NTC EPCOS 100k Thermistor.

[Flateric]

I am trying to get this resistor to read correct values, but cannot for the life of me. It is either reading 4.5c at room temp and is way off when heated, shows 120 when it's really 220.

or

It shows 1024c at room temp.

I have tried every single preset value in both repetier and in marlin.

Any help would be great since I am truely lost on this one it seems, or missing something basic.

Again the thermistor is a " NTC EPCOS 100k Thermistor. "

Thanks guys.

[Polygonhell]

I am trying to get this resistor to read correct values, but cannot for the life of me. It is either reading 4.5c at room temp and is way off when heated, shows 120 when it's really 220.

or

It shows 1024c at room temp.

I have tried every single preset value in both repetier and in marlin.

Any help would be great since I am truely lost on this one it seems, or missing something basic.

Again the thermistor is a " NTC EPCOS 100k Thermistor. "

Thanks guys.

What resistance does it read at room temperature? It should be around 100K if it's not, it's broken, there is something wrong with your wiring, or it's not the thermistor you think it is.
I have several of those and they all read fine. Using marlin I use either the generic 100K table or the epcos specific table, and they are both close to correct.
I have seen similar false readings if there is a partial short in the thermistor path.

[Flateric]

Hmm, I appreciate the answer. I have tried more than one of them, perhaps that channel is bad on my Rambo.

I'll get back to you in a bit with my findings.

Thanks very much!

[Flateric]

Well I can't really explain it, but what I did was tried to revert back to marlin, it uploaded the firmware successfully, then marlin would only report 500c for my extruder and 500c for my heated bed sensor.

This seemed really odd so I decided to start from the begining.

I removed Repetier host from my system entirely.

Re-installed it.

Decided to give it a load and connect and suddenly all my sensors are reading perfectly.

Seems that repetier host was gunked up somehow and giving false readings to me.

[Flateric]

I'm going to try to go back to your version of repetier firmware now Poly and see what that brings me. It is the version of firmware I liked the most so far anyways.

[Polygonhell]

Seems that repetier host was gunked up somehow and giving false readings to me.

I very much doubt it had anything to do with the host software, all that does is parse a string sent from the firmware. If you enable ACK in the log window you can see the string being read.

[Flateric]

Well, it seems that perhaps I suffered some type of board damage or inconsistency when my hot end separated. Only guessing. Not complaining or anything like that. Speculation.

If I take a simply plug swap the thermistors between the heated bed [T2] and the extruder [T0], the heated bed thermistor [now in T0] fails with the same behaviors. The extruders thermistor [now in T2] fuctions perfectly showing that it is not the thermistor or it's wiring faulting on me.

Leading me to believe that the actual thermistor input channel [T0] is faulting not the thermistors [bed or extruder thermistor wiring], since both will operate properly in the heated bed's thermistor input location [T2].

No problem I figured, I'll just switch the extruders thermistor to come from [T1] the secondary extruder thermistor channel. However [T1] is demonstrating the exact same fault as channel [T0] exhibits. And with no thermistor of any type plugged into the first two channels [T0, T1] they still will often (but not at all times, but usually) report a temp of +4.2c. If I do the same test with the heated bed channel [T2] it reports back a 0.00 for temp.

With thermistors hooked up to the two first channels I am however getting consistent readings, they are just very wrong....consistently. I have determined with a laser prob that the outside of the hotend (I understand this is cooler than inside the extruder) is at 205c when my thermistor is giving me a reading of 120c through either [t0 or t1].

If I adjust my repetier host and firmware (marlin or repetier) to allow extrusion at the inaccurately indicated temp from the thermistor I am able to successfully extrude melted filament from my currently borrowed hotend (still waiting for my new replacement to arrive) and print.

So I could continue to adjust my software and gcode to think printing etc is ok at the incorrectly read temps or my thinking is to create a themistor table that corrects the readings my board is reporting to be the correct values and the flaw or fault is thenby passed by the modified thermistor table.

The problem here is I have not go the slightest clue how to go about doing that. Room temp with the EPOC 100k thermistor selected shows 8c, if I select the 200k thermistor then the correct room temp is reported by the thermistor but the reported temp that I can extrude from the hotend at is still an inaccurate 115c while the laser probe shows the hotend at full 200+c operating temp. As the heat goes up the 100k and the 200k top out at around the same 120c reading which is in fact 200+c.

I am assuming a thermistor table correcting for the fault on my board should be able to modify the reported inaccurate reading to be a modified correct one.

I obviously cannot use the autotune PID feature because if I send a M303 s200 to my faulty thermistor setup it will in reality be heating well well past 200c when it is still reading the incorrect value of only 120c. By the time it hit the value read as the requested 200c it obviously would be god knows how hot and likely well past many components limits both physically and eletricly destroying both and serving no useful end.

Obviously the best solution is to simply replace the suspect rambo, a costly choice and one I may have to end up at.

But since the Rambo is functioning correctly in every way other than the thermistor readings being 100c or so lower then reality I am exploring options. Is there any other possibilities you can come up with Poly?

Also, please accept my thanks in advance for you assistance in this not uncomplicated issue. I know it's kind of a pain in the ass and all. But the learning curves are steep and I am doing my best to catch up here.

[Polygonhell]

Lets take a step back.
Your saying either thermistor plugged into T2 works correctly, but neither work if you plug it into T0 is that correct?
Can you show me the portion of configuration.h where you have configured the hotend and bed thermistors?

I very much doubt it is a board issue if T1 does the same thing as T0.
There is only one ADC on the ATMel microcontroller, it's just multiplexed between the inputs, you can burn a pin out if you exceed the input voltage on the pin, but they usually stop responding altogether. It's possible the fault is on the board but I'd be surprised if it affected both pins.

[Flateric]

I just rechecked and redid my flashing with brand new fresh ones from the webpages and so the sections you refer to are completely untouched from the web, or unmolested, LOL.

Unless some of the changes that arduino flashes do not "take" for some special reason?

BRB gonna check that.

[Flateric]

Ok, I'm confusing myself with doubts here, which version from where specifically should I be getting repetier firmware from?

I am currently on

https://github.com/polygonhell/Repetier-Firmware

[Polygonhell]

Ok, I'm confusing myself with doubts here, which version from where specifically should I be getting repetier firmware from?

I am currently on

https://github.com/polygonhell/Repetier-Firmware

That one should be fine, but it isn't configured for the EPCOS thermistor.
However even without changing the tables the temperatures shouldn't be miles off.

[Flateric]

This was my very first real print last night, I'm pretty damned happy with it really.

I think my board is done now man, I managed a few nice prints with my borrowed hot end last night and went to fire it up this morning and I simply get -20 for the extruder and -50 for the bed, other times I get some kind of bizzare checksum error, however now I'm not...

This is my log window on attempt to connect.

14:59:45.701 : OpenGL renderer:GeForce GTX 570/PCIe/SSE2
14:59:45.701 : Using fast VBOs for rendering is possible
14:59:56.666 : start
14:59:56.666 : External Reset
14:59:56.688 : N1 T0 *27
14:59:56.690 : N0 M110 *3
14:59:56.692 : N1 M115 *7
14:59:56.705 : FIRMWARE_NAME:Repetier_0.81 FIRMWARE_URL:https://github.com/repetier/Repetier-Firmware/ PROTOCOL_VERSION:1.0 MACHINE_TYPE:Rostock EXTRUDER_COUNT:1 REPETIER_PROTOCOL:2
14:59:56.705 : Printed filament:0.00 m
14:59:56.705 : Printing time:0 days 0 hours 0 min
14:59:56.712 : N3 M111 S6 *68
14:59:56.718 : N4 M80 *63
14:59:56.722 : N5 M220 S100 *68
14:59:56.731 : N6 M221 S100 *70
14:59:56.739 : N7 M111 S6 *64
14:59:56.750 : extruder 0: temp sensor defect
14:59:56.750 : heated bed: working
14:59:56.750 : Printer set into dry run mode until restart!

And switching the temp sensors around in the sockets has no effect any longer.

[Polygonhell]

You can ignore the checksum error, it's the result of a fix that was made in repetier for a problem someone else on the forum was having with long prints.
I assume you've checked the thermistor wiring?
Seems very odd that both would fail though.