Thermistor set wrong(?) - how to correct it whithout ruining everything else...
Posted by vladek7
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Thermistor set wrong(?) - how to correct it whithout ruining everything else... June 07, 2016 06:52PM |
Registered: 7 years ago Posts: 6 |
Hello everyone
I think I am looking for some advice. But maybe not?
I am building MendelMax 1.5 and I am half way there building mechanics and while still printing some bits I decided to start setting up Arduino and firmware - I have no prior knowledge of it. Nil.
I loaded Merlin on it and connected bed and extruder thermistors and noticed that both are showing exactly the same temperature. It obviously good and that is not a problem.
Problem is with Prusa i3 standing next to it where I am printing remaining parts.
It never before occurred to me that those thermistors could be so accurate and I think I got enough confidence now to say that 15C degrees difference between extruder and bed temperatures (when both cooled down, see attached picture) are waaaay off each other (even for printer put together from cheap £150 Chinese flat pack kit).
Now having comparison I understand why my ABS was so determined to not to stick to 110C hot bed. Turns out it was more like 95C.
Anyway. Thing is I would like to fix that if possible without messing the rest of the settings.
The firmware was preloaded on the board I got with the kit. It's Merlin on it and as far as I can say the mainboard is some sort of Generation 6 single board integrated electronics.
Is there a way of recovering the settings I would need to put in configuration.h in case I need to start from scratch?
If there is a way I would imagine what I would need to do is to put all the setting as they are and play with type of thermistor to get the one matching the hardware installed.
I mean it looks like there are two options:
Thermistor had the wrong type set in configuration.h or its faulty.
At the moment I assume is set wrong because when the bed heats up the temperature grows, stabilizes and goes down when the power is cut from it (and difference was always like that from the day one).
I connected my MendelMax destined thermistor (standard 100k NTC) and it shows the same setting like the extruder one - obviously when both bed and extruder have not been in use for hours.
Is it possible for thermistor to 'operate' consistently when it's actually faulty or will it, in such case stop working completely?
I wonder if it wouldn't be faster simply to replace it?
But then taking apart the bed and Y axis to get to little bugger seems to be a bit excessive to me if it could be mended by reloading the firmware with correct settings.
Any suggestions?
Many thanks for reading.
Edited 1 time(s). Last edit at 06/07/2016 06:53PM by vladek7.
I think I am looking for some advice. But maybe not?
I am building MendelMax 1.5 and I am half way there building mechanics and while still printing some bits I decided to start setting up Arduino and firmware - I have no prior knowledge of it. Nil.
I loaded Merlin on it and connected bed and extruder thermistors and noticed that both are showing exactly the same temperature. It obviously good and that is not a problem.
Problem is with Prusa i3 standing next to it where I am printing remaining parts.
It never before occurred to me that those thermistors could be so accurate and I think I got enough confidence now to say that 15C degrees difference between extruder and bed temperatures (when both cooled down, see attached picture) are waaaay off each other (even for printer put together from cheap £150 Chinese flat pack kit).
Now having comparison I understand why my ABS was so determined to not to stick to 110C hot bed. Turns out it was more like 95C.
Anyway. Thing is I would like to fix that if possible without messing the rest of the settings.
The firmware was preloaded on the board I got with the kit. It's Merlin on it and as far as I can say the mainboard is some sort of Generation 6 single board integrated electronics.
Is there a way of recovering the settings I would need to put in configuration.h in case I need to start from scratch?
If there is a way I would imagine what I would need to do is to put all the setting as they are and play with type of thermistor to get the one matching the hardware installed.
I mean it looks like there are two options:
Thermistor had the wrong type set in configuration.h or its faulty.
At the moment I assume is set wrong because when the bed heats up the temperature grows, stabilizes and goes down when the power is cut from it (and difference was always like that from the day one).
I connected my MendelMax destined thermistor (standard 100k NTC) and it shows the same setting like the extruder one - obviously when both bed and extruder have not been in use for hours.
Is it possible for thermistor to 'operate' consistently when it's actually faulty or will it, in such case stop working completely?
I wonder if it wouldn't be faster simply to replace it?
But then taking apart the bed and Y axis to get to little bugger seems to be a bit excessive to me if it could be mended by reloading the firmware with correct settings.
Any suggestions?
Many thanks for reading.
Edited 1 time(s). Last edit at 06/07/2016 06:53PM by vladek7.
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Re: Thermistor set wrong(?) - how to correct it whithout ruining everything else... June 09, 2016 05:36PM |
Registered: 7 years ago Posts: 6 |
I did some thinking and measuring. Also the atmospheric pressure got up and I have more optimism then when it's raining.
I decided to go for replacement of thermistor. It will be more work but result likely to be more reliable.
When 100k thermistor is connected the temperature reading at room temperature are spot on. When the currently installed thermistor is measured at 25C it reads 50.8k ohm.
There is no thermistor type specified in Merlin tables with such resistance at room temp so I assume the one I have installed is somehow damaged.
I will try to do parallel measurements of the same bed on two RAMPS I have available and see if both show the same after thermistor replacement. It should put my mind at ease...
I decided to go for replacement of thermistor. It will be more work but result likely to be more reliable.
When 100k thermistor is connected the temperature reading at room temperature are spot on. When the currently installed thermistor is measured at 25C it reads 50.8k ohm.
There is no thermistor type specified in Merlin tables with such resistance at room temp so I assume the one I have installed is somehow damaged.
I will try to do parallel measurements of the same bed on two RAMPS I have available and see if both show the same after thermistor replacement. It should put my mind at ease...
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