Bed temperature not stable (Keenovo 157 220V 600W)
Hi all,
After installation and initial setup of my 300 size V3.1, I notice the following in the temperature graph. The hot-end thermocouple is stable as a rock, but the bed thermocouple (integrated in the silicone heater) is very unstable. It seems to go up and down by about 2 degrees (18 - 20 C range in this image). The signal change is slow (thus low-frequency) and happens while the bed it not heated.
I switched the TC to a different input, the same thing happens.
33 Replies
To clarify, it's the undulations in the dark-blue (Heater Bed) line
it also changes over time, while I am doing nothing.
deep-jade•2y ago
Did you run a PID tune on the bed?
Hi @arakon_ . No, i did not - but this is with the bed turned off, no heat is going to the bed.
deep-jade•2y ago
Then I'd hook up a different thermistor to the port to see if it's the thermistor itself, and doublecheck that you set the correct type
I switched it with the thermistor in the hot-end, the problem follows the thermistor (so it's probably the thermistor)
I'm measuring the resistance with a multimeter now, to see if I see the same pattern with everything off
Here you can see what happens when I switch them
@ratrigmig might this be a hardware defect on the thermistor of the Keenovo pad?
Unsure, what about at working temps?
@ratrigmig similar poblems. You can see that the PID can't stabilize the bed because the thermistor is going up and down by itself.
and you can see the wrinkle again while it's cooling, no power to the bed.
Please contact [email protected] (our tech support) he will help and arrange any replacement you might need
Thanks for your input 👍🏻
Just for the sake of keeping this updated while we figure out what's going on, I've noticed that the thermistor output changes when I connect or disconnect the bed power wires to the SSR. The SSR is always off (0 PWM).
As you can see here
Thinking this is an electrical issue now.
While it's still unstable with the bed off, it seems perfectly fine at elevated temperatures. For now, I'm accepting this as a non-problem I suppose.
Jikes, problem potentially found - my mains wall socket's ground pin wasn't actually connected to ground.
Fixing my house before fixing the printer now....
national-gold•16mo ago
Hi,
I have a similar if not the same problem. Can you have a look at this clip pls?
That looks quite similar
the bed goes up and down by 1-2 degrees quite quickly and constantly, yes?
national-gold•16mo ago
yes... what it is quite amazing is that if I heat the bed to 50 and with printer on I disconnect both ac wires from ssr and bed the bed temp stil goes up and down by 1.2 C
I have another vcore and I compared them, at that one bed them drops constantly and at a slower pace, at the new one (one withe the problem) the temp drops in 1 sec by 1-2 C and I can't figure it out
the mains are grounded ( I checked the ground socket with a multimeter between the ground port and the other one)
the bed is also grounded I assume?
national-gold•16mo ago
no 🤦♂️.. is that a possible cause?
it's actually quite dangerous not to ground the bed and can certainly explain why you might be seeing interference on the bed
Ideally connect some part of the aluminium bed to the earth terminal of your power supply
the power supply itself should also have an earth connected to it from your mains plug
this isn't in the documentation because apparantly ratrig can't provide a guide on mains wiring without running some sort of risk, so users are supposed to figure this out themselves (i.e. consult an electrician)
also make sure that the SSR is on the phase line, not on the neutral
national-gold•16mo ago
I got 5 hours left of a print and will earth the bed to see if anything changes
Found the problem 🤦♂️ N and L were swapped between them, now is within 0.2c without even PID tune
do a PID tune and see if it looks similar, You got here img with before and after
national-gold•16mo ago
this might happen again if you plug your plug in the wall socket differently as well
here's what happens when I turn my power plug around
@ratrigmig expected behavior?
Im away from office this week
@pedro_8700 @seven957
quickest-silver•15mo ago
Hi Steef,
For direct tech support with the Rat Rig tech support team, please contact us at [email protected] or [email protected]
@pedro_8700 done! No rush, but might be a safety thing due to euopean plugs being able to be 180 degrees rotated