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erwin!

Temperature sensor is acting strange

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Hello,

I've been printing with my Ultimaker for a while and everything was fine, i printed some good stuff and there were almost no problems. A while ago my temperature sensor started to act strange, when i set the temperature to 230 the temperature was just rising till 230 and when i pressed print the kept changing from around 220 to around 240 (I used cura and pronterface to see the temperature) and it did not print. For some reason the temperature kept rising though and my PEEK insulator started to smoke and molt apart. I got a new PEEK insulator and temperature sensor, the weird temperature problem hasn't stopped yet and i can't print with Pronterface anymore. Cura also gives the changing temperature and will only print if i restart the printing interface around 5 times. I made some screenshots so you can see the problem:

http://tiny.cc/h548qw

http://tiny.cc/f648qw

I can still print but it takes a very long time to start it with Cura, any help would be very appreciated.

Thanks in advance

Erwin

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An interesting problem, very annoying of course.

Maybe there is crosstalk between the heater and the temperature sensor. When the heater switches on, the temperature measurement is affected upwards.

What happens when you heat it up to about 200-230 degrees, and then lower the setpoint to 0?

The result will be that the heater switches off and stays off. It'll be interesting to see whether the "measurement disturbance" is still there or not.

By the way, are the schematic drawings of the electronic circuits available somewhere? Anyone?

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That's the problem, when i set the temperature to 180-240 it just raises to the set temperature and and the sensor just gives the actual information, when it reaches the set temperature it starts to change from 10-20 degrees above it to 10-20 degrees below it (t actually never reaches the set temperatures). When i set the temperature to 0 again the heater goes off and it shows me the dropping temperature without disturbance.

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That's the problem, when i set the temperature to 180-240 it just raises to the set temperature and and the sensor just gives the actual information, when it reaches the set temperature it starts to change from 10-20 degrees above it to 10-20 degrees below it (t actually never reaches the set temperatures). When i set the temperature to 0 again the heater goes off and it shows me the dropping temperature without disturbance.

Are those "reasonable" fluctuations, meaning are they slow enough being cause by "natural" cooling/heating, or are they more like flickering, bouncing +-20C within 1-2 sec?

if it is slow, I assume your PiD settings are off, or you have your fan blowing against the hot end, and you need to calibrate your PiD settings with M303 S210... once the routine is finished, transfer the new PiD values into memory via the UC, or via Daids marlin tool, or enter it manually into the firmware code, compile&upload.

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That's the problem, when i set the temperature to 180-240 it just raises to the set temperature and and the sensor just gives the actual information, when it reaches the set temperature it starts to change from 10-20 degrees above it to 10-20 degrees below it (t actually never reaches the set temperatures). When i set the temperature to 0 again the heater goes off and it shows me the dropping temperature without disturbance.

So the disturbance is related to the heater being on and off.

I must agree with Daid about a loose wire ,or bad connection. You say you checked the wires. Did you really unplug/plug the wires, and unscrewed/screwed all wires?

Do you have a volt meter? I would measure the voltage between pen 3 (gnd) and pen 1 (V_out) on the small thermocouple board. Do you see the same variations there?

(The AD597 chip that is used to amplify the thermocouple readings will give an analog voltage change of 0.3V in case of a temperature change of 30degrees. This is perfectly measurable with a normal voltmeter.)

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Yes, i checked every thing about 4 times, i will use a voltmeter later this week to try that.

I would take the AD597 board out, and check the solder joints under a loupe. it rare occasions solder joints had been a bit dry, or have become dry over time. resoldering the 5 joints to the 2 connectors would help in this context, maybe.

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If your Peek melted, you were actually WAY above 240C, regardless of what the software was saying. I know this because I melted my Peek the first week and the actual temperature was over 460c. In my case, the temperature sensor wires had been pulled out by the bowden tube, which had popped out while I was out of the room for 15 minutes. When I quickly got the wires plugged back in correctly a few minutes later, it showed 460C on my Ulticontroller display and it had already been cooling down a little. Before plugging the wires back in, it showed a much lower temperature that was changing rapidly in random directions.

If the wires are connected perfectly, t sounds to me like the board Joergen described is either poorly soldered, or dead.

 

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Have you updated your firmware recently? It seems like every time I build a new version of Marlin, either using Daid's Marlin Builder or the Arduino IDE, I get a change in temperature control performance (sometimes it's better with a new build but sometimes it's worse). Most anything switching on and off in my machine (steppers, fan, etc.) causes the fluctuations you are seeing. When it's bad the nozzle reading typically gets up to print temperature nice and steady but then the steppers kick in. Then it jumps all around for the duration of the print. It seems like a noise issue to me but it's interesting the the Marlin build affects it with no correlation to any settings that I can see.

 

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If I remember correctly from a talk with Erik the temperature read out is an analog signal that goes from the nozzle to the main board, so I think it's quite perceptive to noise. Maybe you can keep the noise down by not connecting via USB and doing the readout from the UC?

We had a lot of problems with noise inflicted from two separate grounds (from adapter and from USB) when I did some high detail temperature readouts with an Arduino and a separate ADC for another project.

That being said, I don't have any of the problems above, temperature is nice and steady with my UM, but I never connect a computer to the UM (except for firmware upgrades)

 

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If I remember correctly from a talk with Erik the temperature read out is an analog signal that goes from the nozzle to the main board, so I think it's quite perceptive to noise. Maybe you can keep the noise down by not connecting via USB and doing the readout from the UC?

We had a lot of problems with noise inflicted from two separate grounds (from adapter and from USB) when I did some high detail temperature readouts with an Arduino and a separate ADC for another project.

That being said, I don't have any of the problems above, temperature is nice and steady with my UM, but I never connect a computer to the UM (except for firmware upgrades)

Yes--the thermocouple signal is analog and must be amplified before it leaves the extrusion head. I also never use USB except for firmware updates, but my Ulticontroller temp display jumps around a lot. Strangely, with the latest Marlin build, the readout is more steady with the fan on than off, but it still jumps when the steppers come online.

 

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I would take the AD597 board out, and check the solder joints under a loupe. it rare occasions solder joints had been a bit dry, or have become dry over time. resoldering the 5 joints to the 2 connectors would help in this context, maybe.

 

You have made an excellent suggestion, Joergen. Assembly defects could easily be the root cause of my temperature "jitters." I found two solder defects on my Ulticontroller main board that required correction before it operated consistently. The assembly on all these these UM boards (AD575, Arduino, UC) could be better, from what I've seen on my three boards and what others are reporting.

I also think AD575 jitters may be interfering with the PID autotune feature. I've run autotune under several conditions with several temperature targets and the result never works very well (not as well as the Marlin Builder PID defaults or the factory defaults).

When I tear my V2 hotend apart to install my higher temperature resistant custom upgrades, I'll check the AD597 board.

 

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I would just take it off and touch up the 5 joints, and see if it helps

 

I'm too busy printing stuff right now. That will have to wait.

In the meantime, I can build Marlin code and upload it to the printer before each print and I've discovered something significant. The official Marlin .hex file that's included with Cura ("Marlin-Mon, 11 Jun 2012 17:33:42 +0200 - b67dacdc8f1bd489e058e16d92ba29c364b2a8e5") results in significantly more stable temperature control than anything I've ever built using Marlin Builder or the Arduino IDE and Erik's code tree--even when I use the Configuration.h file that is included with Marlin!

Something has changed in the code tree since 11 June, 2012 that affects temperature stability. I've noticed that other LCD display fields have become glitchy, of late, and while the PID LCD fields appear to work in the Official Cura Marlin, Daid informed me that all but P are not displayed correctly and, based on my observations, I think this bug has crept-in since 11 June, 2012. I think there may be more at play than just how I and D are displayed and I also think there might be a change that make the machine more noise sensitive. In fact, everything is glitchy in the newer builds (in addition to LCD display value jitters, user selections are sometimes missed, requiring re-clicking, and fan speed changes are significantly delayed, etc.)

For now, what I need is the exact build tree that was used to make "Marlin-Mon, 11 Jun 2012 17:33:42 +0200..." Using the code tree for the released version of Marlin, I can just change the PID values to match what autotune advises, and also increase the HEATER_0_MAXTEMP to print the materials I have that don't work well at 260 C (even my Ultimachine ABS tests at 270 C prove 260 C results in weakly bonded layers) and hopefully it will work as well as the official Marlin.

-Cal

Update:

There are plenty of code trees from around the June 2012 time frame on

https://github.com/daid/Marlin

and

https://github.com/ErikZalm/Marlin

but I'd like to grab the exact one that was used to create ultimaker_115200.hex and ultimaker_250000.hex

if Daid or Erik can tell me where to find it (or which one on github is the right one).

Update 2:

I built Marlin-test-2 with and without my custom PID values and they both work.

https://github.com/ErikZalm/Marlin/tree/test2

I also increased the max temp limits anticipating my hot end upgrade.

More importantly, the nozzle temperature excursions and jitter, poor fan response, z-axis stepper glitching, and keypress misses are gone too. I don't know why all these problems have crept into more recent Marlin builds--at least on my machine, but the old Marlin works significantly better for me. It works like the day I got it again! :)

 

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