Help PID tuning Dyzend Pro

dc42

@Veti said in Help PID tuning Dyzend Pro:

so this is a thermistor that is not optimal for use with the duet?

It's difficult to get good results from a thermistor over a very wide temperature range using the ADCs in most microcontrollers. Taking the Dyze 500C thermistor, its resistance varies from 8.1Mohms at 10C (a reasonable minimum temperature at which we should expect a reading) to 83.7 ohms at 500C. That's a range of nearly 100000:1.

The optimum series resistor to get the same accuracy at both ends of the range is about the geometric mean of the resistance range, which is 26K for this thermistor. That's almost 12 times the 2.2K series resistor value used on Duet 3, and 5.5 times the 4.7K resistor value used on Duet 2 and many other 3D printer controllers.

If we assume a 4.7K resistor, then at 10C we need to measure a resistance 1723 times the value of the series resistor. There is no way that can be done on an 8-bit controller that has a 10-bit ADC (resolution 1 part in 1024). A 12-bit ADC such as the Duets have could in theory detect it, but noise and ADC gain and offset errors will make the detection unreliable.

The high temperature end of the range is much better, because a 4K7 series resistor is only 56 times the thermistor resistance of 83.7 ohms.

If anyone really wants to get this thermistor working with Duet 2, then I suggest you connect it to one of the thermistor inputs on the expansion connector, with a 27K reference resistor connected between the input and VRef. Then use R27000 in the M305 or M308 command.

chris974M

@dc42 Merci pour vos reponse j'ai une duet 2 wifi + duex5 donc cette thermistance n'est pas utilisable sur cette carte ?

Phaedrux

@chris974M

If anyone really wants to get this thermistor working with Duet 2, then I suggest you connect it to one of the thermistor inputs on the expansion connector, with a 27K reference resistor connected between the input and VRef. Then use R27000 in the M305 or M308 command.

chris974M

@Phaedrux desoler mais je ne comprend pas vraiment bien je dois la connecter a la Duex5 et changer R4700 pour R27000 dans M305 ou M308 ?

Phaedrux

I don't think it's suitable for your needs. Perhaps a thermocouple would be a better solution if you really need the high temps, otherwise the 300c heater and thermistor from dyze is probably a much better choice.

nhof

For Dyzend Pro you could upgrade to something like this and this, or this and this (may want to double check compatibility). Some added cost, to be sure, but much better performance. PT sensors and thermocouples are much more linear so they avoid the adc resolution issues David is talking about.

chris974M

@nhof Donc avec ces modification je pourrais avoir une plage entre 200c et 450c ?

Phaedrux

@nhof I'm a little confused about why Dyze and Slice use high temp thermistors, but I guess it's a cost factor combined with the daughterboard requirements for PT and thermocouples?

nhof

@Phaedrux I'm guessing just to maximize compatibility with the greatest number of control boards. Some customers might not have good amplifier options for their systems? Or a lack of general 'industry' knowledge about other options for temp feedback.

I've used the dyze 500C thermistor before and it worked ok at high temps, on a ramps + marlin board. Haven't tried on the Duet.

These days I just use PT1000s because they works with the thermistor inputs on the duet without an addon board, and they're good enough for what I do.

nhof

@chris974M Yes, the PT100 or thermocouple should work well between 200-450C.

If you have questions on the temperature sensor components you can also check with Dyze Design. They are in Montreal, so they can help you in French as well

chris974M

@nhof Thanks you

FBG

@dc42 said in Help PID tuning Dyzend Pro:

If anyone really wants to get this thermistor working with Duet 2, then I suggest you connect it to one of the thermistor inputs on the expansion connector, with a 27K reference resistor connected between the input and VRef. Then use R27000 in the M305 or M308 command.

Dear dc42, i am very interested in do this. Could you explain a little more, with a schematic?

Best Regards

FBG

@FBG said in Help PID tuning Dyzend Pro:

@dc42 said in Help PID tuning Dyzend Pro:

If anyone really wants to get this thermistor working with Duet 2, then I suggest you connect it to one of the thermistor inputs on the expansion connector, with a 27K reference resistor connected between the input and VRef. Then use R27000 in the M305 or M308 command.

Dear dc42, i am very interested in do this. Could you explain a little more, with a schematic?

Best Regards

I am also using Duet Expansion Breakout Board

dc42

Connect the thermistor between pins 35 (Thermistor3) and 40 (VSSA) of the 50-pin expansion connector
Connect a 27K 1% tolerance resistor between pins 35 (Thermistor3 again) and pin 41 ADVREF) of the expansion connector

That's it.

ejarmo

would you be willing to locate the appropriate pins on a maestro for this process

dc42

@ejarmo said in Help PID tuning Dyzend Pro:

would you be willing to locate the appropriate pins on a maestro for this process

The Maestro does not have an expansion connector with thermistor inputs, so this process does not apply. You would need to desolder one of the existing 2K2 thermistor series resistors and replace it by a 27K resistor.

There is just a chance that you may be able to get the thermistor working with the existing series resistor if you use the new semi-automatic calibration procedure that firmware 3.2beta1 supports. The calibration procedure is described at https://duet3d.dozuki.com/Wiki/Calibrating_thermistor_and_PT1000_readings. Caution, if you are currently running version 2.x firmware on your Maestro then upgrading to 3.x firmware requires significant changes to the config.g file.

chris974M

@dc42 @dc42 désoler pour ma très longue absence je reviens sur se sujet qui est aujourd'hui mon dernier problème que je n'avait pas fini de régler. Sur l'extension a 50 broches j'ai une duex5 de connectez comment je dois procéder ?
Merci pour vos réponses

Phaedrux

@chris974m said in Help PID tuning Dyzend Pro:

@dc42 @dc42 désoler pour ma très longue absence je reviens sur se sujet qui est aujourd'hui mon dernier problème que je n'avait pas fini de régler. Sur l'extension a 50 broches j'ai une duex5 de connectez comment je dois procéder ?
Merci pour vos réponses

sorry for my very long absence I come back to this subject which is today my last problem that I had not finished solving. On the 50 pin extension I have a duex5 to connect how should I proceed? Thank you for your answers

See here on using the Duex
https://duet3d.dozuki.com/Wiki/Duex2_and_Duex5_Features

chris974M

@phaedrux merci pour ta réponse rapide, se n'est pas pour l'utilisation de la duex5 mais pour les branchement de la résistance 27k et de la dyzend

dc42

@chris974m, if you have a Duet Ethernet or Duet WiFi, and you do not have a DueX2 or DueX5 connected, then you can use one of the thermistor inputs on the expansion connector like this:

Connect the thermistor between the chosen thermistor input and VSSA
Connect the 27K resistor between the same thermistor input and VREF