Extruder issue

Hi,

Last year, I wanted to have a reprap but did not have enough money. So I built it myself during one year. I soldered all electronics. Everthing went fine except mechanical construction. I got it at the end. When I run the reprap first it worked great. Extruder temp reached 230 °C and extruded some filament. Suddenly it showed up 352 °C then 8 °C and 0 °C. Now I read 0 °C. I have changed thermistor, nothing happened. Also I read 5.10 V on the thermistor pins. When I wire the pins together, I read 350 °C

Can anyone help me?
Hopefully I could express myself correctly.

King regards,

Yusuf.

Disconnect the thermistor from the board and check the resistance with a meter - for a 100k thermistor, it should be somewhere between 95k to 105k at room temperature.
Also, are you using a Ramps board?

---

_______________________________________
Waitaki 3D Printer

I am using Ramps 1.4. I checked it and it shows 93k.

That's about right then.

It sounds like you may have shorted the input to a voltage over 5V (eg: the voltage used to heat the hot end, usually 12V). This will fry the pin on the Arduino Mega that reads the thermistor input. The only way to truly fix this is to replace your Arduino Mega with a new one.

Another possibility is that you soldered your wires to the thermistor. As the thermistor gets hot, the solder will melt and the connection will fail. It's best to use crimp connectors to connect the wires to the thermistor, as there is no solder to melt. I've used small brass hobby tubing (very cheap at a hobby store) and used this to crimp the thermistor pins to the wires.

If you suspect that you've damaged the thermistor input on the Arduino Mega, you should try testing A13 (the input used for the T0 thermistor) without the RAMPS board on the Arduino Mega to confirm if there is an issue there before doing you consider buying a new one.

Also, if it has failed and you have a RAMPS 1.3 or later, you will have 3 Thermistor inputs on your RAMPS board. You can hook the thermistor up to one of the other thermistor inputs (eg: T2) if you change the pins.h file in the firmware (swap the pin numbers for T2 and T0).

Make sure that you've eliminated all shorts first before trying it again, otherwise you'll just fry that input as well. Note that the short may only happen when it gets hot (ie: whatever is supposed to be insulating the thermistor from the hot end may not be withstanding the heat).


Editing pins.h:
In Marlin, search for: MOTHERBOARD == 33

Then look under it for the first occurrence of:
#define TEMP_0_PIN 13 // ANALOG NUMBERING
#define TEMP_1_PIN 15 // ANALOG NUMBERING

This should be around line 514 (at time of posting) if you're using the latest version of the Marlin firmware.

Change it to:
#define TEMP_0_PIN 15 // ANALOG NUMBERING
#define TEMP_1_PIN 13 // ANALOG NUMBERING

This will swap the T0 and T2 inputs in the firmware. T2 will now be the input for your extruder, and will allow you to use your printer for the moment. As mentioned, the real solution is to replace the Arduino Mega with a new one.

PS: I mention RAMPS 1.3 in case someone else stumbles over this post. I saw you mention RAMPS 1.4, but it applies to both.

Yes. that's good advice to swap the inputs - something I had to do once before to effect a cure.

---

_______________________________________
Waitaki 3D Printer