PID Tuning RTD PT1000 from the 1LC

tmitch205

6HC + 1LC + Slice 50W Heater + Slice RTD PT1000

I have been trying to PID-tune the PT1000 for a while. It starts, gets to temp, then brings to the settling stage (Stage 2). The temp rises and falls until the tuning eventually fails. I suspect this is a current draw issue because I can hear the fan draw down when the heater kicks in during the test and pick back up when the heater reaches temp and kicks off.

Under normal printing, I do not hear the fan draw down when the heater kicks in like I do in the test, and the heater maintains a temp of only +/- 2 degrees.

I recall reading somewhere that the fix was to connect the heater and thermistor to the mainboard and PID-tune it.

Has there been an actual fix for this instead of a workaround?

Phaedrux

What firmware versions are on your boards?

tmitch205

@phaedrux

6HC is v1.01 with 3.4.1
1LC is v1.2 with 3.4.2rc3
1LC updated from 3.4.1 to 3.4.2rc3 when Input Shaper couldn't see the accelerometer. 3.4.2 resolved the accelerometer issue, but the PID Tune issue remains.

tmitch205

@tmitch205 said in PID Tuning RTD PT1000 from the 1LC:

Under normal printing, I do not hear the fan draw down when the heater kicks in like I do in the test, and the heater maintains a temp of only +/- 2 degrees.

Clarification: that is +/- 2° while printing. During tuning, it's a 10° swing both ways while in stage 2.

Phaedrux

@tmitch205 said in PID Tuning RTD PT1000 from the 1LC:

6HC is v1.01 with 3.4.1
1LC is v1.2 with 3.4.2rc3

Mismatched firmware versions can be problematic. Please try updating all to the latest.

Phaedrux

What command are you using to PID tune?

tmitch205

@phaedrux
I have tried M303 H1 S400 and M303 T0 S400 when the firmware was matching, I have not tried the second since the 1LC firmware update.

When both kept failing, I dropped the S down to 250, with the same results.

My config.g for the heater and PT1000 are:

M308 S1 P"121.temp0" Y"PT1000"
M950 H1 C"121.out0" T1
M307 H1 B0 S1.00
M143 H1 S450

gloomyandy

@tmitch205 It may help if you post the details of the error message you get when the PID tuning fails. A screenshot of the temperature graph when it fails might also be of use.

As to the fan speed dropping, what sort of wiring are you using to the 1LC? Perhaps a picture of the setup might help?

Phaedrux

Please also post your full config.g and the results of sending M122 and M122 B# where # is the canbus address of your expansion board. Also send M98 P"config.g" and post the results.

dc42

@tmitch205 said in PID Tuning RTD PT1000 from the 1LC:

Under normal printing, I do not hear the fan draw down when the heater kicks in like I do in the test, and the heater maintains a temp of only +/- 2 degrees.

If you can hear the fan RPM reduce when the heater kicks in then the supply voltage must be dropping. I think either your PSU is weak, or you have a bad connecting in the power wiring to the tool board, or possibly the power wires to the tool board are too thin. Can you use a multimeter to measure the voltage across the pins of the tool board VIN connector while the heater is turning on and off? Be careful not to short them together!

You won't hear such sudden changes during normal printing except when the heater first turns on, because the neater is normally controlled by PID so the power changes are gradual.

tmitch205

@dc42 It was a combination of mismatched firmware between the TB and the MB, as well as a weak PSU... 350W 24V... Switched to a 450 24V, and matched the firmware. It is now completing the PID without the draw-down on the fan.

dc42

@tmitch205 I'm glad you solved it!