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Describe your issue:
I think that the problems, which I thought I had forgotten about the excess temperature in the extruder, are becoming
So I want to put two thermistors, to monitor the temperature in the printing area and in the extruder’s NEMA 14 motor.
Can I connect the two thermistors to the same socket on the EBB42 canboard?
The socket would be the one for the Zprobe, which I have free.
It would be one in PA4 and another in PA5… and in negative:
A)- Can it be the same?
or
B)- Does it have to be the same?
or
C)- Does it have to be different?
And, once connected…
Is the temperature data saved somewhere?
Can it only be seen in the Fluidd interface graph? klippy.log (829.0 KB)
The answer is that no, you can’t connect multiple thermistors to the same socket.
You really don’t need more than one thermistor in the toolhead. There should be no danger of the extruder stepper motor overheating.
For some reason, people run 1A or more through the extruder stepper motor when half (0.5A) is a good place to start.
There’s no need for high currents (which results in high temperatures) through the extruder stepper - if you have to crank up the current going to the extruder stepper then you’ve got a problem in terms of a blockage that you should be looking at first.
I’ve been trying to configure a temperature sensor connected to the Canboard, an EBB42.
But the readings are VERY far from reality, I don’t think it’s just a problem of choosing the type of sensor, since I’ve tried these types, and the reading of the temperature at rest is what I indicated. (It’s the kind of temperature sensor from Aliexpress, I think the Generic 3950, but I’m not sure:
With the printer in standby, changing the “sensor_type”, the reading is:
This makes me suspect that it is not just an error in the type of sensor configured, it has to do with something else. Because the detected temperature is similar, no matter how I configure it, around +100 ºC
Just to be clear, it’s the EBB42 that is reading 100C higher than expected, correct?
If it is, check to see if the “PT100”/JP2 jumper is loaded in the EBB42. It should be empty.
If it’s not that, check your printer.cfg to see if there is a pullup_resistor: parameter in your extruder statement. If it is there, It should be pullup_resistor: 4700 - 4.7k is the default pull up resistance so if it’s not there then no problem. Both the EBB42 and Octopus Pro use 4.7k pullups on the thermistor circuits.
Other than that, please share your latest klippy.log and some drawings/photographs of how things are wired.
I have connected a second thermistor to the EBB42 board in a free shocket, the one intended for the Zprobe.
I thought that the thermistor could be connected to that shocket, and not only to the one intended for them.
The idea with that second thermistor is to monitor the temperature of the stepper motor, since it gets too hot… and in the future, to monitor the temperature of the chamber.
But from what I have read afterwards, I think that a second thermistor cannot be connected to another shocket.
I just did a bit of a deep dive into the EBB42 and you could add another ADC input but it would take a bit of work and is probably not for the faint of heart.
If you go back to the STM32G0B1 datasheet, you’ll see that the only pins capable of being used as ADC inputs (needed to read the value generated by the Thermistor/4.7k resistor voltage divider) are PA0 - PA7. The “PROBE” pin which is the one I think you’re referencing is PB8 and does not have ADC Input capability.
I’ve taken the PA# pin descriptions from the datasheet and put them together so you can see what I mean - Look for the “ADC_IN#” notes that I’ve circled:
Going back to the schematic, PA8 & PA9 are not connected pins BUT they do not have ADC input capability.
I’m just looking at a board I have here (Amazingly enough, I have been looking at the STM32G0B1 datasheet, EBB42 schematics and have an EBB42 on my workbench) if you were to remove the MAX31865 (which is on the backside), then you would have access to PA4 - PA7 (pins 15 - 18) and it wouldn’t that hard if you have the tools and experience to do that.
You would need to take off the MAX31865, run a wire from a pin from 14 to 17, of the MAX31865 footprint, attach a 4.7k 1% pullup to it (use pin 2 of the footprint), wire that to one end of your thermistor and connect the other end of the thermistor to Ground (Pins 9 or 19 on the MAX31865 footprint).
