Good idea! I didnt know I could use TEMP2. I'll try that ASAP, which might be in a few days.
Okay... bad news.
I played around with resistances and different configurations of the bed thermistor and the hotend thermistor, and nothing worked.
I found that the E3D Semitec thermistor is in very good condition. The resistance instantly went down from its starting 121.7 kilo ohm resistance at room temperature when I held onto it.
I pulled the PT100 out of the old hotend and tested its resistance, which was around 3 megaohms. I really have no idea if that's normal. It doesn't seem like it, but then again, the thermistor was working perfectly before disassembly. Possibly a bad reading? It was very hard to get contact when measuring.
I unplugged the bed and first tried the hotend PT100, which read 11000C, the same as the hotend readout. It read 11000C if I had either of the hotend thermistors in either TEMP1 or TEMP3. However, it read 20C when I plugged the bed into TEMP1 or TEMP3 - meaning the connection is still good on TEMP1! Hooray!
I believe this means one of three things:
Option A is that the firmware is somehow not accounting for either hotend thermistor and is instead not reading anything at all. This means that I only have to make a good firmware build and the issue should be resolved. This is my favorite option.
Option B is that the hotend PT100 is busted (it had a weird reading, which I think I'll redo later since it fluctuated so much). That would explain why another PT100 in the bed read correctly, but that one wouldn't. It also means that if I change the firmware the E3D should work correctly.
Option C is my least favorite. The hotend PT100 is broken, AND the E3D is either broken or not supported by the Arduino Mega. I really don't know much about electronics, so I have no idea whether or not a 121.7 kilo ohm thermistor will work correctly on this board.
I'm now able to perform tests again on my machine, so if you have any ideas as to what I should try next, I'm all ears.
Yeah first of all. There no way to connect something different than a pt100 on a ultimaker 2.1.X board without extra hardwae and some firmware modding. I saw long ago a post of someone that did it but he never explained how.
Also the pt100 reading is weird. It should be 100 Ohm at room temperature (more or less). So yeah the pt100 might be damaged.
At least the board connectors are working.
I would love to help you making that thermistor work but I never done it and I think it needs a board in between and using some of the free pins on the board + firmware modding.
Just a little additional stuff.
It's easy to remember, -PT100 is reading 100 Ohm at zero deg. Celsius.
Here's a table for "all" other values;
(Also interesting to know about the original thermocouple in UMO;
Chromel-Alumel thermocouple is reading zero Volt DC when the temperature is zero deg. Celsius. (a mixture of ice cubes and water).)
(The other known referance point is; "clean boiling water" is 100 deg. Celsius at sea level.)
This is just some part of the metric system..
In order to check that if your boards is reading the correct temperature, use resistors to simulate the temperature you want, normally two point, zero deg. Celsius and the high point (say) 260 deg. Celsius.
Remember that normal resistors have tolerances (good ones +/- 2%), so use a good multimeter and the multimeter value for your "calibration"/check.
Alright, the PT100 is dead. It's reading about 3 megaohms whenever I test it, and it looks like the wire is frayed. I'll order a new one ASAP.
To understand, you plugged the thermistor on the pt100 connection to try?
I would try that pt100 on the pt100 bed to see if is the sensor or the plug was damaged when connecting other than a pt100.
If that's the case, you could connect the pt100 to the Second hotend pt100 and make your own Marlin firmware build, changing the Pin.h table so the pt100 sensor for the main hotend is the one of the secondary hotend.Edited by Guest
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