Core Electronics Forum

Hotend nozzle temp issues

Hi
My 3d printer temp for the nozzle is showing is showing -15 deg. I have replace block and the heating element and thermistor. I read online that I can multimeter test the thermistor which should be around 11kohms. I did the reading and it came to 28 ohms. Any other suggestions?

Thanks

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Hi Rolando,

What kind of printer have you got? I had a similar issue on my WanHao duplicator mini when I snapped the thermistor cable, there’s a few standards that get used for the thermocouples/thermistors on FDM printers, so it’s always best to check that you’ve got the right thermistor with the same curve.

Reflashing the firmware on the mainboard and double-checking that the connection and line on the PCB for your thermistor is clean and continuous is always a good first point of call.

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Creality 10s pro

Ah nice,

Fairly sure it’s a 100K NTC thermistor which is the same as the rest of the Creality printers. Have you ordered a replacement for it yet? Core Electronics doesn’t provide this particular thermocouple, although there’s plenty online on eBay, Amazon and from Creality directly.

https://www.amazon.com.au/Printer-Thermistor-Nozzle-Creality-Eewolf/dp/B07BBKWZ5K

Let us know how you go with the fix. If you find that you still run into that issue after replacing it, you should be able to either reflash the firmware, or replace the main board on your printer if it’s died (upgrading to one of the silent main boards is also a great idea)

https://www.amazon.com/Creality-Upgraded-Silent-TMC2208-Driver/dp/B085G7X2CN

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Where can I buy 1. Have not looked for 1 yet.

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Hey Rolando,

I added a couple of Amazon links you can jump onto in the previous post, although if you search on Google for the title of each part there should be plenty of places to pick one up.

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Thankyou very much. I had a quick look myself before I saw your post and I might have had difficult time finding 1.
Thanks

Another question. You said you can redo firmware. Is there thermistor firmware?

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Hey Rolando,

Sorry about the wait, it’s a bit busy at the moment.

No, a thermistor is simply a resistor (in this case of NTC it’s usually a combination of two metals pressed against eachother which changes electrical properties as temperature changes or a semiconductor which changes properties)

You can instead update the firmware on the board of the printer itself. Matterhackers have got a few good tutorials on this.

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Hi
I got a new thermistor. I put it in and still I am getting -15 degree. I put the new thermistor on multimeter test and it read 0.12M ohms. I then connected it to the pcb and then got a reading of 153k ohms. I am not sure which to follow on that ide/coloured ribbon cable to the pcb inside the machine.
I am also looked into redoing the firmware however creality does not look like they have much of that for this machine. I have looked online and tiny machine have firmware but i am not sure how reliable tiny machines are. I also saw a different creality 3d printer having its own thermistor setting as part of its setting to readjust it. Any other ideas would be great or if I have missed something.

Hi
I was wondering if I can get some help. I am trying top upload firmware onto the 3d printer but cant do it. As I am still learning about it I could use some help. I download a few different firmware from tiny machine and creality etc. I put the sd card in under the machine into the lcd board however when i put it on nothing happpens. I even tried connecting the machine via usb cable and going through the computer and cant find any firmware using programs such as pronterface. The firmware but not there.

Thanks

I would strongly not recommend reflashing your software. You need to be sure that the software is the cause of the problem before going that route, and I don’t believe you have proved that yet. For instance, it is still not clear from your description whether or not the hotend is actually heating up. So it’s not clear whether the thermistor is reading the temperature incorrectly, or the hotend heater is not heating. While both problems could be reolated to the software, it is essential to rule out hardware issues first.

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Hi
I put on the printer and manual tried to heat up the hotend, but it did not. Its shows -15 on the lcd.
I bought new hotend and thermistor. Still the same issue. I connected the printer via usb to pronterface and on there it says -15. I cant find any code for the pronterface to see if I can change it on there. How would I test the hotend to see if it works. All I know is to ohms test it. What else can I try?

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This is what I would do. Your actions might depend on your experience and equipment.

  1. To see whether or not the hotend is working, disconnect it from the controller board (or remove it from the machine completely) and provide 24v directly to the hotend terminals. Check (very carefully) whether or not it heats up. Do not allow it to overheat - you are only testing that it gets hot when voltage is supplied. Testing whether or not it can reach the required temperature will wait until you have eliminated more basic problems. If the hotend starts to heat when you supply 24v directly then you know that the hotend is working well enough to install for the rest of the testing. Note: a benchtop power supply is best for this task, but your 24v can be taken from the terminal strips on the power supply. Be careful making the connection because the 240v is exposed - the machine must be unplugged while doing this. Take your time to make a proper cable for testing because 24v at this sort of current can be nasty. If the hotend fails this test then you have a problem with a faulty hotend.

  2. Prove that the thermistor is working. With the hotend disconnected from the controller and and the thermistor connected but not installed, start the cycle to heat the hotend to a known temperature. When the cycle starts, use a hot air blower on the thermistor (gently) and see whether the reported temperature changes. If it does you know that the thermistor is working and is correctly connected to the controller. If you get no reported change in temperature then either the thermistor is not working (or is not the right device) or the controller is not reading the thermistor correctly.

  3. If there is no response when running a heating cycle and heating the thermistor, you need to determine whether the problem is with the thermistor or the controller. You can test the thermistor using a multimeter and a hot air blower - the resistance should change as the temperature of the thermistor changes. To test the controller you can substitute a potentiometer for the thermistor, start a hotend heating cycle, and adjust the resistance. If the reported temperature does not change as the resistance changes then the controller is faulty. If you don’t have a pot just use different resistors. If that process reveals a fault in the controller then it might be hardware or software. You would normally first check for a hardware problem because that is most likely, but it is also more difficult to test. A software problem is less likely, but replacing the software is probably easier than replacing the hardware, but it is not a trivial task and requires very careful preparation.

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Hi
The first 1 was not a problem. I have a power supply as I am just starting to study electronic and communications at tafe I do have breadboard, resistors etc. however I dont have a potentiameter yet.
I heated up the hot end with the power supply I have. I did not quite understand the 2nd and 3rd . I tested the temp on hotend and it climbed to around 60 degrees. I dont understand what I have to do with the thermistor. You said I can use resistors instead of a pot. How can I use the resistors?

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So you can assume the hotend is not the problem. The thermistor is simply a resistor that changes its resistance with temperature. You have already measured its resistance at ambient as between 120k ohms and 153k ohms. So step 2 will involve measuring its resistance at different temperatures as you heat it with the hot air gun (or the hair dryer). This is to confirm that it is operating like a thermistor should.

Step 3 then determines whether or not changes in the resistance of the thermistor are registering with the controller. The potentiometer is simply a replacement for the thermistor that you operate by hand instead of with a hot air gun. For your controller test you could select a pot of 250k ohms, set at about mid range. When you connect it across the thermistor terminals at the controller and start a heat cycle, the controller display should show a temperature of about ambient. As you turn the pot to change the resistance the controller should indicate a changed temperature, just like it would if a real thermistor was conected and was being heated. If you don’t have a pot you can do a series of tests using different resistances - one at about 125k ohms to see that get a reading of about 23 degrees (according to this chart) and then repeat with one of about half that to get a reading of about 37 degrees, and so on. That will prove that the controller is sensing the resistance of the thermistor correctly, so you have confirmed one more part of the puzzle.

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Hi
Then I think I did the thermistor test correctly. What I did last night was connect the thermistor to the pcb. I then connect the multimeter probes to the opposite side of the pcb for the thermistor so that the probes were connect to the legs of the connector which connects onto the connector of the thermistor. I put the heat gun on the other end of the thermistor and the multimeter consistantly changed values. however your last email suggestion controlling particular temps. So I am not sure what I can use to control that as my heat gun does not have a temp control. So I will have to buy a pot to do this. I tested the IDE cable and that is giving reading on the multimeter.

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It’s not necessary to have a control on the heat gun - just use the distance you aim it from and how long you hold it there to change the temperature. Without more detailed information about the values you expect to see you can’t really do much more than prove that it goes up and down as the temperature changes. It should not need much heat to see the change occurring, and you need to be careful about overheating the wire covering.

The values I mentioned in the last paragraph are only to give a guide to sort of values that would give sensible readings from the controller, assuming the particular type of thermistor it expects to see.

I hadn’t considered having the thermistor plugged into the board as you did this test, but the way you have done it has the advantage that you have proven the signal right through to the controller board, so that also eliminates cable and connector.

Rather than trying step 3 as a separate test, you could just repeat that test with the thermistor and hot air gun, watching the multimeter to confirm that the resistance is changing at the controller pins, then start a heat cycle and see if the controller display shows the temperature changing as the heat is applied to the thermistor and the resistance reading on the multimeter changes.

If that doesn’t work then the next step would be to replace the controller. But it is worth trying to update the software before doing that, even though that is a risky process. That’s because if it works then you are OK but if it fails you aren’t any worse off - you still need to replace the controller.

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Hi Rolando,

Jeff is right, testing the thermistor to ensure that the values that it is producing are accurate would be very helpful in troubleshooting the source of the issue on your printer and identifying whether the values the thermistor is returning are being interpreted correctly. If it is not practical to test the thermistor directly, if you hook up a potentiometer in place of your thermistor on the board (or some various resistors of known values) and compare the value registered as the temp on the appropriate curve on a working thermistor. This way, we can ensure that it is not the firmware or the board (or any other components) on your printer that’s causing it to enter thermal runaway.

That being said, I’m quite certain that updating the firmware on the printer may be a solution to this problem and can potentially save you from damaging other components. Ruling out issues with hardware is important (remember to always take the appropriate safety measures, even when you’re working on the ELV side of your board, as the power supply on those printers can kick out a fair amount of juice and components can get quite hot) although Creality printers, in particular, can be a little notorious about not including thermal runaway protection on their stock firmware.

Even if the firmware is not the issue, reflashing it when issues like this first occur to ensure that you don’t cause any further damage to the hot-end or printer (or continuously damaging your thermistor when you replace it making it seem like that’s the issue) wouldn’t hurt and should be relatively easy.

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Hi Bryce
In an earlier email I said I have downloaded several firmware from tiny machines and from creality.
I used the tiny machine firmware first. I then put in on sd card and connect to the inside of printer whats called the lcd pcb and when I witched it on nothing happened. So I don’t know what I did wrong. It is the first time that I update firmware on printer since I got it about 9 months ago. So I am not sure if pcb is reading the sd card or not? I will also try again what Jeff suggested, but if you can get back to me on if you know how to test the sd slot of pcb that would be great. I am leaning more about 3d printers as I have pulled a bit apart now.

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