Dyze extruder
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I have just committed RRF version 1.17-dev1 on github. It includes changes to better support the Dyze thermistor, although I don't yet have one for testing with. See https://github.com/dc42/RepRapFirmware/blob/dev/WHATS_NEW for more details. Caution: I do minimal testing on dev builds.
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they have a pretty compelling reason that their thermistor is better. It has high resolution in the ~180C to ~280C range, which is exactly where we want to heat a hot end. The resolution at room temperature is bad, but that doesn't really matter much to us.
We actually do care about room temperature measurements. (I say this having calibrated my hot end thermistor to read about five degrees high at room temperature because that makes it better around 200 C.) The actual values are not very important, but reliable detection of heater faults is essential for fire prevention. If you have an apparent open condition at room temperature, the business of detecting whether the hot end temperature is rising by the right amount becomes more challenging. As long as the firmware can reliably detect when the thermistor has fallen off the hot end partially or completely it's not a problem, but if users get frustrated with spurious heater faults and use unsafe settings a fire risk can arise. This seems like a pretty important design criterion for a hot end - does it present an increased risk of setting your printer on fire if something goes wrong?
It's not clear to me that thermistor precision is the limiting factor in hot end temperature management. Certainly it isn't on mine, where my thermistor doesn't fit into the proper place on the E3D heater block so it's stuck in place with thermal goop. Making sure that the temperature-measuring device is measuring the temperature of the plastic being extruded is a key concern, particularly when extruding rapidly so that fresh cold filament is coming into the melt zone. The thermal conductivity between the heater, the melt zone, the nozzle, and the temperature sensor matters a lot here, as do the thermal masses of the various parts and the heat flux through the heat break. I'm sure Dyze has done a good job of all this, but I suspect that even in good hot ends these issues are what limits how well we can control the temperature of our extruded plastic.
I'd also point out that the time constant inferred by the Duet temperature calibration process tells us something about our hot ends - precision temperature control in the face of environmental insults (cooling fans, fresh cold filament, retraction) will work much better if that time constant is shorter, so that the PID loop can respond rapidly to changes. Simply changing the PID numbers won't help; the issue is how long the thermistor takes to notice changes in plastic temperature, which has to do with thermal mass and conductivity.
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…I say this having calibrated my hot end thermistor to read about five degrees high at room temperature because that makes it better around 200 C...
I don't know why you found that necessary, but if you measured the actual temperature with a thermocouple inserted into the hot end melt zone then it may mean the thermistor temperature is not quite the same as the melt zone temperature.
The B value of 4388 that I suggest for the E3D thermistor is aimed at giving the most accurate readings at 25C and 220C. The latest 1.17 dev build of RRF supports the Steinhart-Hart C coefficient for more accurate measurement. Without it, the temperature readings at 120C and 290C are less than 3C out.
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…I say this having calibrated my hot end thermistor to read about five degrees high at room temperature because that makes it better around 200 C...
I don't know why you found that necessary, but if you measured the actual temperature with a thermocouple inserted into the hot end melt zone then it may mean the thermistor temperature is not quite the same as the melt zone temperature.
The B value of 4388 that I suggest for the E3D thermistor is aimed at giving the most accurate readings at 25C and 220C. The latest 1.17 dev build of RRF supports the Steinhart-Hart C coefficient for more accurate measurement. Without it, the temperature readings at 120C and 290C are less than 3C out.
It wasn't necessary, exactly; I set the B value based on 200 and 250 C and let it come out to whatever it came out to at room temperature. Initially I totally misread the table and got outrageous values, but once I put the right numbers in, it's only about five degrees off, for a degree or two improvement on the 200-250 C range. It's the principle of the thing. As I said earlier, getting the temperature really exact would be more about improving the thermal design than about calibration. I don't have a better temperature-measuring device, so even the B value I got is based on the manufacturer's table, which is probably not measured either but based on one more Steinhart-Hart coefficient than the version I set up supports.
Also I think the readout when the machine is cold, showing five degrees' imaginary difference between bed and heater, is a healthy reminder of the gap between measurement and reality.
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I have just committed RRF version 1.17-dev1 on github. It includes changes to better support the Dyze thermistor, although I don't yet have one for testing with. See https://github.com/dc42/RepRapFirmware/blob/dev/WHATS_NEW for more details. Caution: I do minimal testing on dev builds.
Thank you David.
I will test the 1.17 dev tonight and report results with my Dyze 500°C thermistor. -
any progress on this? i have a dyzend too and have trouble getting it running on 1.17dev6
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@mb0:
any progress on this? i have a dyzend too and have trouble getting it running on 1.17dev6
I tested the 1.17dev6. It works, however the thermistor still has so much resistance at room temp that the reported temperature is still off and fluctuating. Moreover, the auto range ADC calibration means it sometimes initializes at 2-10°C at room temp or 15-30°C randomly. The room temperature fluctuation mens RRF forbids auto calibration. Dyze Design has a PT100 coming out very soon. I got it early and works well with the pt100 daughterboard. Now things work flawlessly.
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thanks, mind sharing your parameters for the default stuff? i got pid tuning to start after several tries but then complains about temperature overshooting / reaching to fast and aborts.
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Temperature overshooting is likely since the hotend has a big heater. On 24v I used 20% power to tune. On 12v, don't go over 50% PWM.
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Hi, we try many solutions to use dyze 12v 500°C thermistor on duet wifi.
I read this thread but we don't understand if there is solutions for this problem.
Someone had found a good trick?
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The main issue (not just with the Duet) is that at room temperatures the Dyze thermistor has such a large resistance that the firmware thinks that no thermistor is connected. A workaround is to connect a fixed resistor in parallel with the thermistor, just low enough so that the firmware detects that a thermistor is present. A value of about 300-500Kohms would be about right. This will give you an artificially high reading at room temperature, but it will not significantly affect the reading at the temperatures you use for extrusion.
For better accuracy over a large temperature range I suggest a PT100 sensor. I believe Dyze has a PT100 option for their hot end now.
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Dyze have a PT100 available, however it's not advertised. I still got one at the very beginning they were hesitant to sell because the PT100 insulation wasn't up to their spec limiting the temperature under 380°C. I don't use it that high anyway. I can say it works like a charm, the Duet, PT100 and Dyzend really is a winning combination.
I highly encourage anone printing materials at 350°C and under to get the PT100 and the daughterbaord. Just ask Dyze design directly, they are very helpful.
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thank you for this info.
i don't knew that the PT100 will be available.
i ask to dyze asap.
i already have a MAXTempRTD v0.4 (PT100 RTD board). can i use that right?
this module is 2 input ready.
