600'F . I was getting " Error - Problem reading temp, short circuit " repeatedly. Shortly after, it announced " Run complete " while the Pi's screen was covered with " Problem reading temp, short circuit " I understand that the thermocouple and it's cable must be well insulated from circuit ground. I am sure, I have done all needed to be done about that issue. Why the system started acting up in higher temperatures? And what is causing the " short circuit "?
— Reply to this email directly, view it on GitHub https://github.com/jbruce12000/kiln-controller/issues/225, or unsubscribe https://github.com/notifications/unsubscribe-auth/AXA65G6VXGWUR5EQINMQGK33J4ALRAVCNFSM6AAAAACCETI74GVHI2DSMVQWIX3LMV43ASLTON2WKOZTGI2TINZTGE3DGMQ . You are receiving this because you are subscribed to this thread.Message ID: @.***>
As you mentioned a few of the points you made, have been discussed here as possible causes for the thermocouple related errors. There are also a few interesting new possibilities you are sharing. I have to look into those now. That said, it is not clear to me and in my case, - why - these errors start to appear in higher ( above 1100'F ) temperatures? Most if not all mentioned hardware and software issues if present, should be present throughout the firing. I like to put the blame on the cheap thermocouple. Perhaps in higher temperatures, the hot-juction of this cheap unit starts to separate so ever slightly and send " irregular " signal that is read as " noise " by the system. I will replace it with a new ( still cheap ) one and report back. BTW, could you recommend a reliable source for purchasing " good enough " thermocouple?
I am answering my question here in case someone else is interested. I learned that, the physical signal from a thermocouple ( cheap or otherwise ) is not constant in time by lab standards. So, the signal generated by the thermocouples ( cheap or otherwise ) physically are random to the point of being considered badly noisy to begin with. At lower temperatures the random behaviour proportional to temperature is handled by system as if they don't exist. At higher temperature the randomness of their signals increase proportional to temperatures they are exposed to - edging towards crashing the software if tolerances are set too tight. Problems begin when low quality thermocouples [ ADD ] more noise to the unavoidable random signal, especially at higher temperatures. It is silly to increase the acceptable tolerances for errors in the software to accommodate a cheap thermocouple. Therefore, I am buying a better thermocouple-set with cold-junction cover incase the kiln-controller will expand to include cold-junction compensation on day.
I don't think you've understood thermocouples, sorry. The thermocouple tc is made by two dissimilar metals . They are welded at on end. The other end goes to another junction but this one is a virtual one as part of the chip..the effect of this a very small voltage is produced by the temperature difference. The voltage is millivolts so noise from any source can be an issue. However if you connect the tc from.the kiln to the k type converter board 55 type and the same to a Fluke or other tc reader you should see same temp on the Fluke as on the pi system. You need to.use tc wires correctly oriented for this. Please report and let us know how your system.is working.
On Wed, Jul 23, 2025, 9:01 AM TinMaan @.***> wrote:
TinMaan left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3109240442
I am answering my question here in case someone else is interested. I learned that, the physical signal from a thermocouple ( cheap or otherwise ) is not constant in time by lab standards. So, the signal generated by the thermocouples ( cheap or otherwise ) physically are random to the point of being considered badly noisy to begin with. At lower temperatures the random behaviour proportional to temperature is handled by system as if they don't exist. At higher temperature the randomness of their signals increase proportional to temperatures they are exposed to - edging towards crashing the software if tolerances are set too tight. Problems begin when low quality thermocouples [ ADD ] more noise to the unavoidable random signal, especially at higher temperatures. It is silly to increase the acceptable tolerances for errors in the software to accommodate a cheap thermocouple. Therefore, I am buying a better thermocouple-set with cold-junction cover incase the kiln-controller will expand to include cold-junction compensation on day.
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Yes, thank you for reminding the basic theory of the thermocouples. There are lot that I gradually started to understand about kiln building and controlling them thank to all contributors here and the internet. At this stage the practical problems and how to overcome them in execution of the ideas that concern me. My thermocouple is connected properly ( according to me ). It functions perfectly with consistent temperature control errors of amazing * 0.5 F' ~ 0.01 F' * as long as readings are done bellow 1100'F. No overshoots no pauses for kiln to catch up - PERFECT by definition! ( thank you jBruce12000 ). But why the system crashes often above 1100'F!?
I think you may be misdirected by the error interpretation. Looking at the MAX31856 datasheet, I do not see a fault classification that would correlate to Shorted Thermocouple. I see an Open Thermocouple fault. There are 6 different fault states reported by the max31856: Cold Junction out of range (over) (range is -55c to 128c)This is chip temperature, thermocouple in the chip that assumes that the 'cold junction' (junction where the thermocouple wires are connected to copper) is also at this temp. Cold Junction out of range (under) Thermocouple out of range (over 1372C) Thermocouple out of range (under -250C) Input voltage either over/under (this is input power) Open Thermocouple (broken connection in thermocouple/wires)
I am thinking the software is interpreting the fault signal incorrectly. The issue I have had was an Open Thermocouple. Heat cycles can expand/contract connections and can cause loosing up connections. Also, had problems with jumper wires as rondo said. I have also had thermocouples not read until I tapped them. Like maybe a corrosion issue between wire and thermocouple. The connection between the pi and the MAX31856 has not been a problem for a very long time. I have the modules mounted on a perma-proto pcb that is made to plug into a Raspberry pi. Adafruit.com makes them. They are laid out, and look like a breadboard, but are a pcb with a 40 pin connector on it. "https://www.adafruit.com/product/2310". I put a chip on it that converts pi signals to 12v for the relay coils. I also put the Max31856 module on it. Originally, I had made up crimped jumper cables. I had some issues like you are having and converted to solder connection where reasonably possible. I now do not have any unsoldered jumper wires. I also had the thermocouple wires not engaged into the screw terminals on the MAX correctly. I think it would loosen up and I would get intermittent bad readings(downspikes). Like 0 C and the kiln would start running away. All my issues have been the workmanship of connections. Blake
On Tue, Jul 22, 2025 at 10:44 PM TinMaan @.***> wrote:
TinMaan created an issue (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225
Almost there! After an auto-tune the result of calculations were entered in config file, ran the " test 200-250 " almost perfectly. Next was a Bisque Fire test. I volunteered a few pots to be Bisque fired. Entered a custom profile and hit START. All went well all the way up to about 1100'F. It stopped the profile ( Run complete ) a couple of times. The third time it fired well to about 1600'F . I was getting " Error - Problem reading temp, short circuit " repeatedly. Shortly after, it announced " Run complete " while the Pi's screen was covered with " Problem reading temp, short circuit " I understand that the thermocouple and it's cable must be well insulated from circuit ground. I am sure, I have done all needed to be done about that issue. Why the system started acting up in higher temperatures? And what is causing the " short circuit "?
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-- Blake C. Lewis
@BlakeCLewis, as they say, Like minds think alike. I had just finished replacing all possible contact points to soldered joints before checking here for replies. I will build another Pi board + protoboard you linked also for comparison and plan-B. I agree with you also on the possibility of error mis-interpretation by the software. After all the logic set is small and at growing stages. I'll comb through all the possible failure points armed with the information I received here and tighten the knots again with the hope of making the system fail proof ( if that's practically possible ).
I had one failure recently: The kiln is on wheels and I rolled it a bit too far away from the controller. The thermocouple wire is the shortest. Another failure I had years ago was heat on the pi, so I added a fan to the enclosure and switch it on if the cold junction temp is higher than the room temp. I use a thermocouple(second max31856) for room temp. A thermistor would have been cheaper.
On Wed, Jul 23, 2025 at 1:35 PM TinMaan @.***> wrote:
TinMaan left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3109692345
@BlakeCLewis https://github.com/BlakeCLewis, as they say, Like minds think alike. I had just finished replacing all possible contact points to soldered joints before checking here for replies. I will build another Pi board + protoboard you linked also for comparison and plan-B. I agree with you also on the possibility of error miss - interpretation by the software. After all the logic set is small and at growing stages. I'll comb through all the possible failure points armed with the information I received here and tighten the knots again with the hope of making the system fail proof ( if that's practically possible ).
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-- Blake C. Lewis
Try and keep it simple. The 55 chip board is fine for a K type tc. The 56 is more versatile but unnecessary. I've used the 55 chip/board for at least years. If you see in the setup of the pi the tc type is a parameter. It's a PITA when simple stuff doesn't work. It's often quicker to just make second system. Life is short use.your skills where they work. Ronald.
On Wed, Jul 23, 2025, 11:48 AM Blake C. Lewis @.***> wrote:
BlakeCLewis left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3109756734 I had one failure recently: The kiln is on wheels and I rolled it a bit too far away from the controller. The thermocouple wire is the shortest. Another failure I had years ago was heat on the pi, so I added a fan to the enclosure and switch it on if the cold junction temp is higher than the room temp. I use a thermocouple(second max31856) for room temp. A thermistor would have been cheaper.
On Wed, Jul 23, 2025 at 1:35 PM TinMaan @.***> wrote:
TinMaan left a comment (jbruce12000/kiln-controller#225) < https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3109692345>
@BlakeCLewis https://github.com/BlakeCLewis, as they say, Like minds think alike. I had just finished replacing all possible contact points to soldered joints before checking here for replies. I will build another Pi board + protoboard you linked also for comparison and plan-B. I agree with you also on the possibility of error miss - interpretation by the software. After all the logic set is small and at growing stages. I'll comb through all the possible failure points armed with the information I received here and tighten the knots again with the hope of making the system fail proof ( if that's practically possible ).
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-- Blake C. Lewis
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This hasppens consitently above about 800c. it continues when the power off on coolling
When the power is off to THE SSR's eg. the kiln sitter trips, the error stops.
Same behavior on a kiln with mechanical relays
What do the logs tell you?
Anger is usually regrettable, kindness rarely.
On Wed, Jul 23, 2025, 3:55 PM Chip Garner @.***> wrote:
chipgarner left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3110893260
This hasppens consitently above about 800c. it continues when the power off on coolling
When the power is off to THE SSR's eg. the kiln sitter trips, the error stops.
Same behavior on a kiln with mechanical relays
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Ive had similar issues with my pi at higher temps. The temperature would flat line and not change, sometimes it would continually drop when the temperature was actually rising because kiln was full on. If I unplugged thermocouple from pi and directly in to my fluke meter it read perfectly fine at these high temps. So im assuming the fluke meter ignores errors or has better shielding.
Running a ground from pi to the wall outlet ground helped it read at higher temps but the issue was still occurring near top range. I now instead have a ground wire from wall outlet running to one of the thermocouple connectors at block coming out of kiln.
This has resolved the loss of reading at high temps for me. Im using a max31856.
This is first useful news on this issue. My kiln has a steel case that is grounded . So may be thats why I dont have problems. Can you undo your grounding and see if problem reoccurs? Putting a capacitor across the tc wires right at the input module might work to if it's an RFI problem. My question is if it's RFI where is it coming from? BTW you can connect the Fluke up to the same tc as the module. The input on the Fluke will not affect the pi system.
On Fri, Jul 25, 2025, 6:24 PM Kirby @.***> wrote:
keebie81 left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3120916638
Ive had similar issues with my pi at higher temps. The temperature would flat line and not change, sometimes it would continually drop when the temperature was actually rising because kiln was full on. If I unplugged thermocouple from pi and directly in to my fluke meter it read perfectly fine at these high temps. So im assuming the fluke meter ignores errors or has better shielding.
Running a ground from pi to the wall outlet ground helped it read at higher temps but the issue was still occurring near top range. I now instead have a ground wire from wall outlet running to one of the thermocouple connectors at block coming out of kiln.
This has resolved the loss of reading at high temps for me. Im using a max31856.
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I just reread your post. Did you connect a tc wire to ground? This should not work!! The input to the 55 or 56 module is designed as a floating input. So no ground. Explain ground wire to thermocouple connector please.
On Fri, Jul 25, 2025, 6:32 PM ron doctors @.***> wrote:
This is first useful news on this issue. My kiln has a steel case that is grounded . So may be thats why I dont have problems. Can you undo your grounding and see if problem reoccurs? Putting a capacitor across the tc wires right at the input module might work to if it's an RFI problem. My question is if it's RFI where is it coming from? BTW you can connect the Fluke up to the same tc as the module. The input on the Fluke will not affect the pi system.
On Fri, Jul 25, 2025, 6:24 PM Kirby @.***> wrote:
keebie81 left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3120916638
Ive had similar issues with my pi at higher temps. The temperature would flat line and not change, sometimes it would continually drop when the temperature was actually rising because kiln was full on. If I unplugged thermocouple from pi and directly in to my fluke meter it read perfectly fine at these high temps. So im assuming the fluke meter ignores errors or has better shielding.
Running a ground from pi to the wall outlet ground helped it read at higher temps but the issue was still occurring near top range. I now instead have a ground wire from wall outlet running to one of the thermocouple connectors at block coming out of kiln.
This has resolved the loss of reading at high temps for me. Im using a max31856.
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I just reread your post. Did you connect a tc wire to ground? This should not work!! The input to the 55 or 56 module is designed as a floating input. So no ground. Explain ground wire to thermocouple connector please. …
Yeah i thought so too but it works for me. Unless my max31856 board has something weird going on. As seen in pic i have a wire going from positive terminal to ground of wall plug. My kiln outside is grounded also. I measure around 0.4-0.6ohm from case to ground of wall plug. Same from either connection of thermocouple block and kiln case.
From the spec sheet on the chip you are shorting out part of the tc. Unless you are not connecting any other part of the pi system to ground. In other words one side of the tc is grounded but still floating wrt the pi . That would make sense but strange nevertheless.
On Fri, Jul 25, 2025, 6:49 PM Kirby @.***> wrote:
keebie81 left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3120955721
8246A932-0035-4F05-944D-14E2D239F917.jpeg (view on web) https://github.com/user-attachments/assets/d3d6f9da-4e46-4f00-903c-0ab042bae9be IMG_3828.jpeg (view on web) https://github.com/user-attachments/assets/7452c2b8-3256-4517-bf3b-5c1af1e5ec3d
I just reread your post. Did you connect a tc wire to ground? This should not work!! The input to the 55 or 56 module is designed as a floating input. So no ground. Explain ground wire to thermocouple connector please. … <#m_7412426862405523037_>
Yeah i thought so too but it works for me. Unless my max31856 board has something weird going on. As seen in pic i have a wire going from positive terminal to ground of wall plug. My kiln outside is grounded also. I measure around 0.4-0.6ohm from case to ground of wall plug. Same from either connection of thermocouple block and kiln case.
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I am trying to think of what is changing due to heat. Here is a few thoughts. If the kiln is not case grounded, then ground it. It may be, that at temp, due to heat expansion, an electrical short happens. A case ground will make shorts apparent, and is also a safety thing. If the klin is off, klinsitter is not tripped, and you are only switching one side of the 240v (assuming 240v with 2 hot wires), the elements are electrified. It maybe a short from an element to case. Elements have a layer of corrosion and may not have a good contact with the case, so not a "good" short. Heat expansion moving an element may be why it happens at high temps. I had issues with keeping the pi cool when too close to the klin. A heat shield and/or more separation may help. I did both and added a fan to the pi enclosure. I now monitor the MAX31856 internal thermocouple which is right next to the pi. I think the MAX chip has an operating rang of -55C to 128C. The outside of the kiln gets hotter than that. Wiggle the thermocouple wires at the junctions when it happens. If the thermocouple is cracked it may work at lower temps. Take it out and pull the beads off to inspect. Probably not the problem, because the fluke works. Blake
On Fri, Jul 25, 2025 at 11:52 PM rondoc @.***> wrote:
rondoc left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3121265805 From the spec sheet on the chip you are shorting out part of the tc. Unless you are not connecting any other part of the pi system to ground. In other words one side of the tc is grounded but still floating wrt the pi . That would make sense but strange nevertheless.
On Fri, Jul 25, 2025, 6:49 PM Kirby @.***> wrote:
keebie81 left a comment (jbruce12000/kiln-controller#225) < https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3120955721>
8246A932-0035-4F05-944D-14E2D239F917.jpeg (view on web) < https://github.com/user-attachments/assets/d3d6f9da-4e46-4f00-903c-0ab042bae9be>
IMG_3828.jpeg (view on web) < https://github.com/user-attachments/assets/7452c2b8-3256-4517-bf3b-5c1af1e5ec3d>
I just reread your post. Did you connect a tc wire to ground? This should not work!! The input to the 55 or 56 module is designed as a floating input. So no ground. Explain ground wire to thermocouple connector please. … <#m_7412426862405523037_>
Yeah i thought so too but it works for me. Unless my max31856 board has something weird going on. As seen in pic i have a wire going from positive terminal to ground of wall plug. My kiln outside is grounded also. I measure around 0.4-0.6ohm from case to ground of wall plug. Same from either connection of thermocouple block and kiln case.
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-- Blake C. Lewis
Could some one explain how the code " assumes " there is a short circuit present to begin with. What triggers that Error ? I have been using these inexpensive thermocouples with Skutt and CRESS Kilns. Bartlett controllers crash now and then as result of over heating or brownouts but they never complain about short circuit somewhere in the system.
I was assuming, not the code. It looks like the MAX31855, throws errors for short to Ground, and short to Vcc. I looked over the project code and it combines these 2 fault states to 1 message "short circuit". It would be nice to know if it is Vcc or Ground. I think the max sends a pulse through the thermocouple and then looks at the other end of the circuit to detect Open. Short to Vcc: It measures the voltage compared to Vcc Short to grnd: it messures the voltage compared to gnd
" https://www.analog.com/media/en/technical-documentation/data-sheets/max31855.pdf " Table 3 has a description of the faults the MAX31855 reports. It is up to the driver to put a label on the reported error state. So, I was assuming that the error message matches the reported state. and I was also looking at the MAX31856 datasheet, and the fault section is different.
On Sat, Jul 26, 2025 at 4:59 PM TinMaan @.***> wrote:
TinMaan left a comment (jbruce12000/kiln-controller#225) https://github.com/jbruce12000/kiln-controller/issues/225#issuecomment-3123433404
Could some one explain how the code " assumes " there is a short circuit present to begin with. What triggers that Error ? I have been using these inexpensive thermocouples with Skutt and CRESS Kilns. Bartlett controllers crash now and then as result of over heating or brownouts but they never complain about short circuit somewhere in the system.
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-- Blake C. Lewis
@BlakeCLewis, yes this is a thorough answer to my question. With assumption I meant the conclusion that code arrives at to display " ... short circuit " error. I scanned through the dat-sheet you linked. There are a few important suggestions for dealing with noise/signal. Most my LLM searches return these and other suggestions for the subject.