<p>As worked out by dandavis in the comments, this is not plausible:</p>
<blockquote>
<p>thermistors likely use 3.3v or 5v signaling. It would take a lot of sag for those rails to drop below set voltage if fed 12v or 24v; all they need is a volt or two above output. As far as the effect of a sag on the 3.3/5v line, it's impossible to say universally because the thermistor could be on either side of the voltage divider, so it could be too high or too low, or it could use a current source unaffected until the rail dropped to &lt;1v. It could even be a thermocouple instead, so the effect would be how the gain amp responds to sag or the MCU glitches...</p>
<p>I found a schematic and it's on the gnd side of the divider. So that's half the equation solved...</p>
<p>[The EPCOS 100K B57560G104F] is an NTC, so it would appear as warmer. That said, I highly doubt your 3.3v &quot;rail&quot; sags, and if it does, the whole controller would freeze up and nothing would operate</p>
</blockquote>
<p>It turns out the PTFE in the heatbreak was badly burnt out, and friction from this may account for at least a large part of the loss of flow (I've been able to get back some but not all). But I still have not fully explained or solved the problem. In any case, the power supply issue does not seem relevant, answering this question as stated.</p>

CC BY-SA 4.0
2022-05-17T16:59:47.153Z
2022-05-17T16:59:47.153Z
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<p>I've been trying to trace down a mysterious reduction in the flow I can achieve. Since recording <a href="https://youtu.be/_4QEEit5aNo" rel="nofollow noreferrer">this flow test video</a> where I successfully achieved a nominal 30 mm³/s (almost surely with underextrusion, but with no skipping or warping), something happened whereby I'm no longer able to reproduce it.</p>
<p>Shortly after that was recorded, I discovered a burnt-out XT60 connector between the power supply and printer, and replaced it. That made a lot of voltage sag issues (fans slowing down when heaters turned on, etc.) go away, and I'm wondering how it might affect temperature measurement and indirectly flow.</p>
<p>Could the thermistor voltage have been affected by undervoltage/limited current availability from the power supply, and if so, how would that manifest? Hotend (including thermistor) is stock Ender 3. The controller board is SKR E3 Mini V2. Naively, I would expect that if there was actually reduced voltage on the (3.3V?) line feeding into the thermistor, that would appear as higher resistance, and thus lower temperature, driving the controller to heat it well above the requeste temperature, but I'm not sure if that plausibly could have happened.</p>

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2022-05-05T07:22:59.720Z
Heck of a flow test, is that video sped up?
Kilisi
CC BY-SA 4.0
2022-05-05T17:53:40.860Z
@Kilisi: No, it's realtime. 
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CC BY-SA 4.0
2022-05-06T02:22:47.157Z
Very impressive :-)
Kilisi
CC BY-SA 4.0
2022-05-06T02:37:17.233Z
@Kilisi: Yeah, now if only I could still reproduce it. Thus this question.
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CC BY-SA 4.0
2022-05-06T02:37:51.130Z
@Kilisi: Yeah, if only I could still reproduce it. Thus this question.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2022-05-10T05:10:13.640Z
thermistors likely use 3.3v or 5v signaling. It would take a lot of sag for those rails to drop below set voltage if fed 12v or 24v; all they need is a volt or two above output. As far as the effect of a sag on the 3.3/5v line, it's impossible to say universally because the thermistor could be on either side of the voltage divider, so it could be too high or too low, or it could use a current source unaffected until the rail dropped to <1v. It could even be a thermocouple instead, so the effect would be how the gain amp responds to sag or the MCU glitches. In short (haha), we can't say...
dandavis
CC BY-SA 4.0
2022-05-10T12:14:24.930Z
@dandavis: I've specified a particular board and thermistor, so it's not impossible to say.
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CC BY-SA 4.0
2022-05-10T18:54:08.953Z
well i didn't catch the model somehow, my bad. I found a schematic and it's on the gnd side of the divider. So that's half the equation solved. But i was not able to find a part number for the actual thermistor. If you could find out if it's NTC or PTC you'll have your answer.
dandavis
CC BY-SA 4.0
2022-05-10T19:54:14.953Z
@dandavis: It's EPCOS 100K B57560G104F or equivalent.
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CC BY-SA 4.0
2022-05-10T20:02:54.267Z
that's an NTC, so it would appear as warmer. That said, I highly doubt your 3.3v "rail" sags, and if it does, the whole controller would freeze up and nothing would operate.
dandavis
CC BY-SA 4.0
2022-05-11T01:52:13.903Z
OK, so it sounds like there are multiple reasons this isn't possibly the issue. Would you like to write the comments up as an answer so I can accept it?
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<thermistor><power-supply>
Effects of bad power supply on temperature/flow?
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# Effects of bad power supply on temperature/flow?

(Asked by: username_0 on 2022-05-04)

I've been trying to trace down a mysterious reduction in the flow I can achieve. Since recording [this flow test video](https://youtu.be/_4QEEit5aNo) where I successfully achieved a nominal 30 mm³/s (almost surely with underextrusion, but with no skipping or warping), something happened whereby I'm no longer able to reproduce it.

Shortly after that was recorded, I discovered a burnt-out XT60 connector between the power supply and printer, and replaced it. That made a lot of voltage sag issues (fans slowing down when heaters turned on, etc.) go away, and I'm wondering how it might affect temperature measurement and indirectly flow.

Could the thermistor voltage have been affected by undervoltage/limited current availability from the power supply, and if so, how would that manifest? Hotend (including thermistor) is stock Ender 3. The controller board is SKR E3 Mini V2. Naively, I would expect that if there was actually reduced voltage on the (3.3V?) line feeding into the thermistor, that would appear as higher resistance, and thus lower temperature, driving the controller to heat it well above the requeste temperature, but I'm not sure if that plausibly could have happened.

**Tags:** thermistor, power-supply
> **Comments:**
> **username_1**: Heck of a flow test, is that video sped up?  
> **username_0**: @Kilisi: No, it's realtime.   
> **username_1**: Very impressive :-)  
> **username_0**: @Kilisi: Yeah, now if only I could still reproduce it. Thus this question.  
> **username_0**: @Kilisi: Yeah, if only I could still reproduce it. Thus this question.  
> **username_2**: thermistors likely use 3.3v or 5v signaling. It would take a lot of sag for those rails to drop below set voltage if fed 12v or 24v; all they need is a volt or two above output. As far as the effect of a sag on the 3.3/5v line, it's impossible to say universally because the thermistor could be on either side of the voltage divider, so it could be too high or too low, or it could use a current source unaffected until the rail dropped to <1v. It could even be a thermocouple instead, so the effect would be how the gain amp responds to sag or the MCU glitches. In short (haha), we can't say...  
> **username_0**: @dandavis: I've specified a particular board and thermistor, so it's not impossible to say.  
> **username_2**: well i didn't catch the model somehow, my bad. I found a schematic and it's on the gnd side of the divider. So that's half the equation solved. But i was not able to find a part number for the actual thermistor. If you could find out if it's NTC or PTC you'll have your answer.  
> **username_0**: @dandavis: It's EPCOS 100K B57560G104F or equivalent.  
> **username_2**: that's an NTC, so it would appear as warmer. That said, I highly doubt your 3.3v "rail" sags, and if it does, the whole controller would freeze up and nothing would operate.  
> **username_0**: OK, so it sounds like there are multiple reasons this isn't possibly the issue. Would you like to write the comments up as an answer so I can accept it?  

---

## 1 answers

### Answer by username_0 on 2022-05-17. Score: 1

As worked out by dandavis in the comments, this is not plausible:

> thermistors likely use 3.3v or 5v signaling. It would take a lot of sag for those rails to drop below set voltage if fed 12v or 24v; all they need is a volt or two above output. As far as the effect of a sag on the 3.3/5v line, it's impossible to say universally because the thermistor could be on either side of the voltage divider, so it could be too high or too low, or it could use a current source unaffected until the rail dropped to <1v. It could even be a thermocouple instead, so the effect would be how the gain amp responds to sag or the MCU glitches...
>
> I found a schematic and it's on the gnd side of the divider. So that's half the equation solved...
>
> [The EPCOS 100K B57560G104F] is an NTC, so it would appear as warmer. That said, I highly doubt your 3.3v "rail" sags, and if it does, the whole controller would freeze up and nothing would operate

It turns out the PTFE in the heatbreak was badly burnt out, and friction from this may account for at least a large part of the loss of flow (I've been able to get back some but not all). But I still have not fully explained or solved the problem. In any case, the power supply issue does not seem relevant, answering this question as stated.


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