Help with thermocouple


I just got my E3D V6, Only it has a Thermocouple type K.
Now people say that I need a ThermocoupleBoard. How did you guy’s hooked it up?
Just want some information before i order the board. Maybe there are other ways to get the temperature reading from the thermocouple?


Hi, you’ll need some sort of electronic interface to provide amplification and cold junction compensation. This is relatively simple if you have a circuit based around an AD8495 or AD595. The voltage from either of these circuits will be linear with temperature and can be fed straight into the k8200 control board but watch signal polarity! The k8200 firmware will need a tweek to allow for the new temperature to voltage charateristic.


Maybe you can answer another question. I have a 100k ohm NTC, But when i hook it up just as always the repeater software said it is 130 degrees at room temperature. But when i Start heating it goes to the temperature i have set. Any idea how i can get it to my room temperature?


Is the thermistor the one supplied in the kit? It sounds like the thermistor is doing something when heated. I.e ambient temperature =130degC. I assume the heat setpoint is around 190 and you get something similar displayed? This sounds like the thermistor might be a 10kohm unit (have you checked with a meter?) OR the firmware conversion table needs some attention?


Yes it is a 1000K OHM But not the origional. Does that matter?
And yes it moves but room temperature is 130 degrees. so about 100 degrees to much.

I’m now trying to get the framework working but i can’t verify it. It gives an error.
If I can change the framework do you know what i have to change?

Here you can see that it in fact warms up:

It cools fast because i had the fan on it to cool it down haha. I don’t know how hot it extually is and i don’t want to burn my extruder

Ok, there will be slight differences in the thermistor curves between different manufacturers. Next thing to try is to disconnect the sensor from the problematic channel and instead of the sensor connect a 100kohm fixed resistor across the sensor terminals of the controller. What reading do you get?

If i disconnect the plug (extruder themp meter) from the board it gives me 129 degrees. So with nothing on it. Is that correct? or is my board broken :S


And 738 degrees if i connect them together with nothing in between

Oh and afcourse with a 100k NTC it gives 131 degrees and if i put my finger on it it goes to 131.30 degrees or somewhere in between. I have ordered a Thermocouple board now with a thermocouple cable. but i don’t think that it’s going to fix the problem. Also i need the original extruder to print a mount for my new e3d V6.

Does anybody know what tempeture it normally gives when you unplug the NTC?



It does sound like there is a problem with the controller. When the sensors are disconnected from my board the temperature reads 0degC. Can you carry out the same test again but record the voltage across the sensor terminal with 1) no resistor or sensor connected, and 2) with the 10k resistor connected. This will give me some idea as to what the potential divider circuitry around the sensor input

I will measure it in about 2 hours.
Maybe this will help. I had the extruder temp meter on the heated bed input and it gave me a good reading.
So we know it is in the controller it think. Never did anything weird wit the controller.
So if i have nothing connected it gives me 129.70 degrees. If I unplug the heated bed the tempeture dissapears in repeater host but the extruder keeps showing when i unplug it. So it looks like it keeps a voltage on the connector or something.

As I said I will measure the voltage in a couple of hours.


I can’t find anything weird or burnt out?

Extruder gives 1.70 V
Bed 4.50v

Hi Lucas,

These voltages are for both sensors disconnected?

If so, can you do the same measurement with a 10kohm resistor fitted across the terminals on each sensor:

10 k ohm still the same, still 130 degrees. And if i heat by 10 degrees. It gives 10 degrees on the repieter software. same as the 100k ohm

I mean 10 degrees more, so 140

Ok, I’m certain it’s the control board. Maybe it was too hot or the resistor broke. It’s still all original and never had any changes so i hope it’s repairable or warranty. I emailed the place where i ordered it and opened a velleman warranty ticket.

Thanks for the help though!


Hi Lucas,

Sorry for the response, I did mean measure the voltages at the sensor intput terminals with & without the resistor - ignore the indicated temperature reading I was trying to establish what is going on with the input stage with raw signals only. By measuring the voltage this rules out effects of of dodgy / misbehaving software. The voltage readings taken would be down to ohms law alone. In my opinion this does seem to be a weakness in this particular controller’s design.

The signal path is directly linked to the input pin of the microcontroller. The thermistor signals could be considered long in length and run in parallel with ‘dirty’ motor power conductors which are prone to nasty inductive spikes (I know there are protection diodes as part of the motor driver…) and my observations are that the motor signals will couple with the sensor signal straight up to the front door of the microcontroller. There are ‘filter’ capacitors on the sensor inputs but I can’t help but feel that there should be a series resistor on the controller between the sensor input and the filter capacitor / uC connection. This would have the effect of limiting the currrent flowing directly into the microcontroller pin thus in the first instance protecting the upper ESD diode from over current and hence the 5V rail from over voltage.

This should be small relative to the thermistor resistance when hot to maintain the ADC dynamic range but something 100ohm - 1Kohm would do wonders for current limitation when a fault condition exists whether it be high spikey voltages OR someone inadvertantly gets the wiring wrong during first build / modifications… The next improvement which would serve the smaller ohmic series resistor scenario would be to add a ‘transorb’ TVS diode in parallel with the filter capacitor thus directly protecting the microcontroller input from over voltage.

The knock on effect of these hardware refinements would be the need to recalibrate the firmware / tweek the thermistor look-up table…

I invite further comment from the forum…



Resistor 8 is broken.
My dad did the measurements and we could say that.

Something like. It gives 4.9v on the heated bed and 1.5 volts on the extruder.
He tried to make something with another 5 volts and than a controller to set it to 0 degrees and some resistors (don’t know exactly). That worked. But when i heat it goes up very slow to around 40 degrees. When it is clearly over the 200 degrees.

I did never do anything with the firmware so that couldn;t be it.