Issues with E3D-V6 thermistor on UMO+

[brentwerder 13]

Hey all,

Finally getting around to making those E3D mods I said I would a few months back... oops

Kit assembly is now easier than ever - seems like they've modified the electronics to be easier to work. It comes with a neat little 100k ohm Semitec 104GT thermistor which is held in the heater block with a grub screw. The thermistor and fan now come with detachable Molex terminals which make modifications and maintenance 10x easier than dealing with the mess of wires with the old hotend. However, before assembling the heater block, I tested the thermistor resistance and got some crazy number waaay off from what it should be. I did some testing with it in the printer (modified firmware) and got a constant 9 degrees from it at room temperature , which didn't change no matter what I tried - even when unplugged. Definitely dead - currently working with E3D to get a replacement going.

I had my buddy print me a nice little mount (http://www.thingiverse.com/thing:1742018) for the hotend, and it seems to be holding very well. Almost more solid to the touch than the old assembly - even though I accidentally used an Ultimaker 2 mount. The only difference there was the reversed axes, so now the print head is in the back right corner instead of front right. Oh well.

Here's the real issue - the firmware. Since the old thermistor didn't work, I plugged my old PT100 into the slot where the Semitek should go; they're the same diameter and the PT100 is about a millimeter shorter. I know the PT100 works fine, since I hadn't had any issues with it when it was installed in the Original + hotend assembly. However, when using the same firmware, which should account for the PT100, I got the Err: MAXTEMP popup. When connected to my computer, the hotend showed a 11000C readout at room temperature. The readout remains the same when unplugging the thermistor.

I'm afraid to say the motherboard might be the issue here, but I'm not sure. Both thermistors did not change the temperature readout when being plugged/unplugged from the board. Lucky for me, I happen to have a flawless extra board which I can do some testing on, but I'd rather not plug anything into it before getting some feedback from you.

Thanks!

-Brent

[neotko 1,417]

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 October 7, 2016 by Guest

[brentwerder 13]

Good idea! I didnt know I could use TEMP2. I'll try that ASAP, which might be in a few days.

[brentwerder 13]

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.

[neotko 1,417]

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.

[Torgeir 242]

Hi Brent,

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;

http://www.micropik.com/PDF/pt100.pdf

(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.

Thanks.

Torgeir.

[brentwerder 13]

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.