Help PID tuning Dyzend Pro

chris974M

@Phaedrux
Jpenser pouvoir imprimer entre 200c a 400c

chris974M

je pense acheter une thermistance 300c Merci pour vos réponse

dc42

If the thermistor has resistance as high as 4.6M @ 25C then any electronics is going to have difficulty reading it at room temperature.

You could connect a resistor of about 1M in parallel with it. That may be enough to overcome the thermistor-disconnected detection. The thermistor will over-read a lot when cold, but get gradually more accurate as the temperature increases

You should remove the R4700 parameter in your M305 command unless you are using an old Duet (version 0.6 or 0.8.5). It won't do any harm if you are using Duet WiFi or Ethernet, but it will result in incorrect readings if you are using Duet Maestro or Duet 3.

Veti

@dc42 said in Help PID tuning Dyzend Pro:

If the thermistor has resistance as high as 4.6M @ 25C then any electronics is going to have difficulty reading it at room temperature.

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

maybe you could get a https://www.sliceengineering.com/collections/accessories/products/thermistor-high-temperature thermistor. that has a 500k resistance at 25C

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.